Mononuclear cis-dioxovanadium(V) anionic complexes [VO₂L]^-{H₂L=[1 + 1] Schiff base derived from salicylaldehyde (or substituted derivatives) and 2-amino-2-methylpropan-l-ol}: synthesis, structure, spectroscopy, electrochemistry and reactivity studies

Abstract

The compounds [H₃NCMe₂CH₂OH][VO₂L]{H₂L =[1 + 1] Schiff base derived from salicyladehyde (or substituted derivatives) and 2-amino-2-methylpropan-l-ol} have been synthesized in good yields by reaction of the Schiff base (formed in situ) and a further equivalent of the amino alcohol with [VO(acac)₂](Hacac = acetylacetone). The structures of three of the complexes have been solved by single-crystal X-ray studies. All the compounds were also characterized by UV/VIS, FTIR and NMR spectroscopy and by cyclic voltammetry. The three structurally characterized mononuclear complexes contain the cis-dioxovanadium(V) moiety and exhibit distorted square-pyramidal geometry at vanadium which is displaced from the equatorial plane by ≈ 0.5 Å. The crystal and molecular structures of these compounds showed extensive hydrogen bonding between the anionic portion of the complexes and the counter-cations of the amino alcohol which resulted in some unusual metric features of interest to the binding of vanadium in biological systems. Two of the compounds showed the longest V=O distances reported so far for mononuclear cis-dioxovanadium(V) complexes. Three of the complexes undergo photoreduction in the solid state which is attributed to their intermolecular interactions in the crystal.