Crystalline Thymine Dimers Splitting by an Interfacial Photomechanochemical Single Electron Transfer Chain Reaction

Splitting of the cis, syn thymine dimer (TD) into thymine (T) can be achieved in the solid state via an interfacial SET photomechanochemical reaction with N,N,N,N-tetramethyl-1,4-phenylenediamine (TMPD) as the photochemical reductant. Mechanical grinding enabled the uniform deposition of the TMPD sensitizer on the dimer surface, and photoirradiation of this solid-solid mixture (TD+TMPD) triggered electron transfer at the solid-solid interface that was propagated into the bulk of the crystal as a chain reaction. Variables explored included sensitizer loading and preparation strategies that included solid-solid mixing and the deposition of the photosensitizer onto the TD surface from solution. Clean solid-to-solid transformations were observed with product yields as high as ∼95%.