Structure, Spectroscopic Properties and Reactions of Interstellar Molecule HC₂N and Isomers :Ab initio Study

Abstract

Calculations are presented for the molecule HC 2 N and its geometrical isomers. The structures, harmonic frequencies and dipole moments are reported. The potential energy surface of the [H,C,C,N] system is investigated in detail, and the transition states, intermediate complexes, and the energies of barrier for the isomerization and dissociation reactions are computed in order to determine the reaction paths and to estimate the stability of the isomers. The barriers of isomerization among HCCN, HCNC and HNCC are computed to be rather large and dissociations of these molecules are highly endothermic, indicating that these molecules are kinetically stable. The association reactions HC + CN → HCCN, HC + NC → HCNC, and HN + CC → HNCC are barrierless and very exothermic, suggesting that they may be considered as efficient means of producing the HCCN and the isomers in the laboratory and in interstellar space.

Reaction mechanisms and kinetics of the iminovinylidene radical with NO: Ab initio study

“…At the same level CCSD(T)/aug-cc-PVQZ//B3LYP/6-311++G(3df,2p), the calculated singlet-triplet splitting energy of HCCN radical is 0.507 eV, which also agrees satisfactorily with the experimental values (0.48 ± 0.25 and 0.52 ± 0.01 eV). 21,22 In addition, our calculated ground state energy of HNCC is 35.01 kcal/mol (Zero-Point energy corrcted) higher than HCCN by CCSD(T)/aug-cc-PVQZ//B3LYP/6-311++G(3df,2p) level, which is very close to the study of Park et al, 26 35.9 kcal/mol. Furthermore, we also employed the same method to calculate the singlet-triplet splitting energy of the HNCC molecule, and the calculated value, ∼7.3 kcal/mol, is in good agreement with the experimental data (7.2 kcal/mol).…”

“…20 The ground electronic state of iminiovinylidene radical has triplet multiplicity and possesses bent structure such as HCCN. 26 In their high level calculations CCSD(T)/6-311G(d,p), 26 the energy of HNCC is higher than that of cyanomethylene radical by about 35.9 kcal/mole (ZPE-corrected), and its structure including the terminal hydrogen atom is bent, while the nitrogen atom and two carbon atoms almost lie along a line.…”