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Six‐coordinate Co 2+ with imidazole, NH 3 , and H 2 O ligands: Approaching spin crossover
Author(s) -
Schmiedekamp Ann M.,
Ginnetti Anthony,
Piccione Brian,
Can Kevin,
Ryan M. Dominic
Publication year - 2006
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.21282
Subject(s) - chemistry , spin crossover , imidazole , spin states , ligand (biochemistry) , homoleptic , crystallography , protonation , octahedron , spin (aerodynamics) , computational chemistry , stereochemistry , inorganic chemistry , physics , ion , crystal structure , thermodynamics , biochemistry , receptor , organic chemistry , metal
Octahedral, six‐coordinate Co 2+ can exist in two spin states: S = 3/2 and S = 1/2. The difference in energy between high spin (S = 3/2) and low spin (S = 1/2) is dependent on both the ligand mix and coordination stereochemistry. B3LYP calculations on combinations of neutral imidazole, NH 3 , and H 2 O ligands show that low‐spin isomers are stabilized by axial H 2 O ligands and in structures that also include trans pairs of equatorial NH 3 and protonated imidazole ligands, spin crossover structures are predicted from spin state energy differences. Occupied Co d orbitals from the DFT calculations provide a means of estimating effective ligand strength for homoleptic and mixed ligand combinations. These calculations suggest that in a labile biological system, a spin crossover environment can be created. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
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