Matrix isolation IR spectroscopic and ab initio studies of C(3)N(-) and related species

Coupled cluster calculations were carried out for C(3)N(-), CCNC(-), C(3)N, CCNC, C(3)N(+), and C(3)O. They support the experimental identification of the C(3)N(-) ion by means of matrix isolation infrared (IR) spectroscopy. The anion was generated in electric discharges through the cyanoacetylene isotopomers HC(3) (14)N, HC(3) (15)N, and (2)HC(3)N, trapped in cryogenic rare gas matrices (Ne, Ar, Kr), and detected via its two most intense IR absorption bands, assigned to the nu(1) and nu(2) stretching vibrations. C(3)N(-) appears to be quite a stable anion, with a vertical detachment energy predicted to be as high as 4.42 eV. A large equilibrium electric dipole moment of 3.10 D facilitates the investigation of C(3)N(-) by microwave spectroscopy and radio astronomy. Various structural parameters and spectroscopic properties have been calculated for all tetra-atomic species considered.