Sensitized Photodecomposition
of Organic Bisphosphonates
By Singlet Oxygen
- Publication date
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Abstract
During efforts to stabilize metal oxide bound chromophores
for
photoelectrochemical applications, a novel photochemical reaction
has been discovered. In the reaction, the bisphosphonate functional
groups −C(PO<sub>3</sub>H<sub>2</sub>)<sub>2</sub>(OH) in the
metal complex [Ru(bpy)<sub>2</sub>(4,4′-(C(OH)(PO<sub>3</sub>H<sub>2</sub>)<sub>2</sub>bpy)]<sup>2+</sup> are converted into −COOH
and H<sub>3</sub>PO<sub>4</sub>. The reaction occurs by sensitized
formation of <sup>1</sup>O<sub>2</sub> by the lowest metal-to-ligand
charge transfer excited state(s) of [Ru(bpy)<sub>2</sub>(4,4′-(C(PO<sub>3</sub>H<sub>2</sub>)<sub>2</sub>(OH))<sub>2</sub>(bpy))]<sup>2+</sup>* followed by <sup>1</sup>O<sub>2</sub> oxidation of the bisphosphonate
substituent. A related reaction occurs for the bisphosphonate-based
drug, risedronic acid, in the presence of O<sub>2</sub>, light, and
a singlet oxygen sensitizer ([Ru(bpy)<sub>3</sub>]<sup>2+</sup> or
Rose Bengal)
