Photochemistry and DNA photocleavage by a new unsupported dirhodium(II,II) complex.
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abstract
The new complex [Rh2(phen)2(CH3CN)6](BF4)4 (1) was synthesized and characterized in solution and its crystal structure was determined. Irradiation of 1 with visible light (irr>590nm) in water results in the release of two equatorial CH3CN ligands, CH3CNeq, as well as in the formation of mononuclear radical Rh(II) fragments stemming from the homolytic photocleavage of the metal-metal bond. The photoproducts, identified by electrospray ionization mass spectrometry, include [Rh(phen)(CH3CN)(OH)](+) and [Rh(phen)(CH3CN)(H2O)3(BF4)](+). The quantum yield for the photochemical transformation of 1 in H2O exceeds unity (550nm=1.38) indicative of dark reactions following the initial photoprocess. DNA photocleavage was observed for 1 (irr>590nm), whereas the complex is unreactive in the dark. This feature makes 1 a promising photodynamic therapy agent that does not operate via the production of singlet oxygen, 1O2.