Explicitly correlated coupled cluster calculations for the benzenium ion (C_6H~(7+)) and its complexes with Ne and Ar

摘要

Explicitly correlated coupled cluster theory at the CCSD(T)-F12x (x ≥ a, b) level (Adler, T. B.; Knizia, G.; Werner, H.-J. J. Chem. Phys.2007, 127, 221106) has been employed in a study of the benzenium ion (C_6H ~(7+)) and its complexes with a neon or an argon atom. The ground-state rotational constants of C_6H~(7+) are predicted to be A_0 ≥ 5445 MHz, B_0 ≥ 5313 MHz, and C_0 ≥ 2731 MHz. Anharmonic vibrational wavenumbers of this cation were obtained by combination of harmonic CCSD(T*)-F12a values with anharmonic contributions calculated by double-hybrid density functional theory at the B2PLYP-D level. For the complexes of C_6H~(7+) with Ne or Ar, the lowest energy minimum is of π-bonded structure. The corresponding dissociation energies D_0 are estimated to be 160 and 550 cm~(-1), respectively. There is no indication of H-bonds to the aromatic or aliphatic hydrogen atoms. Instead, three nonequivalent local energy minima were found for nuclear configurations where the rare-gas atom lies in the ring-plane and approximatly points to the center of one of the six CC bonds.