ISSN:
0020-7608
Keywords:
Computational Chemistry and Molecular Modeling
;
Atomic, Molecular and Optical Physics
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Accurate ab initio CASSCF, CASPT2, and DFT computations have been performed on three different model systems which emulate the oxygenated active site of hemocyanin (a Cu+ - Cu+ dimer that binds oxygen as peroxide to form oxyhemocyanin). The three models differ in the number of the ammonia molecules (0, 4, and 6 molecules, respectively) which emulate the real histidine metal ligands of the protein matrix. While the CASSCF computations indicate that the ground state wave function of the oxyhemocianin active site is in all cases a singlet, the CASPT2 and the DFT approaches provide a significantly different description and suggest that the greater stability of the singlet versus the triplet state (experimentally observed) is not an intrinsic property of the oxygenated form of the hemocyanin active site but depends on the presence of ligands on copper atoms. These results indicate that the dynamic correlation contributions (included in the CASPT2 and DFT methods) are essential to obtain a proper description of these systems that cannot be correctly emutated using models where metal ligands are not included. © 1996 John Wiley & Sons, Inc.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
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