A cryosolution FTIR and ab initio study of the blue shifting C-H center dot center dot center dot F hydrogen bonded complexes F2ClCH center dot FCD3 and Cl2FCH center dot FCD3

摘要

The mid (4000-500 cm(-1)) and near (10,000-4000 cm(-1)) infrared spectra Of solutions in liquid krypton containing mixtures of F2ClCH and FCD3 or of Cl2FCH and FCD3 show the formation of 1:1 complexes. MP2/6-311++G(2d,2p) ab initio calculations suggest that the main interaction responsible for the formal ion of the complexes is the hydrogen bond between the haloform C-H bond and the fluori tie atom of the base molecule. The observation of blue Shifts upon complexation of 24.8, 51.5 and 87 cm (1) for the fundamental. the first and the second overtone of the haloform nu(1) in F2ClCH, and of 25.0, 50.2 and 87 cm(-1) in Cl2FCH show that in either case the hydrogen bond is of the blue-shifting type. Upon complexation the intensity of the fundamental nu(1) in F2ClCH decreases by a factor of approximately 5, while that in Cl2FCH increases, by a factor of approximately 4. At the same time, the intensities of the first and second overtones reveal only modest decreases. The MP2/6-311++G(2d,2p) calculations predict the existence of more than one conformer for either complex. No spectral evidence for conformational equilibria in the complexes has been detected. One-dimensional anharmonic model calculations have been made to simulate the blue shift and intensity behaviour of the haloform nu(1) vibrations. For both complexes these calculations reproduce the experimental data with reasonable Success.