Discrete variational Xα studies of the electronic structure of amavadin

Abstract

Discrete variational Xα(DVXα) calculations have been carried out for the eight-co-ordinated vanadium-(IV) and -(V) complexes [V(hida)₂]^2–/1–(H₃hida =N-hydroxyiminodiacetic acid). These complexes are minimal models for the corresponding oxidation states of amavadin from Amanita muscaria which, as isolated, consists of an approximately equimolar mixture of the anions [Δ-V{(S,S)-hidpa}₂]^2– and [Λ-V{(S,S)-hidpa}₂]^2–(H₃hidpa =N-hydroxy-2,2′-iminodipropionic acid). The electronic structure and the nature of the metal-ligand bonding of these vanadium-(IV) and -(V) centres is described. The ordering of the d orbitals and their composition is closely related to that established for the oxovanadium(IV) moiety which demonstrates why, for many years, amavadin was mistakenly thought to contain a VO²⁺ centre.