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Issue 30, 2014
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Ligand-based photooxidations of dithiomaltolato complexes of Ru(II) and Zn(II): photolytic CH activation and evidence of singlet oxygen generation and quenching

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Abstract

The complex [Ru(bpy)2(ttma)]+ (bpy = 2,2′-bipyridine; ttma = 3-hydroxy-2-methyl-thiopyran-4-thionate, 1, has previously been shown to undergo an unusual C–H activation of the dithiomaltolato ligand upon outer-sphere oxidation. The reaction generated alcohol and aldehyde products 2 and 3 from C–H oxidation of the pendant methyl group. In this report, we demonstrate that the same products are formed upon photolysis of 1 in presence of mild oxidants such as methyl viologen, [Ru(NH3)6]3+ and [Co(NH3)5Cl]2+, which do not oxidize 1 in the dark. This reactivity is engendered only upon excitation into an absorption band attributed to the ttma ligand. Analogous experiments with the homoleptic Zn(ttma)2, 4, also result in reduction of electron acceptors upon excitation of the ttma absorption band. Complexes 1 and 4 exhibit short-lived visible fluorescence and long-lived near-infrared phosphorescence bands. Singlet oxygen is both generated and quenched during aerobic excitation of 1 or 4, but is not involved in the C–H activation process.

Graphical abstract: Ligand-based photooxidations of dithiomaltolato complexes of Ru(ii) and Zn(ii): photolytic CH activation and evidence of singlet oxygen generation and quenching

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Publication details

The article was received on 01 Apr 2014, accepted on 23 May 2014 and first published on 23 May 2014


Article type: Paper
DOI: 10.1039/C4DT00961D
Author version available: Download Author version (PDF)
Citation: Dalton Trans., 2014,43, 11548-11556
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    Ligand-based photooxidations of dithiomaltolato complexes of Ru(II) and Zn(II): photolytic CH activation and evidence of singlet oxygen generation and quenching

    B. Bruner, M. B. Walker, M. M. Ghimire, D. Zhang, M. Selke, K. K. Klausmeyer, M. A. Omary and P. J. Farmer, Dalton Trans., 2014, 43, 11548
    DOI: 10.1039/C4DT00961D

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