As more complex organic molecules are detected in the interstellar medium (ISM), nucleobase formation in the ISM is increasingly plausible. The abiotic syntheses of nucleobase molecules, however, remains a topic of debate. Additionally, anions are often overlooked as precursors to these important biomolecules, despite the fact that several anions have been detected in interstellar environments. Our recent dissociation and reactivity study1 has provided important insights into possible gas-phase formation routes to uracil. We have built upon this study through an examination of the other pyrimidine nucleobase molecules, thymine and cytosine, as well as the purines adenine and guanine. Although the chemistry of cationic and radical nucleobases have been thoroughly examined, this study represents a novel look at deprotonated nucleobases in an astrobiological context. An ion trap mass spectrometer is used to study the dissociation pathways of these species, and the fragmentation mechanisms are explored using density functional theory (B3LYP/6-311++G(d,p)). The collision induced dissociation of all deprotonated pyrimidines yields OCN–, leading to the formation of smaller imine molecules. Deprotonated purines involve more complex dissociation processes, forming smaller organic anions through the sequential losses of NH3, NH2CN/HNCNH, HCN/HNC, HNCO, and CO (all detected interstellar molecules). Lastly, we have modified our ion trap to allow the introduction of volatile liquid and gaseous neutral reagents. Utilizing this modification, we have investigated the reactivity of the highest intensity fragments for the purposes of structure verification and chemical characterization. 1 Cole, C. A.; Wang, Z.-C.; Snow, T. P.; Bierbaum, V. M. Phys. Chem. Chem. Phys. 2014, 16, 17835-17844.

Dissociation processes of deprotonated nucleobases: Astrobiological implications

249th National Meeting (2015)

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