Knowledge Bank

Explicitly correlated coupled cluster theory at the CCSD(T)-F12x (x = a, b) level nderline{\textbf{127}}, 221106 (2007);\ \hspace*{0.45cm} G.~Knizia, T.~B.~Adler, and H.-J.~Werner, \textit{J.~Chem.~Phys.} nderline{\textbf{130}}, 054104 (2009).} in conjunction with the double-hybrid density functional B2PLYP-D nderline{\textbf{9}}, 3397 (2007).} has been employed in a study of the benzenium ion (C$6$H$\mathrm{7+}$) and its complexes with simple ligands (L = Ne, Ar, N$2$, or CO$2$). nderline{\textbf{115}}, 13664 (2011);\ \hspace*{0.45cm} P.~Botschwina and R.~Oswald, \textit{J.~Chem.~Phys.} submitted.} The ground-state rotational constants of C$6$H$\mathrm{7+}$ are predicted to be A$0$ = 5445 MHz, B$0$ = 5313 MHz, and C$0$ = 2731 MHz. For the complexes with L = Ne, Ar or N$2$, the energetically most favourable structure is of $\pi$-bonded type, but for the most strongly bound complex C$6$H$\mathrm{7+}$ $\cdot$ CO$2$ a conformer with the CO$2$ ligand lying in the ring-plane of the C$6$H$\mathrm{7+}$ moiety is slightly lower in energy.