The Challenge of Characterizing Bimolecular Reactions of Aromatic Compounds via Computational Chemistry. the Case of the N(2D) + Pyridine Reaction and Implications in the Chemistry of the Thermosphere of Titan

Bimolecular reactions involving aromatic compounds are of great interest in many areas of applied science. Given their large weight, an experimental characterization might be difficult using the common experimental methods because of their low vapor pressure. Also the characterization via theoretical methods is difficult, because of the large number of atoms involved and some difficulty in describing delocalization effects with the usual methods for electronic structure calculations. In this contribution, we report a benchmark analysis of the reaction between pyridine and atomic nitrogen in the excited2D state, which is of relevance in different fields in the chemistry of the thermosphere of Titan. We have used different computational strategies, mainly based on DFT methods, which represent a convenient option in the case of large systems. The use of more accurate methods, such as the coupled-cluster theory, might be difficult to implement considering the significant hardware requirements. The results of this analysis suggest that an acceptable computational strategy is represented by the use of hybrid functionals, such as the B3LYP or M062X, in conjunction with the aug-cc-pVTZ basis set. Implications for the chemistry of the atmosphere of Titan (the largest moon of Saturn) are briefly discussed.