Evidence for Bidirectional Noninnocent Behavior of a Formazanate Ligand in Ruthenium Complexes Abhishek Mandal Brigitte Schwederski Jan Fiedler Wolfgang Kaim Goutam Kumar Lahiri 10.1021/acs.inorgchem.5b01408.s004 https://acs.figshare.com/articles/journal_contribution/Evidence_for_Bidirectional_Noninnocent_Behavior_of_a_Formazanate_Ligand_in_Ruthenium_Complexes/2202019 Redox series of the complexes [Ru­(L)­(L′)<sub>2</sub>]<sup><i>n</i></sup>, L = 1,5-diphenyl-3-(4-tolyl)-formazanate and L′ = 2,4-pentanedionate (acac<sup>–</sup>), 2,2′-bipyridine (bpy), or 2-phenylazopyridine (pap), were studied by cyclic and differential pulse voltammetry and by TD-DFT-supported spectroelectrochemistry (UV–vis–NIR, EPR). The precursors [Ru<sup>III</sup>(L<sup>–</sup>)­(acac<sup>–</sup>)<sub>2</sub>], [Ru<sup>II</sup>(L<sup>–</sup>)­(bpy)<sub>2</sub>]­ClO<sub>4</sub>, and [Ru<sup>II</sup>(L<sup>–</sup>)­(pap)<sub>2</sub>]­ClO<sub>4</sub> were identified in their indicated oxidation states by X-ray crystal structure determination. The six-membered formazanato-ruthenium chelate rings have an envelope conformation with puckering of the metal. DFT calculations indicate a pronounced sensitivity of the N–N bond lengths toward the ligand oxidation state. Several electrochemically accessible charge states were analyzed, and the derived oxidation numbers Ru<sup>II</sup>, Ru<sup>III</sup>, or Ru<sup>IV</sup>, L′ or (L′)<sup>•–</sup>, and L<sup>–</sup>, L<sup>•2–</sup>, or the new formazanyl ligand L<sup>•</sup> for the two-way noninnocent formazanate reflect the increasing acceptor effect of the ancillary ligands L′ in the series acac<sup>–</sup> < bpy < pap. 2015-08-17 00:00:00 EPR oxidation numbers RuII acac acceptor effect bpy UV Bidirectional Noninnocent Behavior oxidation states noninnocent formazanate Ruthenium ComplexesRedox series Formazanate Ligand Several electrochemically pap envelope conformation DFT calculations RuIII charge states pulse voltammetry ligand oxidation state