Theoretical Characterization of C6N, C6N-, and C6N+

8 pags, 2 figs., 3 tabs.
This work emphasizes the stability of CN linear carbon chains and carbon clusters containing three-body rings. CN possesses at least 44 neutral isomers and 38 and 35 isomers with a negative or a positive charge. The lowest-energy structures, which can be candidates for laboratory and astrophysical detection, were studied with RCCSD(T)-F12 and MRCI/CASSCF, specifying properties for various electronic states. Neutral CN displays two prominent equilibrium structures, a nitrogen-terminated linear form (XΠ) and a form (XB) containing a three-carbon ring. They are separated by 0.21 eV. For the linear one, Renner-Teller and spin-orbit effects are expected. Its equilibrium spin-orbit constant |A|was predicted to be 29.09 cm, the dipole moment was computed to be 0.2059 D, and B was computed to be 868.20 MHz, very close to the experimental value (B(exp)-B(calc) ∼ 4.9 MHz). The anion presents two stable forms, a linear triplet (XΣ) and a (XA) isomer, whereas for the cation most stable structures are both linear. For the linear anion and the two linear cations B was estimated to be 870.05 MHz, 875.72 MHz, and 917.36 MHz and μ was estimated to be 4.4200 D, 4.2013D, and 0.7828D. For the neutral form, Ae = 45048.74 MHz, Be = 1062.78 MHz, Ce = 1038.30 MHz, and μ = 0.8840 D, whereas for the negative form, Ae = 40087.48 MHz, Be = 1067.35 MHz, Ce = 1039.67 MHz, and μ = 6.2854 D. Below the electron affinity of the most stable isomer (EA = -3.42 eV), the linear anion displays three probably existing electronic states. Detectability is discussed in terms of the symmetry and spin multiplicity of the ground electronic states.
The authors would like to extend their sincere appreciation to the Deanship of Scientific Research at king Saud University for funding research group No. (RGP-333), the MINECO of Spain for the grants FIS2013-40626-P and FIS2016-76418-P, and the COST Actions CM1401 “Our Astrochemical History” and CM1405 “MOLIM.” This work is supported by the French National Research Agency through the project Anion Cos Chem (ANR-14-CE33-0013). The authors acknowledge the CTI (CSIC) and CESGA for computing facilities.