UV-vis-NIR and EPR characterisation of the redox series [MQ3]2+,+,0,−,2−, M = Ru or Os, and Q = o-quinone derivative

0379014 - ÚFCH JH 2013 RIV GB eng J - Journal Article
Das, A. K. - Hübner, R. - Sarkar, B. - Fiedler, Jan - Záliš, Stanislav - Lahiri, G. K. - Kaim, W.
UV-vis-NIR and EPR characterisation of the redox series [MQ3]2+,+,0,−,2−, M = Ru or Os, and Q = o-quinone derivative.
Dalton Transactions. Roč. 41, č. 29 (2012), s. 8913-8921. ISSN 1477-9226. E-ISSN 1477-9234
R&D Projects: GA MŠMT LD11086
Institutional support: RVO:61388955
Keywords : physical chemistry * EPR spectroscopy * UV-vis-NIR
Subject RIV: CF - Physical ; Theoretical Chemistry
Impact factor: 3.806, year: 2012

The neutral title compounds with Q = 3,5-di-tert-butyl-o-quinone or 4,6-di-tert-butyl-N-phenyl-o-iminobenzoquinone (Qx) were studied by UV-vis-NIR spectroelectrochemistry and by EPR spectroscopy in the case of the odd-electron monocation and monoanion intermediates. Supported by DFT and TD-DFT calculations, the results indicate stepwise electron removal from predominantly ligand-based delocalised MOs on oxidation whereas the stepwise electron uptake on reduction involves unoccupied MOs with considerably metal–ligand mixed character. In both cases, the strong near-infrared absorption of the neutral precursors diminishes. In comparison to the ruthenium series, the osmium analogues exhibit larger transition energies from enhanced MO splitting and a different EPR response due to the higher spin–orbit coupling. The main difference between the quinone (1n, 2n) and corresponding monoiminoquinone systems (3n, 4n) is the shift of about 0.6 V to lower potentials for the monoimino analogues. While the absorption features do not differ markedly, the EPR data reflect a higher degree of covalent bonding for the complexes with monoimino ligands.
Permanent Link: http://hdl.handle.net/11104/0210301