Ruthenium arenes photoactivation

Alternatively, arene displacement can also be photo- rather than thermally-induced. In this respect, we studied the photoactivation of the dinuclear ruthenium-arene complex [ RuCl (rj6-indane) 2(p-2,3-dpp)]2+ (2,3-dpp, 2,3-bis(2-pyridyl)pyrazine) (21). The thermal reactivity of this compound is limited to the stepwise double aquation (which shows biexponential kinetics), but irradiation of the sample results in photoinduced loss of the arene. This photoactivation pathway produces ruthenium species that are more active than their ruthenium-arene precursors (Fig. 18). At the same time, free indane fluoresces 40 times more strongly than bound indane, opening up possibilities to use the arene as a fluorescent marker for imaging purposes. The photoactivation pathway is different from those previously discussed for photoactivated Pt(IV) diazido complexes, as it involves photosubstitution rather than photoreduction. Importantly, the photoactivation mechanism is independent of oxygen (see Section II on photoactivatable platinum drugs) (83). 

Fig. 18. The dinuclear complex [ RuCl(ri6-indane)>2(p-2,3-dpp)]2+ (21) can be photoactivated to yield highly reactive and potentially cytotoxic ruthenium species and the arene indane, which could be used as a fluorescent probe.

Magennis SW, Habtemariam A, Novakova O, Henry JB, Meier S, Parsons S, Oswald IDH, Brabec V, Sadler PJ (2007) Dual triggering of DNA binding and fluorescence via photoactivation of a dinuclear ruthenium(II) arene complex. Inorg Chem 46 5059-5068... 

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