SYNTHESIS AND SOLUTION COMPLEXATION BEHAVIOR OF DIMERIC ZINC-SELECTIVE BIS(BENZIMIDAZOLE) DERIVATIVES

The synthesis of (4-tert-butylbenzyl)-2,2'-bis(benzimidazole)-4,4'- di carboxylic acid and its N-substituted analogues is reported, Complexat ion of the ligand by divalent Zn, Cu, Ni, Pb and Cd ions has been stud ied in methanolic solution by H-1 NMR, FT-IR and electrospray mass spe ctrometry. The ligand forms a dimeric neutral M(2)L(2) complex selecti vely with zinc, favoured by the two rigid tetrahedral binding sites cr eated by the cooperative ligation of two orthogonally disposed ligands . Overall binding affinities follow the sequence Zn > Cd approximate t o Ni > Pb > Cu and solution speciation has been defined by ESMS showin g non-selective formation of, for example, ML, MLH, M(2)L(2)X species with all ions but zinc, where the M(2)L(2) species was predominant.