Hydrogen bonding guest-water interactions in pinacolone, tert-butyl amine, and tert-butylmethyl ether: a theoretical study on energetics, structure, and topological + .

Context: In guest-host interactions, guest molecules used for hydrogen bonding potential of clathrate hydrate cages are involved as "promoters" for hydrogen or methane storage. Among the promoter molecules, there are pinacolone and tert-butylmethyl ether containing oxygen atom, and tert-butyl amine among those containing nitrogen atom. The dimer and trimer interactions of these molecules with the water clusters were investigated.

NH as unique non-classical content-former within clathrate hydrates.

High quality FTIR spectra of aerosols of NH-THF and NH-TMO binary clathrate hydrates (CHs) have been measured. Our recently developed all-vapor sub-second approach to clathrate-hydrate formation combined with computational studies has been used to identify vibrational spectroscopic signatures of NH within the gas hydrates. The present study shows that there are three distinct NH types, namely, classical small-cage NH, nonclassical small-cage NH, and NH within the hydrate network.

Molecular Modes and Dynamics of HCl and DCl Guests of Gas Clathrate Hydrates.

Recent years have yielded advances in the placement of unusual molecules as guests within clathrate hydrates (CHs) without severe distortion of the classic lattice structures. Reports describing systems for which observable but limited distortion does occur are available for methanol, ammonia, acetone, and small ether molecules. In these particular examples, the large-cage molecules often participate as non-classical guests H-bonded to the cage walls.

CO2 and C2H2 in cold nanodroplets of oxygenated organic molecules and water.

Recent demonstrations of subsecond and microsecond timescales for formation of clathrate hydrate nanocrystals hint at future methods of control of environmental and industrial gases such as CO2 and methane. Combined results from cold-chamber and supersonic-nozzle [A. S.

Controlling nonclassical content of clathrate hydrates through the choice of molecular guests and temperature.

Low-temperature, low-pressure studies of clathrate hydrates (CHs) have revealed that small ether and other proton-acceptor guests greatly enhance rates of clathrate hydrate nucleation and growth; rapid formation and transformations are enabled at temperatures as low as 110 K, and cool moist vapors containing small ether molecules convert to mixed-gas CHs on a subsecond time scale. More recently, FTIR spectroscopic studies of the tetrahydrofuran (THF)-HCN double clathrate hydrate revealed a sizable frequency shift accompanied by a four-fold intensification of the C-N stretch-mode absorption of the small cage HCN, behavior that is enhanced by cooling and which correlates precisely with similar significant changes of the ether C-O/C-C stretch modes. These temperature-dependent correlated changes in the infrared spectra have been attributed to equilibrated extensive hydrogen bonding of neighboring large- and small-cage guest molecules with water molecules of the intervening wall.