Solute–solvent interactions in cryosolutions: a study of halothane–ammonia complexes

Abstract

The formation of C-H···N bonded complexes of halothane with ammonia has been studied using infrared and Raman spectroscopy of solutions in the liquid rare gases argon, krypton and xenon, of supersonic jet expansions and of room temperature vapor phase mixtures. For the solutions and for the vapor phase experiments, the formation of complexes with 1:1 and 1:2 stoichiometry was observed. The complexation enthalpy for the 1:1 complex was determined to be -20 (1) kJ mol(-1) in the vapor phase, -17.0 (5) kJ mol(-1) in liquid xenon and -17.3 (6) kJ mol(-1) in liquid krypton. For the 1:2 complex in liquid xenon, the complexation enthalpy was determined to be -31.5 (12) kJ mol(-1). Using the complexation enthalpies for the vapor phase and for the solutions in liquid xenon and krypton, a critical assessment is made of the Monte Carlo Free Energy Perturbation approach to model solvent influences on the thermodynamical properties of the cryosolutions. The influences of temperature and solvent on the complexation shifts of the halothane C-H stretching mode are discussed.

Structure, energy, vibrational spectrum, and Bader's analysis of π⋯H hydrogen bonds and H−δ⋯H+δdihydrogen bonds

“…593 Indeed, the interaction R (H c Á Á ÁC 2 ) is stronger once its length is shorter, as highlighted by Parra and Zeng 594 as well as by Remer and Jensen, 595 and thereby indicates an interaction between the H c hydrogen atom of the hydrofluoric acid and the C 2 carbon of the acetylene molecule in the C 2 H 2 Á Á Á2(HF) ternary system. Despite the p hydrogen bond aforementioned, a similar result of shortening of hydrogen bond in halothane:ammonia complexes has been reported by Michielsen, Dom, van der Veken, Herrebout et al 596 In the C 2 H 2 Á Á ÁHF binary, the charge transfer from the CRC bond of the acetylene to the HF molecule causes elongation of the H c -F d bond. This is also confirmed by the 2(HF) dimer along the structure of C 2 H 2 Á Á Á2(HF), where the shorter distance of the hydrogen bond F d Á Á ÁH e provokes enlargement in the H-F bond lengths as follows: r (H c -F d ) 4 r (H e -F f ) .…”

Femtisecond single-mole infrared spectroscopy of molecular clusters

“…112 Some motion is possible in solid quantum matrices, 215 but like the supersonic jet preparation, a matrix remains largely a non-equilibrium environment. In contrast, studies of weakly bound complexes in liquid rare gas solutions 121,122 yield thermodynamic equilibrium data for clusters. The solvent shifts are temperature-dependent and can be identified by comparison to the free jet data.…”

The Halogen Bond

“…As discussed in previous sections, CF 3 I forms fairly strong XBs, and CF 3 Br and CF 3 Cl give weaker and much weaker adducts, respectively, as confirmed, for instance, through FTIR studies of their complexes with trimethylamine in argon, krypton, and xenon matricxes. 422 However, they have quite low boiling points, and less volatile perfluoroalkanes, namely, C 3 to C 8 analogues, have been preferred over trifluorohalomethanes for obtaining crystalline and halogen-bonded adducts. The CF 3 I moiety is present in several hypervalent iodine derivatives (e.g., Togni’s reagent, i.e., the electrophilic trifluoromethylating agent 3,3-dimethyl-1-(trifluoromethyl)-1,2-benziodoxole and the carbonyl analogue 1-(trifluoromethyl)-1,2-benziodoxol-3-(1 H )-one), 532 − 534 and the bonding pattern around the iodine atom in these compounds can be rationalized as the result of the formation of so strong XBs that they are comparable in length to the other bonds involving iodine.…”