Boron dichloride and its cation Geometries, vibrational frequencies, ionization energy and excitation energies

Abstract

The geometries and harmonic vibrational frequencies of BCl ₂ and BCl ₂ ⁺ have been calculated at various levels of ab initio theory [MP2, MP4(SDQ), CISD and CCSD(T)] and density functional theory (BLYP and B3LYP), using a variety of basis sets. These calculations show the neutral molecule to be bent, with a bond angle of ca. 125°, and the cation to be linear. Calculated vibrational frequencies were compared with experimental values, where available, including isotopic shifts. The ionization energy of the BCl ₂ molecule was calculated to be 7.33 eV at the Gaussian-2 level of theory; additionally, the heat of formation of the cation was calculated to be 160.4 kcal mol ^-1 . Finally, CIS and MRDCI calculations were performed, in order to ascertain the position of excited electronic states for both the cation and the neutral molecule; the calculated excitation energies were then compared with reported energies for transitions in these species.