title: Evidence for Bidirectional Noninnocent Behavior of a Formazanate Ligand in Ruthenium Complexes.
abstract: Redox series of the complexes [Ru(L)(L')2](n), L = 1,5-diphenyl-3-(4-tolyl)-formazanate and L' = 2,4-pentanedionate (acac(-)), 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(III)(L(-))(acac(-))2], [Ru(II)(L(-))(bpy)2]ClO4, and [Ru(II)(L(-))(pap)2]ClO4 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(II), Ru(III), or Ru(IV), L' or (L')(•-), and L(-), L(•2-), or the new formazanyl ligand L(•) for the two-way noninnocent formazanate reflect the increasing acceptor effect of the ancillary ligands L' in the series acac(-) < bpy < pap.
authors.affiliation: †Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai-400076, India.
authors.forename: Abhishek
authors.initials: A
authors.lastname: Mandal
authors.affiliation: ‡Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany.
authors.forename: Brigitte
authors.initials: B
authors.lastname: Schwederski
authors.affiliation: §J. Heyrovský Institute of Physical Chemistry, v.v.i., Academy of Sciences of the Czech Republic, Dolejškova 3, CZ-18223 Prague, Czech Republic.
authors.forename: Jan
authors.initials: J
authors.lastname: Fiedler
authors.affiliation: ‡Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Kaim
authors.affiliation: †Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai-400076, India.
authors.forename: Goutam Kumar
authors.initials: GK
authors.lastname: Lahiri