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Energies, structures, vibrational spectra and proton transfer in the imidazole-imidazolium complex are studied by B3LYP/6-311++G method. A strong influence of the complex formation on the vibrational spectra is observed in the N-H stretching mode and in the fingerprint region.

By deliberately causing degradation of components in a dye-sensitized solar cell we have studied failure mechanisms of such cells. The dye, bis(tetrabutylammonium) cis-bis(thiocyanato)bis(2,2'-bipyridine-4-carboxylic acid, 4'-carboxylate)ruthenium(II), The adsorbed to a nanostructured Ti[O.sub.2] film was studied with UV--VIS and IR spectroscopy after being exposed to visual and ultra-violet radiation, increased temperature, air, electrolyte, and water in the electrolyte. The thiocyanate ion ligand is lost in air, at temperatures equal to and above 135 [degrees]C, in electrolyte and possibly upon UV irradiation. The loss of the SC[N.sup.-] ligand in air was accelerated under visual illumination. From working electrodes immersed in the electrolyte or in degraded complete solar cells it was observed that the absorption peak from the thiocyanate ion ligand at around 2100 [cm.sup.-1] had broadened, blue-shifted and decreased. One failure mechanism is thus that the thiocyanate ion ligand is lost from the dye together with the electrolyte. Together with water in the electrolyte (5 v%) the SC[N.sup.-] ligand is exchanged with [H.sub.2]0 and/or O[H.sup.-]. The ligand exchange between SC[N.sup.-] and [H.sub.2]0/O[H.sup.-] was accelerated under visual illumination. [c] 2003 Published by Elsevier Ltd.

Quantum mechanical ab initio Hartree-Fock SCF molecular orbital methods have been used to determine a potential energy surface for the PFSI anion [N(C2F5SO2)2]-, (bis(pentafluoroethanesulfone)imide ion). The anion shows high flexibility, with stable geometry sensitive to the potential energy surface.

The dynamics of lithium ion transport along a poly(ethylene oxide) chain were investigated for the first time using quantum mechanical calculations. The poly(ethylene oxide) oligomer diglyme (CH3O-(CH2CH2O)2-CH3) was utilized as a model system for a poly(ethylene oxide) polymer for this purpose. The imaginary frequencies for the transition states and the related intrinsic reaction coordinate paths were also examined. The results were compared with nuclear magnetic resonance data for the activation energies of conformational transformations in complexed poly(ethylene oxide).

The significance of the role of transcellular biosynthesis of cysteinyl leukotrienes (LT) LTC4, LTD4 and LTE4 and lipoxins (trihydroxylated arachidonic acid derivatives) in bronchial asthma and the proliferation of various cell types should be subjected to more studies. Enzymatic analysis shows inconclusive evidence that the combination of leukotrienes and lipoxins can lead to beneficial synergistic effects and clarifies whether this combination can reach recipient cells in an intact form.

Isotopically diluted HDO molecules in the OD stretching area and deuterated acetonitrile CD3Cn in the CN stretching area were analyzed using infrared spectroscopy. Selective solvation took place because the acetonitrile molecules that are not influenced by water molecules were identified for a wide concentration range. The existence of a wide OD stretching band reveals the powerful propensity of water molecules to self-associate. Spherical clusters are less likely to develop than chains of water molecules connected by hydrogen bands.

Infrared spectroscopy was utilized in the study of the hydration of Mn2+, Fe2+, Co2+, La3+, Nd3+, Dy3+ and Yb3+ ions. The double-difference technique was used to determine spectral differences by removing the undesired spectral contributions from H2O and from HDO molecules in the bulk and giving the infrared spectra of ion-perturbed HDO. The Mn2+, Fe2+ and Co2+ ions produced OD stretching bands at 2427(2) cm(super 1-) and hydration numbers of 6.5(5), 7.3(5) and 6.5(5), respectively. H2O molecules near the La3+, Nd3+, Dy3+ and Yb3+ ions gave similar OD bands ranging from 2414 to 2421 cm(super 1-).0

The solid hexahydrate and the hydration of mercury (Hg)(II), cadmium (Cd)(II) and Zinc (Zn)(II) have been observed utilizing the infrared spectroscopic double-difference technique. The results reveal that the waters of hydration exhibit single infrared spectra OD bands and that the Hg(II) bands in hydrated and solid hexahydrated forms are broader than Cd(II) and Zn(II) bands. In addition, the OD stretching band's lower frequency indicates the strengthening of the Hg-O covalent bond and water molecule polarization.

The infrared vibrational OH stretching spectrum of isotopically isolated HDO molecules in liquid water has been calculated by ab initio methods at the MP2 level for a number of geometrical configurations taken from a Monte Carlo simulation. Each vibrating water molecule with its environment was described by a pentamer supermolecule, surrounded by a large number of point charges representing polarized water molecules. The anharmonic stretching potentials (MP2 force constants up to fifth order) for 40 uncoupled OH water vibrators were calculated. The average computed re distance found for liquid water is 0.01 Å longer than the free-water value. The frequencies were obtained by solving the one-dimensional Schrödinger equation variationally for each OH potential curve. Using the squared dipole moment derivatives, which vary by a factor of 7 over the frequency band, the density-of-states histograms were converted to intensities. The resulting computed average frequency downshift is ∼260 cm-1, compared to ∼310 cm-1 (experimental), with a bandwidth in good agreement with experiment. The remaining discrepancy between theoretical and experimental frequency shifts is to a large part due to the charge transfer within the water clusters. This charge transfer gives rise to an electrostatic field which, at the site of the vibrating H atom, counteracts the downshift induced by the other environmental effects. The agreement between experiment and theory is very satisfactory when this charge transfer effect is corrected for or when point-charge embedded heptamer clusters are considered. [ABSTRACT FROM AUTHOR]

The development of the resonance raman scattering (RRS) to study mechanisms in a sealed dye-sensitized solar cell device based on the N719 dye adsorbed on TiO2 is presented. It concluded that the amount of thiocyanato groups coordinated to the dye was found to decrease with the increased amount of the iodine added or triiodide formed in the electrolyte.