FTIR studies of the CH3CN-BF3 complex in solid Ar, N2, and Xe: Matrix effects on vibrational spectra

FTIR spectra of the four isotopically substituted 1:1 complexes of acetonitrile and boron trifluoride were recorded in Ar, N2 and Xe matrices. In Ar, previously unreported three vibrational modes of the complex were clearly observed. Several significant vibrational bands were also observed in N2 and Xe. The observed frequency shifts on complexation, Δν, were qualitatively in good agreement with the computational results, which were calculated at the B3LYP/6-311++G(d,p) level using the optimized geometry of the C3v eclipsed conformation. The observed magnitudes of Δν for most of the complex bands were larger than the calculated values. The BF3 symmetric deformation mode is an exception. The observed frequency shits for this mode were smaller than the calculated values, especially in N2. This suggests that even an inert matrix can significantly affect the vibrational spectrum of the complex.