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Issue 8, 2013
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A triangular prismatic hexanuclear iridium(III) complex bridged by flavin analogues showing reversible redox processes

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Abstract

[Ir6(μ-alloCl22−)3(Cp*)6(OH)3](PF6)3 (1) having 7,8-dichloroalloxazine dianion (alloCl22−) as bridging ligands was synthesized and characterized by X-ray crystallography, spectroscopic and electrochemical measurements. The alloxazine ligands showed unprecedented coordination modes to link the six Ir(III) centres. The complex exhibited remarkable stability and reversible six-electron redox processes at the bridging alloxazine ligands in organic solvents. The first reversible reduction process occurred on each of three alloxazine ligands in 1 to produce a three-electron-reduced species, [IrIII6Cp*6(μ-alloCl2˙3−)3(OH)3], and was observed as an apparent one-step reduction process at −0.65 V (vs. Fc0/+). The second reversible reduction process on each of the three alloxazine ligands in 1 was recorded at almost the same potential, −0.78 V (vs. Fc0/+), to afford the six-electron-reduced form, [IrIII6Cp*6(μ-alloCl24−)3(OH)3]3−. The radical anion of the alloxazine derivative was detected by EPR measurements at room temperature. After the six-electron reduction of 1 with cobaltocene, the backward oxidation processes of reduced forms with p-chloranil were traced by UV-Vis spectroscopy to confirm the recovery of the original spectrum of 1.

Graphical abstract: A triangular prismatic hexanuclear iridium(iii) complex bridged by flavin analogues showing reversible redox processes

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Publication details

The article was received on 23 Oct 2012, accepted on 27 Nov 2012 and first published on 28 Nov 2012


Article type: Paper
DOI: 10.1039/C2DT32535G
Citation: Dalton Trans., 2013,42, 2773-2778
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    A triangular prismatic hexanuclear iridium(III) complex bridged by flavin analogues showing reversible redox processes

    Y. Inui, M. Shiro, T. Kusukawa, S. Fukuzumi and T. Kojima, Dalton Trans., 2013, 42, 2773
    DOI: 10.1039/C2DT32535G

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