Synthesis, Spectroscopic Characterization and Potentiometric Studies of a Tetradentate [N2O2] Schiff Base, N,N'-bis(2-hydroxybenzylidene)-1,1-diaminoethane and Its Co(II),Ni(II),Cu(II) and Zn(II) Complexes.

The new complexes [M(BHBDAE)(H2O)2] (Co(II), Ni(II), Cu(II) and Zn(II); BHBDAE: N,N'-bis(2–hydroxybenzylidene)–1,1–diaminoethane) have been synthesized and characterized by IR, EPR, 1H NMR, magnetic moment as well as electronic spectroscopy data. The stepwise formation of the complexes has been established in the pH region studied. The results show the formation of 1:1 complexes with amino acids. Protonation constants of Schiff base (H2BHBDAE) and stability constants of their binary Co(II), Ni(II), Cu(II) and Zn(II) complexes have been determined potentiometrically in 50% DMSO–water media at 37°C and ionic strength 0.10 mol dm−3 sodium nitrate. The concentration distribution of the complexes in solution was evaluated.