Carboxy Ester Hydrolysis Promoted by Two New Bimetallic Macrocyclic Complexes. Synthesis, Characterization and Catalytic Activity

Abstract

A dinuclear macrocyclic ligand containing [12]aneN 3 and its two transition metal complexes, [Zn 2 L(OAc) 2 ](ClO 4 ) 2 (1) and [Cu 2 L(OAc) 2 ](ClO 4 ) 2 (2) have been synthesized and characterized on the basis of elemental analyses, molar conductivities, 1 H-n.m.r, IR spectra, electronic spectra and thermal analysis. In addition, the studies on the hydrolysis of a caboxy ester, 4-nitrophenyl acetate (NA), promoted by the two complexes were also investigated. The experimental results indicated that the two complexes can efficiently catalyze hydrolysis of NA, and the k NA for complexes (1) and (2) at pH 7.25, 25°C, were calculated to be 4.46 Â 10 )2 and 4.21 Â 10 )2 M )1 s )1 , respectively, which are better than those of the corresponding mononuclear complex in the same conditions.

SYNTHESIS, CHARACTERIZATION, THEORETICAL AND BIOLOGICAL STUDIES OF A NEW MACROCYCLE SCHIFF BASE WHITH Co(II), Ni(II), Cu(II) AND Zn(II) COMPLEXES

“…[1][2][3][4] A large number of Schiff bases and their complexes have been studied because of their interesting and important properties such as their ability to reversibly bind to oxygen, 5 being anti-bactericide, and fungicide agents, 6,7 and also their application in oxidation reactions of organic compounds. 8,9 These multiple roles played by the naturally occurring macrocycle in biological systems is well known. The chemistry of synthetic macrocycle compounds is also of great importance due to their use as pigments and dyes, MRI contrast agents and models for naturally occurring macrocycles.…”

Coordination behaviour and biopotency of metal NN salen complexes

“…Recently some of these issues have been addressed by employing Schiff bases in oxidation, asymmetric catalysis and epoxidation processes. [7][8][9] The interaction of metal ions with Schiff bases becomes a subject worthy of pursuit and has demonstrated great promise for their extensive applications in catalytic activity in chemical and enzymatic reactions; [10][11][12][13][14] in addition, the use of the metal complexes as therapeutics has become one of the central issues over the last few years. This has given urgency to research to develop a variety of interesting compounds as drugs used in many fields, this is related to the presence of a variety of donor atoms in the system which can interact with metal ions in many different ways and generate novel compounds with a specific design; along these lines, the conjugation between metal ions and biologically active compounds can potentially enhance their biological and biomedical activities.…”

Synthesis and characterization of a new asymmetric dinucleating ligand and its dinuclear nickel(II) complex with (μ–η2)2 phosphate ester bridge

“…Interestingly, Ni(II)-substituted phosphotriesterase has higher specific activity than that of the native Zn(II) enzyme, while the Cu(II)-substituted enzyme has similar activity to the native one [5]. Although different coordination environments are found for the two metal centers in many dinuclear metalloenzymes, a large number of the enzyme mimics reported so far are based on symmetric dinucleating ligands [6][7][8][9][10][11][12][13]. These ligands generally result in the formation of dinuclear complexes with identical coordination geometries for the two metal centers.…”