Influence of synthesis conditions on complexation of Cu (II) with O,N,O tridentate hydrazone ligand. X-ray diffraction and spectroscopic investigations

Abstract

Four novel Cu2+ coordination compounds with a (E)-N′-(2-hydroxybenzylidene)-2-phenylacetohydrazide (HBPAH, H2L) have been synthesized and characterized by single crystal X-ray diffraction method, IR, UV–Vis and EPR spectroscopy.In all obtained compounds the ligand is coordinated in typical O,N,O-tridentate chelate manner. It has been shown that synthesis conditions have a great influence on a structure of resulting complex compounds. Depending on starting Cu2+ compounds, concentration of reagents, pH and the presence of secondary ligands the HBPAH coordinates as a neutral molecule, mono- or dianion with formation of four different complexes: [Cu(HL)(H2L)]NO3 (I), [Cu(HL)Cl] (II), [Cu2(HL)2Cl2] (III) and [Cu2(L)2Py2] (IV). Complex I is interesting by the presence of two differently coordinated ligand molecules. Mononuclear complex compound II and its dimeric analogue III were obtained from the same reagents: CuCl2 and HBPAH but in different reaction conditions. In dimeric complex IV the HBPAH molecules are coordinated as dianions in imidol tautomeric form, the pyridine molecules act as secondary ligands complementing the coordination polyhedra of Cu2+ ions.Study of UV–Vis and EPR spectra of complex compounds I-IV in solutions showed that all the complexes undergo partial solvolysis upon dissolution.