Infrared and Raman Studies of Crystalline HCl, DCl, HBr, and DBr

Synthesis and Characterization of Poly(hydrogen halide) Halogenates (-I)

Herein, we report the synthesis and characterization of a variety of novel poly(hydrogen halide) halogenates (-I). The bifluoride ion, which is known to have the highest hydrogen bond energy of ≈160 kJ mol-1 , is the most famous among many examples of [X(HX)n ]- anions (X=F, Cl) known in the literature. In contrast, little is known about poly(hydrogen halide) halogenates containing two different halogens, ([X(HY)n ]- ). In this work we present the synthesis of anions of the type [X(HY)n ]- (X=Br, I, ClO4 ; Y=Cl, Br, CN) stabilized by the [PPh4 ]+ and [PPN]+ cation. The obtained compounds have been characterized by single-crystal X-ray diffraction, Raman spectroscopy and quantum-chemical calculations. In addition, the behavior of halide ions in hydrogen fluoride was investigated by using experimental and quantum-chemical methods in order to gain knowledge on the acidity of hydrogen halides in HF.

IR spectroscopic study of the HCl···O3 molecular complex in liquid argon

Infrared spectra are reported of ozone and HCl dissolved in liquid argon (86-134 K) at concentrations varying from 5×10(-5) to 9×10(-6) M for HCl, and from 1×10(-3) to 5×10(-5) M for ozone. At low concentrations of O3 and of HCl, no spectral features due to O3-HCl complex were found. At higher concentrations (1×10(-3) of ozone vs 5×10(-5)-9×10(-6) of HCl), a new band near 2840 cm(-1) due to the HCl···O3 complex was observed. FWHM of νHCl of the complex is 8 cm(-1). From the temperature dependence of the absorption band intensity, the enthalpy of the complex formation was estimated, ΔH°=4.7±0.4 kJ mole(-1). The optimized geometry of the cis-HCl···O3 complex and a value of 6.3 kJ mole(-1) for its binding energy were determined by ab initio calculations.

Determination of the intermolecular potential energy surface for (HCl)2 from vibration--rotation--tunneling spectra

An accurate and detailed semiempirical intermolecular potential energy surface for (HCl)2 has been determined by a direct nonlinear least-squares fit to 33 microwave, far-infrared and near-infrared spectroscopic quantities using the analytical potential model of Bunker et al. [J. Mol. Spectrosc. 146, 200 (l99l)] and a rigorous four-dimensional dynamical method (described in the accompanying paper). The global minimum (De= -692 cm-1) is located near the hydrogen-bonded L-shaped geometry (R=3.746 angstroms, theta1=9 degrees, theta2=89.8 degrees, and phi=180 degrees). The marked influence of anisotropic repulsive forces is evidenced in the radial dependence of the donor-acceptor interchange tunneling pathway. The minimum energy pathway in this low barrier (48 cm-1) process involves a contraction of 0.1 angstroms in the center of mass distance (R) at the C2h symmetry barrier position. The new surface is much more accurate than either the ab initio formulation of Bunker et al. or a previous semiempirical surface [J. Chem. Phys. 78, 6841 (1983)].