abstract
This report describes the syntheses and structural characterizations of four new cobalt(III) compounds (1-4) derived from a tetradentate Schiff base ligand and their catalytic oxidation of different o-aminophenols in aerobic condition. X-ray crystal structural studies reveal that both pseudohalide ions and solvents used for the syntheses have significant influence on the structural diversity in these systems. All these compounds show the diverse catalytic activity towards the aerial oxidation of different o-aminophenols. As expected, the substitutionally labile coordination sites available for substrate binding is responsible for significantly higher catalytic activity of 1 and 2 then others. Literature reports reveal that although significant attention has been made to the catalytic oxidation of some substituted o-aminophenols in terms of the isolations and characterizations of their oxidised products with the native enzyme and its models, but the detailed kinetic studies were not available in the literature. Herein, we have examined the detailed kinetic studies of the aerobic oxidation of two substituted o-aminophenols, namely 2-amino-5-methylphenol and 2-amino-4-methylphenol, using 1 and 2 as catalysts. ESI mass spectrometry provides significant information to get insight into the mechanistic details and further disclose that the methyl substation in aromatic ring does not inhibit formation of the complex-substrate aggregate but it resulted the phenoxazine chromophore instead of phenoxazinone chormophore.
keywords
PHENOXAZINONE SYNTHASE; COORDINATION CHEMISTRY; CATECHOL OXIDASE; ANTIMICROBIAL ACTIVITY; MULTIDENTATE LIGANDS; OXIDATION; MIMICKING; MECHANISM; DIOXYGEN; BINDING
subject category
Chemistry
authors
Jana, NC; Patra, M; Brandao, P; Panja, A
our authors
Paula Cristina Ferreira da Silva Brandão
Assistant Researcheracknowledgements
A.P. also gratefully acknowledges the financial support of this work by the University Grant Commission, India (Sanction no. F. PSW-229/15-16(REO)). Panskura Banamali College acknowledges the grants received from Department of Science and Technology (DST), Govt. of India through FIST program (SR-FIST-Col/295 dated 18/11/2015). The authors thank Jadavpur University, Kolkata, India, for providing the Mass spectrometry facility.