Low- and high-spin iron (II) complexes studied by effective crystal field method combined with molecular mechanics

• Published in: Journal of computational chemistry 2003-11, Vol.24 (14), p.1703-1719
• Main Authors: Darkhovskii, M. B., Pletnev, I. V., Tchougréeff, A. L.
• Format: Article
• Language: English
• Subjects: effective crystal field; potential energy surfaces; quantum mechanics/molecular mechanics; transition metal complexes
• ISSN: 0192-8651; 1096-987X
• DOI: 10.1002/jcc.10300

A computational method targeted to Werner‐type complexes is developed on the basis of quantum mechanical effective Hamiltonian crystal field (EHCF) methodology (previously proposed for describing electronic structure of transition metal complexes) combined with the Gillespie–Kepert version of molecular mechanics (MM). It is a special version of the hybrid quantum/MM approach. The MM part is responsible for representing the whole molecule, including ligand atoms and metal ion coordination sphere, but leaving out the effects of the d‐shell. The quantum mechanical EHCF part is limited to the metal ion d‐shell. The method reproduces with reasonable accuracy geometry and spin states of the Fe(II) complexes with monodentate and polydentate aromatic ligands with nitrogen donor atoms. In this setting a single set of MM parameters set is shown to be sufficient for handling all spin states of the complexes under consideration. © 2003 Wiley Periodicals, Inc. J Comput Chem 14: 1703–1719, 2003