title: Different manifestations of enhanced π-acceptor ligation at every redox level of [Os(9-OP)L2]n, n = 2+, +, 0, - (9-OP-= 9-oxidophenalenone and L = bpy or pap).
abstract: The title complexes were isolated as structurally characterised compounds [OsII(9-OP)L2]ClO4, L = 2,2'-bipyridine (bpy) or 2-phenylazopyridine (pap), and were compared with ruthenium analogues. A reversible one-electron oxidation and up to three reduction processes were observed by voltammetry (CV, DPV) and spectroelectrochemistry (UV-vis-NIR, partially EPR). Supporting calculations (DFT, TD-DFT) were used to assess the oxidation state combinations of the different redox active ligands and of the metal, revealing the effects of Os versus Ru exchange and of bpy versus pap acceptor ligation. Several unexpected consequences of these variations were observed for members of the new osmium-containing redox series. Remarkably, the EPR results exhibit a clear dichotomy between the complex ion [OsIII(9-OP-)(bpy)2]2+and the radical species [OsII(9-OP˙)(pap)2]2+, which has not been similarly observed for the analogous [RuIII(9-OP-)L2]2+systems. This difference, unprecedented for 5dnsystems, is attributed to the superior stabilisation of the OsIIstate by the strongly π-accepting pap ligands. The reduced forms [OsII(9-OP-)(pap˙-)(pap)] and [OsII(9-OP-)(pap˙-)2]-exhibit strong inter-ligand interactions, leading to spin isomers and electron hopping.
authors: Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India. lahiri@chem.iitb.ac.in.
authors: Arijit Singha
authors: AS
authors: Hazari
authors: Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany. kaim@iac.uni-stuttgart.de.
authors: Alexa
authors: A
authors: Paretzki
authors: J. Heyrovský Institute of Physical Chemistry, v.v.i., Academy of Sciences of the Czech Republic, Dolejskova 3, CZ-18223 Prague, Czech Republic.
authors: Jan
authors: J
authors: Fiedler
authors: J. Heyrovský Institute of Physical Chemistry, v.v.i., Academy of Sciences of the Czech Republic, Dolejskova 3, CZ-18223 Prague, Czech Republic.
authors: Stanislav
authors: S
authors: Zalis
authors: Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany. kaim@iac.uni-stuttgart.de.
authors: Wolfgang
authors: W
authors: Kaim
authors: Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India. lahiri@chem.iitb.ac.in.
authors: Goutam Kumar
authors: GK
authors: Lahiri