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Please use this identifier to cite or link to this item: http://dspace.library.iitb.ac.in/jspui/handle/100/13896

Title: Bis(acetylacetonato)ruthenium Complexes of Noninnocent 1,2-Dioxolene Ligands: Qualitatively Different Bonding in Relation to Monoimino and Diimino Analogues
Authors: DAS, D
SARKAR, B
KUMBHAKAR, D
MONDAL, TK
MOBIN, SM
FIEDLER, J
URBANOS, FA
JIMENEZ-APARICIO, R
KAIM, W
LAHIRI, GK
Keywords: TRANSITION-METAL-COMPLEXES
DENSITY-FUNCTIONAL THEORY
DINUCLEAR RUTHENIUM COMPLEXES
NUCLEAR-MAGNETIC-RESONANCE
INDUCED ELECTRON-TRANSFER
CHARGE-DISTRIBUTION
SEMIQUINONE LIGANDS
QUINONE COMPLEXES
OXIDATION-STATE
PARAMAGNETIC RESONANCE
Issue Date: 2011
Publisher: WILEY-BLACKWELL
Citation: CHEMISTRY-A EUROPEAN JOURNAL,17(39)11030-11040
Abstract: Coordination compounds [Ru(acac)(2)(Q)] (acac = acetylacetonate; Q = o-benzoquinone) were prepared as complexes 1 (Q = o-benzoquinone), 2 (Q = 3-methoxy-o-benzoquinone), 3 (Q = 4-methyl-o-benzoquinone), and 4 (Q = 3,5-di-tert-butyl-o-benzoquinone). The structures of 1 and 2 were determined to reveal a Ru(III)/o-benzosemiquinone formulation, supported by analysis of experimental data (spectroscopy, magnetism of 1) and by DFT calculations. The S = 1 ground state calculated for 1 stands in contrast to the spin-paired analogues with arylimino-o-benzosemiquinonato and diimino-o-benzoquinone ligands. The close contacts of about 5.3 angstrom possible between semiquinone O atoms of different molecules in the crystal allow for intermolecular spin-spin interactions and an overall complex magnetic behavior. One quasireversible oxidation and two reversible one-electron reductions yielded the corresponding molecular ions, which were characterized by UV-visible-NIR and EPR spectroelectrochemistry in terms of [Ru(III)(acac)(2)(Q(0))](+), [Ru(III)(acac)(2)(Q(2-))](-), and [Ru(II)(acac)(2)(Q(2-))](2-) descriptions in agreement with DFT results. The use of acceptor-substituted 1,2-dioxolenes resulted in the isolation of ionic species Na[Ru(acac)(2)(Q)] (Na(5); Q = 4-chloro-o-benzoquinone) and Na(6) (Q = 4-nitro-o-benzoquinone), which were similarly investigated as compounds 1-4. Magnetic susceptibility and EPR results confirm an S = 1/2 ground state based on ruthenium(III). The combined studies reveal a remarkable substituent sensitivity, and in comparison to recently analyzed Ru(acac)(2) complexes with o-benzoquinone monoimine and diimine ligands, the all-O-donor-containing new systems are distinguished by a qualitatively different metal-ligand interaction based on closer intermolecular radical-radical contacts and on weaker intramolecular d pi-pi* interactions.
URI: http://dx.doi.org/10.1002/chem.201101009
http://dspace.library.iitb.ac.in/jspui/handle/100/13896
ISSN: 0947-6539
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