Hydrolysis of p-nitrophenyl picolinate catalyzed by metal complexes of N-alkyl-3,5-bis(hydroxymethyl)-1,2,4-triazole in CTAB micelles

Abstract

Two lipophilic ligands containing triazole and hydroxyl groups, N-alkyl(C n H 2 n+1 )-3,5-bis(hydroxymethyl)-1,2,4-triazole ( n = 10 and 12), were synthesized. Effects of their Cu(II) and Ni(II) complexes on the hydrolysis of p-nitrophenyl picolinate (PNPP) in cetyltrimethylammonium bromide (CTAB) micelles have been investigated kinetically, and some kinetic parameters of the reactions were obtained by employing the ternary complex kinetic model for metallomicellar catalysis. It was found that Cu(II) complexes of these triazole-based ligands showed more effective catalytic activity on the hydrolysis of PNPP than Ni(II) complexes. Also, the apparent first-order rate constants for product formation in the metallomicellar phase ( k N ′ ), the association constants between the substrate and the binary complex ( K T ), and the association constants between the metal ion and the ligand ( K M ) increased with an increase in pH value, which may be attributed to an increase in the nucleophilicity of the hydroxyl groups in the ligand or the electrophilicity of the substrate at higher pH. In addition, at constant pH, k N ′ and K T increased with an increase in the hydrocarbon chain length of the ligand, while K M decreased.