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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.

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The complexes of glyoxal (Gly), methylglyoxal (MGly), and diacetyl (DAc) with water have been studied using Fourier transform infrared (FTIR) matrix isolation spectroscopy and MP2 calculations with 6-311++G(2d,2p) basis set. The analysis of the experimental spectra of the Gly(MGly,DAc)/H2O/Ar matrixes indicates formation of one Gly...H2O complex, three MGly...H2O complexes, and two DAc...H2O ones. All the complexes are stabilized by the O-H...O(C) hydrogen bond between the water molecule and carbonyl oxygen as evidenced by the strong perturbation of the O-H, C=O stretching vibrations. The blue shift of the CH stretching vibration in the Gly...H2O complex and in two MGly...H2O ones suggests that these complexes are additionally stabilized by the improper C-H...O(H2) hydrogen bonding. The theoretical calculations confirm the experimental findings. They evidence the stability of three hydrogen-bonded Gly...H2O and DAc...H2O complexes and six MGly...H2O ones stabilized by the O-H...O(C) hydrogen bond. The calculated vibrational frequencies and geometrical parameters indicate that one DAc..H2O complexes, two Gly...H2O, and three MGly...H2O ones are additionally stabilized by the improper hydrogen bonding between the C-H group and water oxygen. The comparison of the theoretical frequencies with the experimental ones allowed us to attribute the calculated structures to the complexes present in the matrixes.

The complexes formed by trans- and cis-HONO isomers with nitrogen and carbon monoxide have been observed and characterized in argon matrices. Six perturbed trans-HONO vibrations and four perturbed cis-HONO vibrations were identified for both the N2 and CO complexes. The perturbation of the OH group vibrations proves that all four complexes are hydrogen bonded; the blue shifts of the CO vibrations in trans- and cis-HONO complexes as compared to CO monomer indicate the OC···HONO structures in which carbon atoms are the acceptor sites. The strength of interaction, as evidenced by the perturbation of the OH vibrational modes of the nitrous acid, increases from cis- to trans-isomer and from nitrogen to carbon monoxide. Theoretical studies of the structure and spectral characteristics of the complexes formed between the two isomers of nitrous acid and nitrogen or carbon monoxide were carried out on the electron correlation level with the 6-31G(d,p) basis set. The binding energy and the calculated spectral parameters are in very good agreement with experimental data.