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Abstract: The CASPT2 potential energy curves for S-loss dissociation from the X2Πg, A2Πu, , , 14Σ−, 14Π, 12Σ−, and 24Σ− states of the ion were calculated. A conical intersection point between the and potential energy surfaces was found. At the CASSCF level we located the minimum energy crossing points (MECPs) for the X2Πg/14Σ−, A2Πu/14Σ−, /14Σ−, /14Σ−, A2Πu/12Σ−, and /12Σ− state-pairs and calculated spin–orbit coupling values. MECP for the /12Σ− state-pair was not found. We suggest photodissociation processes via A2Πu and . Photodissociation mechanisms via A2Πu, , and proposed in the previous experimental studies are discussed. [Copyright &y& Elsevier]

Abstract: The weak hydrogen bonding structures of protonated triethylamine in aqueous solution were investigated by Raman spectroscopy as a function of hydrostatic pressure. The formation of a weak hydrogen bond was directly evidenced by a low-frequency shift of the hydrogen-bonded C–H stretches in the protonated triethylamine moiety. For pure triethylamine, an increase in pressure leads to a blue frequency shift of the C–H bands. Nevertheless, the high pressure study of the C–H bands for a dilute protonated triethylamine/D2O solution yielded an unusual nonmonotonic pressure dependence. This result indicates charge-enhanced C–H⋯O hydrogen-bond formation at high pressure. [Copyright &y& Elsevier]

Abstract: Gel-like mixtures were prepared by mixing 1,3-dimethylimidazolium methyl sulfate with tungsten(VI) oxide nanopowder. Close interactions of the charge-enhanced C–H⋯O type have been analyzed via high-pressure infrared and Raman spectroscopy. The presence of tungsten(VI) oxide nanopowder has a negligible effect on the peak frequency of the methyl C–H stretching band. However, the pressure dependence of imidazolium C–H stretching modes displays significant changes as tungsten(VI) oxide nanoparticles were added. The results demonstrate that the imidazolium C–H⋯O3W interactions can offer an additional stability to perturb the local structure of 1,3-dimethylimidazolium methyl sulfate. Such a molecular ordering may trigger clustering of the surrounding anions and cations and interconnect neighboring WO3 nanoparticles to form physical gel. Raman spectra of a gel-like 1,3-dimethylimidazolium methyl sulfate/tungsten(VI) oxide mixture revealed a new low energy band at 788cm−1. We attribute the 788cm−1 band to the interactions between the ionic liquid and surface WO3. [Copyright &y& Elsevier]

Abstract: Our results demonstrate that the equatorial C–H groups of 1,3-dioxane form hydrogen-bond-like C–H⋯O interactions more readily than do the axial C–H groups. The peak frequency of the strong axial C–H stretch band of 1,3-dioxane in a dilute D2O solution possesses an unusual non-monotonic pressure dependence, which indicates enhanced C–H⋯O hydrogen bond formation at high pressure. We performed density functional theory calculations to predict the relative energies and total interaction energies of 1,3-dioxane/(water) n clusters and found that the equatorial C–H groups are more favorable sites for hydrogen bonding than are the axial C–H groups. [Copyright &y& Elsevier]

We have investigated the effect of pressure versus C–H–O interactions in 1,4-dioxane/D2O mixtures. Hydrogen bond-like C–H–O interaction may be a distinct possibility to understand the origin of the spectral features observed under high pressure. Based on the results of density functional theory calculations, the structural identification of the pressure-induced hydrophobic isomers is complicated by the presence of more than one stable isomeric form. This study demonstrates that high pressure can be used as a valuable means of triggering hydrogen bond-like C–H–O interactions. [Copyright &y& Elsevier]

Abstract: The 12Π(X2Π), 22Π, 12Σ+, 32Π, 42Π, and 22Σ+ states of the OCS+ ion were studied using the CASSCF and CASPT2 methods with a contracted ANO basis and 32Π and 42Π are characterized as shake-up ionization states. The CASSCF frequency calculations indicate that the 12Π, 22Π, 12Σ+, and 22Σ+ primary ionization states represent minima in the potential energy surfaces (PESs), and accurate CASPT2 adiabatic excitation energy (T 0) calculations support assignments of the A, B, and C states to 22Π, 12Σ+, and 22Σ+, respectively. The CASSCF frequency calculations indicate that 32Π and 42Π represent saddle points in the PESs. We found minima in the PESs of the 52A′ and 42A″ states (related to 42Π), and the CASPT2 T 0 values for 52A′ and 42A″ are between the T 0 values of B2Σ+ and C 2Σ+. The observed satellite bands between the B and C bands in spectrum can be (partially) attributed to 52A′ and 42A″. [Copyright &y& Elsevier]