The energy difference between the triplet and the ground state optimized geometries is reported as the adiabatic energy of the lowest-energy triplet state of 6MP. The oxidation potential (Eox °) of 6MP was estimated using equation ( ) and the vertical ionization energy (VIE) of 6MP using the methodology described by Crespo-Hernández and co-workers. Initially, the ground state geometries for the neutral and deprotonated forms of 6MP were optimized at the B3LYP/6-31++G(d,p) level of theory. The optimized ground state geometries were then used to obtain the VIEs at the UB3LYP/6-31++G(d,p) level of theory. This simple method has been previously used to determine the redox potentials of the DNA canonical bases, 6thioguanosine, and other nucleobase derivatives. 𝐸 𝑜𝑥 °= (-2.59 ± 0.26) + (0.56 ± 0.03) × 𝑉𝐼𝐸