Inter- and intramolecular photoactivation of artemisinin and derivatives by xanthone-based triplet and singlet sensitizers.

Molecular dyads and triads were synthesised using mono- and diaminoxanthones as chromophores and artesunate as a pharmacophore. During photolysis, non-fluorescent xanthone as well as the fluorescent aminoxanthone hybrids ART-XO and (ART)2-XO underwent peroxide rearrangement, resulting in quenching of fluorescence alongside peroxide decomposition. The most probable pathway involves O-O-bond activation through singlet and triplet energy transfer (en-T). The activation of artemisinin by xanthone is due to intermolecular triplet en-T, which leads to two characteristic peroxide rearrangement products.