Reaction of N, N-phenylenebis(salicyalideneiminato)cobalt(III) and l-cysteine in mixed aqueous medium: kinetics and mechanism

Abstract

The redox kinetics involving the reaction of N, N 0 -phenylenebis(salicyalideneiminato)cobalt(III) ([CoSalophen] þ ) and l-cysteine (LSH) was studied using pseudo-first order approach under the following conditions,The redox reaction was 1 st order in both [CoSalophen þ ] and [LSH], with the overall 2 nd order. Hydrogen ion concentration effect revealed the activeness of both the protonated and deprotonated form of the reductant, positive Brønsted-Debye salt effect and was also ion catalyzed. There was no evidence suggesting an intermediate complex of significant stability in the reaction. Free radical was detected to take part and as such the reasonable mechanistic pathway for the reaction is suggested to be outer-sphere, hence proposed.

Thermodynamics and Kinetic Investigation of Reaction of Acriflavine with L-cysteine in Aqueous Medium

“…The result of the stoichiometry is in the similitude of the previous report in the reduction of N,N 1 -phenylenebis(salicyalideneiminato)cobalt(III) by l-cysteine [ 18 ].…”

“…Excess methanol was introduced at the end of the reaction, and a separation funnel was used to separate the two layers (gelatinous and non-gelatinous layers) that were formed. Fourier Transform Infrared (FTIR) spectroscopic was run for the gelatinous layer, and the UV–Visible spectrum of the l-cysteine (CSH) treated with two drops of 5% hydrogen peroxide was compared with the spectrum of the non-gelatinous layer of the reaction product [ 2 , 18 ].…”

“…Its thiol group (–SH), thiolate ion (CS − ), and thiyl radical species (CS * ) are capable of initiating reduction reaction in acidic, aqueous, or buffer media [ 11 – 13 ]. The electron transfer reactions of l-cysteine have been investigated in a good number of researches such as reduction of trinuclear Mn(IV) species in which the rate was found to increase in aqua media [ 14 ], [Mn 4 O 6 ] 4+ core resulted in a significant decrease in the observed second-order rate constants in aqua media enriched with deuterium water and a proton-mixed single electron transfer reaction was proposed [ 15 ], 11-tungstophosphovanate(V) resulted in a first order with respect to [redox species] [ 16 ], Hexacyanoferrate(III) showed an increased reaction rate with increase in hydroxide ion concentration and the product was found to be sulfenic acid [ 17 ], and [CoSalophen] + complex established the importance of deprotonated and protonated form of l-cysteine in the electron transfer process [ 18 ]; in the view to gain more understanding of the character of enzymes containing thiol group in bio-systems.…”

A kinetic study and mechanisms of reduction of N, N′-phenylenebis(salicyalideneiminato)cobalt(III) by L-ascorbic acid in DMSO-water medium

“…Cobalt (II) chloride hexahydrate, salicyaldehyde, 1,2-phenylenediamine, chloroform, ethanol, H 2 O 2 , and diethyl ether were all obtained from Merck. The Schiff base, Bis (salicylidene)-1,2-phenylenediamine, (Salophen) and the complex, N,N′ -phenylene bis- (salicylideneiminato)cobalt (III), ([Co(Salophen)] + ) were synthesized and characterized according to earlier published report ( Pizzolato et al., 2013 ; Abdulsalam et al., 2020 ). The complex structure is revealed in Scheme 1 below.…”

“…So far, various kinetics and mechanisms of Salophen complexes of iron ( Ibrahim et al., 2019a , 2019b ; Subramaniam et al., 2014 ), cobalt ( Abdulsalam et al., 2020 ) and manganese ( Jena et al., 2018 ) have been recently reported. Herein, we report on the kinetic study and mechanisms of reduction of N, N′ -phenylene bis (salicyalideneiminato)cobalt (III) complex ([Co(Salophen)] + ) by H 2 A in a mixed aqueous medium.…”