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 VO 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.