NDLI: Exclusive selectivity of multidentate ligands independent on the oxidation state of cobalt: influence of steric hindrance on dioxygen binding and phenoxazinone synthase activity

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Panja, Anangamohan
Description	Author Affiliation: Panja A ( Postgraduate Department of Chemistry, Panskura Banamali College, Panskura RS, Purba Medinipur, West Bengal 721 152, India. ampanja@yahoo.co.in.)
Abstract	The present report describes the syntheses, characterizations, crystal structures and study of the phenoxazinone synthase activity of two peroxo-bridged dicobalt(III) complexes, $[Co_{2}(L^{1})_{2}(μ-O_{2})](ClO_{4})_{4}·2CH_{3}CN$ (1) and $[Co_{2}(L^{2})_{2}(μ-O_{2})](ClO_{4})_{4}$ (2), and three mononuclear cobalt(II) complexes, $[Co(L^{3})(CH_{3}CN)](ClO_{4})_{2}$ (3), $[Co(L^{4})(H_{2}O)](ClO_{4})_{2}$ (4) and $[Co(L^{5})(H_{2}O)](ClO_{4})_{2}$ (5), derived from the pentadentate ligands $L^{1}–L^{5},$ which are the 1:2 condensation products of triamines and 2-acetylpyridine or 2-pyridinecarboxaldehyde (6-methyl-2-pyridinecarboxaldehyde). X-ray crystallography reveals exclusive selectivity of the acyclic Schiff dibasic form of the ligands over the heterocyclic analogues, and this selectivity is found to be insensitive to the oxidation state of cobalt. Other first row transition metals have been characterized in either form of the ligands in their complexes but it is specific for cobalt established in the present study. The pronounced effect of the methyl substitutions is observed from their crystal structures; substitution at imine-C does not have any significant influence on the peroxo-bridging but substitution at sixth position of pyridyl ring prevents the formation of peroxo-bridging, and both the steric and electronic factors play vital roles on such chemical diversity. All the complexes show the phenoxazinone synthase mimicking activity and the comparative catalytic activity has been explored. Although electrochemical behaviors of all the complexes are very similar, their relative catalytic activity mimicking the function of phenoxazinone synthase arises from the electronic and steric factors of the methyl substitution.
ISSN	14779226
Issue Number	21
Volume Number	43
e-ISSN	13645447
Journal	Dalton Trans.
Language	English
Publisher	Royal Society of Chemistry
Publisher Date	2014-06-07
Publisher Place	Great Britain (UK)
Access Restriction	Subscribed
Subject Keyword	Cobalt Chemistry Coordination Complexes Oxazines Chemical Synthesis Oxidoreductases Oxygen Crystallography, X-Ray Ligands Models, Molecular Oxidation-Reduction Pyridines Journal Article Research Support, Non-U.S. Gov't
Content Type	Text
Resource Type	Article
Subject	Inorganic Chemistry

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