Late Transition Metal Amido Complexes: Electronic
... Lappart herby established the synthetic strategies and structural motifs of the amido ligand (NR2-) and furthermore explored the reactivity of amido metal bonds.[2a] During the past decades, this type of ligands have developed an increasing dominant role in ligand design due to their unique and ...
... Lappart herby established the synthetic strategies and structural motifs of the amido ligand (NR2-) and furthermore explored the reactivity of amido metal bonds.[2a] During the past decades, this type of ligands have developed an increasing dominant role in ligand design due to their unique and ...
From nucleotides to ribozymes — A comparison of their metal ion
... hammerhead sequence) does not show its best activity in the presence of Mg2+ but Mn2+ [73]. This observation is even more pronounced in the case of the recently described so-called extended hammerhead ribozyme [69,74-76], where so far the maximum cleavage rate has not been reached [45,46,74]. Intere ...
... hammerhead sequence) does not show its best activity in the presence of Mg2+ but Mn2+ [73]. This observation is even more pronounced in the case of the recently described so-called extended hammerhead ribozyme [69,74-76], where so far the maximum cleavage rate has not been reached [45,46,74]. Intere ...
Cd adsorption onto Anoxybacillus flavithermus
... (pH 5.2), and 1:2 and 1:50 in the cadmium acetate solutions (pH 7.3 and 5.7, respectively). All solution samples were transferred into liquid cells. The bacterial pellets from a set of eighteen independently grown 400-mL cultures were combined to make three samples (pHs 3.9, 5.8, and 7.0), while a d ...
... (pH 5.2), and 1:2 and 1:50 in the cadmium acetate solutions (pH 7.3 and 5.7, respectively). All solution samples were transferred into liquid cells. The bacterial pellets from a set of eighteen independently grown 400-mL cultures were combined to make three samples (pHs 3.9, 5.8, and 7.0), while a d ...
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... the 4-position was selected for the isoelectronic replacement far apart from the metal ion because we expected the most dramatic influence on the solubilty while only minor changes in the coordination chemistry should take place, since the rather small change in the ligand backbone should not dimini ...
... the 4-position was selected for the isoelectronic replacement far apart from the metal ion because we expected the most dramatic influence on the solubilty while only minor changes in the coordination chemistry should take place, since the rather small change in the ligand backbone should not dimini ...
THE ADSORPTION OF CO, N2 AND Li ON Ru(109) AND Ru(001
... high vacuum and surface science techniques. The investigations focused on the effect of the metal surface morphology on the simplest of the surface reactions; adsorption, desorption, and dissociation. Building on the previous conclusion that CO dissociates on the step sites of Ru(109) producing mobi ...
... high vacuum and surface science techniques. The investigations focused on the effect of the metal surface morphology on the simplest of the surface reactions; adsorption, desorption, and dissociation. Building on the previous conclusion that CO dissociates on the step sites of Ru(109) producing mobi ...
Dehydrogenation of Methanol by Vanadium Oxide and Hydroxide
... ary reactions with methanol in which one or both hydroxo groups are replaced by methoxo groups to generate VmOn-2(OH)(OCH3)+ or VmOn-2(OCH3)2+, respectively. Some of these secondary reaction products exhibit mass interferences with the primary reaction products of VmOn+, which renders the quantitati ...
... ary reactions with methanol in which one or both hydroxo groups are replaced by methoxo groups to generate VmOn-2(OH)(OCH3)+ or VmOn-2(OCH3)2+, respectively. Some of these secondary reaction products exhibit mass interferences with the primary reaction products of VmOn+, which renders the quantitati ...
coord_chem_2
... Complex from Its Magnetic Properties. The complex ion [Ni(CN4)]2- is diamagnetic. Use ideas from the crystal field theory to speculate on its probably structure. Solution: Coordination is 4 so octahedral complex is not possible. ...
... Complex from Its Magnetic Properties. The complex ion [Ni(CN4)]2- is diamagnetic. Use ideas from the crystal field theory to speculate on its probably structure. Solution: Coordination is 4 so octahedral complex is not possible. ...
Polyhedral Oligomeric Silsesquioxane
... FTIR and UVvis studies support the formation of the thiolPd2þ complex. As shown in Figure 1a, the FTIR spectrum of Pd(OAc)2 displays two peaks at 1633.8 and 1601.4 cm1, representing the CO stretching modes of the metal-bonded μ-acetate ion. By contrast, these two peaks weaken when the Pd(OAc)2 i ...
... FTIR and UVvis studies support the formation of the thiolPd2þ complex. As shown in Figure 1a, the FTIR spectrum of Pd(OAc)2 displays two peaks at 1633.8 and 1601.4 cm1, representing the CO stretching modes of the metal-bonded μ-acetate ion. By contrast, these two peaks weaken when the Pd(OAc)2 i ...
Investigation of molecular structures and adsorption mechanisms of
... of L-Phe-L-Ala-PO3H2 (MD1), L-Phe-L-Val-PO3H2 (MD2), L-Phe-b-Ala-CH(OH)-PO3H2 (MD3), and L-Phe-L-AlaCH(OH)-PO3H2 (MD4) phosphonodipeptides adsorbed on colloidal silver surface have been measured. The respective vibrational band assignments have been proposed. The analysis of the SERS spectra shows t ...
... of L-Phe-L-Ala-PO3H2 (MD1), L-Phe-L-Val-PO3H2 (MD2), L-Phe-b-Ala-CH(OH)-PO3H2 (MD3), and L-Phe-L-AlaCH(OH)-PO3H2 (MD4) phosphonodipeptides adsorbed on colloidal silver surface have been measured. The respective vibrational band assignments have been proposed. The analysis of the SERS spectra shows t ...
Chapter 21 Transition Metals and Coordination Chemistry
... 4d and 5d metals are similar in size Lanthanide contraction: The decrease in the atomic radii of the lanthanide series elements, going from left to right in the periodic table Caused by increase in nuclear charge Offsets the normal increase in size due to going from one principal quantum lev ...
... 4d and 5d metals are similar in size Lanthanide contraction: The decrease in the atomic radii of the lanthanide series elements, going from left to right in the periodic table Caused by increase in nuclear charge Offsets the normal increase in size due to going from one principal quantum lev ...
UNIT - I THE SOLID STATE KEY CONCEPTS
... 5. Non stoichiometric cuprous oxide can be prepared in the laboratory. In this oxide, copper to oxygen ratio is slightly less than 2:1 can you account for the fact that the substance is a p-type semiconductor? 6. The unit cell of an element of atomic mass 50 u has edge length 290pm. Calculate its de ...
... 5. Non stoichiometric cuprous oxide can be prepared in the laboratory. In this oxide, copper to oxygen ratio is slightly less than 2:1 can you account for the fact that the substance is a p-type semiconductor? 6. The unit cell of an element of atomic mass 50 u has edge length 290pm. Calculate its de ...
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).