resumo
The present report describes synthesis, characterization, crystal structures and catecholase activity of a series of five new manganese(III) complexes (1-5) derived from redox-noninnocent tetrabromocatecholate ligand in combination with different substituted pyridines. X-ray crystallography reveals that the geometry of manganese(III) centers in 1 and 2 is square pyramidal and they are pseudo-dimeric in the solid state resulting from the weak bonding of manganese(III) with a catecholate oxygen atom from the adjacent manganese(III) unit together with other weak interactions like hydrogen bonding and pi center dot center dot center dot pi stacking interactions. On the other hand, complexes 3-5 are discrete octahedral structures. All the complexes exhibit strong catecholase activity and their diverse catalytic activity can nicely be explained by the nature of substitution at pyridine ring - better electron donor inhibits the reduction of the metal center thereby lowering catecholase activity and vice versa (1 and 2 vs. 3-5). Besides the donor property of ancillary ligands, the structural distortion has also significant role in the biomimetic catalytic activity (1 vs. 2). (C) 2016 Elsevier Inc. All rights reserved.
palavras-chave
PHENOXAZINONE SYNTHASE ACTIVITY; INDUCED VALENCE TAUTOMERISM; CATECHOL OXIDASE ACTIVITY; MANGANESE(III) COMPLEXES; MULTIDENTATE LIGANDS; MIMICKING ACTIVITY; CRYSTAL-STRUCTURES; DINUCLEAR; OXIDATION; SERIES
categoria
Biochemistry & Molecular Biology; Chemistry
autores
Jana, NC; Brandao, P; Panja, A
nossos autores
Paula Cristina Ferreira da Silva Brandão
Investigador Auxiliaragradecimentos
A.P. would like to thank the Department of Science and Technology (DST), New Delhi, under FAST Track Scheme (Order No. SB/FT/CS-016/2012, dated 20/12/2013) for financial support.