abstract
Three new azide-bound cobalt(iii) complexes, [Co(HL1)(N-3)(4)] (1), [Co(L-2)(N-3)(3)] (2) and [Co(L-3)(N-3)(3)] (3), where L-1, L(2)and L(3)areN,N-dimethyldipropylenetriamine,N-1-isopropyldiethylenetriamine andN,N-diethyldiethylenetriamine, respectively, were synthesized and structurally characterised. X-ray crystallographic studies reveal that the structures of both2and3are very similar in which three terminal azide ions together with a triamine coordinate the metal centre. Complex1on the other hand is significantly different from the other two as the metal centre in1is bonded with four terminal azide ions and two donor sites of triamine L-1, leaving the tertiary amine group protonated. All the complexes are stabilized by rich hydrogen bonding interactions, leading to hydrogen bonded supramolecular chain structures. It is worth noting that complex1is the first example in cobalt(iii) coordination chemistry in which all four azide ions coordinate the metal centre terminally. All these compounds exhibited efficient catalytic activity towards the oxidative coupling ofo-aminophenols to phenoxazinone chromophores under aerobic conditions and the role of the structural factors in the catalytic activity has been explored. A mass spectrometry study was carried out to identify the products and important reactive intermediates and to support the mechanistic proposal.
keywords
CATECHOL OXIDASE ACTIVITY; PHENOXAZINONE SYNTHASE; SCHIFF-BASE; COORDINATION CHEMISTRY; STREPTOMYCES-CHRYSOMALLUS; FUNCTIONAL-MODEL; DFT CALCULATIONS; OXIDATION; LIGANDS; 2-AMINOPHENOL
subject category
Chemistry
authors
Jana, NC; Brandao, P; Panja, A
our authors
Paula Cristina Ferreira da Silva Brandão
Assistant Researcheracknowledgements
A. P. gratefully acknowledges the financial support of this work by the Government of West Bengal through the Department of Science & Technology and Biotechnology, Kolkata, India (Sanction No. 331/ST/P/S&T/15G-8/2018, dated-19.06.2019).