Reaction of N, N ¹ -phenylene bis(salicyalideneiminato)cobalt(III) and l-cysteine in mixed aqueous medium: kinetics and mechanism

Abstract

The redox kinetics involving the reaction of N, N′-phenylene bis(salicyalideneiminato)cobalt(III) ([CoSalophen] ⁺) and l-cysteine (LSH) was studied using pseudo-first order approach under the following conditions, [H ⁺] = 1.0 × 10 ⁻³ mol/dm ³, μ = 0.1 C ² mol/dm ³ (NaCl), λ _max = 470 nm and T = 27 ± 1 °C in DMSO: H ₂O; 1:4 v: v medium. The redox reaction was 1 ^st order in both [CoSalophen ⁺] 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.

Abstract

Inorganic chemistry; Kinetics; Mechanisms; N,N′-phenylenebis(salicyalideneiminato)cobalt(III); l-Cysteine; Mixed aqueous medium