Trans ligand influence in cobalt(III) Schiff base complexes: Electronic and steric effects on the kinetics of hydrolysis

2002 ◽  
Vol 34 (6) ◽  
pp. 387-393 ◽  
Author(s):  
Mehdi Amirnasr ◽  
Rasoul Vafazadeh
Keyword(s):  
Schiff Base ◽  
Schiff Base Complexes ◽  
Steric Effects ◽  
Kinetics Of Hydrolysis ◽  
Kinetics Of ◽  
Electronic And Steric Effects

Ring-opening copolymerization of epoxide and dianhydride in the presence of manganese(III) asymmetrical bis-Schiff base catalysts

2014 ◽  
Vol 92 (11) ◽  
pp. 1098-1105 ◽  
Author(s):  
Deng-Feng Liu ◽  
Lu-Qun Zhu ◽  
Jing Wu ◽  
Li-Ying Wu ◽  
Xing-Qiang Lü
Keyword(s):  
Schiff Base ◽  
Ring Opening ◽  
Monomer Conversion ◽  
Structure Design ◽  
Steric Effects ◽  
Chain Growth ◽  
Electronic Effects ◽  
Reaction Conditions ◽  
Base Catalysts ◽  
Electronic And Steric Effects

Based on a series of asymmetrical bis-Schiff base H2Ln (n = 1–4) ligands with different electronic and steric effects, a series of [Mn(Ln)Cl] complexes 1–4 are obtained and shown to be effective catalysts in ring-opening copolymerization of epoxides and dianhydrides. Through the structure design, the input of electron-withdrawing bromine substituent para to the phenoxide group of the complexes is considerately beneficial to the improved activities. Moreover, steric and electronic effects of the suitable MeO substituent at the ortho orientation on the phenoxide group may both play a role in the formation of alternating ring-opening copolymers under the identical reaction conditions. In three cocatalysts tested, n-Bu4NBr is positive to monomer conversion and chain growth of polymer.

Synthèse et étude du réarrangement des diazoles-1,3: alkyl-1 alkylthio-2 (allylthio, arylthio, cycloalkylthio) imidazoles. Partie II. Réarrangement et réactions parasites

1979 ◽  
Vol 57 (7) ◽  
pp. 822-830 ◽  
Author(s):  
Jacky Kister ◽  
Georges Assef ◽  
Gilbert Mille ◽  
Jacques Metzger
Keyword(s):  
Structural Effect ◽  
Steric Effects ◽  
Steric Interactions ◽  
Ortho Effect ◽  
Rearrangement Reaction ◽  
Kinetics Of ◽  
Electronic And Steric Effects

The kinetics of the [Formula: see text] rearrangement reaction for a series of 1-alkyl-2-alkylthio (or allylthio, arylthio, cycloalkylthio) imidazoles has been studied at various temperatures. The rearrangement and hydrolysis results have been compared with those of 1-alkyl-2-methylthio-Δ-2-imidazolines and 1-alkyl-2-methylthio-Δ-2-tetrahydropyrimidines. Electronic and steric effects are discussed and a parallel between pKa and rearrangement is proposed. The limit of this parallel is either a structural effect such as direct (ortho effect) or indirect (cycle deformation) steric interactions or geometric modifications of the heterocycles studied (five- or six-membered cycles). All these results permitted the coherent choice of the amplification compound of a nonconventional photographic process.

scholarly journals Kinetics and Mechanism of Catalyzed Oxidation of L-Cysteine by Salen Schiff Base Complexes of Co(III), Fe (III) and Cr(III)

2021 ◽  
Vol 13 (2) ◽  
pp. 25
Author(s):  
Hamzeh M. Abdel-Halim ◽  
Hutaf M. Baker ◽  
Akef I. Alhmaideen ◽  
Adnan S. Abu-Surrah
Keyword(s):  
Schiff Base ◽  
Metal Ion ◽  
Reduction Potential ◽  
Order Conditions ◽  
Schiff Base Complexes ◽  
Kinetics Of Oxidation ◽  
First Order ◽  
Constant Ph ◽  
Kinetics Of ◽  
Catalyzed Oxidation

Kinetics of oxidation of L-cysteine by new series of substituted ONNO-donor salen-type Schiff base complexes of general formula [MIII(L)Cl] (M = Co, Fe, Cr; L = Schiff base ligand) have been studied in aqueous solutions. Measurements were run at constant temperature (25º C), constant ionic strength (0.20 M), and constant pH (7.0) under pseudo-first order conditions, in which the concentration of cysteine is around two orders of magnitude greater than that of metal complex. The observed rate constant was determined by following the change in absorbance of reaction mixture at a predetermined wavelength with time. Results show that the rate of oxidation depends on the type of metal center, with Co(III) complexes were found to have the highest rates due to higher reduction potential of Co(III). The oxidation rate was also found to depend on steric factor and the electron withdrawing / releasing ability of the ligand bound to the metal ion.

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