ABSTRACT:The effective crystal field (ECF) methodology previously developed for description of the electronic structure of transition metal complexes (TMCs) is combined with molecular mechanics (MM) formalism. In this way, a new method for calculations of potential energy surfaces of the Werner-type TMC is developed. It is based on a combined quantum mechanics (QM)-MM approach with the ECF method taking part of the QM and advanced MM package MMPC developed for the metal ion complex computations and based on the CHARMM organic force field. The MM region consists of ligand atoms and metal ion coordination sphere, leaving out effects of d-shell, while the QM region is limited to metal ion d-shell. Crystal field matrix for the d-shell is calculated with use of the local ECF method. It is shown that the procedure proposed reproduces with considerable accuracy geometry characteristics of values of the Fe(II) complexes with both mono-and polydentate ligands.

ABSTRACT:In the present work the semiempirical effective crystal field (ECF) method previously designed for electronic structure calculations of transition metal complexes and utilizing non-Hartree-Fock trial wave function and parameterized for complexes of doubly charged Cr 2ϩ , V 2ϩ , Mn 2ϩ , Fe 2ϩ , Co 2ϩ , and Ni 2ϩ cations is extended to complexes of triply charged cations of 3d-elements. With the parameters adjusted the ECF method is applied to calculations of ground states and low-energy spectra of the d-shells of fluoro-, chloro-, aqua-, amino-, and cyano-complexes of the triply charged cations. Obtained total spin and symmetry of the ground states match the experimentally observed ones. Satisfactory agreement between the calculated and experimental d-shell electronic transition energies is achieved as well.

In the present work the semiempirical effective crystal field (ECF) method previously designed for electronic structure calculations of transition metal complexes and utilizing non-Hartree-Fock trial wave function and parameterized for complexes of doubly charged Cr 2ϩ , V 2ϩ , Mn 2ϩ , Fe 2ϩ , Co 2ϩ , and Ni 2ϩ cations is extended to complexes of triply charged cations of 3d-elements. With the parameters adjusted the ECF method is applied to calculations of ground states and low-energy spectra of the d-shells of fluoro-, chloro-, aqua-, amino-, and cyano-complexes of the triply charged cations. Obtained total spin and symmetry of the ground states match the experimentally observed ones. Satisfactory agreement between the calculated and experimental d-shell electronic transition energies is achieved as well.