Chelation activity of N'1,N'6-bis((E)-3,4-dihydroxybenzylidene)adipohydrazide towards some transition metal ions

Abstract

New chelating agent, N'₁,N'₆-bis((E)-3,4-dihydroxybenzylidene)adipohydrazide (DBAH) was synthesized and its crystal structure was analyzed by X-ray single crystal diffractometer. Homometallic complexes of Zr(IV), Co(II), Ni(II), Cu(II), Cd(II) and heterometallic complex of Co(II)/Zn(II) or Co(II)/Zn(II)/Cd(II) have been synthesized and characterized by spectroscopic and physicochemical methods. The data confirms the formation of bi- and tetra-metallic complexes. The ligand behaves as a neutral tetradentate in the Co(II) and Ni(II) complexes; tetranegative tetradentate in Zr(IV) and Cd(II) complexes and binegative octadentate in [Co₂Zn₂(DBAH)Cl₆] and [Co₂ZnCd(DBAH-4H)(H₂O)₄Cl₄].H₂O. A tetrahedral structure was proposed for the Ni(II), Zr(IV) and Co(II)/Zn(II) complexes; square-planar for the Cu(II) complex and octahedral geometry for the Co(II) complex. The ESR spectrum confirms the proposed structure of the Cu(II) complex. The thermal analyses confirm the stability of these complexes in the range 275-418 °C. The molecular modeling of [Co₂Zn₂(DBAH)Cl₈] was drawn and its parameters were calculated.