Extensive Quantum Chemistry Study of Neutral and Charged CN Chains. An Attempt to Aid Astronomical Observation
arXiv:2112.09285 · doi:10.1021/acsearthspacechem.9b00321
Abstract
Many molecular species can presumably still be observed in space if they are adequately characterized chemically. In this paper, we suggest that this could be the case of the neutral (CN) and anion (CN) cyanopropynylidene chains, which were not yet identified in space although both the neutral (CN and CN) and anion (CN} and CN) neighboring members of the homologous series were observed. Extensive data obtained from quantum chemical calculations using density functional theory (DFT), coupled cluster (CC), and quadratic configuration interaction (QCI) methods for all charge and spin states of interest for space science (doublet and quartet neutrals, triplet and singlet anions, and singlet and triplet cations) are reported: e.g., bond metric and natural bond order data, enthalpies of formation, dissociation and reaction energies, spin gaps, rotational constants, vibrational properties, dipole and quadrupole momenta, electron attachment energies () and ionization potentials (). The fact that (not only for CN but also for CN and CN) the quantum chemical methods utilized here are able to excellently reproduce the experimental value -- which is often a challenge for theory -- is particularly encouraging, since this indicates that theoretical estimates of chemical reactivity indices (which are key input parameters for modeling astrochemical evolution) can be trusted. The presently calculated enthalpies of formation and dissociation energies do not substantiate any reason to assume that CN is absent in space. To further support this idea, we analyze potential chemical pathways of formation of both CN and CN, which include association and exchange reactions.
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