Mononuclear species LnL and LnLH−1 based on 1,10-phenanthroline dibenzoimidazole derivatives as catalysts for hydrolysis of 2-hydroxypropyl-4-nitrophenyl phosphate (HPNP)

Abstract

Two novel multidentate ligands: 2,9-bis-½1 0 -ð2 00 -benzimidazolylÞ-2 0 -aza-n-propyl-1,10-phenanthroline(L 1 ) and 2,9-bis-½2 0 -ð2 00 -benzimidazolylÞ-3 0 -aza-n-butyl-1,10-phenanthroline(L 2 ) were synthesized and characterized by elemental analysis and 1 H-n.m.r. spectroscopy. Protonation of the ligands and the stability of complexes of the ligands with rare earth metal ions were investigated. The mononuclear metal complexes [Gd III and Sm III ] of the ligands were studied as catalysts for the transphosphorylation of the RNA-model substrate 2-hydroxypropyl-p-nitrophenylphosphate(HPNP). Kinetic studies show the second-order rate constants of HPNP hydrolysis catalyzed by complexes LnL and LnLH )1 , respectively. We found that both LnL and LnLH )1 have catalytic activity, but GdL 1 H )1 was the most efficient catalyst of them, which indicated that the structure of the ligands has obviously influence on the activity of corresponding complexes. A new mechanism was proposed for HPNP hydrolysis reaction catalyzed by LnL and LnLH )1 .