Spectroscopy and photophysics of dimethyl-substituted alloxazines

We have calculated the electronic structure and absorption spectra from the ground state and the first triplet excited state for five dimethylalloxazines, using the TD-DFT approach. The results of the calculations were correlated to experimental spectral and photophysical data, including the transient spectra reported here containing triplet–triplet absorption data, using the proximity effect theory to explain the variations of the ISC rates with the substitution pattern and solvent. Additionally, singlet oxygen yields were measured for these compounds, demonstrating their high efficiency as singlet oxygen photosensitizers.