Issue 30, 2014

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

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

Supplementary files

Article information

Article type
Paper
Submitted
01 Apr 2014
Accepted
23 May 2014
First published
23 May 2014

Dalton Trans., 2014,43, 11548-11556

Author version available

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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