The electronic structure of VO²⁺, CrO³⁺, and MoO³⁺ complexes

Abstract

THE electronic structures of the d¹ chromophores VO²⁺, CrO³⁺, and MoO³⁺ have been the subject of much debate^1–4, particularly after the early molecular orbital (m.o.) calculations of Gray et al.^5,6. An important feature of the electronic spectral assignments suggested^5,6 was that the first two absorptions correspond to the d–d transitions d_xy→d_xz,yz and d_xy→${\text{d}}_{x^{\text{2}}-y^{\text{2}}}$ respectively, in the d-orbital sequence d_xy (b₂) < d_xz, d_yz(e) < ${\text{d}}_{x^{\text{2}}-y^{\text{2}}}$ (b₁) < d_z2(a₁). These assignments have found general acceptance and have formed the basis for the interpretation⁷ of the electron spin resonance (ESR) spectra and bonding parameters of these complexes. We report here experimental results contradicting the assignment of the second absorption.