Effects of pH, Temperature and Ca2+ Content on the Conformation
... Na and K" binding; however some conclusions can be drawn from the fluores cence phase plots (Burstein 1977) which are shown in Fig. 2. The fluorescence phase plot, i.e. the relationship between fluorescence intensity at a fixed emission wavelength and the intensity at any other fixed wavelength, ha ...
... Na and K" binding; however some conclusions can be drawn from the fluores cence phase plots (Burstein 1977) which are shown in Fig. 2. The fluorescence phase plot, i.e. the relationship between fluorescence intensity at a fixed emission wavelength and the intensity at any other fixed wavelength, ha ...
Clusters and Polynuclear Compounds
... fascinating chemical oddities. The exponential growth of their chemistry has been made possible by the advent of X-ray crystallography and many other spectroscopic techniques. The term “metal atom cluster” was introduced in 1964 by F. A. Cotton to designate a finite group of metal atoms held togethe ...
... fascinating chemical oddities. The exponential growth of their chemistry has been made possible by the advent of X-ray crystallography and many other spectroscopic techniques. The term “metal atom cluster” was introduced in 1964 by F. A. Cotton to designate a finite group of metal atoms held togethe ...
Transition Metal Polyhydrides: From Qualitative
... A large number of calculations on pure hydride systems have been carried out on neutral triatomic MH2 species, probably because of their simplicity. Most of this work focuses on the study of the formation of a dihydride complex from the reaction of H2 with the metal atom. In many cases, the goal of ...
... A large number of calculations on pure hydride systems have been carried out on neutral triatomic MH2 species, probably because of their simplicity. Most of this work focuses on the study of the formation of a dihydride complex from the reaction of H2 with the metal atom. In many cases, the goal of ...
Solvation structure around ruthenium(II) tris(bipyridine)
... We have used classical MD simulations to study the solvation of [Ru(bpy)3]2þ in a series of polar solutions and its interaction with halide anions. The MDynaMix code20 was used to run classical MD simulations of [Ru(bpy)3]2þ, Liþ, Cl, and I ions in aqueous, ethanol, and acetonitrile solutions, whi ...
... We have used classical MD simulations to study the solvation of [Ru(bpy)3]2þ in a series of polar solutions and its interaction with halide anions. The MDynaMix code20 was used to run classical MD simulations of [Ru(bpy)3]2þ, Liþ, Cl, and I ions in aqueous, ethanol, and acetonitrile solutions, whi ...
The low frequency modes of solvated ions and ion pairs in aqueous
... associates as well? In the present study, we investigate the hydration behavior of iron(II) and iron(III) chloride salts in aqueous phase, using THz/FIR Fourier transform spectroscopy. THz/FIR absorption spectroscopy has proven to be a powerful tool to analyse electrolyte solutions at high concentra ...
... associates as well? In the present study, we investigate the hydration behavior of iron(II) and iron(III) chloride salts in aqueous phase, using THz/FIR Fourier transform spectroscopy. THz/FIR absorption spectroscopy has proven to be a powerful tool to analyse electrolyte solutions at high concentra ...
Solvation Effects on Transition Metal Hydricity
... We were also able to estimate the pKa of the hydride of [HNi(DHMPE)2][BF4] (3) in H2O. Dissolution of [Ni(DHMPE)2] (2) in D2O results in a broad peak at 53.8 ppm in the 31P NMR spectrum (Figure S8). Over the course of hours, the signal sharpens and shifts to a singlet at 54.7 ppm, which matches the ...
... We were also able to estimate the pKa of the hydride of [HNi(DHMPE)2][BF4] (3) in H2O. Dissolution of [Ni(DHMPE)2] (2) in D2O results in a broad peak at 53.8 ppm in the 31P NMR spectrum (Figure S8). Over the course of hours, the signal sharpens and shifts to a singlet at 54.7 ppm, which matches the ...
Structural Diversity in Metal Phosphonate Frameworks: Impact on
... R-PO3H2 and its two deprotonated forms, R-PO3H and R-PO32– exhibit an interesting, pH-dependent behavior (Figure 14.2). Usually the first proton is very acidic, while the second is a couple orders of magnitude less acidic.83–89 There is a plethora of published crystal structures of ‘‘free’’ (not met ...
... R-PO3H2 and its two deprotonated forms, R-PO3H and R-PO32– exhibit an interesting, pH-dependent behavior (Figure 14.2). Usually the first proton is very acidic, while the second is a couple orders of magnitude less acidic.83–89 There is a plethora of published crystal structures of ‘‘free’’ (not met ...
N,NH-Dialkyldithiocarbamate chelates of indium(III
... Thermogravimetric curves were obtained using a Shimadzu model TGA-50 thermobalance, at a heating rate of 108C minÿ1 in a dynamic atmosphere of dry nitrogen ¯ux of 0.83 mL sÿ1 and a 445±695 K range. The standard molar enthalpies of fusion and the heat capacities of the solid and liquid forms of the c ...
... Thermogravimetric curves were obtained using a Shimadzu model TGA-50 thermobalance, at a heating rate of 108C minÿ1 in a dynamic atmosphere of dry nitrogen ¯ux of 0.83 mL sÿ1 and a 445±695 K range. The standard molar enthalpies of fusion and the heat capacities of the solid and liquid forms of the c ...
University of Groningen Catalytic oxidations by vanadium
... not stable under the applied reaction conditions. Examples include the corresponding vanadium(V) compounds of carboxyphenylsalicylideneamine (H2CPS), pyridine-2-carboxylic acid (Hpic), and nitrilotriphosphoric acid (H3ntp) [6,18,19]. These ligands dissociate from the metal ion in the presence of aci ...
... not stable under the applied reaction conditions. Examples include the corresponding vanadium(V) compounds of carboxyphenylsalicylideneamine (H2CPS), pyridine-2-carboxylic acid (Hpic), and nitrilotriphosphoric acid (H3ntp) [6,18,19]. These ligands dissociate from the metal ion in the presence of aci ...
High-Affinity Adaptors for Switchable Recognition of Histidine
... Therefore, stoichiometrically and structurally well-defined attachment of spectroscopic probes is hardly possible. Furthermore, high-affinity binding of protein-based recognition units is often only reversible under drastic denaturing conditions (13) Miller, L. W.; Cornish, V. W. Curr. Opin. Chem. B ...
... Therefore, stoichiometrically and structurally well-defined attachment of spectroscopic probes is hardly possible. Furthermore, high-affinity binding of protein-based recognition units is often only reversible under drastic denaturing conditions (13) Miller, L. W.; Cornish, V. W. Curr. Opin. Chem. B ...
"Fundamentals of Rotation--Vibration Spectra" in
... Energy Surfaces for High-resolution Molecular Spectroscopy and Reaction Dynamics, this handbook), where the atoms or nuclei move in an effective potential V (R) defined by the solution of the electronic Schrödinger equation. R is the distance between the nuclei. We consider molecules in their elect ...
... Energy Surfaces for High-resolution Molecular Spectroscopy and Reaction Dynamics, this handbook), where the atoms or nuclei move in an effective potential V (R) defined by the solution of the electronic Schrödinger equation. R is the distance between the nuclei. We consider molecules in their elect ...
Chapter 24 Chemistry of Coordination Compounds
... Addition of NH3 ligand to Cu(H2O)4 changes its color Chemistry of Coordination Compounds ...
... Addition of NH3 ligand to Cu(H2O)4 changes its color Chemistry of Coordination Compounds ...
Taking advantage of luminescent lanthanide ions
... (5D4 A 7F0) cm21, respectively. However, GdIII emits in the UV, and it is not very useful as luminescent probe for bioanalyses because its luminescence interferes with either emission or absorption processes in the organic part of the complex molecules. On the other hand, it can efficiently transfer ...
... (5D4 A 7F0) cm21, respectively. However, GdIII emits in the UV, and it is not very useful as luminescent probe for bioanalyses because its luminescence interferes with either emission or absorption processes in the organic part of the complex molecules. On the other hand, it can efficiently transfer ...
Fulltext PDF - Indian Academy of Sciences
... Until this route was discovered, only two methods were known to give sulphurtriimides, using either NSF3 12 or OSF4 13. The first is quite hazardous, because the starting material is S4N4, which tends to explode very easily and the second is limited to the tris(trimethylsilyl)sulphurtriimide S(NSiMe ...
... Until this route was discovered, only two methods were known to give sulphurtriimides, using either NSF3 12 or OSF4 13. The first is quite hazardous, because the starting material is S4N4, which tends to explode very easily and the second is limited to the tris(trimethylsilyl)sulphurtriimide S(NSiMe ...
HAT(CN)6: a new building block for molecule
... HAT(CN)6 with ®rst row transition metals such as Co and Zn. The resulting dark blue-green powders are soluble in polar organic solvents such as acetonitrile, which is a good indication that discrete molecules are being formed. Although X-ray quality single crystals have not been obtained, several sp ...
... HAT(CN)6 with ®rst row transition metals such as Co and Zn. The resulting dark blue-green powders are soluble in polar organic solvents such as acetonitrile, which is a good indication that discrete molecules are being formed. Although X-ray quality single crystals have not been obtained, several sp ...
CARBON-HYDROGEN-TRANSITION METAL BONDS
... the crystal structure data available on agostic C-H-M systems and the structures of some of the compounds are represented in Fig. 2. As noted above, the early crystal structure determinations did not observe the agostic hydrogen directly but evidence for interaction between the C-H group and the met ...
... the crystal structure data available on agostic C-H-M systems and the structures of some of the compounds are represented in Fig. 2. As noted above, the early crystal structure determinations did not observe the agostic hydrogen directly but evidence for interaction between the C-H group and the met ...
Spin crossover
Spin Crossover (SCO), sometimes referred to as spin transition or spin equilibrium behavior, is a phenomenon that occurs in some metal complexes wherein the spin state of the complex changes due to external stimuli such as a variation of temperature, pressure, light irradiation or an influence of a magnetic field.With regard to a ligand field and ligand field theory, the change in spin state is a transition from a low spin (LS) ground state electron configuration to a high spin (HS) ground state electron configuration of the metal’s d atomic orbitals (AOs), or vice versa. The magnitude of the ligand field splitting along with the pairing energy of the complex determines whether it will have a LS or HS electron configuration. A LS state occurs because the ligand field splitting (Δ) is greater than the pairing energy of the complex (which is an unfavorable process).Figure 1 is a simplified illustration of the metal’s d orbital splitting in the presence of an octahedral ligand field. A large splitting between the t2g and eg AOs requires a substantial amount of energy for the electrons to overcome the energy gap (Δ) to comply with Hund’s Rule. Therefore, electrons will fill the lower energy t2g orbitals completely before populating the higher energy eg orbitals. Conversely, a HS state occurs with weaker ligand fields and smaller orbital splitting. In this case the energy required to populate the higher levels is substantially less than the pairing energy and the electrons fill the orbitals according to Hund’s Rule by populating the higher energy orbitals before pairing with electrons in the lower lying orbitals. An example of a metal ion that can exist in either a LS or HS state is Fe3+ in an octahedral ligand field. Depending on the ligands that are coordinated to this complex the Fe3+ can attain a LS or a HS state, as in Figure 1.Spin crossover refers to the transitions between high to low, or low to high, spin states. This phenomenon is commonly observed with some first row transition metal complexes with a d4 through d7 electron configuration in an octahedral ligand geometry. Spin transition curves are a common representation of SCO phenomenon with the most commonly observed types depicted in Figure 2 in which γHS (the high-spin molar fraction) is plotted vs. T. The figure shows a gradual spin transition (left), an abrupt transition with hysteresis (middle) and a two-step transition (right). For a transition to be considered gradual, it typically takes place over a large temperature range, even up to several hundred K, whereas for a transition to be considered abrupt, it should take place within 10 K or less.These curves indicate that a spin transition has occurred in a metal complex as temperature changed. The gradual transition curve is an indication that not all metal centers within the complex are undergoing the transition at the same temperature. The abrupt spin change with hysteresis indicates a strong cooperativity, or “communication”, between neighboring metal complexes. In the latter case, the material is bistable and can exist in the two different spin states with a different range of external stimuli (temperature in this case) for the two phenomena, namely LS → HS and HS → LS. The two-step transition is relatively rare but is observed, for example, with dinuclear SCO complexes for which the spin transition in one metal center renders the transition in the second metal center less favorable.There are several types of spin crossover that can occur in a complex; some of them are light induced excited state spin trapping (LIESST), ligand-driven light induced spin change (LD-LISC), and charge transfer induced spin transition (CTIST).