Utilization of LVO–2 species (L2– is a tridentate ONS donor) as an inorganic analogue of carboxylate group: A journey to a new domain of coordination chemistry

The anionic cis-dioxovanadium (V) complex species LVO– 2 of tridentate biprotic dithiocarbazatebased ligands H2L (S-methyl-3-((5-R-2-hydroxyphenyl)methyl)dithiocabazate, R = H, L = L1; and R = Br, L = L2) can bind alkali metal ions. The products [LVO2M(H2O)n] (M = Na+, L = L1, 1; L = L2, 2 and M = K+, L = L1, 3) have extended chain structures in the solid state, stabilized by strong hydrogen bonding and Coulombic interactions as revealed from X-ray crystallography. The LVO–2 moieties here behave like analogues of carboxylate groups and display interesting variations in their binding patterns. It appears that 1 is a single stranded helicate with LVO–2 units forming the strands which surround the labile sodium ions occupying positions on the axis. The compounds are stable in water and methanol as solvents, while in aprotic solvents of higher donor strengths, viz. CH3CN, DMF and DMSO, they undergo photo-induced reduction when exposed to visible light, yielding green solutions from their initial yellow colour. The putative product is a mixed-oxidation (-oxo)divanadium (IV/V) species as revealed from EPR, electronic spectroscopy, dynamic 1H NMR, and redox studies.