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Infrared spectra are reported of a strongly hydrogen-bonded complex between ammonia and hydrogen chloride trapped in argon and nitrogen matrices. There are substantial differences between the spectra of the complex in the two matrices, and these are attributed to increased proton transfer from hydrogen chloride to ammonia in the more polar nitrogen matrix. The corresponding gas-phase complex would be expected to display less proton transfer than the complex in an argon matrix.

The complexes formed between cis- and trans-HONO isomers and ammonia have been observed and characterized in argon matrices. Five perturbed HONO vibrations and one perturbed NH3 deformation vibration were identified for the H3N···HONO-trans complex, and one perturbed HONO vibration and perturbed NH3 deformation vibration were identified for the H3N···HONO-cis complex. The OH stretching vibration in the H3N···HONO-trans complex is ca. 800 cm-1 red-shifted and NOH bending vibration is ca. 190 cm-1 blue-shifted with respect to the trans-HONO monomer, indicating formation of a very strong molecular hydrogen bond. Theoretical studies of the structure and spectral characteristics of the H3N···HONO-trans and H3N··· HONO-cis complexes were carried out on the electron correlation level and G-311+G(2df,2pd) basis set. The calculated binding energy at the MP2 level is −40.13 and −36.39 kJ mol-1 for the H3N···HONO-trans and H3N···HONO-cis complexes, respectively. The calculated spectra reproduce very well the frequencies and the intensities of the measured spectra.

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Ammonia and hydrogen chloride vapors from thermal decomposition of NH 4 Cl co-deposited with excess neon at 4-5 K formed the H 3 N-HCl complex. Strong, broad 2084 cm -1 and strong, sharp 1060.2 cm -1 absorptions are assigned to the H-Cl stretching and symmetric NH 3 bending modes and weaker 2017.4 and 708.9 cm -1 bands to the overtone of the NH 3 mode and the H-Cl librational fundamental of the 1:1 complex. Complementary experiments were done with neon/argon mixtures, argon, and krypton to investigate the 1:1 complex in a range of matrix environments. Vibrational assignments are supported by 15 NH 4 Cl, ND 4 Cl, and 15 ND 4 Cl isotopic substitution. The neon matrix spectrum suggests a strong hydrogen bond, slightly stronger than in the gas-phase complex, but not as strong as found in the argon and krypton matrix hosts owing to increased solvation by the more polarizable matrix atoms.