Remarkable reactivity of alkoxide/acetato-bridged binuclear copper(II) complex as artificial carboxylesterase

Abstract

Bromo-containing binuclear Schiff base copper(II) complex, CuL(OAc), with an alkoxo/acetato-bridged moiety was employed as a model of carboxylesterases to promote the hydrolytic cleavage of p-nitrophenyl picolinate (PNPP). Furthermore, the reactivity of a mononuclear complex (CuHL) was evaluated for comparing it with that of binuclear one. The results reveal that the as-prepared binuclear CuL(OAc) efficiently accelerated the hydrolysis of PNPP, giving rise to excess four orders of magnitude rate enhancement in contrast to the un-catalyzed reaction. CuL(OAc) represented an enzyme-like bell-shaped pH-responsive kinetic behavior. Moreover, the binuclear one is more reactive than its mononuclear analogue (CuHL) by two orders of magnitude. The total efficiency of CuL(OAc) is about 61-fold than that of its mononuclear analogue, CuHL. In addition, a contrast experiment reveals that binuclear CuL(OAc) displayed good activity in the hydrolysis of PNPP as well another active ester, i.e., S-2-benzothiazolyl 2-amino-alpha-(methoxyimino)-4-thiazolethiolacetate (AE-active ester). Noteworthyly, it was found that mononuclear one inspired more obvious rate enhancement in the hydrolysis of AE-active ester relative to PNPP hydrolysis. The estimated pK of bound water on the binuclear CuL(OAc) using second derivative method (SDM) is relatively smaller than that for CuHL by a gap of about 0.8 pK unit, which facilitates the hydrolysis of PNPP. Four orders of magnitude rate enhancement was observed for the catalytic hydrolysis of p-nitrophenyl picolinate (PNPP) by one μ-alkoxide/acetato-bridged binuclear copper(II) complex under physiological conditions. Substrate specificity of the resulting binuclear complexes was observed for the hydrolysis of PNPP and AE-active ester.

Catalytic Chemosensing Assay for Selective Detection of Methyl Parathion Organophosphate Pesticide

“…It should be noted that through the metal‐catalyzed hydrolysis, diazinon (aromatic phosphate ester) and 4‐nitrophenyl acetate (carboxylate ester) formed 2‐hydroxylate‐4‐methyl‐6‐isopropyl‐pyrimidine/ o , o ‐diethyl thiophosphate anion (DTP derivative) and 4‐nitrophenolate/acetate, respectively (Supporting Information Figure S4). Although Cu II complexes are well‐known to catalyze hydrolysis reactions, complex 1 represents the first Cu I ‐based bimetallic complex used to promote this Lewis acid catalytic transformation in both air and N 2 condition (Table ). The catalytic selectivity of 1 for methyl parathion is due to the formation of [ 1⋅ methyl parathion] intermediate via coordination between Cu I and the P=S moiety during the hydrolysis .…”

Designing the electronic and geometric structures of single-atom and nanocluster catalysts

“…Also, Jiang and co-workers have reported binuclear Cu 2 complexes as carboxylesterase mimics which employed an alkoxo/acetato-bridged moiety as a model to promote the hydrolytic cleavage of p-nitrophenyl picolinate. 105,106 Beloglazkina et al synthesised a mixed-valence Cu complex with a tridentate N 2 S type organic ligand as an N 2 O reductase mimic, where it is oen regarded as a mimic model for N 2 O reductase. 107 Generally, the geometric structures about the metalcontaining active sites can be readily elucidated by a combination of single-crystal XRD and spectroscopic techniques (NMR and electron paramagnetic resonance (EPR)).…”

Elucidating the Roles of Distinct Chemical Factors in the Hydrolytic Activities of Hetero- and Homonuclear Synthetic Analogues of Binuclear Metalloenzymes

“…In the last few decades, a wide range of binuclear metal complexes have been developed to catalyze diverse chemical reactions. − These complexes were largely inspired by the hetero- and homobinuclear metal centers of natural enzymes. − Despite the impressive advances made in the field, the ultimate goal of designing efficient enzyme mimics is still elusive. Currently, metal complexes exhibit much slower activities and lower turnover numbers in comparison to the natural enzymes.…”