BEHAVIOR OF BORON-TRIFLUORIDE IN CRYOSOLUTIONS - A COMBINED AB-INITIO, MONTE-CARLO, AND FTIR INVESTIGATION

Solutions of BF3 in liquefied Ar, N-2, and Ar/N-2 mixtures have been i nvestigated using Monte Carlo simulations and infrared cryospectroscop y. The simulations show that in pure liquefied Ar only solvation of BF 3 occurs, but that in solutions that contain N-2, also van der Waals c omplexes of the types BF3. N-2 and N-2. BF3. N-2 are formed. The fract ions of monomer and complexes are calculated to vary with temperature and with concentration of N-2. In the infrared spectra of BF3 issolved in liquid Ar/N-2 mixtures, the BF3 bands have complex structures, whi ch in the case of upsilon(3) clearly resolve into triplets. This is at tributed to the formation of 1:1 and 1:2 complexes of BF3 with N-2 mol ecules. The evolution of the relative intensities of the components of the BF3 multiplets as a function of temperature and as a function of concentration agree with the Monte Carlo predictions. From a temperatu re-dependent study, the complexation enthalpy for BF3. N-2 in liquefie d argon was determined to be -4.8(5) kJ mol(-1).