Crystal-field splittings and optical spectra of transition-metal mixed-ligand complexes by effective Hamiltonian method

• Published in: International journal of quantum chemistry Vol. 57; no. 4; pp. 663 - 671
• Main Authors: Soudackov, A. V., Tchougreeff, A. L., Misurkin, I. A.
• Format: Journal Article
• Language: English
• Published: New York John Wiley & Sons, Inc 15.02.1996
• ISSN: 0020-7608; 1097-461X
• DOI: 10.1002/(SICI)1097-461X(1996)57:4<663::AID-QUA13>3.0.CO;2-1

Many of the important properties of transition‐metal complexes depend on the low‐energy excitation spectrum formed by d‐electrons of the central transition‐metal atom. The spectra of this type are usually fit to the well‐known crystal field theory or to the angular overlap model. The result of the fitting is a set of parameters which are considered as characteristics of the electronic structure of the complex such as strength of the ligand field or types and extent of metal‐ligand bonding. We present here a short account of the effective Hamiltonian method recently developed to calculate the splitting of the d‐levels by the ligands and the resulting d‐d spectra of transition‐metal complexes together with some results of its application to the mixed‐ligand complexes with the general formula ML4Z2, where M = V, Co, Ni; L = H2O, NH3, Py; and Z = H2O, NCS−,C −l. Particular attention is paid to the V(H2O)4Cl2 and Co(H2O)4Cl2 compounds. The former seems to have tetragonal structure, whereas for the latter, our method predicts a spatially degenerate ground state for the tetragonal arrangement of the ligands. That must lead to the Jahn‐Teller distortion, which is actually observed. © 1996 John Wiley & Sons, Inc.