Synthesis, characterization and stability constants of polynuclear metal complexes

Unsymmetric tridentate ligands, 4-methyl-2,6-di(4-methyliminomethyl)phenol (HL1), 4-(t-butyl)-2,6-di(4-methylphenyliminomethyl)phenol (HL2), 2,6-di(4-bromophenyliminomethyl)-4-methylphenol (HL3), 2,6-di( 4-bromophenyliminomethyl)4-(t-butyl) phenol (HL4), 2,6-di( 4-hydroxyphenyliminomethyl)-4-methylphenol (HL5) and 4-(t-butyl)2,6-di(4-hydroxyphenyliminomethyl) phenol (HL6), and their binuclear Cu-II, Co-II and Ni-II complexes were synthesized and characterized by elemental analysis, FT-IR, u.v.-vis spectrometry magnetic moments, H-1(C-13)-n.m.r. and mass spectral data. Also, the electrical conductivities of the complexes have been measured using 10(-3) M solutions in MeCN. The complexes are weak electrolytes. In the electronic spectra of the complexes of the HL1-HL6 ligands, the 480-410 nm band has been determined as the charge-transfer band. While the HL5 and HL6 ligands have five potential donor atoms, other ligands have only three. Protonation constants of the ligands have been studied in dioxan-water mixtures. In addition, the antimicrobial properties of the ligands and their metal complexes have been studied: Bacillus megaterium, Micrococcus luteus, Corynebavterium xenosis, Enterococcus faecalis, bacteria and Saccoramyces cerevisia, yeast. The keto-enol tautomeric equilibria of the ligands have been investigated in polar and non-polar solvents.