Computational study of the linear proton bound ion–molecule complexes of HCNH+ with HCN and HNC

Abstract

This work reports the results of a high level ab initio study of the linear proton bound ion-molecule complex of HCNH(+) with HCN and its isomer HNC. The energetics, equilibrium geometries, and predicted equilibrium rotational constants of three strongly interacting ion-molecule complexes are reported from calculations performed at the coupled-cluster calculations including singles, doubles, and perturbative triple excitations (CCSD(T))∕aug-cc-pVnZ (n = 2-5) level of theory. Harmonic vibrational frequencies from calculations performed at the CCSD(T)∕aug-cc-pVnZ (n = 2-4) level of theory are presented. Additional calculations are performed at the CCSD(T)-F12b∕VnZ-F12 level of theory, and the associated energetics, equilibrium geometries, and equilibrium spectroscopic properties are reported. Anharmonicity is treated with the vibrational configuration interaction method, and the predicted anharmonic vibrational frequencies are reported. The results of these calculations show that of the four possible linear interactions of HCNH(+) with HCN and HNC, there are three strongly interacting proton bound complexes. Further, the study presents results that the fourth possible interaction provides the basis for a novel HNC to HCN isomerization pathway in the interstellar medium.

Estimating local bonding/antibonding character of canonical molecular orbitals from their energy derivatives. The case of coordinating lone pair orbitals

“…As anticipated, the protonations on each side of CO have opposite effects on the CO bond length, in agreement with the opposite characters of the corresponding lone pairs. In contrast, both protonations of CN ‐ shortens the CN bond, in agreement with the antibonding character of both C and N lone pairs. For N 2 , we observe that the protonation slightly shortens the NN bond, in contrast to the ionization.…”

The neutral photochemistry of nitriles, amines and imines in the atmosphere of Titan

“…However, the situation is more complicated. Indeed, in Titan's upper atmosphere, the HCNH + ion is abundant so that HNC will react with HCNH + leading to HCN + HCNH + products (Cotton et al, 2013). Then, net production of HNC from this ionic reaction is reduced.…”

Protonierung kontra Oxoniumsalz‐Bildung: Abstimmung der Basizität und Stabilität von Cyanoborat‐Anionen

“…Weniger ist dagegen über Verbindungen des Typs R ‐CN‐H⋅⋅⋅NC‐ R + bekannt. Eine theoretische Studie zu HCN‐H⋅⋅⋅NCH + , dem eine gewisse Bedeutung im interstellaren Medium zukommen soll, ist eine der wenigen Ausnahmen …”

“…Die Schwingungsanalyse zu [H 4 2 ] − mit einer symmetrischen N⋅⋅⋅H⋅⋅⋅N‐Bindung ( C 2 v ‐Symmetrie) lieferte eine imaginäre Frequenz (−158 cm −1 ). Dieser Befund ähnelt dem für HCN‐H⋅⋅⋅NCH + . Der kurze experimentelle N⋅⋅⋅N‐Abstand von 255.64(13) pm in ist nah an den berechneten Werten für [H 4 2 ] − (252.7 pm; Tabelle ) und HCN‐H⋅⋅⋅NCH + (253.8 pm; CCSD(T)/aug‐cc‐pV5Z).…”