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Please use this identifier to cite or link to this item: http://dspace.library.iitb.ac.in/jspui/handle/100/13854

Title: Oxidation State Analysis of a Four-Component Redox Series [Os(pap)(2)(Q)](n) Involving Two Different Non-Innocent Ligands on a Redox-Active Transition Metal
Authors: DAS, D
SARKAR, B
MONDAL, TK
MOBIN, SM
FIEDLER, J
KAIM, W
LAHIRI, GK
Keywords: DENSITY-FUNCTIONAL THEORY
ELECTRONIC-STRUCTURE
RADICAL COMPLEXES
2-(ARYLAZO)PYRIDINE COMPLEXES
EXCITATION-ENERGIES
RUTHENIUM
EPR
CHEMISTRY
OSMIUM
MOLECULES
Issue Date: 2011
Publisher: AMER CHEMICAL SOC
Citation: INORGANIC CHEMISTRY,50(15)7090-7098
Abstract: Complexes [Os(pap)(2)(Q)] (1-4) have been obtained and structurally characterized for pap = 2-phenylazopyridine and Q = 4,6-di-tert-butyl-N-aryl-o-iminobenzoquinone (aryl = phenyl (1), 3,5-dichlorophenyl (2), 3,5-dimethoxyphenyl (3), or 3,5-di-tert-butylphenyl (4)). The oxidized form (3)(ClO(4))(2) was also crystallographically characterized while the odd-electron intermediates [Os(pap)(2)(Q)](+) (1(+)-4+) and [Os(pap)(2)(Q)](-) (2(-)) were investigated by electron paramagnetic resonance (EPR) and UV-vis-NIR spectroelectrochemistry in conjunction with density functional theory (DFT) spin density and time-dependent DFT (TD-DFT) calculations. The results from the structural, spectroscopic, and electrochemical experiments and from the computational studies allow for the assignments [Os(II)(pap(0))(2)(Q(0))](2+), [Os(II)(pap(0))(2)(Q(center dot-))](+), [Os(IV)(pap(center dot-))(2)(Q(2-))], and [Os(II)(pap(center dot-))(pap(0))(Q(2-))](-), with comproportionation constants K(c) approximate to 10(3.5), 10(10), 10(18), and 10(5), respectively. The redox potentials and the comproportionation constants exhibit similarities and differences between Ru and Os analogues. While the Q:based redox reactions show identical potentials, the more metal-involving processes exhibit cathodic shifts for the osmium systems, leading to distinctly different comproportionation constants for some intermediates, especially to a stabilization of the neutral osmium compounds described in this article. The example [Os(pap)(2)(Q)]" illustrates especially the power of combined structural and EPR analysis with support from DFT towards the valence state description of transition metal complexes incorporating redox non-innocent ligands.
URI: http://dx.doi.org/10.1021/ic200615s
http://dspace.library.iitb.ac.in/jspui/handle/100/13854
ISSN: 0020-1669
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