10.1081/SIM-100002039
The research focuses on the synthesis and characterization of a linear pentadentate ligand, N-(2-hydroxyethyl)-N′′-(2-hydroxybenzyl)-diethylenetriamine (HL), and its zinc(II) complex. The study investigates the promoted hydrolysis of 4-nitrophenyl acetate (NA) by the zinc(II) complex. The ligand and its complex were synthesized using reagents like 2-chloroethanol, diethylenetriamine, and salicylaldehyde, and characterized using IR spectra, 1H NMR spectra, and elemental analyses. The protonation constants of HL and the stability constants of its Zn(II) complexation were determined through pH potentiometric titration at 25°C and I = 0.1 mol/L KNO3. The kinetics of NA hydrolysis catalyzed by the complex were studied spectrophotometrically at 25°C and I = 0.1 mol/L KNO3 in a CH3CN solvent, with the second-order rate constants (kc) for NA hydrolysis being obtained. The experiments involved the preparation of the ligand and its complex, pH titration to determine protonation and complexation equilibria, and kinetic studies to measure the rate of NA hydrolysis catalyzed by the complex.
10.1039/DT9820001825
The research investigates the kinetic template effect of copper(II) ions in the condensation reaction of salicylaldehydato-ion (sal) with diethylenetriamine (dien). The study aims to understand how copper(II) ions influence the reaction mechanism and kinetics, particularly in promoting first-order reactions within its coordination sphere. The key chemicals used include salicylaldehydato-ion, diethylenetriamine, copper(II) nitrate, and various solvents such as methanol and 1,2-dichloroethane. The researchers found that in the presence of copper(II), the reaction proceeds through a first-order kinetic process, forming a labile ternary complex where interligand condensation occurs. The study concludes that while copper(II) ions can reduce the reaction order, the activation energy for the template reaction is higher compared to the bimolecular condensation, indicating that the coordination of functional groups to the metal perturbs the optimal reaction geometry. This perturbation results in a less favorable entropy of activation for the template reaction, highlighting the limitations of metal ions in mimicking the efficiency of enzyme-catalyzed reactions.
10.1016/s0022-328x(97)00456-7
The study investigates the formation of dimeric and trimeric molybdenum(II) complexes containing 2-substituted 3-bonded butadienyl bridging ligands. The starting material used is [MoCI(CO)2(@-CH2(COCI)C=CH2)phen] (phen = 1,10-phenanthroline) (1). When 1 reacts with 1,2-ethanediol or N,N'-diethylethylenediamine in a 2:1 mole ratio, dimeric complexes [MoCI(CO)2(@-CH/(COACH2)C=CH2)phen]2 are formed, where A represents the substituent group (A = O for ester, A = NEt for amide). Reactions with hydroquinone or 1,4-phenylenediamine yield monomeric complexes [MoCI(CO)2(@-CH2(COA)C=CH2)phen], while dimeric complexes are isolated from reactions involving 4,4'-ethylenedianiline or p-xylylenediamine. Attempts to prepare a novel complex bridged by three linked amide substituted butadienyl groups using diethylenetriamine were unsuccessful. However, reaction of 1 with triethanolamine or tris(2-aminoethyl)amine in a 3:1 mole ratio gives trimeric complexes [MoCI(CO)2(~/a-CH2(COACH2CH2)C=CH2)phen]3 N (A = O, NH) in good yield. The study establishes conditions for the formation of these complexes and examines the boundaries of dimer and trimer formation using various bifunctional and trifunctional reagents.
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