title: Ancillary ligand control of electronic structure in o-benzoquinonediimine-ruthenium complex redox series: structures, electron paramagnetic resonance (EPR), and ultraviolet-visible-near-infrared (UV-vis-NIR) spectroelectrochemistry.
abstract: The compounds Ru(acac)2(Q) (1), [Ru(bpy)2(Q)](ClO4)2 ([2](ClO4)2), and [Ru(pap)2(Q)]PF6 ([3]PF6), containing Q = N,N'-diphenyl-o-benzoquinonediimine and donating 2,4-pentanedionate ligands (acac(-)), π-accepting 2,2(/)-bipyridine (bpy), or strongly π-accepting 2-phenylazopyridine (pap) were prepared and structurally identified. The electronic structures of the complexes and several accessible oxidized and reduced forms were studied experimentally (electrochemistry, magnetic resonance, ultraviolet-visible-near-infrared (UV-vis-NIR) spectroelectrochemistry) and computationally (DFT/TD-DFT) to reveal significantly variable electron transfer behavior and charge distribution. While the redox system 1(+)-1(-) prefers trivalent ruthenium with corresponding oxidation states Q(0)-Q(2-) of the noninnocent ligand, the series 2(2+)-2(0) and 3(2+)-3(-) retain Ru(II). The bpy and pap co-ligands are not only spectators but can also be reduced prior to a second reduction of Q. The present study with new experimental and computational evidence on the influence of co-ligands on the metal is complementary to a report on the substituent effects in o-quinonediimine ligands [Kalinina et al., Inorg. Chem. 2008, 47, 10110] and to the discussion of the most appropriate oxidation state formulation Ru(II)(Q(0)) or Ru(III)(Q(• -)).
authors: †Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
authors: Ankita
authors: A
authors: Das
authors: †Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
authors: Prabir
authors: P
authors: Ghosh
authors: ‡Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany.
authors: Sebastian
authors: S
authors: Plebst
authors: ‡Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany.
authors: Brigitte
authors: B
authors: Schwederski
authors: §Discipline of Chemistry, School of Basic Sciences, Indian Institute of Technology Indore, Indore 452017, India.
authors: Shaikh M
authors: SM
authors: Mobin
authors: ‡Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany.
authors: Wolfgang
authors: W
authors: Kaim
authors: †Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
authors: Goutam Kumar
authors: GK
authors: Lahiri