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.