Synthesis of new Cu(II)-chelating ligand amphiphiles and their esterolytic properties in cationic micelles

Abstract

Four new tetradentate 2,6-disubstituted pyridine and tridentate 2-substituted pyridine ligands were synthesized. Two of these compounds possessed a metal ion binding subunit in the form of a 2,6-disubstituted-4-N,N'-dimethylamine pyridine moiety. Cu²⁺-complexes of these ligands incorporated in cetyltrimethylammonium bromide (CTABr) micelles speeded the cleavage of p-nitrophenyldiphenyl phosphate and p-nitrophenyl hexanoate at pH 7.6. On the basis of a kinetic version of Job plot analysis, a 1:1 ligand/Cu²⁺ stoichiometry was found to be the most active species. In CTABr micelles, the pK_a values for the Cu²⁺-coordinated hydroxyl or pendant -CH₂OH in these ligands were between 7.8 and 7.9. The metallomicellar systems displayed catalytic (turnover) behavior in the presence of excess substrates.