Effects of physical orientation of dye molecules and molecular orbitals on performance of solid-state dye sensitized solar cells.

Performance of Dye-sensitized devices depends on the photon absorption and carrier injection properties of the sensitizer (dye). The orientation of the dye molecule affects the photon absorption cross-section, injection efficiency and carrier transport. These effects are studied, using three variants of cyanine dyes in n-TiO2/Dye/p-CuSCN heterojunction. The results show correlation of dye-molecule's orientation on the short-circuit-photocurrent (Isc). The open-circuit-voltage (Voc) is also subjective. The orientation of the dye molecule influence the photon-harvesting efficiency and obstruct the hole-conductor penetrating onto the working-electrode. Additionally, Cumulative effects of e-e, e-h, spin-coupling and HOMO/LUMO distribution are identified.

An investigation of the interaction of iminosulfurane transdermal penetration enhancers with model skin preparations using NMR spectroscopy.

The (31)P NMR resonance from the inner and outer leaflets of DMPC in unilamellar vesicle bilayers has been split by use of the slowly penetrating paramagnetic shift reagent, Pr(3+). The perturbing effect of subsequently added iminosulfurane transdermal penetration enhancers (TPEs) is to accelerate the collapse of this splitting, especially in the case of the bromo derivative 3. The aforementioned acceleration of the splitting is enhanced by the addition of 16 mol% cholesterol. Conversely, 33 mol% cholesterol appears to seal the bilayer to the effect of the TPEs--even when present at 20 mol%. These observations are consistent with the deep penetration of the TPEs into the DMPC bilayer, i.e., the perturbation of the bilayer is transmembrane and supports a model in which a subset of the bromo TPE derivative 3 is kinetically trapped in the bilayer. This feature leads to an enhanced residence time of 3 in the bilayer, and by extension to the skin, and therefore to an explanation for the markedly enhanced activity of the bromo TPE derivative relative to that of other halogenated derivatives in the series of iminosulfuranes studied.

Mechanistic studies on percutaneous penetration enhancement by N-(4-halobenzoyl)-S,S-dimethyliminosulfuranes.

Halogen-substituted iminosulfuranes are transdermal penetration enhancers (TPEs) in permeation studies using hairless mouse or human cadaver skin. The interaction of N--(4--R-benzoyl)-S,S-dimethyliminosulfuranes 1--4, where R=H, Cl, Br, and I, with l-alpha-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) has been studied using differential scanning calorimetry, isothermal titration calorimetry, nuclear Overhauser effect spectroscopy (NOESY), and NMR spectroscopy, and by calculation of the iminosulfurane polarizabilities in order to elucidate the molecular basis of the TPE activity. The active compounds reduce the melting temperature of the gel-to-liquid-crystal phase transition and induce multiple components in the transition excess heat capacity profile. The partitioning of the bromo derivative 3, the most active compound, into DMPC is unique in that 3 may be trapped in the bilayer, affording an enhanced residence time and a reason for its high TPE activity. The entropy decrease associated with the transfer of 3 to the bilayer is much lower than that for the other compounds, indicating that 3 occupies or induces sites that afford it considerable local motional freedom. Correlations between the iminosulfurane TPE activities, the partition coefficients, and NOESY crosspeak volume were observed. Molecular polarizabilities are not consistent with a TPE mode of action involving interaction of these agents with protein side chains.

Percutaneous penetration enhancement activity of aromatic S, S-dimethyliminosulfuranes.

The activity of three series of iminosulfuranes (classes I-III) as potential transdermal penetration enhancers was investigated. These dimethyl sulfoxide (DMSO) related compounds were synthesized from activated DMSO by trifluoroacetic anhydride. Structure confirmation was accomplished by 1H NMR, and 13C NMR spectroscopy and elemental analysis prior to in vitro testing. Hydrocortisone (HC) was used as a model drug, and the effect of the iminosulfuranes on the penetration of HC through hairless mouse skin was evaluated. All enhancers tested were applied to the skin as saturated suspensions in propylene glycol to ensure their maximum thermodynamic activity. Three compounds, S,S-dimethyl-N-(4-bromobenzoyl)iminosulfurane (9), S,S-dimethyl-N-(5-nitro-2-pyridyl)iminosulfurane (13), and S, S-dimethyl-N-(4-phenylazaphenyl)iminosulfurane (16) showed statistically significant activity quantitated by amounts of model drug permeated through the skin in 24 h (Q(24)), and flux values, compared to control (propylene glycol without enhancer). Highest Q(24) and flux values were obtained for 9: 996.2+/-192.5 microg/cm(2) and 42.9+/-7.5 microg/cm(2) per h, respectively. All arylsulfonyl substituted compounds showed lower or similar enhancement activity when compared to control. S, S-dimethyl-N-(benzenesulfonyl)iminosulfurane (1), S, S-dimethyl-N-(2-methoxycarbonylbenzenesulfonyl)iminosulfurane++ + ( 7) and S,S-dimethyl-N-(4-chlorobenzenesulfonyl)iminosulfurane (8) decreased the permeation of HC significantly (P<0.05). It is possible that these agents work as retardants under these experimental conditions. None of the enhancers tested showed significant skin model drug retention, suggesting that these compounds could be useful for increasing systemic rather than local drug delivery.

Structure-activity relationship analysis of substituted 4-quinolinamines, antagonists of immunostimulatory CpG-oligodeoxynucleotides.

On the basis of a systematic SAR analysis of substituted quinolines, a derivative 32 was synthesized that shows half-maximal inhibition of the immunostimulatory effect of CpG-oligodeoxynucleotides in vitro at the concentration of 0.24 nM.

N-(4-bromobenzoyl)-S,S-dimethyliminosulfurane, a potent dermal penetration enhancer.

N-Aroyl-, N-Arylsulfonyl-, and N-Aryl-S,S-dimethyliminosulfuranes have been synthesized and evaluated as potential dermal penetration enhancers. The title compound and Azone exhibit similar activities for permeation of hydrocortisone through hairless mouse skin.