Slow charge recombination in dye-sensitised solar cells (DSSC) using Al2O3 coated nanoporous TiO2 films

The conformal growth of an overlayer of Al2O3 on a nanocrystalline TiO2 film is shown to result in a 4-fold retardation of interfacial charge recombination, and a 30% improvement in photovoltaic device efficiency.     

Long-range sigma-pi interactions in tetrahydro-4H-thiopyran end-capped oligo(cyclohexylidenes). Photo-electron spectroscopy, ab initio SCF MO calculations, and natural bond orbital analyses

Long-range sigma-pi interactions in tetrahydro4H-thiopyran end-capped oligo(cyclohexylidenes) were identified by He(I) photoelectron spectroscopy (PES) and ab initio RHF/6-31G* calculations. The vertical ionization energies Ivj of the highest occupied molecular orbitals (MO's) were assigned using Koopmans' theorem (Iv,j = -epsilonj) and by correlation with the ionizations of related reference compounds. The experimental (PES) and theoretical (RHF/6-31G*) results are in good agreement. For tercyclohexylidene derivatives which contain two nonconjugated pi-bonds splittings deltaIv,j of the pi-bands in the range from approximately 0.5 to 0.7 eV (delta-epsilonj approximately 0.6 to 0.9 eV). For the bi- and tercyclohexylidene compounds containing two sulfur atoms at their alpha- and omega-end positions the pi-type sulfur lone pair bands [Lppi(S)] split significantly by deltaIvj approximately 0.3 to 0.4 eV (delta-epsilonj approximately 0.3 to 0.4 eV), i.e. sigma-pi interactions over distances of ca. 8 and 12 A, respectively, occur. The magnitude of the interactions and the observed splittings are independent of the anti and syn conformations of the oligo(cyclohexylidene) hydrocarbon skeletons. RHF/6-31G* Natural Bond Orbital analyses reveal that the Hax-C-C-Hax precanonical MO's (PCMO's) centered on the cyclohexyl-type rings are paramount for the relay of the through-bond sigma-pi interactions; no through-space sigma-pi interactions were identified.     

On the volatility and disproportionation of hypoiodous acid

The partition coefficient of hypoiodous acid at 20 °C has been determined to be 930. This determination is based on measured values of the instantaneous iodine partition coefficient /IPC/ vs. time after the introduction of molecular iodine into an air-water system at pH=9.     

Neue Halogenozinkate(II) MZnX4 (MI = Li,Na; X = Cl,Br) mit Olivinstruktur

New Halogenozincates M ZnX₄ (M^I = Li, Na; X = Cl, Br) of Olivine Type The hitherto unknown tetrabromozincates Li₂ZnBr₄ and Na₂ZnBr₄ have been prepared. Quaternary halides Li₂Zn(Cl, Br)₄ and Li₂Zn(Br, I)₄ have been not obtained due to decomposition to mixtures of LiCl and ZnBr₂, and LiBr and ZnI₂. The crystal structures of the olivine-type bromides and of the high-temperature polymorph of Li₂ZnCl₄ have been determined by neutron powder diffraction using the Rietveld method (space group Pnma, Z = 4, a = 1 360.41(4), b = 788.47(2), c = 647.07(2) pm, R_I = 9.07% (Li₂ZnBr₄), a = 1 446.32(5), b = 853.02(3), c = 676.61(2) pm, R_I = 9.29% (Na₂ZnBr₄), a = 1 277.60(3), b = 741.76(2), c = 611.10(1) pm, R_I = 7.63% (Li₂ZnCl₄)). The Raman spectra as well as the results of thermal analyses (DSC) and conductivity measurements (impedance spectroscopy) are presented and discussed. Contrary to Li₂ZnCl₄, Li₂ZnBr₄ and Na₂ZnBr₄ do not undergo any phase transition between 20°C and their melting points.     

A strongly positive dendrimer effect in asymmetric catalysis: allylic aminations with Pyrphos-palladium functionalised PPI and PAMAM dendrimers

A remarkable and unprecedented increase in catalyst selectivity in dendrimer catalysis is observed for the Pyrphos-Pd catalysed allylic amination of 1,3-diphenyl-1-acetoxypropene as a function of the dendrimer generation (with up to 64 metal sites). This steady increase in ee-values for the allylic amination is less pronounced for the poly(propyleneimine)-derived catalysts than for the corresponding palladium-PAMAM dendrimer catalysts for which an increase in selectivity from 9% ee for a mononuclear reference system to 69% ee for the Pd64-dendrimer was found.     

Bindungsverhältnisse in den kristallinen Phasen von Rubidiumhydroxid und -deuterohydroxid,RbOH und RbOD

Bonding Conditions in Crystalline Phases of RbOH and RbOD The crystalline modifications of RbOH and RbOD have been investigated between 16 K and melting point employing X-ray, neutron diffraction and calorimetric methods as well as IR and Raman spectroscopy. The results elucidate the bonding interactions in these phases. For crystal data see ?Inhaltsubersicht”?. The structurally distinct influence of the asymmetric charge distribution of the hydroxide ion decreases with increasing temperatures: In the TlI-type structure the anions are hydrogen bonded forming infinite chains at low temperatures. The hydrogen bonds break open by warming up. Phase transformations above 300 K (RbOD) resp. 265 K (BbOH) are associated with the discontinous expansion of rocking vibrations of the anions. In the high temperature form with KaCI-type structure the anions rotate quasi-freely     

Intramolecular coupling of BrO stretching vibrations in solid bromates, infrared and Raman spectroscopic studies on M(BrO3)2.6H2O (M = Mg, Co, Ni, Zn) and Ni(ClO3)2.6H2O

Infrared and Raman spectra of the isostructural cubic halate hexahydrates M(BrO3)2.6H2O (M = Mg, Co, Ni, Zn) and Ni(ClO3)2.6H2O (space group, Pa3; Z = 4) are presented. They are discussed with respect to the strength of the O-H...OXO2 hydrogen bonds (hydrogen bond acceptor capability, synergetic effect) and the order of the BrO stretching modes. In the case of undistorted bromate ions, e.g. at C3 lattice sites, the order of the symmetric (v1) and asymmetric (v3) XO stretching modes is v1 < v3 as for ClO3- but in contrast to IO3- with v1 > v3. The relative order of v1 and v3 of halate ions is mainly governed by the specific masses of the halogen atoms and the angles of the XO3- ions. The latter decrease in the sequence ClO3- (107degrees) > BrO3-> IO3- (< 100 degrees). The Raman scattering intensities of the asymmetric XO stretching modes v3 of the title compounds are unusually low (< 5% those of v1).