Synthesis, structure and properties of (VIVO)2MII (M = Cu, Zn) trinuclear complexes derived from a new macrocyclic oxamido vanadium (IV)-oxo ligand

A novel macrocyclic oxamidato-bridged vanadium (IV)-oxo mononuclear ligand VOL (VOL = vanadium (IV)-oxo H2L = 2,3-dioxo-5,6:13,14-dibenzo-7,10,12-trimethyl-1,4,8,11-tetraazacyclo-tetradeca-7,12-diene) (1) has been synthesized by solvent-thermal in situ reaction and characterized by electron paramagnanetic resonance (EPR). Subsequently, using VOL as a precursor, its derivative trinuclear complexes [(VOL)2Cu(CH3OH)2](ClO4)2⋅2CH3OH (2) and [(VOL)2Zn(CH3OH)2](ClO4)2⋅2CH3OH (3) have been prepared and the crystal structures of the two complexes have been identified by the same method with 1. Thermal stabilities of compounds 1, 2 and 3 were studied and the results revealed that 1, 2 and 3 could be stable up to 205 °C, 234 °C and 250 °C, respectively. Moreover, the simulation of the EPR spectra of 1, 2 and 3 indicated the three oxo-vanadium samples were not oxidized and all of them remained in the active +4 oxidation state.

► A novel macrocyclic oxamidato-bridged vanadium (IV)-oxo mononuclear ligand has been prepared.
► Two new trinuclear complexes have been synthesized using VOL as a precursor.
► TGA showed thermal stability of the two trinuclear complexes is higher than the mononuclear.
► EPR spectra indicated the three oxo-vanadium samples remained in the active +4 oxidation state.