Complexes of type C6H7+center dot L (L = N-2 and CO2) studied by explicitly correlated coupled cluster theory

Abstract

Complexes of the benzenium ion (C6H(7)(+)) with N-2 or CO2 have been studied by explicitly correlated coupled cluster theory at the CCSD(T)-F12x (x = a, b) level [T. B. Adler et al., J. Chem. Phys. 127, 221106 (2007)] and the double-hybrid density functional B2PLYP-D [T. Schwabe and S. Grimme, Phys. Chem. Chem. Phys. 9, 3397 (2007)]. Improved harmonic vibrational wavenumbers for C6H7+ 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 et al., J. Chem. Phys. 136, 154304 (2012)]. The energetically most favourable conformer of C6H7+ center dot N-2 shows a pi-bonded structure similar to C6H7+ center dot Rg (Rg = Ne, Ar) [P. Botschwina and R. Oswald, J. Phys. Chem. A 115, 13664 (2011)] with D-e approximate to 870 cm(-1). For C6H7+ center dot CO2, a slightly lower energy is calculated for a conformer with the CO2 ligand lying in the ring-plane of the C6H7+ moiety (D-e approximate to 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 C6H7+. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4714347]