Crystal structures of transition metal complexes with an asymmetrical tridentate Schiff-base ligand

The asymmetrical tridentate Schiff base (H2L = (E)-N′-(2-hydroxybenzylidene)-4-hydroxybenzohydrazide) has been designed and synthesized. The four transition metal complexes with this ligand [Cu(HL)(NO3)](H2O) (1), [Zn2(HL)2(bipy)(H2O)2](NO3)2 (2), [Cu(HL)(H2O)]2(NO3)2 (3) and [Cu(HL)(Me2NCO)]2 (4) have been studied. The unsaturated coordination site of metal ion in complexes 1 and 2 is occupied by secondary ligand of nitrate and 4,4′-bipyridine. The crystal structure of complex 1 exhibits supramolecular framework with homochirality. Complexes 3 and 4 are dinuclear complexes bridged by the phenol oxygen atoms and the fifth coordination is occupied by H2O molecular and DMF anion respectively. Hydrogen bonding and π–π stacking exist in all four complexes to construct supramolecular architecture.