Spectroscopic and pH-metric studies on the complexation of a novel tripodal amine-phenol ligand towards Al(III), Ga(III) and In(III)

The aqueous coordination chemistry of a newly synthesized tripodal amine-phenol ligand, cis,cis-1,3,5-tris{(2-hydroxybenzyl)aminomethyl}cyclohexane (THAC) towards H+, Al3+, Ga3+ and In3+ ions have been investigated in aqueous medium of 0.1 M KCI ionic strength and 25 +/- 1 degrees C by potentiometric and spectrophotometric methods. Three protonation constants assigned to phenolic hydroxyl groups were determined and were used as input data to evaluate the formation constants of the metal complexes. The ligand formed various monomeric metal complex species MLH3, MLH2, MLH, ML and MLH-1 with Ga(III) and In(III); MLH3, ML and MLH-1 with Al(III). The calculated stability constants followed the order Ga(III)> In(III)>Al(III), and their pM values at physiological condition were found to be higher than the corresponding transferrin complexes. (C) 2012 Elsevier B.V. All rights reserved.