Search results for "OMOP"
showing 10 items of 624 documents
Coordination behavior of sulfathiazole. Crystal structure of [Cu (sulfathiazole) (py)3Cl] superoxide dismutase activity
1995
Abstract The preparation, spectroscopic, magnetic properties, and crystal structure of [Cu(stzxpy) 3 Cl] (stz − stands for the deprotonated form of sulfathiazole, 4-amino-N-2-thiazolylbencenosulfonamide) are reported. Crystals are orthorhombic, space group Pbca, with cell constants a = 15.834(2), b = 17.512(4), and c = 18.79(2) A, and Z = 8. The structure was solved and refined to R = 0.041 (R W = 0.040). The structure consists of mononuclear units linked via hydrogen bonds to form the tridimensional pyramid. The geometry of CuN3N*NCl chromophore is distorted square-pyramid. The superoxide-dismutase mimetic activity of the compound is measured and compared with those of the SOD enzyme, the …
Comparison of Alkoxy-substituted 4,4´-Distyrylbiphenyls and the Corresponding 4,4´-Distyrylbenzenes
2008
Abstract Configurationally highly pure (E,E)-4,4´-bis(styryl)biphenyls 2a - e were obtained by Siegrist reactions of 4,4´-dimethylbiphenyl 3 and alkoxy-substituted benzaldimines (4a - e). DSC measurements have indicated different crystalline modifications of these conjugated compounds. The stilbenoid chromophores of 2a - e are compared to the stilbenoid chromophores in the OPV series, which have a similar length of conjugation. The intense fluorescence and the high transparency in the visible region are promising properties for an application of the donor-substituted compounds 2a - e in twophoton absorption (TPA) techniques.
Soluble oligo(phenylenevinylene)s with electron withdrawing substituents for the use in light emitting diodes
2000
Poly(p-phenylenevinylene) (PPV) and its derivatives are one of the most widely used classes of phosphors in light emitting diodes. Central problems are the imbalanced charge carrier injection and transport properties due to the high lying conduction band. A series of good soluble oligo(phenylenevinylene)s (OPV) with five benzene rings and a variety of electron withdrawing and accepting substituents have been prepared and may serve as model compounds for PPV with increased electron affinity. The central ring of the OPVs is substituted with two octyloxy groups to ensure good solubility and the lateral styrene units carry further chromophoric groups of different electronic character. The synth…
Large Quadratic Hyperpolarizabilities with Donor–Acceptor Polyenes Exhibiting Optimum Bond Length Alternation: Correlation Between Structure and Hype…
1997
Donor-acceptor polyenes of various lengths, and that combine aro- matic electron-donating moieties with powerful heterocyclic electron-withdraw- ing terminal groups, have been synthe- sized and characterized as efficient non- linear optical (NLO) chromophores. Their linear and nonlinear optical proper- ties have been investigated, and variations in these properties have been related to ground-state polarization (dipole p) and structure. In particular, unprecedented quadratic hyperpolarizabilities (p) have been achieved (up to p(0) =I500 x 10-30esu) by reduction of the bond- length alternation (BLA) in the polyenic chain. In each series of homologous com-
Extension of Conjugation Leading to Bathochromic or Hypsochromic Effects in OPV Series
2004
Four OPV series 1-4 (a-d) with a terminal dialkylamino group as electron donor were prepared by Wittig-Horner reactions. To study the influence of the push-pull effect on the long-wavelength absorption, three of the four series contained terminal acceptor groups (CN, CHO, NO(2)). The length of the chromophores strongly affects the intramolecular charge transfer (ICT)-an effect which superimposes upon the extension of the conjugation. Increasing numbers n of repeat units cause an overall bathochromic shift for the purely donor-substituted series 1 a-4 a and the series 1 b-4 b with CN as weak acceptor. The two effects annihilate each other in the series 1 c-4 c with terminal CHO groups, so th…
Probing the spectral dynamics of single terrylenediimide molecules in low-temperature solids
1999
Abstract Fluorescence excitation lines of single terrylenediimide (TDI) molecules were recorded in the matrices polyethylene (PE) and hexadecane (HD) in the temperature range between 1.4 and 13 K. From line width distributions at 2.5 K in both matrices it was concluded that the disorder, theoretically modeled by a distribution of two-level systems (TLSs), is about three times stronger in PE. Temperature-dependent measurements of the line shape of single chromophores showed a reversible broadening and shift of the zero-phonon lines. We attributed this behavior to dephasing caused by pseudolocal phonons and to spectral diffusion caused by fluctuating TLSs of the disordered host. Following the…
Photoinduced phenomena in corona poled polar organic films.
2005
Abstract Organic materials have received considerable attention because of their large dipole moments and optical nonlinearities. The optically induced switching of material properties is important for studying the optoelectronic effects including second harmonic generation. Organic materials for photonic applications contain chromophore dipole which consist of acceptor and donor groups bridged by a delocalized π-electron system. Both theoretical and experimental data show a reversible highly dipolar photoinduced intra molecular charge transfer in betaine type molecules accompanied by change of the sign and the value of the dipole moment. The arrangement of polar molecules in films is studi…
ChemInform Abstract: Phenylethynyl- and Phenylethenylmetacyclophanes.
2010
The cyclophanes 6,8,10 and 13–15 were synthesized by cesium assisted ring closure reactions. The main interest in these systems concerns the interaction of the unsaturated bridge with the tolan and the stilbene chromophores, respectively.
Energy transfer rates and pathways of single donor chromophores in a multichromophoric dendrimer built around a central acceptor core.
2004
An artificial light-harvesting dendrimer showing highly efficient electronic excitation energy transfer from four peripheral donors to one central acceptor has been investigated by single-molecule spectroscopy at low temperatures. Confocal imaging in combination with frequency selective excitation spectroscopy gives direct access to energy transfer rates of individual donors and allows the determination of energy transfer pathways within a single multichromophoric aggregate.
Consequences of the One-Electron Reduction and Photoexcitation of Unsymmetric Bis-imidazolium Salts
2012
Coupling of uronium salts with in situ generated N-heterocyclic carbenes provides straightforward access to symmetrical [4](2+) and unsymmetrical bis-imidazolium salts [6](2+) and [9](2+) . As indicated by cyclic and square-wave voltammetry, [6](2+) and [9](2+) can be (irreversibly) reduced by one electron. The initially formed radicals [6](.+) and [9](.+) undergo further reactions, which were probed by EPR spectroscopy and density functional calculations. The final products of the two-electron reduction are the two carbenes. Upon irradiation with UV light both [6](2+) and [9](2+) emit at room temperature in solution but with dramatically different characteristics. The different fluorescenc…