2'-Methoxyacetophenone: An Efficient Photosensitizer for Cyclobutane Pyrimidine Dimer Formation.

Stationary and time-resolved experiments show that 2'-methoxyacetophenone (2-M) is an interesting compound for the investigation of triplet states in thymine samples. Time-resolved emission experiments show that the fluorescence lifetime of 2-M is 660 ps. A similar time constant of 680 ps is found in transient IR experiments. The data indicate efficient intersystem crossing (≈97%) from the fluorescent singlet state to the triplet state. The lifetime of the triplet state of 2-M dissolved in D2O at room temperature and ambient oxygen concentration is 400 ns. 2-M has a strong absorption in the UV-A range and can photosensitize the triplet state of a thymidine dinucleotide with light at a wavelength of 320 nm. The experiments show that 2-M is well-suited for time-resolved experiments on the triplet-sensitizing process.