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Issue 45, 2016
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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)

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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 5dn systems, is attributed to the superior stabilisation of the OsII state 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.

Graphical abstract: 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)

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Publication details

The article was received on 28 Sep 2016, accepted on 14 Oct 2016 and first published on 17 Oct 2016


Article type: Paper
DOI: 10.1039/C6DT03764J
Citation: Dalton Trans., 2016,45, 18241-18251
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    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)

    A. S. Hazari, A. Paretzki, J. Fiedler, S. Zalis, W. Kaim and G. K. Lahiri, Dalton Trans., 2016, 45, 18241
    DOI: 10.1039/C6DT03764J

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