Synthesis and spectral investigations of vanadium(IV/V) complexes derived from an ONS donor thiosemicarbazone ligand

Four oxovanadium and one dioxovanadium complex with 2-hydroxyacetophenone N(4)-phenylthiosemicarbazone (H₂L) which are represented as VOLphen]·2H₂O (1), VOLbipy] (2), VOLdmbipy] (3), VOL]₂ (4) and VO₂HL]·CH₃OH (5) have been synthesized and characterized by elemental analyses, electronic, infrared and EPR spectral techniques. In all the complexes 1–4 the ligand coordinates through phenolic oxygen, azomethine nitrogen and thiolate sulfur. But in complex VO₂HL]·CH₃OH, coordination takes place in thione form instead of thiolate sulfur. All the complexes except VO₂HL]·CH₃OH are EPR active due to the presence of an unpaired electron. In frozen DMF at 77 K, all the oxovanadium(IV) complexes show axial anisotropy with two sets of eight line patterns.