Infrared and ab initio study of the van der Waals complex formed between allene and BF3

Abstract

The mid infrared spectra of allene (C3H4) and boron trifluoride (BF3) mixtures, dissolved in liquid argon (84–125 K) and in liquid nitrogen (80–113 K), are discussed. In all spectra, the formation of a 1:1 van der Waals complex C3H4·BF3 was observed. From spectra recorded between 85 and 108 K, the complexation enthalpy in liquid argon, ΔHLAr°, was determined to be -9.2(3) kJ mol-1. Using the self-consistent isodensity polarized continuum model to correct for the solvent influences, and applying statistical thermodynamics to account for zero-point vibrational and thermal influences, the gas phase complexation energy ΔEcexp was estimated to be -14.9(6) kJ mol-1. The analysis was completed by carrying out abinitio calculations at the MP2/6-311++G(d,p), the MP2/6-311++G(3df,2pd)//MP2/6-311++G(d,p) and the MP2/aug-cc-PVTZ//MP2/6-311++G(d,p) level. At the latter level, the calculated complexation energy, -13.96 kJ mol-1, closely agrees with the experimental value.