Complexes of type C _6H _7+·L (L = N _2 and CO _2) studied by explicitly correlated coupled cluster theory

摘要

Complexes of the benzenium ion (C _6H _7+) with N _2 or CO _2 have been studied by explicitly correlated coupled cluster theory at the CCSD(T)-F12x (x a, b) level [T. B. Adler, J. Chem. Phys. 127, 221106 (2007)10.1063/1.2817618] and the double-hybrid density functional B2PLYP-D [T. Schwabe and S. Grimme, Phys. Chem. Chem. Phys. 9, 3397 (2007)10.1039/b704725h]. Improved harmonic vibrational wavenumbers for C _6H _7+ have been obtained by CCSD(T)-F12a calculations with the VTZ-F12 basis set. Combining them with previous B2PLYP-D anharmonic contributions we arrive at anharmonic wavenumbers which are in excellent agreement with recent experimental data from p-H _2 matrix isolation IR spectroscopy [M. Bahou, J. Chem. Phys. 136, 154304 (2012)10.1063/1.3703502]. The energetically most favourable conformer of C _6H _7+·N _2 shows a π-bonded structure similar to C _6H _7+·Rg (Rg Ne, Ar) [P. Botschwina and R. Oswald, J. Phys. Chem. A 115, 13664 (2011)10.1021/jp207905t] with D _e ≈ 870 cm ~(-1). For C _6H _7+·CO _2, a slightly lower energy is calculated for a conformer with the CO _2 ligand lying in the ring-plane of the C _6H _7+ moiety (D _e ≈ 1508 cm ~(-1)). It may be discriminated from other conformers through a strong band predicted at 1218 cm ~(-1), red-shifted by 21 cm ~(-1) from the corresponding band of free C _6H _7+.