Evaluation of the Efficiency of Intersystem Crossing to a Triplet State of Fullerene in Complexes with Amino Acids

The important photophysical process that determines the efficiency of photosensitizers is saturation of the triplet state through the intersystem crossing during light absorption. We studied the C₆₀ fullerene complexes with the amino acids (glycine, lysine, methionine, and threonine) as promising photosensitizers. The calculations for all these complexes demonstrate high values of the transition rate constants to the triplet states and a high probability of generating reactive oxygen species upon excitation in visible light. The carboxyl groups of amino acids, which are not involved in electronic excitation, can be used to conjugate photoactive complexes with a tumor-targeting drug delivery system, such as specific DNA aptamers.