The excited states of singlet and triplet state were optimized in water using the TD-PBE0/IEFPCM/6-311+G(d,p) level of theory. The lowest-energy triplet state of 6mercaptopurine was also optimized using the same functional and basis set used in the TD-DFT optimizations but using unrestricted DFT and charge and multiplicity of 0 and 3, respectively.