A Noble-Gas Hydride in a Nitrogen Medium: Structure, Spectroscopy, and Intermolecular Vibrations of HXeBr@(N2)22.

Noble-gas hydrides have been extensively studied in noble gas matrices. However, little is known on their stability and properties in molecular hosts. Here, HXeBr in the N2 environment is modeled at the B3LYP-D level of theory in a complete single shell of 22 N2 molecules. The system is compared to similar models of HXeBr in CO2 and Xe clusters. The optimized structure of (HXeBr)@(N2)22 is of low symmetry and is highly anisotropic. None of the N2 molecules are freely rotating, and the host molecules are not symmetrically positioned with respect to the HXeBr axis. The axes of the N2 molecules are nonuniformly distributed. The computed anharmonic H-Xe stretching frequency of HXeBr in the N2 cluster is in good accord with the experimental value. The soft-mode frequencies of the cluster including both intermolecular vibrations and librations, have a broad distribution that ranges from 8.7 to 107 cm(-1). It is expected that these findings and specifically, the single-shell model, may shed light also on the local structure and vibrations of other impurities in a molecular media.

A small neutral molecule with two noble-gas atoms: HXeOXeH.

A novel noble-gas compound, HXeOXeH, is identified using IR spectroscopy, and it seems to be the smallest known neutral molecule with two noble-gas atoms. HXeOXeH is prepared using, for example, UV photolysis of water in solid xenon and subsequent annealing at 40-45 K. The experimental observations are fully supported by extensive quantum chemical calculations. A large energy release of 8.3 eV is computationally predicted for the decomposition of HXeOXeH into the 2Xe + H2O global energy minimum. HXeOXeH may represent a first step toward the possible preparation of (Xe-O)n chains and it may be relevant to the terrestrial "missing xenon" problem.

Theoretical prediction of chemically bound compounds made of argon and hydrocarbons.

Equilibrium structures, vibrational properties, and stabilities of organo-argon compounds, HArC4H and HArC6H, are studied at the MP2=full/6-311++G(2d,2p) level of theory. Ab initio calculations show that the two molecules are metastable, but protected against the Ar + HY (Y = C4H or C6H) dissociation by high barriers, and these species are energetically stable with respect to the three separate fragments (H + Ar +Y). The implied kinetic stability of HArC4H and HArC6H molecules suggests that these species should very likely be candidates for experimental observation. The results may open possibilities of organic chemistry of light noble gas elements.

Prediction of a linear polymer made of xenon and carbon.

Electronic structure calculations predict the existence of a novel type of a chemically bound noble gas compound. The predicted species is an extended linear and periodic polymer, made of the repeat unit -(XeCC)-, where CC is the acetylenic group. The polymer has a strong partly ionic nature, with positive partial charge on the xenon atoms and a negative one on the CC groups. High energy barriers are found for the removal of a Xe atom from the chain, indicating high stability. This is the first polymer with a noble-gas-containing building block.

A gate to organokrypton chemistry: HKrCCH.

An organic molecule containing krypton, HKrCCH, is reported. The preparation of HKrCCH includes 193-nm photolysis of H2C2/Kr solid mixtures at 8 K and subsequent thermal mobilization of hydrogen atoms at >/=30 K. The identification is based on infrared absorption spectroscopy and supported by ab initio calculations which show ionic and covalent contributions to the bonding. We believe that a series of similar organokrypton molecules can be prepared as computationally demonstrated for HKrC4H and HKrC3H3. These results feature a generally novel way for activating chemically the H-CC- group, which can find practical applications of the krypton catalysis.