Bis(2,2′-bipyridine) (1,2 diimino-9,10-anthraquinone) ruthenium(II) derivatives:: A ZINDO analysis of a redox series involving coupled proton and electron transfers

The complex bis(2,2'-bipyridine)(1,2-diimino-9,10-anthraquinone)ruthenium(II) can be reduced or oxidized in protic or aprotic media generating various species. The first two reduced species in protic medium and the first two reduced species in aprotic medium were studied by electrochemistry, spectroelectrochemistry, and electronic, NMR, EPR, and infrared spectroscopy and identified as containing different redox/protonation states of the anthraquinone ligand. The ZINDO method was employed to assign electronic transitions and predict their energies; The extent of electronic coupling between the metal and ligand centers was deduced from the ZINDO analysis as a function of net oxidation state and proton complement.