Table summarizes the spectral and lifetime data of the amino substituted purines in the gas phase, including the ranges of the 2C-R2PI spectra of each molecule within which one can observe sharp features and broad features. The lifetime of unsubstituted purine has not been reported in the gas phase. Previous pump-probe experiments performed for purine in acetonitrile and in aqueous solution reported lifetimes of singlet excited states which amount to 360 and 645 ps, respectively. This singlet photorelaxation of unsubstituted purine is then followed by population of the lowest-energy triplet state with a quantum yield of approximately 0.9 with a much longer excited-state lifetime.(11) However, these measurements were performed in solution at significant excess energy relative to the origin transition. Meanwhile in the gas-phase, Schneider et al. reported a narrow rotational envelope of the origin peak, indicating a long lifetime(66) Thus, we can safely assume that purine has a relatively long lifetime in the gas phase. Therefore, the primary chromophore, the purine substructure, is not the reason for adenine's and guanine's photostability, which instead is due to their ligand substructures, a conclusion shared by ref . However, the effects of amino and oxo C2 and C6 substitutions are not additive and the mechanisms for each combination need to be individually described . This conclusion is in line with the work of Martinez-Fernandez et al. who examined how addition of a single amino or oxo group affects photostability and derived a mechanistic understanding of this effect . Their study is limited to purines with a single substituent, as doubly-substituted purines further complicate their mechanism. The current study builds on those findings with the diamino substitution adding another datapoint to the palette of substituent combinations.