Synthesis, crystal structure of copper(II) complexes comprising 2-(biphenylazo)phenol and 1-(biphenylazo)naphthol ligands and their catalytic activity in nitroaldol reaction

New series of copper(II) complexes of the type [Cu(L)2] (L = L1–L5) comprising bidentate 2-(biphenylazo)phenol (HL1–HL4) and 1-(biphenylazo)naphthol (HL5) ligands have been synthesized. The composition of complexes and ligands (HL1–HL4) has been established by elemental analysis and spectral (FT–IR, UV–Vis, 1H NMR and EPR) methods. Molecular structures of copper complexes [Cu(L3)2] (3) and [Cu(L5)2] (5) were established by X-ray crystallography. These Copper(II) biphenylazo complexes exhibit a very good catalytic activity towards nitroaldol reaction of various aldehydes with nitromethane