Synthesis, Structures and Catecholase Activity of a New Series of Dicopper(II) Complexes of Reduced Schiff Base Ligands

Abstract

A series of dinuclear Cu II complexes of reduced Schiff bases from substituted salicylaldehydes and amino acids have been synthesized and characterized. They are:cyclohexane-1-carboxylic acid; R = H and x = 1 (5), R = Cl and x = 2 (6), R = CH 3 and x = 2 (7)}, [Cu 2 (RSch12)

Structural, magnetic, electrochemical, catalytic, DNA binding and cleavage studies of new macrocyclic binuclear copper(II) complexes

“…The initial rate values for the binuclear copper(II) complexes 2a, 2b and 2c are 3.6 Â 10 À5 , 5.8 Â 10 À5 and 7.3 Â 10 À5 Ms À1 , respectively. The oxidation of catechol to o-quinone requires the presence of two metal ions in close proximity; hence, the initial rate values of binuclear complexes are comparatively high [44][45][46][47][48]. The catalytic activity of the complexes are found to increase as the macrocyclic ring size increases, because of the intrinsic flexibility of the ligand makes the metal ion to reduce easily and binds with the substrate and the same was supported by both spectral and electrochemical studies.…”

A dicopper complex with distant metal centers. Structure, magnetic properties, electrochemistry and catecholase activity

“…As can be seen from data in Table 3, in both solvent mixtures an increase in pH causes a slight improvement in catalyst performance, while a much more noticeable enhancement is observed when solvent is changed from MeCN/H 2 O to MeOH/ H 2 O; at pH 7.5 catalytic efficiency is 20 times better in the latter than in the former. The k cat /K M value obtained for this complex in MeOH/H 2 O pH=8.0 is better than most of the dinuclear copper complexes whose catecholase activity has been reported recently [20,21,25,27,43], suggesting the action of a mechanism that depends on other factors different from the Cu-Cu distance.…”

“…However, Yang et al [20] described the catecholase activity of a series of related phenoxo bridged dicopper complexes with Schiff base ligands derived from salicyladehyde and amino acids in which even though the Cu-Cu distance in all the complexes is very close to 3 Å , the catalytic activities vary almost 20-fold among the complexes with different amino acid moieties, suggesting the relevance of other structural factors besides Cu-Cu distance. In Sreenivasulu's work [21], eight different complexes with Cu-Cu distances between 2.99 Å and 3.06 Å exhibited very different catalytic activities.…”

Tetrameric Self-Assembly of a Cu(II) Complex Containing Schiff-Base Ligand and Its Unusually High Catecholase-like Activity

“…observed from Cu 4 L 4 is comparable to those with moderate to high catecholase activities. [8][9][10][11][12][13][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] It is noticeable that the four copper ions are non-coupled in Cu 4 L 4 whereas most model complexes with high catecholase activities are di-or tri-nuclear copper …”

“…[4][5][6][7] Numerous model compounds for this enzyme have been reported. 4,[8][9][10][11][12][13] All over these works, the effect of various structural factors on the catecholase activity has been analyzed, but up to now there are no concluding results that could recognize the structural features that enhance catalytic activity. One of the ways to understand the nature of the multicopper enzymes is the construction and characterization of model compounds.…”