Electronic Structure and Spectra of Linkage Isomers of Bis(bipyridine)(1,2-dihydroxy-9,10-anthraquinonato)ruthenium(II) and Their Redox Series

Linkage isomers of bis(bipyridine)(1,2-dihydroxy-9,10-anthraquinonato)ruthenium(II), 1,2- and 1,9-coordinated
complexes, and several of their oxidation products have been prepared chemically and/or electrochemically. For
the 1,2-coordinated complex, the one- and two-electron oxidized species have been characterized, and for the
1,9-coordinated complex, the one-electron oxidized species has been characterized. The rich redox activity of
these complexes leads to ambiguity in assessing the electronic structure. This paper reports EPR spectra of odd-electron species and detailed analyses of electronic spectra and structure of the complexes, based on INDO
molecular orbital calculations. Results of calculations on the related 1-hydroxyanthraquinone complex and the free
ligands,1,2-dihydroxy-9,10-anthraquinone (alizarin) and 1-hydroxyanthraquinone, are also briefly discussed.