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ORAL PRESENTATIONS
New Chemistry Among Metal-Rich Tellurides of the Rare Earth Metals
John D. Corbett
Department of Chemistry, Iowa State University, Ames, IA (USA)
Exploration of the telluride chemistry of the combined group 3 transition metals
and the lanthanides reveals a rich variety of new chemistry, especially for Sc, Y, Dy, Lu.
The small electron-poor metal Sc combined with the large Te "spacer" affords significant
metal aggregation in new lower dimensional isotypes of electron-richer group 4 metal
chalcogenides, viz., as Sc2Te, Sc8Te3, Sc9Te2, hexagonal Sc6MTe2 (M = Fe–Ni).
Significant differences between the related pairs of compounds will be described. Other
unusual results include the unique Sc5Ni2Te2, Y5M2Te2 (M = Fe–Ni), which exhibit novel
"cut-and-paste" relationships with Gd3MnI3-type, the condensation reactions that convert
Sc2Te to orthorhombic Sc6MTe, M = Pd, Cu, Ag, Cd, and the unique Sc14M3Te8, M = Ru,
Os. Related explorations of tellurides of the heavy lanthanides, Gd, Dy, and Lu
especially, will also be outlined, particularly for R2Te, other R6MTe2, R11Te4, and LuxTe
(x = 7, 8). The results demonstrate some important relationships between this 5d orbital
chemistry and that of the 3d and 4d transition metal elements. Important factors in EHTB
band results, orbital and bonding properties, and matrix effects will also be presented.
Dimensionally Limited Transition Metal Pnictides: Synthesis and Characterization.
Stephanie L. Brock
Department of Chemistry, Wayne State University, Detroit, MI 48202
The dimensionality of materials plays a large role in material physical properties,
and when limited, can result in drastically altered behavior. Dimensional limiting can be
imposed by control of particle growth, as when extended solids are made as nanometer
sized particles, or can arise spontaneously as a structural motif in an extended solid, such
as the presence of 1-D chains or 2-D planes within a crystal. The main objectives of the
Brock group are to prepare new low-dimensional materials using a combination of
solution and solid-state techniques, and develop a fundamental understanding of the
relationship between structure, dimensional limiting, and physical properties (magnetic,
electronic, optical) in these materials. In this presentation, two examples of our efforts to
prepare dimensionally limited transition metal pnictides will be discussed. First, a newly
developed route for the synthesis of binary pnictide nanoparticles of iron and manganese
based on reactions between metal carbonyls and phosphines/arsines will be introduced
and the magnetic properties of the resultant materials discribed. Second, a series of solid
state materials featuring 1-D mixed pnicogen (P, As) chains in the solid state (Cu2P3xAsxI2; x<0.5) will be described along with the influence of arsenic incorporation on the
structure, stability, and optical properties. Finally, the specific role of dimensional
limiting in the development of properties in these two different classes of materials will
be discussed.
1
Dimensional Reduction in Niobium Oxychloride Cluster Compounds: Synthesis and
Crystal structure of Cs2InNb6Cl15O and its relationship with AxNb6Cl12O2
Yan Zhihua and A. Lachgar
Department of Chemistry, Wake Forest University, Winston-Salem, NC 27109
Low-dimensional materials containing transition metals attract significant
attention due to their remarkable structural and physical properties and wide range of
applications. Our investigation of the use of a combination of oxygen and chlorine as
ligands in octahedral Nb6 clusters to prepare low-dimensional cluster-based materials led
to the discovery of a number of novel phases with surprisingly diverse topologies.1-4 The
presentation will describe the synthesis, single crystal x-ray diffraction studies of a new
member of this family, InxNb6Cl15O, which has a 2D framework. Crystals of
Cs2InNb6Cl15O were initially found as minor by-product in a reaction aimed to prepare
CsxInyNb6Cl12O2 from a mixture of NbCl5, Nb2O5, Nb, In, and CsCl in a sealed quartz tube
at 720 °C. Cs2InNb6Cl15O crystallizes in the monoclinic system (space group: P 21/c) with
a = 15.9699(3), b = 11.7073(2), c = 13.0993(2) Å, β = 100.58(1)°, V = 2407.4(8) Å3, and
Z = 4. Its 2D framework is based on octahedral niobium oxychloride clusters
(NbClO)ClO linked through four outer chlorine ligands (Cla) to four different clusters to
generate layers // to the (ac) plane. Two adjacent layers are linked through two oxygen
ligands (Oi and Oa) in the b direction to generate double layers with cluster connectivity
(NbClO)ClClO. The In and Cs cations are disordered on 4 sites located on the surface of
the double-layers. The relationship between the structure of Cs2InNb6Cl15O and that of
InxNb6Cl12O2, and the role played by the oxygen ligands will be discussed.
(NbClO)Cl
AxNb6Cl12O2
Cs2InNb6Cl15O
O
(3D)
(2D)
Views of the cluster units and their linkages leading to the 3D framework in AxNb6Cl12O2 and
a 2D framework in Cs2InNb6Cl15O.
(NbClO)ClO
References:
1. E. V. Anokhina, T. Duraisamy, A. Lachgar, “Preparation of Low-dimensional Cluster
Materials: Synthesis, Structure and Properties of A2Ti2Nb6Cl14O5 (A = K, Rb, Cs), a Series of
One-dimensional Titanium Niobium Oxychlorides” Chem. Mater. 2002, 14, 4111-4117.
2. E. V. Anokhina, Cynthia S. Day, Hans-Jürgen Meyer, Markus Ströbele, Susan M. Kauzlarich,
Hyungrak Kim, Myung-Hwan Whangbo, Abdessadek Lachgar, “Preparation, Structure, and
Properties of a Series of Anisotropic Oxychloride Cluster Compounds AxNb6Cl12O2 (A = K,
Rb, Cs, or In)” Journal of Alloys and Compounds, 2002, 338, 218-228.
3. E.V. Anokhina, C. S. Day, A. Lachgar, “A New Quasi-One-Dimensional Niobium
Oxychloride Cluster Compound Cs2Ti4Nb6Cl18O6.
Structural Effects of Ligand
Combination,” Inorg. Chem., 2001, 40, 5072-5076.
4. E.V. Anokhina, C. S. Day, A. Lachgar, “A new layered niobium oxochloride cluster
compound with novel framework topology”, Chem. Comm. 2000, 16 1491-1492.
2
The New Supertetrahedral Clusters [M4Sn4S17]10- (M = Mn, Co, Zn)
Oleg Palchik, Ratnasabapathy G. Iyer, J. H. Liao, Mercouri G. Kanatzidis
Department of Chemistry and Center for Fundamental Materials Research
Michigan State University, East Lansing, Michigan, 48824
We used the alkali metal polysulfide technique and conventional direct
combination reactions to synthesize a family of supertetrahedral mixed metal clusters.
Unlike other known supertetrahedral clusters which can be considered as excised
fragments form the diamond lattice, the ones we describe here have a different structural
motif.
In this talk we present extension of our work for the preparation of the complex
new compounds using polychalcogenide-flux method. These isostructural compounds
were synthesized in K2S/S flux and they have general stoichiometry of K10M4Sn4S17,
where M=Mn, Fe, Co, Zn, Cd and Hg. All this group posses same structural motif:
[M4Sn4S17]10- isolated clusters, which is surrounded by K+ ions. They all possess sharp
optical absorption in the UV-VIS-NIR region. The incorporation of the magnetic ions
(e.g. Fe2+) in the structure gives rise to interesting magnetic properties. Moreover, due to
the molecular nature of the K10M4Sn4S17 they are soluble is different solvents (e.g. water,
formamide). Last property makes this group of compounds especially attractive for
applications as precursors for the sophisticated mesoporous structures.
Use of Mn2(CO)10 Carbonyl Complexes as Precursors
for the Synthesis of MnPn (Pn= P, As) Nanoparticles
Susanthri C. Perera†, Georgy Tsoi‡, Lowell Wenger‡, and Stephanie L. Brock†
Department of Chemistry†, Department of Physics‡, Wayne State University, Detroit, MI
48202.
Over the past few years, interest in fine magnetic particles has grown enormously
because of their unusual magnetic behavior compared to conventional bulk materials. A
number of previous studies have reported the suppression of long-range magnetic order in
nanocrystalline materials due to the presence of single magnetic domain structures.
Therefore, nanoparticulate ferromagnets demonstrate size dependent coercive fields. So
far, studies have been mainly focused on nanoparticles of transition metals (Co, Fe),
alloys (Fe-Pt), and transition metal oxides (ferrites, etc.). TM (transition metal) pnictides
(pnicogen = group 15 elements; P, As) are a class of compounds that show a broad range
of electronic and magnetic properties including ferromagnetism, magnetooptical and
magnetoelastic properties. Therefore, nanoparticulate TM pnictides are expected to
exhibit novel, perhaps even superior, magnetic and optical properties in relation to their
bulk analogs. Accordingly our group has begun to explore the suitability of different
methodologies for the production of TM pnictide nanoparticles.
We initiated our investigation using desilylation strategies, which are formally
non-redox and well established for main group materials. This method is successful for
preparation of FeP nanoparticles but to date, we have not been able to make MnP by this
approach. Recently, we were able to produce nanoparticles of MnP by redox chemistry
between zero-valent manganese carbonyl complexes and a variety of phosphines. The
application of this new route to the synthesis of other transition metal pnictide phases,
especially MnAs and CoP, along with optimized synthetic parameters, structural
characterization, and magnetic properties of the resulting materials, will be discussed.
3
Magnetic Ordering in Gd2Cl3 — An Example of Burdett’s Coloring Problem
Timothy Hughbanks and Lindsay E. Roy
Department of Chemistry, Texas A&M University, College Station, TX 77842-3012
Spin density functional (SDFT) calculations of the d-f exchange coupling for the
pseudo 1-D chain compound Gd2Cl3 has been carried out using the 1-D model,
Gd8Cl12(OPH3)4, by considering seven variations in the ordering of the 4f7 moments. The
calculations indicate that this semiconducting system should exhibit antiferromagnetic
ordering of the 4f7 moments in a pattern consistent with published spin polarized neutron
diffraction data. An attempt to account for the calculated magnetic energies of spin
patterns using an Ising model was unsuccessful, indicating that the latter model is
inappropriate. The qualitative features can be interpreted using a perturbative molecular
orbital (PMO) model that focuses the influence of the 4f7-d exchange interaction on the dbased molecular orbitals. Fundamental to the d-electron mediated exchange mechanism
is the intra-atomic 4f7-d exchange interaction. The essence of this interaction is present in
the Gd atom [4f75d16s2], which is computationally investigated within SDFT. The on-site
perturbation induced 4f7-d exchange is equivalent to use of different Hückel “α
parameters” for different 5d spins — what Burdett would have called a ‘coloring
problem’. In Gd2Cl3, the d-electron mediated f-f exchange interaction was interpreted
using basic perturbation theory. Computed density of states and spin polarization
information was used to support the perturbation-theoretic analysis.
Synthesis and Characterization of Novel Quaternary Alkali Metal Thioarsenates
Using the Molten Flux Method
Ratnasabapathy G. Iyer and Mercouri G. Kanatzidis
Department of Chemistry and Center for Fundamental Materials Research
Michigan State University, East Lansing, MI 48824
Our group has been involved in a systematic investigation of the reactivity of
different metals in alkali polythioarsenate fluxes. These fluxes have proved to be every
bit rich and promising as its phosphate counterpart in delivering a plethora of structurally
diverse quaternary compounds. These reactive fluxes play the role of a solvent in
allowing diffusion of reactants and also participate in the reaction. The melting points of
these fluxes are in the 250°C-650°C temperature range, enabling reactions to be carried
out at low temperatures of 300°C -500°C. The outcome of a reaction in such a flux is a
function of the basicity of the flux, giving the chemist a certain degree of control. In a
polythioarsenate flux, anionic building blocks of the kind [AsxSy]n- are formed depending
on the kind of metal present and the basicity of the flux. Using Sn, we have isolated
compounds ranging from a molecular structure (Cs2SnAs2S9) to a two-dimensional
structure (Rb2SnAs2S6). In gives molecular Cs6InAs3S13 while Pb leads to RbPbAsS4.
Going to the transition metals, we prepared K4MnAs2S8, Cs2CuAsS5 and A4CdAs2S9. The
compounds obtained in these fluxes are very different from the ones obtained in the
chalcophosphate fluxes. All the compounds have been structurally characterized using
single crystal X-ray diffraction. Physical characterizations include UV-Vis spectroscopy,
Infrared and Raman spectroscopy, and Differential Thermal Analysis.
4
Synthesis, Structural and Physicochemical Characterization of MnP@InP, New
Magnet-Semiconductor Core-Shell Nanoparticles
Kanchana Somaskandan1, Georgy Tsoi2, Lowell Wenger2, Stephanie L. Brock1
1
Department of Chemistry, 2 Department of Physics, Wayne State University, Detroit, MI
48202
The aim of this research is to develop a synthetic strategy for III-V based magnetsemiconductor core-shell nanoparticles, and study the effect of size limitation on the
properties in these materials. The targeted core-shell nanoparticles are heterostructures in
which a magnetic core is coated by a semiconductor shell resulting in a ferromagneticsemiconductor junction within each particle. These would mimic heterostructured thin
films, which have potential spin-dependent applications in new magneto-electronic and
magneto-optical devices.
So far, only II-VI and III-V based semiconductorsemiconductor core-shell nanoparticle systems have been reported. These materials
exhibit unusual optical properties including tunable band gaps and sharp luminescence.
Here, the synthesis of MnP@InP semiconductor-magnet core-shell nanoparticles is
reported. The synthesis involves preparation of the magnetic transition metal (Mn)
phosphide core nanoparticles followed by precipitation of semiconducting InP on the
surface. The resultant particles are isolated by size selective precipitation and
characterized by UV/Visible spectroscopy, X-ray powder diffraction, high resolution
transmission electron microscopy, and SQUID magnetometry. The effect of synthetic
conditions on size, sample homogeneity, and resultant physical properties will be
discussed.
Electrochemical Synthesis of Micro- and Nanostructured Films for Use in
Photoelectrochemical Hydrogen Production
Kyoung-Shin Choi
Department of Chemistry, Purdue University, West Lafayette, IN 47907.
Developing materials that can produce an economical and environmentally benign
source of energy is undoubtedly one of the world’s most pressing technical challenges.
Our current research effort is focused on developing high performance micro- and nanostructured electrode materials for use in photoelectrochemical hydrogen production.
When photoelectrodes are prepared as polycrystalline films, interfacial structures have a
substantial impact on the overall efficiency of the photoelectrode because the size,
crystallinity, morphology, and texture of the particles dramatically change catalytic
activity, charge recombination rate, and charge transport properties of the photoelectrode.
However, most of the previous studies on photoelectrode materials have focused on
identifying a few candidate materials and optimizing their composition without
systematically addressing interfacial issues. This was because synthetic methods
formerly available to produce photoelectrode materials (e.g. spray pyrolysis, sol-gel,
electron-beam evaporation, spin coating) possess limited control over the morphological
features of the particulate films.
To develop highly efficient, area-effective
photoelectrode materials an innovative interfacial synthetic technology will have to be
developed so that the structure-property relationship necessary to design the best
interfacial structure can be elucidated.
We are currently developing a novel synthetic strategy that combines a soft
solution electrochemical process with a biomineralization inspired concept. In this
approach we electrochemically organize organic matrices on the electrode surface to
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direct and regulate the nucleation and growth processes of inorganic materials. This
method provides us with a high degree of synthetic freedom for interfacial engineering
and makes it possible to tune interfacial structures as well as compositions of the
photoelectrode materials. In this presentation, we will introduce principles of our new
synthetic method and discuss in detail the effects of compositions and interfacial
structures on the photoelectrochemical activities of the photoelectrode materials.
Yb8Ge3Sb5: a New Mixed Valent Zintl Phase Containing (Ge3)4- Anions
James R. Salvador† Daniel Bilc‡ S.D. Mahanti‡, and Mercouri G. Kanatzidis†
† Department of Chemistry and Center for Fundamental Material Research
‡ Department of Physics and Astronomy and Center for Fundamental Material Research
Michigan State University East Lansing MI 48824
The new Zintl phase Yb8Ge3Sb5 has been produced by direct combination of the
elements and crystallizes in the tetragonal space group I4/mmm with lattice parameters
a = 15.8965(8)Å, c = 6.8206(5)Å. This rare-earth metal rich phase can be charge
balanced in the following manner (Yb2+)6 (Yb3+)2 (Ge3)4- (Sb2-) (Sb3-)4 and is therefore a
mixed valent compound. The use of electropositive elements with the ability to be mixed
valent for the exploratory synthesis of Zintl phases is a relatively new concept, and has
the potential to greatly expanding the structural diversity of Zintl ions. The compound
presented here has several unique structural features including a new Zintl ion (Ge3)4which polymerizes to form a 1-dimensional chain of edge sharing tetrahedra. Magnetic
susceptibility, electrical transport and Hall effect measurements as well as ab-initio band
structure calculations will be presented to support the notion that this compound
represents a mixed valent system.
High Temperature and Ambient Temperature NMR Investigation of Metal
Selenophosphate Syntheses
Christian G. Canlas, Mercouri G. Kanatzidis, and David P. Weliky*
Department of Chemistry, Michigan State University
Many different metal selenophosphate compounds can be synthesized in high
temperature (400 – 600 C) melts and these compounds contain a rich variety of metal
selenophosphate anions. In order to understand better the chemistry which occurs in these
melts, syntheses have been carried out in situ in the NMR spectrometer and 31P NMR has
been applied to identify and quantify reactants, intermediates, and products over the time
course of the reaction. For example, in a melt containing Ag:P:Se in a 2:1:3 mol ratio,
there are two distinct 31P signals which can be tentatively assigned to the PSe43– and
P2Se64– anions, and which correlate with the final ambient temperature products, Ag7PSe6
and Ag4P2Se6, respectively. The observed signals are relatively broad, which could be
diagnostic of chemical exchange in the melt or of solid precipitation in the melt. For the
PSe43– signal, the solid state NMR technique of magic angle spinning narrows the
lineshape, which suggests that this anion exists in some solid or at least slowly-rotating
form at high temperature. In a parallel study, ambient temperature 31P NMR has been
applied to the metal selenophosphate product compounds, and a correlation was observed
between the 31P chemical shift and the presence or absence of a P–P bond in the
selenophosphate anion. This correlation will be useful in anion identification in the hightemperature melts. In addition, 31P spin-lattice relaxation times were measured at ambient
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temperature and showed a surprisingly large range (20 – 3000 s) among the different
compounds. Two of the compounds which demonstrate fast relaxation were also shown
to have detectable ESR signals. Although these compounds are not paramagnetic per se,
they appear to contain paramagnetic impurities whose chemical identity is currently
under investigation. Overall, NMR has been shown to be a promising technique for
understanding the high temperature syntheses of metal selenophosphates.
Physics among light-weights: Superconductivity in MgB2
Paul C. Canfield
Ames Laboratory and Department of Physics and Astronomy, Iowa State Univeristy
Superconductivity in MgB2 was discovered a little over two years ago. During the
past 24 months our understanding of this simple binary compound has grown at a break
neck rate and MgB2 has proven to be of great interest to both the basic as well as the
applied research communities. In this talk I will try present an overview of why this is
the case.
High purity, polycrystalline MgB2 can be synthesized in a variety of forms
ranging from sintered pellet to wire segment to thin film by simply exposing high purity
boron with the desired morphology to Mg vapor near 900 C. For pure MgB2 Tc in near
40 K, there is a clear boron isotope shift in Tc, the low temperature resistivity is near 0.5
micro-Ohm-cm, and the anisotropy of Hc2(T) ranges from 2 close to Tc to near 6 at low
temperatures. Carbon doped MgB2 can be synthesized by exposing the binary, carbonrich, compound B4C to Mg vapor near 1200 C. The transition temperature is reduced to
near 22 K, the normal state resistivity appears to increase substantially, and the
anisotropy in Hc2(T) at the lowest measured temperatures is close to 2. Remarkably, even
with all of the changes mentioned above, the carbon doped MgB2 still manifests a clear
two-gap signature in the low temperature specific heat data, implying that the two
superconducting gaps are quite robust.
TRANSITION METAL ZINTL PHASES: NIOBIUM ARSENIDES AND BEYOND
Franck Gascoin and Slavi C. Sevov
Department of Chemistry and Biochemistry, University of Notre Dame
Notre Dame, Indiana, 46556
Compared to the large number of Zintl phases, there are only a few transition metal Zintl
phases. Despite the large variety of transition metals and the numerous feasible
combinations with main-group elements, this field remains quite underdeveloped and
unexplored. We have been interested in the solid-state chemistry of the system alkali
metal – niobium – arsenic and have undertaken extensive and systematic studies of these
systems. This has led to the discovery of the first mixed-valence transition metal Zintl
phases, namely, K38Nb7As24, Cs9Nb2As6, and K9Nb2As6. Furthermore, another
degree of complexity was reached when a supplementary p-block element was used.
Compounds such as Cs7NbIn3As5, K8NbPbAs5, K6NbTlAs4, or the more complex
Cs24Nb2In12As18, are some of the first discoveries in these complex and promising
systems.
7
Charge, orbital and spin ordering in transition-metal oxide perovskites.
Patrick M. Woodward,
Department of Chemistry, The Ohio State University, Columbus, OH 43210.
Transition-metal oxides adopting the perovskite structure (or closely related
structure types) are well known for their interesting electronic properties (i.e. High TC
superconductivity, colossal magnetoresistance, etc.). I will discuss structure-bondingproperty relationships and phase transition behavior of a variety of compounds taken
from one of the following two families: oxygen-deficient double-cell perovskites
LnBaM2O5+x (Ln = Nd, Sm, Tb, Ho, Y; M = Fe, Co, Mn), and ordered double-edge
perovskites A2MnMO6 (A = Sr, Ca; M = Mo, Ru). Many of the compounds with a single
transition metal ion undergo a transition from a delocalized to a localized electronic
configuration, upon cooling from room temperature. The localization of the conduction
electrons is shown to trigger phenomena such as charge and orbital ordering, magnetic
ordering, macroscopic phase segregation, and charge disproportionation. Chargeordering is not common when multiple transition metal ions are present, but oxidation
state degeneracies can be utilized to achieve strong interactions between the magnetism
and electronic transport properties. Variable temperature synchrotron x-ray and neutron
powder diffraction measurements are used in combination with transport and magnetic
susceptibility measurements to characterize the behavior of these compounds.
New Semiconducting Sn- and Sb-Chalcogenides
A. Assoud, H. Kleinke
University of Waterloo, Department of Chemistry, Waterloo, ON, Canada N2L 3G1
We are interested in finding new materials suitable for the thermoelectric energy
conversion. Promising materials comprise heavy elements, small band gaps (< 0.6 eV)
and low symmetry, yet highly degenerated bands in the vicinity of the Fermi level.
Recently we turned our attention towards Sr seleno-stannates, a hitherto unexplored
system. Related compounds, e.g. in the A/Sn/Se (with A = alkaline metal) or Eu/Sn/Se
system, typically contain the Sn atoms in the oxidation state +4, and then large band gaps
(> 1 eV) - unless mixed-valent Se is present, one example for latter being Eu4Sn2Se10.
Smaller band gaps may be achieved by using mixed valent Sn atoms, for the unoccupied
SnIV-s states will not differ much in energy from the occupied SnII-s states. With this
contribution, we present our first three new compounds in this area, which comprise
either mixed valent Sn or Se, or - in a quaternary compound - SnIV and SbIII.
Sr4Sn2Se10 occurs in the Eu4Sn2Se10 structure type. Characteristic motifs of this
structure are [SnIV4Se14]12- fragments and (Se3)2- chains. SrSn2Se4 crystallizes in a distorted
variant of the SrIn2Se4 structure type. In this structure, the SnII and SnIV atoms are both
tetrahedrally coordinated, but exhibit quite significantly different Sn-Se bond lengths.
[SnIVSe4]4- and [SnIISe4]6- tetrahedra are connected via edges to form dimeric units
[SnIISnIVSe6]6-, which are connected to the next units via corners to build zigzag chains.
Sr3SnSb2Se8 adopts a new structure type. This type exhibits corner sharing tetrahedra
[SnIV2Se6]6- that form a chain along the a axis. Edge sharing Sb-centered pseudo octahedra
build chains that are connected via corners. Electronic structure calculations reveal a
small band gap of 0.2 eV for SrSn2Se4, a large band gap of 1 eV for Sr4Sn2Se10 and
metallic properties for Sr3SnSb2Se8.
8
N-based Inorganic Materials by Experiment and Theory
Richard Dronskowski
Institute of Inorganic Chemistry, Aachen University of Technology (RWTH), 52056
Aachen, Germany
Inorganic materials containing nitrogen atoms, such as main-group molecular and
extended nitrides, transition-metal and rare-earth nitrides, main-group and transitionmetal cyanamides/carbodiimides, as well as transition-metal oxynitrides, offer a beautiful
playground for combined experimental and theoretical research in solid-state chemistry.
Explosive sulfur nitride, being subject to a crystallographic phase transformation
very close to its deto-nation temperature, readily reacts to yield a copper-rich amorphous
solid, the structure of which is successfully modeled on the basis of infrared/EXAFS data
and density-functional (DFT) calculations. Similar total-energy calculations utilizing
periodic boundary conditions are needed to clarify questions of phase and structural
stability for the binary nitrides of the 3d metals, and DFT techniques must also be used to
predict or understand phenomena of magnetic ordering and structural distortions,
especially for the binary systems Fe/N and Ce/N. Possibly driven by the search for
carbon nitride, the list of main-group and transition-metal cyanamides/carbodiimides
(pseudo-sulfides by electron count and anionic volume) is constantly growing. Their
structural and electronic varieties, however, pose an enormous challenge for DFT
calculations when it comes to reliable energetics and magnetic moments. Although
promising in terms of a synthetic "tuning" of the anionic part, only a very small number
of metal oxynitrides has been synthesized so far, and erroneous phase entries — now
spotted quite easily by ab initio theory — have been overlooked for many years.
Nonetheless, there is a good chance of making novel oxynitrides of the magnetically
active as well as early transition metals by means of unconventional synthetic methods,
i.e., thermolysis of organometallic precursors and thin-film sputtering, respectively.
Theory plays a major role in the structural characterizations of these electronically
interesting materials.
Low Density Metal Organic Frameworks for Fuel Gas Storage
J.L.C. Rowsell, N. Rosi, and O.M. Yaghi
Materials Design and Discovery Group, Department of Chemistry,
University of Michigan, Ann Arbor, MI 48109.
The reversible sorption of gas molecules in metal-organic frameworks (MOFs)
has successfully been used to demonstrate their high porosity. This process is now being
realized as a practical way to store chemical energy; namely, as low hydrocarbons such
as methane. Our group has demonstrated the ability to tailor the surface interactions and
pore size metrics within one isotopic series of zinc carboxylates, simply by
functionalizing the organic component. This synthetic control allows optimization of the
sorption properties of the material, such as total guest uptake and reversibility of guest
sorption. We are now searching for new MOF topologies comprised of lighter metals in
order to obtain greater gravimetric storage capacities. Under this protocol, several Group
2 carboxylate frameworks have been synthesized and structurally characterized, each
exhibiting secondary building units defined by the typical coordination geometry of the
metal.
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Beyond crystallography: the structure of complex and nanocrystalline
Materials
Simon Billinge
Department of Physics and Astronomy, Michigan State University, East Lansing, MI
48824
Increasingly we want our advanced materials to have precise and directed
functionality. There is a general relationship between the structural complexity of the
material and the uniqueness of its function. The ultimate functional materials are
enzymes; complex biological proteins that catalyze specific reactions in a cell. These
molecules contain many thousands of atoms that fold into a unique structure. Other
examples are materials with finely balanced competing interactions close to a phase
transition that result in large, and often useful, material susceptibilities. Colossal
magnetoresistant manganites and high-temperature superconductors are key examples.
One thing these funtional materials share in common is the presence of meaningful
structures on the nanometer lengthscale. One of the great challenges facing us is to
characterize these nanostructues both quantitatively and reliably. I will discuss x-ray and
neutron total-scattering approaches we are using to address this problem. By way of
example I will focus on correlated electron materials where a competition between
electronic, magnetic and lattice degrees of freedom results in a rich variety of properties
and ground-states. I will discuss how nanostructures and nano-scale inhomogeneities are
key to understanding the properties.
Polyanions in Solids
Wolfgang Jeitschko
Institut für Anorganische und Analytische Chemie Universität Münster Wilhelm-KlemmStrasse 8 48149 Münster, Germany
After a brief introduction on Zintl compounds and the concept of the two-electron
bond, the talk will focus on some recent work of our group with the emphasis on the
structural chemistry of polyphosphides and polyantimonides of binary and ternary rare
earth and transition metals. The concept of the two-electron bond serves well for
polyphosphides where it allows to rationalize chemical bonding and to predict some
physical properties, because in these compounds the phosphorus atoms usually do not
exceed the coordination number four. In contrast, in polyantimonides the antimony atoms
have a tendency for higher coordination numbers and fractional bonds have to be counted
to rationalize their crystal structures.
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The fascinating world of the thiophosphates of transition elements and/or
lanthanides
Stéphane Jobic
Institut des Matériaux Jean Rouxel, BP 32229, 44322 Nantes cedex 3, France
The low dimensional materials AxMQy (A= alkali metal, M= transition metal,
lanthanide and/or main group element, Q= S, Se) exhibit structural arrangements that
depend strongly upon the A/M ratio and the nature of the countercation. To some extent,
such compounds can be viewed as strongly covalently bonded, negatively charged
domains electrostatically shielded from each other by alkali metal countercations. Owing
to existence of covalent and ionic chemical link, this type of materials can often be
considered as ionic Ax+[MQy]x- salts. Hence, exfoliation and dissolution processes in polar
organic solvents can be envisioned. Recently, studies in solution have been carried out on
KNiPS4 and KPdPS4 inorganic compounds. Both exfoliate in DMF and DMSO but two
types of behavior in solution are displayed. While 1/∞[PdPS4]- chains are maintained in
solution leading to a complex fluid behavior, 1/∞[NiPS4]- chains undergo a solvent induced
fragmentation with a reorganization into crown shaped discrete [Ni3P3S12]3- oligomers
which can be stabilized in the solid state by metathesis. The reconstruction of the infinite
1
/∞[NiPS4]- from these discrete entities can also be done by playing with the nature of the
organic countercation and the followed chemical route.
Moreover, beside this exceptional chemical reactivity of the KMPS4 phases,
thiophosphates of cerium have recently received much attention in the quest of new
colored inorganic materials for pigment applications. Indeed, the Ce3+ cation appears as a
desirable element in generating color because of its ability to present a parity and spin
allowed Ce-4f1 → Ce-5d1 electronic transition. The position in energy of the related
absorption threshold can be shifted in energy by playing with the ionicity of the Ce-S
bonding. The control of the optical gap can practically be achieved via an inductive effect
on the Ce-S bond from a third M element. The more covalent the M-S bond, the more
ionic the Ce-S bond and the wider the Ce-4f/Ce-5d gap, and vice versa. Recently, the
exploration of the K/Ce/P/Q (Q = S, Se) systems led to the stabilization of new phases
which can be considered as a new member of the (KI4(P2)VIIIQII
I V -II
III
VIII -II
III V -II
6)l(K 3P Q 4)m(Ln 4(P2)
3S 18)n(Ln P Q 4)o family (Ln= La, Ce; Q= S, Se).
Vacancy-doped Nd1-xTiO3. Magnetic and transport properties at the metal-insulator
transitions.
Athena Safa-Sefat
McMaster University, Hamilton L8S 4M1, CANADA
The parent NdTiO3 compound is a Mott antiferromagnetic insulator with an
orthorhombic Perovskite structure. By introducing cation vacancies (x) on the Nd-site,
Nd1-xTiO3 undergoes two metal to insulating transitions (MITs). The focus of this paper
is the a detailed investigation of the polycrystalline sample compositions, in the vicinity
of the two MITs, through electrical resistivity, magnetic susceptibility, Seebeck and Halleffect measurements. For the polycrystalline samples, Nd1-xTiO3 undergoes MITs at
vacancy compositions of x= 0.20 and x ~ 0.08. Disorder and Anderson localization play a
significant role in the MIT at x= 0.20. The composition range 0.08 < x < 0.20 are metals.
A Kondo-like electronic ground state bridges the insulator and correlated metals near x=
0.08. Compounds with x< 0.08 order antiferromagnetically and are semiconductors.
11
Moreover, crystal-growth by the ‘modified Bridgeman method’ at different key
compositions of the solid-solution is done; the single crystals are compared with the
sintered polycrystalline sample results.
Discovering New Oxides
Kenneth R. Poeppelmeier
Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113
Solid state chemistry relies heavily on exploratory synthesis, and it is well
recognized that the complexity of the possibilities open defies predictability.1
La4Cu3MoO12 exemplifies unpredictability.2,3 Despite the fact that the perovskite
structure would seem favorable based on cation size, the rare-earth hexagonal YMnO3type structure forms. The formation of many oxides with unpredictable structures can be
attributed to a balance between stable and unstable compositions. A surprising number of
the members of the Ln4Cu3MoO12 and Ln’2Ln”2-Cu3MoO12 (Ln = La – Nd, Sm – Lu)
families form, all crystallizing in a hexagonal structure similar to that of YMnO3. Some
do not form because either the average lanthanide size is too small or the difference
between the size of Ln’ and Ln” is too large. Furthermore, even if Ln’4Cu3MoO12 and
Ln”4Cu3MoO12 form single phases, attempts to synthesize the corresponding solution
phase, Ln’2Ln”2Cu3MoO12, may result in a mixture of simpler metal oxides! The
explanation illuminates the importance of unstable “umbrella” stoichiometries for the
formation of unconventional structures in multication systems.4
References
1. Uma, S.; Corbett, J. D. Inorg. Chem. 1999, 38, 3831-3835.
2. Vander Griend, D. A.; Boudin, S.; Poeppelmeier, K. R.; Azuma, M.; Toganoh,H.
Takano, M. J. Am. Chem. Soc. 1998, 120, 11518-11519.
3. Vander Griend, D. A.; Boudin, S.; Caignaert, V.; Poeppelmeier, K. R.; Wang, Y.;
Dravid, V. P.; Azuma, M.; Takano, M.; Hu, Z.; Jorgensen, J. J. Am. Chem. Soc. 1999,
121, 4787-4792.
4. Vander Griend, D. A.; Malo, S.; Wang, T. K. and Poeppelmeier, K. R. J. Am. Chem.
Soc., 1999, 122, 7308-7311 (2000).
HYDROTHERMAL SYNTHESIS OF THREE DIMENSIONAL STRUCTURES
USING METAL OXIDE-FLUORIDES AND NEUTRAL BIDENTATE LIGANDS.
Paulette R Guillory, Heather K Izumi, Duward F Shriver, Kenneth R. Poeppelmeier*
Northwestern University, Department of Chemistry, Evanston, IL 60208-3113
Non-centrosymmetric materials are of interest because their symmetry-dependant
properties, such as piezoelectricity, ferroelectricity, and second order non-linear optical
(NLO) behavior, are the basis of numerous technological applications. LiNbO3, a well
known inorganic NLO material, exhibits an out-of-center distortion in the individual
[NbO6/2]- octahedra postulated to cause the non-linear response. These out-of-center
distortions are replicated by metal oxide fluoride anions (MOF5-2), where the polar
distortion in the octahedra is inherent in the molecule itself, and not a product of a phase
transition. Compounds constructed with these metal oxide fluoride anions have
historically crystallized without internal disorder, or crystallized with order but with an
12
anti-parallel arrangement of the anions, forming a centrosymmetric compound.
Understanding the mechanism of crystal formation may enable the synthesis of a noncentrosymmetric compound where the octahedral anions crystallize without disorder, and
without anti-parallel arrangement.
Metal oxide fluoride anions, particularly TaOF5-2, NbOF5-2, MoO4F2-2 and WO4F2-2
are easily synthesized using hydrothermal synthesis. The metal oxides are reacted with a
hydrofluoric acid solution inside of Teflon pouches in a stainless steel, constantvolume reactor. The reactions are monitored and studied using a composition space
diagram, similar to a ternary phase diagram, where the products are related to the initial
mole fractions of the reactants. The molar ratio of each reactant is recorded, with the
other variables (temperature and amount of solvent) held constant.
One method to control the internal ordering of the metal oxide fluoride (i.e.
[NbOF5] 2-] is through the use of a neutral bidentate ligand to coordinate to the cation (i.e.
Cd2+) in a cis fashion. This cis coordinate cationic complex will bond to the oxide on the
niobium, creating an ordered structure. If the anions are also in parallel arrangement, the
structure will be non-centrosymmetric. This area is being explored using early transition
metal (Nb, Ta, Mo, W) oxide fluorides, late transition metal (Ni, Cu, Ag, Zn, Cd) cations,
and neutral ligands (2,2’-dipyridyl amine).
A polymorph of CuNb(Pyridine)4OF5 using the anionic NbOF5-2, and cationic Cd+2
was synthesized. The basic chain of the two polymorphs is identical, but differ in
packing, and also the ordering of the oxide and fluoride ligands in the octahedral [NbOF5]
2unit. Further study of this polymorphism will lead to an understanding of synthetic
methods and allow a rational synthetic method to be devised to construct these materials.
Combinatorial Techniques for the Discovery & Optimization of Solid State
Materials
Konstantinos Chondroudis
Symyx Technologies, Inc., Santa Clara, CA 95051
Combinatorial synthesis and screening of extraordinarily large numbers of
different organic compounds has been widely applied in the pharmaceutical industry for
drug discovery. At Symyx, combinatorial high throughput synthesis and screening
techniques have been implemented to create integrated workflows that enable scientists
to discover and optimize materials across a broad range of applications at an accelerated
rate compared to traditional techniques. Solid-state materials are a crucial component of
many new devices for technologically important areas. In this talk we will discuss how
combinatorial techniques were used to discover and optimize such solid-state materials
for various applications.
13
3-Dimensionally Ordered Macroporous (3-DOM) Solids as Nanostructured
Li-ion Battery Materials
Scott J. Barry, Erin M. Sorensen and Kenneth R. Poeppelmeier
Department of Chemistry, Northwestern University
Recently, three-dimensionally ordered macroporous (3DOM) solids (≥50 nm pore
diameter) fabricated by colloidal crystal template directed synthesis have attracted
interest owing to their unique photonic, catalytic, electrochemical and biosensing
properties. For example, electrochemical analysis of a 3DOM nickel sample indicated
that the entire powder surface is electrochemically active and uniformly accessible [Stein,
et. al. Adv. Mater., 1999, 11, 1003] . Compared to microporous (< 5 nm pore diameter)
Raney nickel, which demonstrates at most 1.5% surface utilization, 3DOM solids offer
exciting prospects for the development of new electrode materials.
Here, we explore the viability of 3DOM solids as nanostructured electrodes for
lithium-ion batteries by examining the fabrication, characterization, and electrochemical
performance of 3DOM Li4Ti5O12, a commonly cited anode for lithium-ion batteries. In
doing so we have investigated the molecular chemistry of inorganic-organic precursors
for the synthesis of new 3DOM solids.
R3M6+xAl26T: Cubic Intermetallic Phases with a Stuffed BaHg11 Structure grown
from Aluminum Flux
S. E. Latturner, D. Bilc, S. D. Mahanti and M. G. Kanatzidis
Department of Chemistry and Department of Physics, Michigan State University, East
Lansing, MI 48824
Elements such as transition metals and silicon are often added to aluminum alloys
to optimize their properties. Much of the improved behavior is due to the formation of as
yet unexplored multinary intermetallics within the aluminum matrix; investigation of
these adventitious compounds is necessary to understand and control the characteristics
of the bulk alloy. With this in mind, a wide variety of new intermetallic materials with a
cubic, stuffed BaHg11 structure have been synthesized by the combination of a rare earth
or alkaline earth metal R, a late transition metal M, and an early transition metal T in an
excess of molten aluminum. These compounds, with formula R3M6+xAl26T, grow from
the aluminum flux as large spheroid crystals. Due to the highly reducing nature of
aluminum, it is also possible to synthesize these compounds using complex oxide
precursors such as perovskites; for example, the combination of SrTiO3 and Au in excess
Al produces Sr3Au7Al26Ti. Structural characterization of R3Au6+xAl26T compounds by
powder and single crystal X-ray diffraction indicates that the unit cell varies with the
radii of the early transition metal T and the rare earth / alkaline earth R as expected.
Varying amounts of disorder and trends in partial occupancies of the stuffed site—the site
that is vacant in the parent compound BaHg11—are also indicated by the diffraction
studies of this family of compounds. Magnetic susceptibility data reveals that the
transition metal atoms in these materials do not possess local magnetic moments.
14
Novel inorganic-organic hybrid materials containing [Nb6Cl12(CN)6]4− cluster
Bangbo Yan and A. Lachgar
Department of Chemistry, Wake Forest University, Winston-Salem, NC 27109
Hybrid inorganic organic materials are of great interest due to their potentially useful
properties as catalysts or separations agents. Our work in this area focuses on the
synthesis of extended solids based on octahedral [Nb6X12]n+ (X=Cl, Br, O) clusters using
transition metal complexes as bridges. Here we report two novel compounds:
[Nb6Cl12(CN)6{Cu(en)2}3]2[Nb6Cl12(CN)6] (1) and [Nb6Cl12(CN)6{Zn(en)}2] (2). Crystals
of 1 were prepared by layering aqueous solutions of [N(CH3)4]4[Nb6Cl12(CN)6] with a
solution of Cu(en)2Cl2 in ethanol. The structure of 1 consists of a discrete [Nb6Cl12(CN)6]4cluster, and two [Nb6Cl12(CN)6{Cu(en)2}3]2+ units in which the cluster unit
[Nb6Cl12(CN)6]4- connects to three{Cu(en)2}2+ groups that adopt a facial arrangement on
the octahedral cluster. Compound 2 was synthesized through the reaction of
Na4[Nb6Cl12(CN)6] and Zn(en)[ClO4]2 in H 2O/EtOH solution. The crystal structure of 2
contains [Nb6Cl12(CN)6]4− clusters linked by {Zn(en)}2+. Each cluster [Nb6Cl12(CN)6]4connects to six {Zn(en)}2+ groups, and each {Zn(en)}2+ group connects to three clusters
[Nb6Cl12(CN)6]4− to form layers running parallel to the ab plane. Within the layer,
puckered rings are formed by three [Nb6Cl12(CN)6]4− clusters and three {Zn(en)}2+ groups.
The {Zn(en)}2+ groups are projecting above and below the layer into the rings of the
adjacent layers. Crystal data for 1: P3, a = 20.550(4) Å, c = 8.780(3) Å, V = 3211.1(13)
Å3, dcalc = 2.335 g/cm3, Z = 3, R1 = 0.098, wR2 = 0.186; for 2: P-3m1, a = 1.891(3) Å, c
= 8.721(3) Å, V = 895.8(4) Å3, Dcalc = 2.565 g/cm3, Z = 1, R1= 0.062, wR2 = 0.160.
Deltahedral Germanium Clusters: Oligomerization and Functionalization
Slavi C. Sevov
Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN
46556
Deltahedral germanium clusters of nine atoms, Ge94-, have been characterized in
binary compounds with the alkali metals, i.e. A4Ge9. These compounds dissolve readily
15
in ethylenediamine and provide the corresponding nine-atom clusters in solution. It
seems that the clusters in solution carry different charges of -2, -3 and -4, and are in
equilibria between themselves and solvated electrons. Clusters with different charges can
be crystallized from such solutions by using countercations with appropriate sizes and
shapes that depend on the sequestering agents for the alkali-metal cations.
The use of soft oxidizing agents such as EPh3 and E'Ph4 where E = P, As, Sb, Bi
and E' = Ge, Sn, Pb leads to either oxidative addition and formation of species such as
[Ph2E–Ge9–EPh2]2-, [Ph3E'–Ge9]3-, and [Ph3E'–Ge9–E'Ph3]2- or oxidative coupling to
form [Ge9–Ge9]6-, [Ge9=Ge9=Ge9]6-, and [Ge9=Ge9=Ge9=Ge9]8-. The synthesis and
characterization of these and other novel species will be discussed in the talk.
POSTER PRESENTATIONS
Near Room-Temperature Ferromagnetism Found in ZnSnP2:Mn
Single Crystals Grown via Sn-Flux
Jennifer A. Aitkena, Georgy Tsoib, Lowell Wengerb and Stephanie L. Brocka
a
Department of Chemistry, Wayne State University, Detroit, MI 48202.
b
Department of Physics, Wayne State University, Detroit MI 48202.
As we move further towards miniaturization of electronic and memory devices we
look for multifunctional materials. One such area emerging from this rationale is the
field of spintronics, where researchers wish to exploit not only the charge carriers of a
material but also the spin of those charge carriers. A material with room-temperature
ferromagnetism and an existing technology base for use in applications would be an ideal
candidate for spin-based devices.
Near room-temperature ferromagnetism has recently been discovered in several
Mn-doped chalcopyrite materials, namely CdGeP2:Mn, ZnGeP2:Mn, ZnSnAs2:Mn and
ZnGeAs2:Mn. Although these materials lack an existing technology base, their
ferromagnetic behavior at practical temperatures makes them possible candidates for
room-temperature spintronic devices.
Here we report a novel dilute, magnetic semiconductor (DMS) chalcopyrite,
ZnSnP2:Mn. The material is grown as relatively large single crystals, 3 x 1 x 1 mm, in
liquid Sn at 650 ºC. Although liquid Sn has been used for many years to grow
chalcopyrites and other types of materials, this is the first time that a DMS material has
been produced in this way. The compound undergoes an antiferromagnetic to
ferromagnetic transition at very low temperatures and a ferromagnetic to paramagnetic
transition near room temperature. Here we will report the optical, thermal and magnetic
properties of this promising, new DMS material.
16
Synthesis and Characterization of Cadmium Selenide Aerogels
Indika U. Arachchige, Jaya L. Mohanan, and Stephanie L. Brock*
Department of Chemistry, Wayne State University, Detroit, Michigan 48202
Aerogels are a unique class of inorganic polymers that have low densities, large
open pores and high inner surface area. This results in interesting physical properties as
well as a wide variety of potential applications as catalysts, sensors and novel
electrochemical device components. So far, a great deal of research has been conducted
on aerogels based on single and mixed metal oxides. However, non-oxide aerogels, with
the exception of carbon aerogels, are virtually nonexistent. We have recently synthesized
a pure chalcogenide based semiconductor aerogel of CdS from controlled aggregation of
primary particles followed by super-critical fluid extraction. In this study, we seek to
explore the generality of the method and report herein the synthesis of CdSe aerogels.
Preliminary characterization of CdSe aerogel is done using X-ray diffraction,
transmission and scanning electron microscopy, surface area analysis, optical absorption,
luminescence and UV-visible spectroscopy. The effect of synthetic parameters on the
particle size, morphology, surface area, and optical properties will be discussed.
Towards Synthesis and Characterization of Homogenous Transition Metal Arsenide
Nanoparticles
Palaniappan Arumugam and Stephanie L. Brock*
Department of Chemistry, Wayne State University, Detroit, MI-48202
Bulk transition metal arsenides, such as CoAs and FeAs, are studied extensively
because of their technological importance as semiconductors and magnetic materials,
respectively. In recent years it has been shown that physical properties of materials can
be tuned by controlling the size of the particles to the nanometer regime (1-100 nm). To
distinguish properties that are inherent to nanoscale structures from those of bulk or
polydisperse materials, synthesis of monodisperse nanoparticle samples is essential. To
date, the size dependent properties of transition metal arsenide particles have not been
explored, perhaps because of the unavailability of reliable synthetic methods to produce
near monodisperse nanoparticle samples of these phases with control of stoichiometry.
To address these concerns, we have recently developed a new synthetic methodology to
produce transition metal phosphides based on reduction of transition metal phosphates.
The application of this methodology to arsenide phases of Fe, Co, and Ni will be
discussed. Specifically, the synthesis and characterization of transition metal arsenate
nanoparticles will be described along with our attempts to reduce these materials, either
supported on substrates or in solution.
Non-centrosymmetric Ba3Ti3O6(BO3)2
Hyunsoo Park, Anthony Bakhtiiarov, Wei Zhang, Ignacio Vargas-Baca and Jacques
Barbier.
Department of Chemistry, McMaster University, Hamilton, Canada.
17
The compound previously reported as Ba2Ti2B2O9 (Millet, Roth and Parker, J. Am.
Ceram. Soc. 69, 811-814, 1986) has been reformulated as Ba3Ti3B2O12,
or
Ba3Ti3O6(BO3)2. Small single crystals have been recovered from a melt with a
composition of BaTiO3:BaTiB2O6 (molar ratio) cooled between 1100 and 850°C. The
crystal structure has been determined by X-ray diffraction: hexagonal system, noncentrosymmetric P-62m space group, a = 8.7377(11) Å, c =
3.9147(8) Å, Z = 1, wR(F2) = 0.039 for 504 unique
reflections. The Ba3Ti3O6(BO3)2 structure consists of a
framework of triple [001] octahedral chains bridged by
orthoborate groups with Ba2+ cations occupying 13coordinated sites in irregular pentagonal channels (cf. Figure).
Ba3Ti3O6(BO3)2 is isostructural with K3Ta3O6(BO3)2 (Abrahams,
Yontz, Bernstein, Remeika and Cooper, J. Chem. Phys. 75, 54565460, 1981) and with the high-T form of K3Nb3O6(BO3)2 (Becker,
Bohaty and Schneider, Cristallogr. Rep. 42, 213-217, 1997). A bond valence analysis of
the Ba3Ti3O6(BO3)2 structure reveals the presence of residual bond strain which may be
associated with the apparent marginal stability of Ba3Ti3O6(BO3)2 as compared to BaTiO3
and BaTiB2O6. Attempts to extend this structural series via other substitution reactions
have so far been unsuccessful. Preliminary measurements of nonlinear optical properties
on microcrystalline samples show that the second harmonic generation efficiency of
Ba3Ti3O6(BO3)2 is about 18 times larger than that of KH2PO4.
Exploring Octahedral Tilting Distortions in A2MM’O6 Variably Ordered Double
Perovskites Using Neutron Powder Diffraction.
Paris W. Barnes*, Michael W. Lufaso‡, Patrick M. Woodward*, and Pavel Karen†. *Department of Chemistry, The Ohio State University, Columbus, OH, 43210; ‡-Ceramics
Division, National Institute of Standards and Technology, Gaithersburg, MD 208998520; †-Department of Chemistry, University of Oslo, 0315 Oslo, Norway.
The perovskite structure with 1:1 M-site cation ordering (or double perovskite;
A2MM’X6) is a well known and extensively studied structure type in solid state
chemistry. The ideal double perovskite has cubic symmetry, but many are distorted from
the ideal structure. Structural distortions seen in perovskites are caused by electronic
factors (i.e., Jahn-Teller ions), M-cation displacement from the center of the MX6
octahedra (i.e., cations with a stereoactive lone pair of electrons), and most commonly,
octahedral tilting. Tilting of the octahedra within the perovskite structure leads to
lowering of its symmetry. A major factor that influences the degree of octahedral tilting
in a given compound is the nature of the cuboctahedral A-cation. Perovskites with Ba2+
as the A-site cation typically exhibit cubic symmetry and those with Ca2+ have
orthorhombic or monoclinic symmetry. Changes (or lack of) in space group symmetry
for A = Ba2+ and Ca2+ are often easily seen in the X-ray powder diffraction data (XRPD)
of their respective compounds. Yet, compounds with A=Sr2+ are prone to subtle
octahedral tilting distortions that are not readily seen in XRPD, so many are mistakenly
assigned to the incorrect space group. In this study, ten double perovskites with A = Sr2+
(M3+ = Al, Sc, Cr, Mn, Fe, Co, Ga, Y; M5+ = Nb, Sb), Ca2CrTaO6, and Ba2YNbO6 were
examined using Rietveld refinements of neutron powder diffraction data (NPD) in order
to appropriately discern their respective crystallographic symmetry. The approach taken
for determining appropriate possible space groups, the reliability of peak splitting seen in
the XRPD data for determining space group symmetry, the extent of M-site cation
18
ordering, and the degree of octahedral tilting seen in this family of compounds will be
discussed.
Electronic structure of K2Bi8Se13
Daniel I Bilc, P. Larson1, S. D. Mahanti and M. G. Kanatzidis2
Department of Physics and Astronomy, Michigan State University, E. Lansing, MI
48823, 1Naval Research Laboratory, Washington D. C.,
2
Department of Chemistry, Michigan State University, East Lansing, MI 48823
A novel material belonging to the class of complex Bi-Te-Se systems, K2Bi8Se13 , has
been discovered at MSU and it shows great potential for thermoelectric performance.
This compound forms in two distinct phases α-K2Bi8Se13 (triclinic with space group P-1)
and β-K2Bi8Se13 (monoclinic with space group P 21/m). The β-phase has structural
disorder, there are four sites with mixed K/Bi occupancy. To understand the electronic
properties of these two different phases we have carried out electronic structure
calculations within ab initio density functional theory (DFT) using full potential
linearized augmented plane wave (LAPW) method. The α-phase is found to be a
semiconductor with an indirect band gap of 0.47eV. For the β-phase we have chosen two
different ordered structures with extreme occupancies of K and Bi atoms at the "mixed
sites". Both systems are semi-metals. To incorporate the effect of mixed occupancy we
have chosen a 1x1x2 supercell with an alternative K/Bi occupancy at the "mixed sites".
This system is found to be a semiconductor with an indirect gap of 0.38eV. We have
shown that the mixed occupancy is crucial for the system to be a semiconductor because
the Bi atoms at the "mixed sites" stabilize the Se-p orbitals of the nearest neighbors Se
atoms by lowering their energy. We find a strong anisotropy in the effective mass near
the conduction band minimum, with the smallest effective mass along the mixed K/Bi
chains (parallel to the c-axis) through Bi-Se framework. This large anisotropy suggests
that β-K2Bi8Se13 has a great potential for a n-type thermoelectric material.
*
Supported by the office of Naval Research and DARPA through grant N00014-01-10728.
Synthesis and Structural Characterization of Novel Ternary Phases in the
Systems RE-TM-Ga (RE = Ce, Yb; TM = Rh, Ir, Pd, Pt)
a
Svilen Bobev,ª John L. Sarrao,b Joe D. Thompsonb and Zachary Fiskc
Los Alamos National Laboratory, LANSCE-12, MS-H805, Los Alamos, NM 87545
b
Los Alamos National Laboratory, MST-10, MS-K764, Los Alamos, NM 87545
c
National High Magnetic Field Laboratory (NHMFL), Florida State University,
Tallahasse, FL 32306
Several novel ternary phases RE-TM-Ga (RE = Ce, Yb; TM = Rh, Ir, Pd, Pt) were
synthesized in high yields by standard solid-state techniques from pure elements at
elevated temperatures. Pure gallium, intended as a solvent, was used in excess and large
single crystals of the title compounds were successfully grown from these solutions.
Their crystal structures were determined by both single crystal and powder X-Ray
crystallography. All Rh and Ir compounds crystallize in a new hexagonal structure types
19
(related to the YPt2In-type), featuring corrugated TMGa2-layers stacked in a typical hcp
sequence (ABAB) along the c-axis and separated by RE2Ga3-layers. The latter are heavily
disordered in the xy plane and this phenomenon appears to be a purely statistical effect no evidence for ordering in an a 3 × a 3 supercell was found. More likely, the
disordered RE2Ga3-layers can “slip” easily in the xy plane, creating stacking faults and
hence – extreme difficulties for the correct structure determinations. On the other hand,
employing Pd in place of Rh or Ir, yields ternary derivative of the BaAl4-type (bodycentered tetragonal space group) with random statistical distribution of Pd and Ga on the
two crystallographic sites. Lastly, Pt-based analogs crystallize in the known hexagonal
structure type Ce2Pt6Ga15 with double PtGa2-layers, which are again separated by
disordered RE2Ga3-layers. Most of the title compounds exhibit long-range magnetic
ordering, while some of them, typically the Ir-based phases, do not show any signs of
magnetic order down to 2K. The resistivities, measured in the temperature range 2–290K
(with the current applied along the c-axis of the crystal) are metallic and relatively
featureless. More careful and precise property measurements are currently underway.
Local Structural Study of Colossal Dielectric Constant CaCu3Ti4O12
Using the Atomic Pair Distribution Function Technique
E. S. Bozin (1), V. Petkov (2), P. W. Barnes (3), P. M. Woodward (3), S. J. L. Billinge (1),
S. D. Mahanti (1), and T. Vogt (4)
(1)
Department of Physics and Astronomy, Michigan State University
(2)
Department of Physics, Central Michigan University
(3)
Department of Chemistry, Ohio State University
(4)
Physics Department, Brookhaven National Laboratory
Cubic insulating CaCu3Ti4O12 has attracted significant attention as it exhibits a giant
dielectric constant response with a very unusual temperature dependence. We report on
local structural studies using the atomic pair distribution function approach over the
temperature range where an enormous reduction of the dielectric constant is observed.
Although there is no indication of a structural phase transition, the local structural study
reveals an unusual temperature dependence for the atomic displacement parameters of
Ca/Cu sublattice suggesting presence of the local disorder. Temperature dependent
modeling of the structure, using bond valence concepts, suggests that the calcium atoms
become underbonded below approximately 260 K, which provides a rationale for the
unusually high Ca displacement parameters observed at low temperature.
HIGHLY REDUCED POLYOXOMETALATES WITH AN UNUSUAL
ARCHITECTURE
Nathalie Calin and Slavi C. Sevov
Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN
46556
Polyoxoanions are a unique class of metal-oxygen clusters with a multitude of structures
and many interesting properties in different fields including catalysis, medicine, and
20
materials science. Although the first polyoxometalates were reported almost two
centuries ago, the majority of species have been structurally characterized only recently.
The mechanism of formation of polyoxoanions is still not well understood and mostly
described as self-assembly. Several strategies for the construction of specific
architectures from molecular building blocks have been described in recent years. A
popular strategy in the realization of such materials involves the use of hydrothermal
synthesis and structure directing templates. The success of this strategy can be
demonstrated by the development of low-dimensional as well as three-dimendional
microporous transition-metal phosphates. We are interested in the synthesis of extended
hybrid structures constructed from metal organic derivatives of polyoxometalates and
diphosphonate ligands. This has led to the discovery of a novel mixed-valence
molybdodiphosphonate and its one- and two-dimensional derivatives, and a new
pentamolybdodiphenylphosphonate decorated by transition-metal complexes.
Lu8Te and Lu7Te. Novel Substitutional Derivatives of Lutetium Metal
Ling Chen and John D. Corbett *
Department of Chemistry, Iowa State University, Ames, Iowa, 50011
Monocrystals of Lu8Te are synthesized by disproportation of Lu7Te at 1000 – 1200 °C or
by direct reaction of Lu plus Lu2Te3 at 1000 °C for two weeks. Lu7Te is produced by arc
melting of a suitable Lu–Lu2Te3 mixture, with good crystals being formed by subsequent
annealing at 1300 °C. The structures of Lu8Te (P 6 2m, Z = 1) and Lu7Te (Cmcm,Z = 4)
exhibit h.c.p. packing (AB···) of distorted, not close packed, layers along one short axis (
c , a , respectively).
Puckered Lu, Te layers are stacked normal to (010)
or (001) in six or eight layer repeat sequences, with Te substituting for every third or
every other Lu in every third or fourth layer, respectively. Strong Lu–Te bonding is
indicated. Both Te substitutions decrease the volume per atom from that in h.c.p. Lu and
also decrease the coordination number of all atoms from 12 to 9–11.
Acknowledgement: this work is supported by Dept. of Energy, National Science
Foundation, Grant DMR-0129785.
21
Structure and Magnetic Property of Heavy Metal Ba-(In or Tl)-Bi Zintl Phase
System
Ara Cho and Slavi C. Sevov
Department of Chemistry & Biochemistry, University of Notre Dame
Zintl phases have been studied for many years. Zintl compounds have alkali or
alkaline-earth metals as electropositive donors and p-block elements as electronegative
acceptors. So Zintl phase compounds are classically called “polar intermetallic
compounds”. The electron transfer from the donor to the acceptor allows the latter to
fulfill the octet rule. To do so, the p-block elements can form 2c-2e- bonds between each
other and/or carry lone pairs of electron. Zintl phases are diamagnetic but in some rare
cases can exhibit a metallic character due to delocalized extra electrons.
In this poster, we will discuss the structure and properties of heavy metal Zintl
phase system: Ba-(In or Tl)-Bi. They are allowed in zintl concept but they have metallic
characters as a rare case.
New low dimensional NaM1-xP2S6 thiophosphates (M = Cr, V) : synthesis, structures
and exfoliation properties
S. Coste(1), E. Gauthier(1), E. Michel(1), R. Brec (1), S. Jobic (1) and M. G. Kanatzidis(2)
(1)
Laboratoire de Chimie des Solides, Institut des Matériaux Jean-Rouxel, UMR 6502
CNRS, Université de Nantes, 2 rue de la Houssinière, BP 32229, 44322 Nantes Cedex 3,
France (2)Department of Chemistry and Center for Fundamental Materials Research,
Michigan State University, East Lansing, Michigan 48824
A number of quaternary alkali (A) and transition metal (M) chalcogenophosphates
with crystal formula AwMxPySz (M = Cr, V)i have been recently prepared employing the
traditional ceramic route from direct combination of the reagents in stoichiometric
amounts. A potentially interesting property of some low-dimensional compounds is their
exfoliation in polar solvents. A prime example of this behavior is LiMo3Se3 ii and the
transition metal thiophosphate compounds KNiPS4 iii and APdPS4 iv. These compounds are
composed of infinite anionic 1/∞[Mo3Se3], 1/∞[NiPS4] and 1/∞[PdPS4] chains respectively.
While the 1/∞[NiPS4] chains undergo an autofragmentation under the action of the solvent
to give rise to unprecedented discrete crown-shaped [Ni3P3S12]3- anions v, the 1/∞[PdPS4]
and 1/∞[Mo3Se3] chains are maintained in solution 48, vi inducing complex fluid and liquid
crystal behavior, respectively. Because of the potentially interesting physical properties
and chemical reactivity of low dimensional materials in solution, we recently embarked
on a quest for new soluble alkali metal containing chain-like thiophosphates with
magnetically active transition metal elements (i.e.V3+ (d2, S=1) and Cr3+ (d3, S=3/2)). Such
systems would be highly worthy of investigation because dilute nematic suspensions
might be oriented and controlled by applying magnetic or electric fields. We report here
the preparation of 1D-NaCrP2S648 c and mixed-valent 1D-NaV0.837(6)P2S6 vii compounds,
their crystal structures and their unusual exfoliation which gives rise to complex fluid
behavior. The gel forming properties in solution for 1D-NaV0.837(6)P2S6 are also reported.
22
23
Rational Synthesis of New Ternary Pnictides and Chalcogenides using a Structure
Map
S. Derakhshan, H. Kleinke
University of Waterloo, Department of Chemistry, Waterloo, ON, Canada N2L 3G1
Recently, we developed a structure map for metal-rich transition metal pnictides
and chalcogenides M2Q, using a structural factor as the ordinate, namely the averaged
coordination number of the Q atoms <C.N.(Q)>, and a combination of atomic factors as
the abscissa, namely principal quantum numbers, valence-electrons, and radii. M stands
for all metal atoms of groups 3-5, and Q for the elements of the groups 15 and 16,
excluding the elements of the second period, N and O. The map includes the ternaries
(M,M')2Q and M2(Q,Q').
This structure map has subsequently been used to predict some crystal structures
correctly: both new arsenides ZrTiAs and ZrVAs were supposed - based on the map - to
form the La2Sb type, which we then confirmed via single crystal structure studies. This
was particularly interesting, as these were the first transition metal arsenides to form this
type.
On the other hand, the phosphide ZrTiP was reported before to crystallize in the
Co2Si type. According to the structure map, the Hf arsenides HfTiAs and HfVAs and
phosphides HfTiP and HfVP should all adopt the Co2Si type as well. Since only the last
one, HfVP, was known (which does form the Co2Si type), we proceeded with trying to
prepare the other three Hf pnictides. All of them were prepared, and our structure
investigations proved once more the usability of our structure map: all of these four Hf
compounds occur in the Co2Si type, as predicted. This contribution deals with these
compounds, in particular concentrating on the differences to the Zr pnictides.
Synthesis and Characterization of Noncentrosymmetric Chain Compounds,
A3M2AsSe11 (A=K, Rb, Cs; M=Nb, Ta)
Junghwan Do and Mercouri G. Kanatzidis
Department of Chemistry and Center for Fundamental Materials Research
Michigan State University, East Lansing, MI 48824
Several noncentrosymmetric quaternary niobium and tantalum selenoarsenates,
A3Nb2AsSe11 (A=K, Rb, Cs) and K3Ta2AsSe11, were synthesized by the
polychalcoarsenate flux method. All the compounds crystallize in the
noncentrosymmetric monoclinic space group Cc. All the structures are comprised of the
same type of chain anions, [M2AsSe11]3- (M=Nb, Ta) separated by alkali metal cations.
Each of the two crystallographically independent niobium or tantalum atoms in the
anionic chain is coordinated by seven selenium atoms in a distorted pentagonal prismatic
arrangement. Two pentagonal prisms that contain one M4+ ion coordinated by 3Se2- +
3Se22- and the other M4+ ion coordinated by 2Se2- + 3Se22- share a common face to form a
[M2Se5(Se2)3]8- dimeric core that propagates along the chain through a pyramidal [AsSe 3]1anion to complete a [M2Se2(Se2)3(AsSe3)]3- anionic chain. The As3+ cations with
nonbonded electron pairs play an important role in the formation of the
noncentrosymmetric compounds. The origin of noncentrosymmetric space group Cc of
the compounds may be understood by examining the structure concerning the lone pair
polarization arrangement of As3+ cations. The structures of the compounds were
determined by single crystal X-ray diffraction. The physical properties of the compounds
24
were studied by UV-Vis spectroscopy, Raman spectroscopy and Differential Thermal
Analysis.
Optical properties of CeBO3 and CeB3O6 compounds: first-principle calculations
and experimental results
Goubin F.a, Jobic S.a, Rocquefelte X.a, Brec R.a, Montardi Y.b
Institut des Matériaux Jean Rouxel, 2 rue de la Houssinière, BP 32229, 44322 Nantes
Cedex 03, France
b
Rhodia Electronics and Catalysis 52 rue de la Haie Coq, 93308 Aubervilliers, France
a
In the quest of second generation inorganic UV absorbers, Ce(III) containing compounds
have been synthesized and their optical properties determined by UV-visible diffuse
reflectance measurements and electron energy-loss spectroscopy (EELS). The optical
absorption mechanism and the dielectric constant were investigated using first-principles
density functional theory.
The cerium borates o-CeBO3, m-CeBO3 and CeB3O6 have been shown to be isostructural
to their lanthanum derivatives. It has been evidenced that a Ce3+ 4f-5d transition is
responsible for a weak absorption peak around 3.5 eV while the O2p-Ce5d charge
transfer gives rise to a strong absorption peak around 7 eV. Starting from selfconsistent
full potential LAPW calculations, the dielectric tensors of the three compounds were
computed and compared to experimental data. It results a satisfactory fit between the
observed and the calculated extinction coefficient k and the refractive index n. Compared
with O2p-Ce5d charge transfer intensity, an unexpected low k value associated to the Ce3+
4f-5d transition was found.
Crystallographic, Electronic and Magnetic Studies of ξ2-GaM (M = Cr, Mn or Fe):
From Antiferromagnetism to Ferromagnetism
Olivier Gourdon, Sergey Bud’ko, Darrick Williams and Gordon J. Miller*
Department of Chemistry and Ames Laboratory, US Department of Energy,
Iowa State University, Ames, Iowa 50011-3111
The study of the crystal structure, electronic structure and magnetic properties of the
ξ2-GaM (M = Cr, Mn or Fe) alloys is motivated by the recent reinvestigation of the
crystallographic Al8Cr5 structure type of ξ2-GaMn. Moreover, previous crystallographic
studies shown that the Al8Cr5 structure type can be also adopted by GaCr and GaFe
binaries alloys. Band structure calculations using self-consistent spin-polarized TBLMTO method were performed to understand the electronic structure and the magnetic
properties expected. The calculations show than from Cr to Fe a change of the magnetic
interactions from an antiferromagnetic coupling to a ferromagnetic coupling is observed
and susceptibility measurements confirm this evolution.
25
Experimental and theoretical studies of two new ternary intermetallic compounds in
the Ln (Ln=La and Ce)-Nickel-Aluminum phase diagrams: Ce4Ni6Al23 and
La4Ni5.8Al22.2
Delphine Gout, Evan Benbow, Olivier Gourdon and Gordon J. Miller*
Department of Chemistry,
Iowa State University, Ames, Iowa 50011-3111
The Al-rich portion of the ternary Ce-Ni-Al has been investigated and a new ternary
phase of composition Ce4Ni6Al23 has been synthesized. The crystal structure has been
solved by single X-Ray diffraction. Band structure calculations, using TB-LMTO-ASA
method, have been performed to understand its electronic structure and the results are
discussed in connection with others Ce-Ni-Al intermetallic compounds which possess
similar local environments and similar magnetic dense-Kondo behavior or possible
valence fluctuation behavior. Analysis from Crystal Orbital Hamilton populations
(COHP) reveal that the Al-rich compounds may be considered as “polar intermetallic” as
the Fermi level coincides to the separation of bonding and antibonding states of the Ni-Al
framework Since the Ce-f orbitals may play a role in these properties, the LanthanumNickel-Aluminum system has been also investigated. However, the same experiments in
this system give a new structure type with a formulation La4Ni5.8Al22.2. The structure of
this new compound is quite interesting since it exhibits in the center of the unit cell a
large open cavity which could be filled by a guest atom such as hydrogen or small
alkaline metals.
Studies of the Electronic Properties of BaV10O15: Crystallographic Phase Transition,
Electrical Transport and Magnetic Properties
Craig Bridges and J.E. Greedan*
Brockhouse Institute for Materials Research and Department of Chemistry,
McMaster University, Hamilton L8S 4M1 CANADA
BaV10O15 can be regarded as a “Ba-doped” variation of V2O3 where the Ba ions substitute
in the close packed oxide layers. The Ba ions direct the occupation of the octahedral sites
by the V2+/V3+ ions. The resulting structure is closely related to that of V2O3 but with
subtle differences. A remarkable crystallographic phase transition occurs at 125K from
Cmca to Pbca, which, it will be argued, is driven in part by V-V bond formation resulting
in one of the shortest V-V distances, 2.5334(5) Å, known in vanadium oxide chemistry.
The phase transition is reflected in the transport properties, both resistivity and Seebeck
effect. A complex magnetic phase transition sets in below Tc = 42K as confirmed by
neutron scattering and specific heat studies. The V-sublattice is geometrically frustrated
and the exchange interactions are strongly antiferromagnetic, θ = -1141(23) K. Only a
very small fraction of the entropy is removed below Tc, ~ 4 %, and it is likely that only a
fraction of the spins are ordered. This interpretation is supported by the neutron data.
These results point to a very heterogeneous magnetic ground state for this material.
26
HYDROTHERMAL SYNTHESIS OF THREE DIMENSIONAL STRUCTURES
USING METAL OXIDE-FLUORIDES AND NEUTRAL BIDENTATE LIGANDS.
Paulette R Guillory, Heather K Izumi, Duward F Shriver, Kenneth R. Poeppelmeier*
Northwestern University, Department of Chemistry, Evanston, IL 60208-3113
Non-centrosymmetric materials are of interest because their symmetry-dependant
properties, such as piezoelectricity, ferroelectricity, and second order non-linear optical
(NLO) behavior, are the basis of numerous technological applications. LiNbO3, a well
known inorganic NLO material, exhibits an out-of-center distortion in the individual
[NbO6/2]- octahedra postulated to cause the non-linear response. These out-of-center
distortions are replicated by metal oxide fluoride anions (MOF5-2), where the polar
distortion in the octahedra is inherent in the molecule itself, and not a product of a phase
transition. Compounds constructed with these metal oxide fluoride anions have
historically crystallized without internal disorder, or crystallized with order but with an
anti-parallel arrangement of the anions, forming a centrosymmetric compound.
Understanding the mechanism of crystal formation may enable the synthesis of a noncentrosymmetric compound where the octahedral anions crystallize without disorder, and
without anti-parallel arrangement.
Metal oxide fluoride anions, particularly TaOF5-2, NbOF5-2, MoO4F2-2 and WO4F2-2
are easily synthesized using hydrothermal synthesis. The metal oxides are reacted with a
hydrofluoric acid solution inside of Teflon pouches in a stainless steel, constantvolume reactor. The reactions are monitored and studied using a composition space
diagram, similar to a ternary phase diagram, where the products are related to the initial
mole fractions of the reactants. The molar ratio of each reactant is recorded, with the
other variables (temperature and amount of solvent) held constant.
One method to control the internal ordering of the metal oxide fluoride (i.e.
[NbOF5] 2-] is through the use of a neutral bidentate ligand to coordinate to the cation
(i.e. Cd2+) in a cis fashion. This cis coordinate cationic complex will bond to the oxide on
the niobium, creating an ordered structure. If the anions are also in parallel
arrangement, the structure will be non-centrosymmetric. This area is being explored
using early transition metal (Nb, Ta, Mo, W) oxide fluorides, late transition metal (Ni,
Cu, Ag, Zn, Cd) cations, and neutral ligands (2,2’-dipyridyl amine).
A polymorph of CuNb(Pyridine)4OF5 using the anionic NbOF5-2, and cationic Cd+2 was
synthesized. The basic chain of the two polymorphs is identical, but differ in packing,
and also the ordering of the oxide and fluoride ligands in the octahedral [NbOF5] 2- unit.
Further study of this polymorphism will lead to an understanding of synthetic methods
and allow a rational synthetic method to be devised to construct these materials.
Exploring Fe-rich intermetallics with the NaZn structure-type : R(Fe Si ) (R
13
x 1-x 13
= La, Ce)
!#"$%"'&)(*+ ,%&.-0/1 "2
A growing number of intermetallic compounds, called “polar intermetallics”,
have been synthesized and studied for relationships between their chemical bondingstructure- properties. Polar intermetallics involve the combinations of
&3&546"-'7%8/1 "9 ,%&
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27
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.CB
he structures of polar intermetallics often cannot be
rationalized by any simple electron counting rules, such as Wade’s rules or the Octet rule,
but do show optimum bonding from theoretical calculations.
The overall goals of my research are to extend the concepts of polar intermetallics to late
transition metals. To accomplish this goal, I have focused on the synthesis and
characterization of iron-based intermetallics because of their large collections of
compounds.
Especially, I have focused on studying R(Fe, Si)13, (R= La, Ce, Ba, Sr) compounds with
structures related to the cubic NaZn13-type. I will report on
LaFe13-xSix(X= 1.04-3.4) with cubic NaZn13 structure and CeFe13-xSix(X= 4-4.5)
which has a tetragonal modification of NaZn13 –type as studied by single crystal and
powder x-ray diffraction.
Theoretical calculations on models of various icosahedral clusters provide clues to
understand my structural observation. Preliminary theoretical results will be reported.
Reference :
&(EF"G3H
'/I2KJJ0.LC>M.N'?.1OPQ+RSTUSVOW>X
Y
Y[Z
1. D
2. A. Fujita, et. al., Phys. Rev. B, 65, 014410, 2002
3. Cao, L.Z., J. Alloys. Compd. 2002, 336, 18
Solid State Synthesis and Characterization of the [C10N12]4- Anion.
A Possible Precursor for the Synthesis of Carbon-Nitrogen Networks
Lykourgos Iordanidis and Omar M. Yaghi
Materials Design and Discovery Group, Department of Chemistry, University of
Michigan, 930 N. University Avenue, Ann Arbor, MI 48109
Over the last two decades there have been considerable research efforts in the synthesis
of carbon nitride networks due to their potential as hard, lightweight, and thermally stable
materials. The results of these efforts are often controversial, mainly due to the lack of
definitive structural data. In an attempt to obtain a better insight of the above systems, we
decided to study the trimerization/polymerization reactions of NaN(CN)2. The reaction of
NaN(CN)2 at ~600 °C produces yellow-brown rods with the composition Na4C10N12. The
structure of Na4C10N12 consists of [C10N12]4- molecules arranged in columns, in a “herringbone” pattern. The [C10N12]4- molecules consist of a three-membered fused-ring system
C7N6 and three terminal N-C≡N groups attached in the three corners of the fused-ring.
Na4C10N12 is stable in water where it dissolves very easily yielding a pale yellow basic
solution. The [C10N12]4- molecule can be recrystallized in its protonated form from water
with the help of other alkali metal ions such as K+ or Cs+ by slow evaporation. The triple
protonated salt can be formed by slow acid diffusion. In these compounds, some of the N
atoms belonging to C7N6 ring are protonated and the structures are stabilized by extensive
hydrogen bonding not only between the [HxC10N12](4-x)- molecules but also with water
molecules. Some preliminary results will be presented using alkali metal eutectic systems
e.g. Li0.6K0.4Cl and Li0.5K0.2Cs0.3Cl, to further polymerize the free terminal cyanide groups.
Depending on the reaction temperature (300-600 ºC) a variety of products were formed
with colors ranging from yellow to orange to red to dark red.
28
The Niobium Oxide Fluoride Anion in the Linear Chain
Heather K. Izumi, Margaret E. Welk, Charlotte L. Stern, Kenneth R. Poeppelmeier
Northwestern University, Evanston, IL 60208-3113
Two new linear chain transition metal oxide fluoride compounds,
noncentrosymmetric,
chiral
Cd(NC5H4NH2)4NbOF5
and
centrosymmetric
Cu(NC5H4NH2)4NbOF5 (NC5H4NH2 = 3–aminopyridine), were synthesized under mild
hydrothermal conditions. Previously, the [NbOF5]2- anion in a linear chain motif was
crystallographically disordered as in Cu(N2C5H6)4NbOF5. There is supporting data for an
ordered [NbOF5]2- anion in Cd(N2C5H6)4NbOF5 owing to an asymmetrical bond network
surrounding the anion that is absent in the Cu containing compound. Both compounds
exhibit extensive hydrogen bonding from the amine groups to the electronegative fluoride
ligands. Crystal data for Cd(NC5H4NH2)4NbOF5: tetragonal, space group P43 (No. 78),
with a = 8.4034(4), c = 34.933(3), and Z = 4; for Cu(N2C5H6)4NbOF5: monoclinic, space
group P21/n (No. 14), with a = 8.822(1), b = 16.385(3), c = 8.902(1), β = 109.270(3), and
Z = 2.
Synthesis and Characterization of New Materials Featuring 1-D Mixed Pnicogen
Tubular Polymers in the Solid State: Cu2P3-xAsxI2, x 1.5
Buddhimathie Jayasekera, Jennifer A. Aitken, Mary J. Heeg and Stephanie L. Brock
Department of Chemistry, Wayne State University, Detroit, MI 48202
The 1-D pnicogen halides (Pnicogen = Group 15 element) are a small class of
relatively unexplored materials in solid state chemistry: so far limited to Cu-P-X (X = Cl,
Br, I). We have begun to look at the potential for producing heavier pnicogen analogues
of these materials, starting with the neutral pnicogen material Cu2P3I2. The structure of
Cu2P3I2 features neutral 1-D polymers of phosphorus consisting of fused four- and fivemembered rings, surrounded by columns of Cu+ and I-. Cu2P3I2 exhibits moderate copper
ionic conductivity therefore our specific aim is to test whether the incorporation of a
heavier pnicogen, such as As, would decrease the interaction between copper ions and the
pnicogen chains, thereby resulting in augmented transport properties. Unfortunately, our
attempts to synthesize a pure As analogue of Cu2P3I2 have not met with success. We have,
however, been able to synthesize a series of compounds with mixed pnicogens chains,
Cu2P3-xAsxI2, where x 1.5. These new materials are isostructural to Cu2P3I2 and have
been characterized by single crystal and powder diffraction techniques. The stabilities
and physical properties of these phases will be discussed in light of the degree of As
incorporation in the structure.
29
Synthesis and Characterization of New Quaternary Alkali Metal Bismuth
chalcogenides:
K1+xAg2-xBi9S15, Rb2Ag3xBi8-xSe13, Rb2CuBi3Se6 and Rb2Cu4-3xBi8+xSe15.
Jun-Ho Kim and Mercouri G. Kanatzidis
Department of Chemistry and Center for Fundamental Materials Research, Michigan
State University, East Lansing, MI 48824
Group 15 chalcogenide compounds have stimulated great interest as they show potential
applications in thermoelectric devices. The efficiency of a thermoelectric material is
determined by the figure of merit ZT = S2σ/κ with the Seebeck coefficient S, the
electrical conductivity σ, and the thermal conductivity κ. For example Bi2Te3, CsBi4Te6
and β-K2Bi8Se13 show promising properties with ZT of ~1, ~0.8 and ~0.2. Materials with
more complex compositions and structures may have complex electronic structures which
may lead to high thermopower and low lattice thermal conductivity. To do research on
new materials with complex structures, the alkali metal chalcogenide flux technique was
adopted in compositionally multiple systems, giving new quaternary compounds such as
K1.31Ag1.69Bi9S15, Rb2Ag1.5Bi7.5Se13, Rb2CuBi3Se6 and Rb2Cu3.1Bi8.3Se15. All crystal
structures are composed of NaCl and Bi2Te3 type building units, which form two- or
three-dimensional anionic frameworks with alkali metal ions between the layers or filling
tunnels. Participation of Ag and Cu in well-known mineral bismuth chalcogenide salts
has provided a variety of new structures but not well characterized yet in their
physicochemical properties. In this research with Ag and Cu, the new compounds
obtained were examined with respect to thermoelectric properties as well as structures
and physical properties. Here we present the synthesis, structure, and characterization of
the aforementioned quaternary bismuth chalcogenide compounds.
High Dielectric Permitivity in the Oxynitride Perovskites BaTaO2N and SrTaO2N
Young-Il Kim and Patrick M. Woodward
Department of Chemistry, The Ohio State University, Columbus, Ohio 43210
The syntheses, crystal structures and optical absorbance spectra of six perovskite
oxynitrides, AMO2N (A = Ba, Sr, Ca; M = Ta, Nb) have been investigated. The average
crystal structure of BaTaO2N is a cubic perovskite, with a Ta–O/N distance of 2.056 Å,
while SrTaO2N and CaTaO2N are distorted by octahedral tilting and show noticeably
smaller Ta–O/N distances, roughly 2.02 Å. Each of the niobium oxynitrides is
isostructural with its tantalum analog, though the Nb–O/N distances are observed to be
slightly longer. The optical band gaps are estimated from diffuse reflectance spectra to be
as follows: BaTaO2N, 1.8 eV, SrTaO2N, 2.1 eV, CaTaO2N, 2.4 eV, BaNbO2N, 1.8 eV,
SrNbO2N, 1.9 eV, and CaNbO2N, 2.1 eV. Computational studies were performed using
DFT method to understand how the electronegativity of anion, structural distortion, and
induction of A cation influence on the electronic structure of oxynitride compounds.
Impedance spectroscopy was carried out on sintered pellets of the ATaO2N and
BaNbO2N to investigate the dielectric and electrical transport properties. The tantalum
compounds are semiconductors/insulators with conductivities of ~10−5 S/cm (A = Ba, Sr)
and ~10−8 S/cm (A = Ca). Interpretation of the impedance data for BaTaO2N and
SrTaO2N reveals that these two compounds have unexpectedly high bulk dielectric
constants, κ ~ 4900 and 2900 respectively at room temperature. The dielectric constants
of both compounds are frequency dependent and show a relatively weak, linear
30
dependence upon temperature with no sign of a phase transition over the temperature
range 300−180 K.
Polar Chains and Interpenetrating Nets; Two Structure Types designed with
[Cr2O7]2-.
Amy L. Kopf, Paul A. Maggard, Charlotte L. Stern, Kenneth R. Poeppelmeier;
Northwestern University, Evanston, IL 60208-3113
Noncentrosymmetric (NCS) materials are of interest to the industrial community for
numerous applications because of such properties as piezoelectricity, ferroelectricity, and
second order non-linear optical (NLO) behavior. . LiNbO3, a well-known inorganic NLO
material, exhibits an out-of-center distortion in the individual [NbO6/2]- octahedra, which
is postulated to cause the non-linear response. Analogous distortions are well known in
early transition metal oxide fluoride anions such as [NbOF5]2- and [WO2F4]2-. Assymetric
metal oxide anions such as [Cr2O7]2- exhibit a net polarization which, when aligned,
mimic the electronic properties of distortion in the oxide fluoride anions and may also
result in NLO behavior. Currently, research is being pursued to elucidate the
crystallization properties of the dichromate anion with late-transition metal cations and
amino-group containing ligands. Low temperature hydrothermal methodology having a
highly acidic environment containing a mineralizer is used to synthesize the crystalline
materials.
Synthesis and Characterization of K39In80 with Remarkably Specific
and Transferable Cation Dispositions
Bin Li and John D. Corbett
Ames Laboratory-DOE and Department of Chemistry, Iowa State University,
Ames, Iowa 50011, USA
The titled compound K39In80 has been synthesized by fusion of the elements in
stoichiometric proportion in Nb containers. The trigonal structure was established by
single-crystal X-ray means (P-3m1, Z = 2, a = b =17.211(2) Å, c = 28.888(6)Å; R1/wR2
= 3.1/7.8%). It is a new intermediate between K17In41 and K22In39 compounds with a
complex structure. The crystal structure can be described as a three-dimensional indium
network composed of five kinds of clusters: three type of empty In12 icosahedra, A (12
exo-bonds, -3m), B (12 exo-bonds, m), and C (6 exo-bonds, -3m); In17 icosioctahedra
centered by a tetrahedron of In atom (D, 3m); and a rather dismantled In15 spacers (E,
3m). The measurements of the electrical resistivity show that the titled compound is
metallic. Remarkably specific and transferable potassium dispositions occurring around
each anion clusters were observed in the title compound as well as in K17In41 and K22In39,
which makes it easy to understand their structural relationship among these three
structures. All the three structures are characterized by a K136 clathrate-33 network of
alkali metal atoms. The main differences among them are their larger clusters within the
K28-atom cage. The larger cluster [In(In4In12)] inside the K28-atom cage is half or totally
substituted by [K(K4In15)] (In15 spacer) with the increasing of K content from K17In41 to
K39In80 and K22In39. The cations on this kind of regular cation positions can also only be
sodium or the mixture of sodium and potassium, as in: (KNa)23In39 (Pnma) and
31
(KNa)22In39 (R-3m). The presence of the regular cation positions is probably decisive for
the formation of the whole structures.
Acknowledgment: This research was supported by the Office of the Basic Energy
Sciences, Materials Sciences Division, U.S. Department of Energy. Ames Laboratory is
operated for DOE by Iowa State University under Contract W-7405-Eng-82.
Discovery of New Stable Icosahedral Quasicrystal in Sc-Cu-Zn System
Qisheng Lin and John D. Corbett
Department of Chemistry and Ames Laboratory, Iowa State University, Ames, IA 50010
Stable icosahedral quasicrystals have been found as an almost single phase in nominal
Sc15Cu15Zn70 alloy by a quench and anneal process. The icosahedral quasicrystals have
the composition Sc16.2(3)Cu12.3(3)Zn71.5(6), with quasilattice constant of 4.9906Å determined
by the Elser’s method. An electron diffraction study confirmed that the icosahedral
quasicrystals have a primitive lattice. Triacontahedral single grain crystals with
dimensions up to 150 µm have been grown by using melt-spinning techniques. X-ray
structure refinements reveal that its crystalline approximant, Sc3Cu2Zn16, crystallizes in
space group Im 3 , with a = 13.732 (2) Å, Z = 8. The local atomic cluster contains five
shells: tetrahedron (4) + pentagon dodecahedron (20) + icosahedron (12) +
icosidodecahedron (30) + 72-atoms soccer ball (72) = 138 atoms. The 3D structure is
formed by interpenetrating of the 138-atom clusters in bcc manner. What interested in the
structure is the existence of tetrahedral, excluding the local five-fold symmetry. The
structure therefore helps to understand how an internal symmetry-breaking cluster can
build up to form a bulk quasicrystal.
Synthesis, Structure and Properties of the New Intermetallic Compounds SrPdTl2,
SrPtTl2, BaPdTl2 and BaPdTl2*
Shengfeng Liu and John D. Corbett
Ames Laboratory and Department of Chemistry, Iowa State University,
Ames, Iowa 50010
The title compounds have been synthesized and characterized structurally and through
physical property measurements and electronic structure calculations. Single-crystal Xray diffraction analysis revealed that they crystallize with the MgCuAl2 structure type
(space group Cmcm, Z=4). Single crystal X-ray data yielded a=4.486(2), b=10.991(5),
c=8.154(1) Å for SrPdTl2, a=4.491(3), b=10.990(6), c=8.140(4) Å for SrPtTl2,
a=4.5933(3), b=11.2843(5), c=8.2571(9)Å for BaPdTl2, a=4.5454(9), b=11.417(2),
c=8.2617(17) Å for BaPtTl2, respectively. Their structures may be described as palladium
or platinum filled versions of the host lattices SrTl2 or BaTl2, respectively. The
compounds exhibit a complex three-dimensional network build of four-bonded thallium
atoms in fused distorted hexagonal tunnels that bind the Sr/Ba and transition metal atoms.
The Pd or Pt is encapsulated at the side of each tunnel within a distorted trigonal prism.
Electronic band structure calculations (EHTB) on SrPdTl2 and BaPdTl2 demonstrate the
effects of the conversion, with strong Pd-Tl and Pt-Tl bonding and appreciable electron
transfer from Tl to Pd or Pt. Property measurements show that SrPdTl2 is metallic, as
expected.
32
*
This research was supported by Dept. of Energy, BES, Materials Sciences
Crystal Structure and Property Relationships of Dielectric Perovskites
Michael W. Lufaso
Ceramics Division, NIST, Gaithersburg, MD 20899-8520
Materials with a high dielectric constant, low dielectric loss and near zero
temperature coefficient of resonant frequency have potential application as dielectric
resonators at microwave frequencies. Perovskites of the general formula A3MM'2O9 (A =
Ba; M = Zn, Mg; M' = Nb, Ta) with a 2:1 ratio of octahedrally coordinated M and M'
cations have been investigated extensively as promising materials suitable for microwave
dielectric applications. The relationship of the crystal structure and chemical factors
influencing the dielectric properties are not fully understood.
Structure - property relationships of 2:1 ordered perovskites were investigated by
comparing crystal structures obtained from Rietveld refinements of X-ray and neutron
diffraction data and the dielectric properties. A preliminary bond valence sum analysis in
relation to the dielectric properties is presented. Crystal structures predicted from
modeling are compared to those obtained from refinements of experimental diffraction
data.
Reduced Cluster Products of Cyanide-Melt Synthesis
Carmela Magliocchi and Timothy Hughbanks
Department of Chemistry, Texas A&M University, College Station, Texas 77842-3012
The tightly cross-linked Mo3nSe3n+2 (n = 2, 3, … )clusters and chain compounds react
with alkali metal cyanide or cyanide salt mixtures at temperatures of 450-675oC to yield
reduced, cyanide-terminated molybdenum chalcogenide clusters. These clusters are
thermodynamically stable species in MCN melts at specific temperatures, and are stable
in basic aqueous solutions. We are studying these electroactive clusters as isolated
species and hope to exploit them as building blocks for materials with novel properties.
Cyclic voltammetric measurements performed on [Mo6Se8(CN)6]n- solutions in basic
aqueous media show multiple reversible redox waves corresponding to [Mo6Se8(CN)6]6-/7-,
[Mo6Se8(CN)6]7-/8-, and [Mo6Se8(CN)6]8-/9- couples. Clusters with a cubane core,
[Mo4Se4(CN)12]n-, are also obtained from cyanide melts and show multiple redox waves
corresponding to [Mo4Se4(CN)12]6-/7- and [Mo4Se4(CN)12]7-/8- couples. Reduction to give
the anionic cluster compound Na8[Mo6Se8(CN)6]•20H2O was accomplished. Several
[Mo4Se4(CN)12]8- cluster-containing compounds have also been synthesized including
K7Na[Mo4Se4(CN)12]•5H2O•MeOH and Cs7Na4[Mo4Se4(CN)12]Cl3. The process by which
clusters are excised from the CN-linked chain compound, K6Mo6Se8(CN)5 will also be
discussed.
33
Synthesis, Structure and Bonding of Rare-Earth Ternary Chalcogenides
Carmela Magliocchi, Jane Meng, and Timothy Hughbanks*
Department of Chemistry, Texas A&M University, College Station, Texas 77842-3012
Rare earth metal-rich compounds, Gd6MTe2 (M = Co, Ni) and Er6RuTe2, were
synthesized in direct reactions between the R, R3M, and R2Te3 (R = Gd, Er, M = Co, Ni,
Ru). These materials all adopt the same Zr6CoAl2 structure type with space group P62m
(No. 189, Z = 1). Single crystal structures of Gd6CoTe2 and Er6RuTe2 were determined
and lattice parameters are a = b = 8.3799(5), c = 3.9801(4) Å, and a = b = 8.1473(5) Å, c
= 3.9962(4) Å, respectively. Gd6NiTe2 was characterized by X-ray powder diffraction;
lattice parameters are a = b = 8.412(2), c = 3.9577(9) Å. However, by slightly varying the
synthetic conditions, an interesting competing phase, Gd4NiTe2, was discovered. This
compound crystallizes with space group Pnma (No. 62, Z =1); lattice parameters are a =
15.548(9)Å, b = 4.113(2)Å, and c = 11.752(7)Å.
Toward the Design and Synthesis of Organic Networks
N.J. Melcer, D.T. Vodak, O.M. Yaghi
University of Michigan, Ann Arbor, Michigan
The rational design and synthesis of extended networks comprised of covalent
interactions is an aim lying at the interface of organic and solid-state synthesis. An
outstanding challenge in chemistry has been to obtain such materials in crystalline form,
which is vital for their proper characterization and ultimate utility. Here we report the
synthesis and crystal structures of extended spiro-orthocarbonate, spiro-phenylacetal and
triazine solids.
Oligospiro-orthocarbonate is synthesized in one step from pentaerythritol and
tetraethylorthocarbonate at 260ºC. A white, insoluble, microcrystalline solid is obtained
whose structure consisted of hexagonally packed pentameric chains. The crystal structure
was determined through a combination of electron diffraction, powder X-ray diffraction
and solid-state nuclear magnetic resonance spectroscopy techniques.
This approach has also been applied to the reaction of bifunctional aldehydes and
alcohols. An off-white, highly insoluble, crystalline solid was obtained in the solid-state
reaction at 200ºC. Its structure was confirmed to be the trans-acetalated product through a
combination of powder X-ray diffraction, infrared spectroscopy, elemental analysis, mass
spectrometry, thermogravimetric analysis, and electron diffraction techniques.
Extended triazine solids are synthesized by affecting cyclotrimerization of polynitriles
and are characterized by single crystal X-ray diffraction. Here we report the synthesis and
crystal structures of tris-(p-cyanophenyl)-s-triazine, tris-(m-cyanophenyl)-s-triazine and a
pentameric oligomer of the m-dicyanobenzene monomer synthesized from a simple one
step cyclotrimerization reaction.
34
Effects of Texture and Microstructure on Charge Mobility in MOCVD-Derived
CdO Thin Films Grown whith a Thermally Stable, Low-Melting Precursor
Andrew W. Metz, John R. Ireland, Yu Yang, Jun Ni, Charlotte L. Stern, Kenneth R.
Poeppelmeier, Carl R. Kannewurf, and Tobin J. Marks*
Department of Chemistry, the Materials Research Center, and the Department of
Electrical and Computer Engineering, Northwestern University, Evanston, IL 60208
A series of low-melting thermally-stable cadmium MOCVD precursors has been
synthesized, structurally/spectrascopically characterized and implemented in the growth
of highly conductive and transparent CdO thin films. One member of the series,
bis(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato)(N,N-Diethyl-N’,N’-Dimethylethylenediamine)cadmium(II), Cd(hfa)2(N,N-DE-N’,N’-DMEDA),
represents a
particularly significant improvement over previously described Cd precursors owing to
its low melting point and robust thermal stability. High-quality CdO films were grown
on Corning 1737F glass and single-crystal MgO (100) between 300°C and 412°C by
MOCVD. Processing parameters are shown to have large effects on microstructure,
optical, and electrical properties. Both neutral impurity and grain boundary scattering are
found to be important in the present films, even with carrier concentrations that are as
high as 1.2*1020 cm-3. Conductivities and mobilities as high as 11,000 S/cm and 307
(cm2/V•s), respectively, are obtained for epitaxial films (FWHMω = 0.30°, FWHMφ =
0.27°) grown in situ on MgO (100) at a relatively low growth temperature (400°C)
despite the appreciable lattice mismatch of 8.7%.
POROSITY STUDIES OF METAL-ORGANIC MATERIALS
Andrew R. Millward, Mohamed Eddaoudi, Jaheon Kim, Nathaniel L. Rosi, Andrea C.
Sudik, Omar M. Yaghi
University of Michigan, 930 N University, Ann Arbor, MI 4810
Metal-organic frameworks (MOFs) have great potential for applications in gas storage,
sensing and catalysis. The porosity of candidate materials is established through gas
sorption isotherm experiments by measuring the increase in equilibrium mass as a
function of relative pressure. Several extended MOFs and molecular compounds have
been tested and show porosity as determined from the isotherm data of N2, Ar, CH4, H2,
C6H6 and other adsorbate gases. Apparent Langmuir surface areas of up to 4450 m2/g
have been estimated, and pore volumes have been calculated in excess of 1.5 cm3/g.
These results illustrate that many of these hybrid metal-organic materials are among the
most porous crystalline materials known.
The Crystal and Electronic Structures of Ternary Oxides constructed from edge
sharing Sn4+ , Sb5+, or Bi5+ Centered Octahedra.
Hiroshi Mizoguchi, Nattamai S. P. Bhuvanesh, Hank W. Eng, and Patrick M. Woodward,
Department of Chemistry, The Ohio State University, Columbus, OH, 43210.
Experimental and computational studies were performed to understand the electronic
structure of rutile (SnO2), trirutiles (ASb2O6, ABi2O6, A = Mg, Zn), ilmenites (ASnO3,
A=Ca, Zn, Cd; ASbO3, A=Na, K; ABiO3, A=Na, Ag), and PbSb2O6-type oxides (ASb2O6,
35
A=Ca, Sr, Ba, Cd; ABi2O6, A=Sr, Ba), containing the main group ions: M = Sn4+, Sb5+,
and Bi5+. Among these compounds the oxides ABi2O6 (A=Sr, Ba) have been synthesized,
for the first time, using a low temperature hydrothermal process beginning from NaBiO3.
In all semiconductive compounds which have edge shared octahedral, the lowest energy
states in the conduction band arise primarily from the antibonding M 5s(6s) - O 2p
interaction at the Γ point. In SnO2 which is constructed by combination of two rutilechains running along the c-axis, the conduction band width is dominated by both
interchain and intrachain Sn 5s-O 2p interactions. The wide conduction band dispersion
along the Γ to Z line originates from the strong orbital interaction along the rutile chain in
Z point, due to the symmetry of crystal structure. The conduction band dispersion along
Γ to A line in PbSb2O6-type oxides (A=alkaline-earth ion) is not strong, because of the Aion’s small electronegativity. These band gaps tend to occur around 5 eV. On the other
hand, in CdSb2O6 the Cd2+ ion exhibits a strong inductive effect that widens the
conduction band and lowers the band gap (3.9 eV) significantly. However, the
interaction that gives rise to the conduction band dispersion along the Γ to A line is only
a bonding interaction, therefore, the conduction band dispersion is smaller than observed
in SnO2.
Towards Mesoporous Chalcogenide Semiconductors: Sol-gel Chemistry vs.
Supramolecular Templating
Jaya L. Mohanan, and Stephanie L. Brock*
Wayne State University, Detroit, MI 48202
Although metal oxide based mesoporous materials have been extensively explored for
several years, the development of non-oxide mesoporous materials has been relatively
slow. Recently, our group successfully synthesized high surface area aerogels of a
chalcogenide semiconductor, CdS, for the first time. This was achieved by combining
sol-gel chemistry, using a nanoparticulate precursor, and supercritical fluid drying.
Though these aerogels have interesting structural and optical properties, they encompass
a wide pore distribution, ranging from the micro-to-macro regime. Currently, we are
attempting to prepare mesoporous chalcogenides via supramolecular templating using a
nanoparticle precursor. In this work, we will compare the above aerogels to templated
mesoporous materials with respect to their morphology, surface area, porosity, and
optical properties. Also, our extension to chalcogenide aerogels other than CdS will be
discussed.
Tracking and understanding first-order structural transition in Er5Si4
Y. Mozharivskyj and G.J. Miller
Ames Laboratory, Iowa State University, Ames, Iowa 50011
Temperature-dependent single crystal X-ray diffraction studies revealed a
reversible first-order phase transition in Er5Si4. The high-temperature phase adopts an
orthorhombic Gd5Si4-type structure with the Si-Si dimers between slabs, and the lowtemperature phase has a monoclinic Gd5Si2Ge2-type structure, in which half of the Si-Si
interslab dimers are broken. Unlikely to Gd5Si2Ge21 and other related compounds, the
structural change in Er5Si4 is not coupled with magnetic transition and the structural
36
sequence with temperature is opposite. For the first time, we were able to observe
temporally and spatially resolved transformation of the monoclinic and orthorhombic
lattices, which provides multiple clues to understanding the mechanism of the transition
at the atomic level.
The B1g normal mode, that lowers the symmetry from Pnma to P1121/a, has been
identified using Landau theory. The mode induces shear movement along the a axis, thus
breaking half of the interslab silicon dimers, and simultaneously rotates slabs, as
observed at the transition point. The orthorhombic-to-monoclinic transformation leads to
intrinsic twinning, possibly microscopic, in the monoclinic phase.
The distortion follows the conventional Gibbs free energy/entropy relationship:
optimization of Er-Si interactions upon the orthorhombic-to-monoclinic transition
minimizes the electronic energy for the low-temperature monoclinic form, but entropy
contribution stabilizes the orthorhombic form at high temperatures
1
V. K. Pecharsky, A. O. Pecharsky, and K. A. Gschneidner, J. Alloys Compd. 344, 362
(2002).
Fundamental Topologies in Metal-Organic Frameworks
Nathan W. Ockwig, Michael O’Keeffe, and Omar M. Yaghi*
The Materials Design and Discovery Group, Department of Chemistry, University of
Michigan, 930 N. University Ave., Ann Arbor, MI 48109-1055, USA
Metal-organic frameworks (MOFs) are a rapidly advancing class of materials that
have witnessed an explosion of new compounds from a vast variety of metal-ligand
combinations. Despite the tremendous number of new MOF structures reported there are
relatively few detailed analyses of the underlying framework topologies of these
materials. We have embarked on the systemization of these topologies, methods of
structure analysis, and finally topology recognition within MOF structures. The
principles developed from this study are being used to identify commonly occurring (or
default) and rare (or non-default) topology types. In addition, these principles can be
used to provide chemists with methods of designing crystals with targeted topologies and
physical properties.
37
Synthesis, Structure, and Powder Second-Harmonic Generating Properties of New
Mixed Metal Oxides
Kang Min Ok and P. Shiv Halasyamani*
Department of Chemistry and Center for Materials Chemistry, University of Houston,
136 Fleming Building, Houston, TX 77204-5003
Several new mixed metal oxides have been synthesized by standard solid-state reactions.
The structures of the oxides have been investigated by powder and single crystal X-ray
diffraction. In addition, the powder second-harmonic generating (SHG) properties of each
material have been measured. The relative SHG efficiencies may be understood by
examining the structure of each material. Through the powder SHG measurements, we
estimate the average non-linear optical bond susceptibility, < d2ωijk >, as well as determine
the phase-matchability for each material. In addition, structure-property relationships are
elucidated.
Novel Polyanionic Arsenic Structures
Ivaylo Petrov and Slavi Sevov
Studied were solutions of various arsenic- and alkali metal-containing solid-state
precursors in ethylenediamine and 2,2,2-crypt. Thus, an intermetallic with nominal
composition Na3Cs3Nb2As6 (contains [NbAs4]7-) dissolves readily and forms a dark-red
solution. Red crystals of [Na-(2,2,2-crypt)]Cs5[NbAs8]2 were isolated and characterized.
The new compound contaions Nb-centered crown-like As88- anions. Similarly, an
intermetallic of nominal composition K38Ta7As24 forms a green-red solution which
provides orange crystals of [K-(2,2,2-crypt)]2As4. This compound contains the novel
square-like molecules of As42- that are isostructural with the known Sb42- and Bi42-.
Low Temperature Synthesis of New Lead Oxides and Oxyhalides.
Yetta Porter and P. Shiv Halasyamani
Department of Chemistry and Center for Materials Chemistry, University of Houston,
136 Fleming Building, Houston, TX 77204-5003
Nonlinear optic materials have optical properties that can be modified by light as
it passes through the material. These materials have many applications in devices such as
tunable parametric oscillators and frequency doublers. All nonlinear optic materials
crystallize in noncentrosymmetric space groups. This symmetry requirement is evident
in 21 of the 32 space groups; of these 21, twenty exhibits second harmonic generation
(SHG). This nonlinear optic property doubles the frequency of laser radiation. There is
much interest in finding materials exhibiting SHG efficiently. Our group has devised a
theory to synthesize new mixed metal oxidic compounds utilizing cations which undergo
second-order Jahn-Teller distortions. These electronic distortions cause acentric
environments about the cations, therefore, creating units with net polarizations. This
asymmetry is not a sufficient condition to produce crystallographic noncentrosymmetry.
The units must align in an antiparallel manner to form a macroscopically
38
noncentrosymmetric material. Once the material is formed, second harmonic generation
measurements were conducted on a modified powder Kurtz-NLO system using 1064 nm
radiation, with the intensities compared to the reference material, quartz. An analysis of
the structure is used to explain the origins of the SHG. There has been considerable
research conducted to find alternatives to the conventional solid-state method of
synthesizing new mixed metal oxides and oxyhalides. In this case, a low temperature,
aqueous, reflux system was used to form new lead oxides and oxyhalides. This method
lead to facile synthesis and high yields. We report three new structure types with one
crystallizing in a noncentrosymmetric (NCS) group. Second harmonic generation
measurements were conducted on the NCS compound.
Rapid Acquisition Pair Distribution Function (RA-PDF) Analysis: a Local Strcture
Probe
Xiangyun Qiu and Simon J.L. Billinge
Department of Physics and Astronomy, Michigan State University, E. Lansing, MI 48824
Peter J. Chupas and Clare P. Grey
Department of Chemistry, State University of New York at Stony Brook, Stony Brook,
NY 11794
Jonathan C. Hanson
Department of Chemistry, Brookhaven National Laboratory, Upton, NY 11973
Peter L. Lee
Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439
Atomic pair distribution function (PDF) technique has proved to be a powerful tool to
study the local structure of structurally complex materials. However, the long data
collection time (8 hours) required by conventional PDF experiments is a key limiting
factor to its wider application. Here we present that, high-energy synchrotron radiation
coupled with an area detector (image plate) can reduce measuring time to seconds or
minutes, with momentum transfer Qmax ≤ 28.5 A-1. Crystalline materials with different
structural complexities (Ni, AlF3, and the layered Aurivillius type oxides α-Bi4V2O11 and
γ-Bi4V1.7Ti0.3O10.85) were measured to test the validity of this quantitative PDF data
analysis. All experimental PDFs are of high quality and highly reproducible when
samples are similar. The new combination of real space probe and fast counting time
opens up a broad field for future application to wide varieties of materials of both
scientific and technological interest. Structural changes under in-situ conditions and time
development of chemical reactions and biological systems can also be studied.
39
Using Theory to Find High Spin Rare Earth Clusters
Lindsay E. Roy and Timothy Hughbanks
Department of Chemistry, Texas A&M University, College Station, TX 77843-3012
Open-4f-shell rare-earth elements provide one of the richest regions for interesting and
useful magnetic and conducting properties. However, efforts are needed to advance our
understanding of the key factors controlling magnetic properties in order to guide rational
experimental development of this field. Our goal is to provide a basis of correlating
structure, bonding, and magnetic properties of rare-earth molecular compounds with
more specific applicability in a manner analogous to the Goodenough rules, or the HayThibeault-Hoffmann and Kahn-Briat models. We have developed a semi-quantitative
analysis of d-electron mediated f-f exchange in rare-earth metal-rich cluster compounds
to construct and check features of a generally applicable qualitative approach to
understanding their magnetic coupling. Results from benchmark systems include
investigations of indirect 4f7-4f7 coupling in cluster and condensed-cluster gadolinium
materials. Spin density functional theory (SDFT) molecular orbital and band structure
calculations were performed and we show that open-d-shell clusters facilitate strong
ferromagnetic coupling whereas closed-d-shell systems prefer antiferromagnetic
coupling. This method has been successful evaluating the ground state for model cluster
systems based on GdI2, Gd[Gd6FeI12], and condensed cluster system, Gd2Cl3. A detailed
discussion of Gd[Gd6FeI12] will be presented, using a perturbative molecular orbital
(PMO) model that focuses on the influence of the 4f7-d exchange interaction on the dbased molecular orbitals. Extension of our analysis to prospective magnetic clusters is
underway involving Gd5O(OPri)13, whose relatively short Gd-Gd contacts and the cationic
nature of the cluster core, [Gd5(µ5-O)(µ3- OPri)4(µ-OPri)4]5+, suggest that this cluster may
be reduced and f-f exchange coupling could be enhanced through metal-metal bonding.
A DFT Study on the Interstitial Chemical Shifts of Main Group Element Centered
Hexazirconium Halide Clusters
Jingyi Shen and Timothy Hughbanks
Department of Chemistry, Texas A&M University, College Station, TX 77843-3012
NMR spectra of the interstitial atoms in the zirconium halide clusters have been very
useful in understanding the chemistry of these clusters in both solids and solution.
Compared with ordinary diamagnetic molecules, these interstitial nuclei are highly
deshielded. Trends have been observed as the bridging halides progress from Cl to I. A
qualitative DFT study based on Ramsey’s equation has been carried out aiming to
establish the correlation between the trend of interstitial chemical shifts and the change in
electronic structure. The influence of halide variation on electronic structure was studied
with two series of model compounds [(Zr6Z)X12](H2O)6n+ (Z=B, C, X=Cl, Br, I). The
effect of terminal ligands on overall electronic structures was also studied with model
compounds [(Zr6B)Cl12]L6n+, where L= H2O, PH3, HCN and OPH3.
Inverse
proportionality has been found between the chemical shifts and the calculated energy
gaps ∆E(t1u- t1u*) for each series of compounds, where t1u and t1u* orbitals are the bonding
and antibonding orbitals resulted from the interaction between the zirconium cage
bonding orbitals and the interstitial 2p orbitals. We conclude that the deshielding of the
interstitial atoms is mainly attributable to the paramagnetic contribution which arises
from the second order mixing involving the t1u and t1u* orbitals in the applied magnetic
40
field. A quantitative study on the nuclear magnetic resonance shielding tensors for the
[(Zr6B)X12](H2O)6n+ (X=Cl, Br, I) series has also been performed with DFT/GIAO
method.
Synthesis, structure, and thermoelectric properties of AδMo3Sb5Te2
N. Soheilnia, H. Kleinke
University of Waterloo, Department of Chemistry, Waterloo, ON, Canada N2L 3G1
Thermoelectric materials may either convert heat (more precisely, a temperature
gradient) into electricity or vice versa. The materials commercially used are usually
narrow gap semiconductors comprising heavy elements. Several new materials are
currently under investigation because of their promising thermoelectric properties, in
particular; the telluride CsBi4Te6 and the antimonide LnδM4Sb12 with 0 ≤ δ ≤ 1, with Ln
being a lanthanoid and M a late transition element such as Fe, Co, Ni, … LaFe3CoSb12
exhibits outstanding thermoelectric properties, for its good thermopower and electrical
conductivity are combined with an extraordinarily low thermal conductivity. The latter
stems from the high vibrations of the La atom situated in a large "cage" of Sb atoms, a
phenomenon usually referred to as rattling.
We recently succeeded in modifying Mo3Sb7 to obtain the semiconducting
antimonide-telluride Mo3Sb5Te2, which comprises a calculated band gap of 0.45 eV. Our
next steps to render this material more useful involve incorporation of small cations into
an Sb8 cube of this structure: this void may get filled to, e.g., 14 % with Mg atoms as
confirmed via single crystal structure studies. This contribution describes the syntheses of
AδMo3Sb7 and AδMo3Sb5Te2 with A = Mg, Ni, and Cu. Adding Mg cations leads to an
increase of valence-electrons as well as a decrease of the band gap. However, as 55
valence-electrons per formula unit are needed to fill all states below the gap, the filled
Mg-containing material has an ideal formula of "MgδMo3Sb5+2δTe2-2δ". Physical property
measurements confirm the prediction that these materials are semiconducting.
Synthesis and Characterization of Nanoscale Transition Metal Phosphides
Produced via Precursor Reduction
Kimber L. Stamm, Stephanie L. Brock
Wayne State University, Detroit, MI 48202
Bulk transition metal phosphides exhibit interesting magnetic and electronic properties,
yet there are few reports of exploring these materials and their properties on the
nanoscale. Our lab has developed a synthesis based on reduction of nanoscale phosphate
precursors under flowing H2/Ar to yield various phases of dimensionally limited
phosphides. In order to avoid sintering, the nanoparticle precursors must first be
dispersed onto substrate surfaces prior to annealing. This method has successfully
produced nanoparticles of FeP and Fe2P on mica.
Another way to limit the degree of sintering is by using a template with ordered
nanoscale pores. We are investigating the suitability of porous alumina membranes
(Anodisc, Whatman) for the production of wire-like morphologies. These materials will
be limited to nanoscale dimensions in only two directions and are therefore expected to
41
have orientation dependant properties. Our synthetic efforts to produce crystalline
nanowires of iron phosphides (FeP and Fe2P) will be discussed and these materials will
be compared to the 3-D limited nanoparticles produced by sintering on mica.
Discrete and Extended Metal-Organic Frameworks of Iron
Andrea C. Sudik, Jaheon Kim, Omar M. Yaghi
Materials Design and Discovery Group, Department of Chemistry, University of
Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055
Although the majority of metal-organic frameworks contain transition metals, relatively
few have been reported with iron, an avenue which could lead us to target biologically
relevant structures. More specifically, the redox activity, enzymatic activity and electrontransfer properties inherent to iron, make it an attractive metal for inclusion. Efforts to
incorporate iron into extended arrays have afforded a series of ferrous, ferric, and mixedvalent, infinite two- and three-dimensional frameworks, some of which contain
magnetically or electronically interesting building units, such as the oxo-centered [Fe3O
(ROOC)3L3]+/0 trimer or the [Fe2(ROOC)2L2] paddle-wheel dimer. Conditions have also
been discovered to isolate a two-dimensional framework composed of dimeric ironcarboxylate clusters which structurally resemble those found in the active site of methane
monooxygenase, a bacterial enzyme which catalyzes the conversion of methane to
methanol.
The above approach for preparation of extended solids using metal-carboxylate building
blocks can also be translated to molecular chemistry, serving as a viable route for
generation of porous, finite species. Modification of the above synthesis using a less
labile iron counterion has resulted in the isolation of an anionic truncated tetrahedron,
[Fe12O4(p-C14H8O4)6(SO4)12(pyr)12]8- (A), composed of sulfate capped triiron units with pbiphenyldicarboxylate serving as the link. Preliminary sorption data suggests these
molecules are indeed porous, adsorbing a variety of inert gases and organic vapors, with
approximate surface area, 494 m2/g. Understanding the synthetic parameters under which
the vertex clusters in (A) form, we have been able to introduce both linear and branched
organic di- and tri-carboxylate linkers to produce the overall same truncated tetrahedron
polyhedron (B). Upon discovery of (A), it was thought that analogous discrete sulfate
terminated supramolecules could also be obtained in the presence of other carboxylic acid
linkers. These ongoing investigations also include the synthesis and characterization of a
finite triangle whose vertices are composed of polyoxo-hexairon clusters.
[Fe12O4(p-C14H8O4)6(SO4)12(pyr)12] [H2N(CH3)2]8
C27H18O6)4)(SO4)12(pyr)12][H2N(CH3)2]8
(A)
[Fe12O4(p-
(B)
42
Synthesis of Transition-Metal Phosphides by Direct Reduction of their Phosphates
Christina M. Sweeney, Kimber L. Stamm, and Stephanie L. Brock
Department of Chemistry, Wayne State University, Detroit, MI 48202
Phosphates of a number of metals, including Mo, W, Fe, Ni, and Ru, are known to reduce
to single-phase phosphides upon reductive annealing. It has been suggested that the
prediction of which metal phosphates will successfully produce phosphides is directly
related to redox properties of the metal. Metals whose oxides will not reduce to the
metallic state, such as Mn and Ga, also will not undergo reduction from phosphate to
phosphide. However, based on this premise, several additional late metal phosphates
may be capable of reduction to phosphide. We are testing this hypothesis for the metals
Ag, Rh, Ir, and Re. Our attempts to prepare crystalline phosphate precursors by solution
precipitation, and the results of our subsequent reductive annealing, will be discussed.
Investigation of Metal Clusters as Molecular Precursors for Transition Metal
Pnictide Nanoparticle Synthesis
Kristy Symons†, Arvind Kumar‡, Kenton H. Whitmire‡, Stephanie L. Brock†
†
Department of Chemistry, Wayne State University
‡
Department of Chemistry, Rice University
The focus of our research is to synthesize transition metal pnictide (pnicogen = Group 15
element) nanoparticles from single source precursors. Transition metal pnictides
constitute an important area of study due to their intriguing magnetic properties;
however, controlling stoichiometry in these materials remains a challenge. The use of
molecular, or single source precursors should provide control of the stoichiometry of the
resulting nanoparticles. We are interested in identifying appropriate precursors for our
targeted phases, and using these for the synthesis of nanoparticles through thermal
decomposition in coordinating solvents. The clusters Mn(CO)5BiPh2 and {Mn(CO)}3Bi
are currently under investigation as precursors for the synthesis of manganese bismuthide
nanoparticles. The thermal degradation of the metal clusters in solution and in the solid
state will be discussed.
Aromaticity in Sn- and Pb- based Zintl Phases.
Iliya Todorov and Slavi Sevov*
Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame,
Indiana 46556
Although aromaticity has been extensively studied for more than a century, there
is still no generally acceptable definition. This concept was invented to account for the
unusual stability of certain organic molecules: the aromatic compounds. The most
significant feature that they exhibit is a planar structure with a delocalized system of
(4n+2) -electrons.The most general point of view on aromaticity combines geometry
(bond length equality), energy (aromatic stabilization energy) and magnetism
(diamagnetic susceptibility exaltations). However this property has never been
investigated carefully and systematically in all-metal species. Here we report the
discovery of three isostructural Zintl phases with aromatic anionic pentagonal rings made
of Sn and Pb, Sn56- and Pb56-. Furthermore two other phases having anionic pentagonal
43
rings have been discovered in a detailed study of the Li-Eu-Sn system. All compounds
have been synthesized by direct fusion of the elements at 800° C and characterized by
single crystal X-ray diffraction. These are the first heavy main-group species with an
aromatic ring. It is very unusual that such heavy atoms can form aromatic structures.
Reactions of nine-atoms germanium clusters in solution
Angel Ugrinov and Slavi Sevov
Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame IN
Interest in synthesis, isolation and characterization of delthahedral Zintl ions from
solutions dates back to the 19th century. Numerous attempts to use these species in
various reactions have been made, some successful and some not. It has been shown, for
the first time in our group, that “normal” 2-center-2-electron bonds can form between
such clusters with delocalized bonding, Ge94- for example. Based on the existence of the
dimers of [Ge9-Ge9]6-, and the chain of [-(Ge9)2--]∞, it is only natural to look also for
oligomers of various sites.
The poster presents some of the results of our investigation of reactions with the
germanium nine-atom clusters in solution. We show that it is possible to attach group 15
or group 14 substituents to such clusters. Ethylenediamine solutions of the precursor
A4Ge9 (A=K or Rb) react with SbPh3, BiPh3 or SnPh4 and give yield [Ph2SbGe9SbPh2]2(same for Bi), [Ph2SbGe9Ge9SbPh2]4-, [PhGe9SbPh2]2-, [Ph3SnGe9SnPh3]2- and [Ge9SnPh3]3. The same reactions with AsPh3 and PPh3 provide linear trimer of germanium clusters,
[Ge9=Ge9=Ge9]6-. Later we found that the trimer can be just using high concentration of
precursor in en and appropriate cation sequestering agent. Following the same idea but
changing the cation sequestering agent we obtained a tetramer, [Ge9=Ge9=Ge9=Ge9]8-.
Aqueous Tetraperoxo Cr(V) will not Reduce Directly to Cr(III) Hydroxide
Douglas A. Vander Griend
Department of Chemistry & Biochemistry, Calvin College
3201 Burton Street SE, Grand Rapids, MI 49546
Joshua S. Golden and Charles A. Arrington Jr.
Department of Chemistry, Furman University
3300 Poinsett Highway, Greenville, SC 29613-1120
The reaction of chromium with hydrogen peroxide in basic media hinges on the
chemistry of tetraperoxo chromium(V). Several intermediates, including a triperoxo
species, can be identified kinetically in the reaction that produces Cr(O2)4-3 from CrO42-.
More stable in base that peroxide itself, Cr(O2)4-3 can then convert to only a
chromium(VI) species, even under reducing conditions which ultimately generate
chromium(III). Both the one electron reduction of chromium(VI) and the complementary
oxidation of chromium(V) likely produce superoxide, which may play a key role in the
toxicity of high-valent chromium.
44
Synthesis and Characterization of New Intermetallic Tetrelides Using Al as a Flux
Xiuni Wu and Mercouri G. Kanatzidis*
Department of Chemistry and Center for Fundamental Materials Research, Michigan
State University, East Lansing, MI 48824
Metal silicides and germanides have received wide applications as advanced structural
materials and electronic device materials. Conventional methods to synthesize these
materials rely on direct combination of elemental reactants at high temperatures,
normally over 1500°C, and powder samples are usually obtained from such methods. The
use of metal fluxes presents the advantages such as lower reaction temperatures, facilitate
the growth of single crystals, etc. In our group, the application of Al as the flux to
synthesize new multinary intermetallic compounds containing a rare earth metal, first or
second row late transition metal, aluminum, and silicon or germanium has shown great
success. Recently, we have been exploring the system containing third row transition
metals instead of first or second row transition metals. Gold was first selected because of
its noble metal status and unusual electronegativity. In the Au-containing system, two
analogs were obtained: REAuAl4Ge2 (RE = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm, Yb)
and REAuAl4(AuxGe1-x)2 (RE = Ce, Eu). At the same time, we started extending our study
of synthesizing intermetallic tetrelides to a new systemT1/T2/Al/Si(Ge) (T1 and T2 are
transition metals) using Al as the high temperature solvent. From this system, ternary
compounds are readily formed. Co19Al42Si13-x (x = 0.2) and V2Al5Ge5 are two new ternary
phases formed from this system presenting interesting structures. All the materials have
been structurally characterized by energy dispersive spectroscopy (EDS) and X-ray
diffraction analysis. Magnetic susceptibility measurements have also been conducted.
Investigation of Niobium oxychloride cluster compounds: Synthesis and crystal
structure of the composite layered compound Nb10Cl16O7
Yan Zhihua, Abdou Lachgar
Department of Chemistry, Wake Forest University, Winston-Salem, NC 27109
Our investigation of niobium oxychlorides containing octahedral Nb6 clusters led to the
discovery of the oxychloride Nb10Cl16O7. The compound was obtained from solid-state
reaction of a mixture of NbCl5, Nb2O5 and Nb powder in a sealed silica tube at 820°C. Its
crystal structure was determined by single crystal X-ray diffraction techniques (space
group I 2/m, a = 12.876(1) Å, b = 3.2580(3) Å, c = 15.529(1) Å, = 103.92(1)°, V =
632.37(10) Å3, Z = 4). The framework Nb10Cl16O7 is based
on (NbClO)Cl cluster units that share two inner oxygen and four outer chlorine ligands
located in the equatorial plane to form a cluster chain with connectivity formula
(NbCl6iO4iO)Cl Cl. The cluster chain is linked to a double chain formed of NbCl4O2
octahedra sharing chlorine edges and oxygen vertices. The double chains connect
neighboring cluster chains by sharing two outer chlorine and four inner oxygen ligands of
the cluster to form a two-dimensional framework.
45
Cluster
chain
Double
chain
Hydrothermal synthesis and crystal structure of hybrid metal phosphate-oxalates:
[Mn2(H2PO4)4(C2O4)2](C10N4H28) 5H
2O and [In6(PO4)8(C2O4)3](C10N4H28)3
Yue Zhao, Yumi Okuyama, Abdou Lachgar
Department of Chemistry, Wake Forest University, Winston-Salem, NC 27109
Two novel framework materials in the metal-phosphate-oxalate system have been
prepared by hydrothermal reaction carried out in Teflon-lined stainless steel Parr
autoclave at 150 °C for 3 days using 1,4-Bis(3-aminopropyl)piperazine as structuredirecting agents (SDA). The compound [Mn2(H2PO4)4(C2O4)2](C10N4H28) 5H
)
2O (
crystallizes in the triclinic system, space group P-1 (No. 2), a=10.1087(9) Å, b=11.342(1)
Å, c=16.751(2) Å, =80.79(1)°, =77.13(1)°, =86.945(5)°, V=1848(5) Å3, Z=2. (I) has
a 1D framework formed of vertex-sharing MnO6 and H2PO4 polyhedra linked by bridging
oxalate ligands to form hybrid chains running along a axis. The chains are separated from
each other by the SDA molecules and interact through hydrogen bonding. The compound
[In6(PO4)8(C2O4)3](C10N4H28)3(
crystallizes
)
in the trigonal system, space group P-3c1
(No. 165), a=14.004(2) Å, c=15.191(3) Å, V=2580.0(7) Å3, Z=2. Its 3D framework is
formed of InO6 octahedra and PO4 tetrahedra sharing corners to form inorganic rods along
c axis. The rods are linked via oxalate ligands to generate large channels in which
disordered SDA cations are located.
1D framework of ( )
3D framework of (
46
)
One-Dimensional coordination polymer based on octahedral [Nb6Cl12(CN)6]4- cluster
units and [Mn(III)(salen)]+ metal complex as building blocks
Huajun Zhou and Abdou Lachgar
Department of Chemistry, Wake Forest University, Winston-Salem, NC 27109
A novel one-dimensional framework based on octahedral niobium cyanohalide cluster,
[Nb6Cl12(CN)6][Mn(salen)(MeOH)]2[Et4N]2.
2MeOH
(salen
=
N,Nethylenebis(salicylideneaminato)) was prepared by reaction of aqueous solution of
[Et4N]4[Nb6Cl12(CN)6] with a solution of the complex [Mn(salen)]ClO4 in methanol at RT.
The compound was characterized by single-crystal X-ray diffraction and IR. The
compound crystallizes in the monoclinic system, space group P 21/c, a = 13.227(1) Å, b =
21.800(2) Å, c = 13.781(1) Å and = 93.648(6)°, Z = 2. The framework is built of
[Nb6Cl12(CN)6]4- cluster units that share two trans apical cyanide ligands with Mn ( )
leading to the formation of trimeric units [Mn-(NC)[Nb6Cl12(CN)4](CN)Mn]. Each
Mn(III) is trans- coordinated by one cyanide ligand from the cluster and one methanol, in
addition to the salen ligand. The trimers are connected to each other through hydrogen
bonding to form anionic chains along the crystallographic a axis
{[(Nb6Cl12)(CN)6][Mn( )(salen)(MeOH)]2}2-. Hydrogen bonding O – H ---N forms
between the methanol ligands on manganese and cyanide ligands from two neighboring
clusters. A c-glide plane relates adjacent chains to each other.
47
i
a) Derstroff, V.; Ksenofontov, V.; Gûtlich, P.; Tremel, W. Chem. Commun. 1998, 2, 187-188. b) Coste,
S.; Kopnin, E.; Evain, M.; Jobic, S.; Payen, C.; Brec, R. J. Solid State Chem. 2001, 162, 195-203. c) Coste,
S.; Kopnin, E.; Evain, M.; Jobic, S.; Brec, R.; Chondroudis, K.; Kanatzidis, M. G. Solid State Sci. 2002, 4,
709-716. d) Kopnin, E.; Coste, S.; Jobic, S.; Evain, M.; Brec, R. Mat. Res. Bull. 2000, 35, 1401-1410.
ii
Tarascon, J.M.; Hull, G.W.; Disalvo, F.J. Mat. Res. Bull. 1984, 19, 915-924.
iii
Elder, S.H.; Van der Lee, A.; Brec, R.; Canadell E. J. Solid State Chem. 1995, 116, 107-112.
iv
a) Chondroudis, K.; Kanatzidis, M. G.; Sayettat, J.; Jobic, S.; Brec, R. Inorg. Chem. 1997, 36, 58595868. b) Coste, S.; Hanko, J.; Bujoli-Doeuff, M.; Louarn, G.; Evain, M.; Brec, R.; Alonso, B.; Jobic, S.;
Kanatzidis, M. G. J. Solid State Chem., accepted (2003).
v
a) Sayettat, J.; Bull, L.M.; Jobic, S.; Gabriel, J.C.P.; Fourmigué, M.; Batail, P.; Brec, R.; Inglebert, R.-L.;
Sourisseau, C. J. Mater. Chem. 1999, 9, 143-153. b) Sayettat, J.; Bull, L.M.; Gabriel, J.C.; Jobic S.;
Camerel, F.; Marie, A.-M.; Fourmigué, M.; Batail, P.; Brec, R.; Inglebert, R.-L. Angew. Chem. Int. Ed.
1998, 37, 1711-1714.
vi
a) Tarascon, J.M.; Disalvo, F.J.; Chen, C.H.; Carroll, P.J.; Walsh, M.; Rupp, L. J. Solid State Chem.
1985, 58, 290-300. b) Davidson, P.; Gabriel, J.C.P.; Levelut, A.M.; Batail, P. Europhysics letters 1993, 21,
317-322.
vii
Coste, S.; Gautier, E.; Evain, M.; Bujoli-Doeuff, M.; Brec, R.; Jobic S. and Kanatzidis, M.G. Chem.
Mater., accepted 2003.
Yb2Ga4Ge6 and Yb3Ga4Ge6: Novel Zintl Phases Grown From Molten Ga. X-ray
Structure Determination, Electronic Structure Calculations and Physical Properties
Marina A. Zhuravleva(a), James Salvador(a), Daniel Bilc(b), S. D. Mahanti(b), John Ireland(c),
Carl R. Kannewurf(c), and Mercouri G. Kanatzidis(a)
(a)
Department of Chemistry, Michigan State University, E. Lansing, MI 48824
(b)
Department of Physics and Astronomy, Michigan State University, E. Lansing, MI
48824
(c)
Department of Electrical Engineering and Computer Science, Northwestern University,
Evanston, IL 60208
Two new intermetallic compounds, Yb2Ga4Ge6, Yb3Ga4Ge6, were obtained from the
reactions in molten Ga. The crystal structures of these compounds were studied with
single crystal X-ray diffraction. The Yb2Ga4Ge6 crystallizes in an orthorhombic cell a =
4.1698(7) Å, b = 23.254(4) Å, c = 10.7299(18) Å, Z = 4 in a polar space group Cmc21.
The structure of Yb3Ga4Ge6 is monoclinic, space group C2/m, Z = 4, cell parameters a =
23.941(6) Å, b = 4.1928(11) Å, c = 10.918(3) Å, β = 91.426(4)°. The structures of these
two families of compounds can be described using a Zintl concept of bonding, in which
the three-dimensional [Ga4Ge6]n- framework serves as a host and an electron sink to the
electropositive Yb atoms. Even though the ideal Zintl ion formulation could be given for
the anionic [Ga4Ge6] network, these compounds are metallic conductors. The relation of
crystal structure of Yb3Ga4Ge6 to that of Yb2Ga4Ge6 lies in a monoclinic distortion of
orthorhombic cell of Yb2Ga4Ge6 and a reduction of the [Ga4Ge6] network by two electrons
per formula unit. The results of the theoretical electronic structure calculations, transport
data and magnetic measurements are also reported.