Photocleavage of the 1,3-dimethyluracil cyclobutane dimer sensitized by (1,10-phenanthroline)tricarbonylrhenium(I) chloride. Self inhibition by the monomer

The complex Re(o-phen)(CO)3Cl is used as a photolyase model. The phosphorescence of the complex is quenched by the 1,3-dimethyluracil cyclobutane dimer with kq=5.4×107 M−1 s−1. The quenching is accompanied by the cleavage of the dimer. However, this sensitized photolysis cannot be driven very far because the regenerated monomer quenches the triplet of the complex more efficiently (kq=1.2×109). The sensitized monomerization is thus limited by self inhibition.