Electronic structures and d—d spectra of vanadium(IV) and VO2+ complexes: discrete variational Xα calculations

Abstract

Discrete Variational Xα(DVXα) calculations at three successive levels of approximation have been carried out for the vanadium(IV) complexes VCl₄, [VCl₅]^–, [VOCl₄]^2–, [VO(NCS)₄]^2–, [VO(NCS)₄(OH₂)]^2–, [VO(CN)₅]^3–, [VO{OC(NH₂)₂}₂Cl₂] and [VO(NMe₃)₂Cl₂]. The electronic structures and the nature of the metal-ligand bonding are described and compared with previous theoretical results and a detailed comparison between observed and computed d–d electronic transition energies is presented. Near-quantitative agreement is obtained for the observed band maxima. The calculated assignments from the most accurate calculations are also in agreement with experiment. In contrast to previous theoretical treatments of [VOCl₄]^2–, which predict the reversed order of the first two absorptions, the DVXα results yield the correct energy-level scheme. The ESR g and A values for this species are also well reproduced theoretically.