Syntheses, characterization and antibacterial activity of mononuclear and dinuclear copper(II) complexes containing a hydrazone ligand

An aroylhydrazone compound (HL) was prepared and explored as a ligand (HL = N'-(2-hydroxy-4-methoxybenzylidene)-3-hydroxy-4-methoxybenzohydrazide). Reaction of the aroylhydrazone ligand with copper bromide and copper chloride afforded two new copper(II) complexes, [Cu2Br2L2] (1) and [CuL(DMF)]Cl (2), respectively. The aroylhydrazone ligand and copper complexes were characterized by CHN elemental analyses and infrared spectroscopy. Structures were further confirmed by single crystal X-ray diffraction experiments. The aroylhydrazone compound coordinates to Cu atoms through its phenolate oxygen, imino nitrogen and carbonyl oxygen. The Cu atom in 1 adopts a square pyramidal coordination, with three donor atoms of one L and one phenolate oxygen of a second L in the basal plane, and with one Br ligand at the apical position. The Cu atom in 2 is square pyramidal, with three donor atoms of one L and one oxygen of a DMF ligand in the basal plane, and with one Cl ligand at the apical position. Crystal structures of the aroylhydrazone and the copper complexes are stabilized by hydrogen bonds. The complexes possess antibacterial activities against B. subtilis, S. aureus and E. coli.