A remarkably efficient synthesis of pure cis-stilbenoid hydrocarbons using trans-dibromoalkenes via palladium catalysis

A remarkably versatile synthesis of cis-stilbenoid hydrocarbons containing highly functionalized phenyl groups is developed via an efficient palladium-catalyzed coupling of aryl Grignard reagents with trans-1,2-dibromoalkenes (generally obtained via bromination of the corresponding dialkylacetylenes) in tetrahydrofuran.     

Application of multidimensional affinity high-performance liquid chromatography and electrospray ionization liquid chromatography-mass spectrometry to the characterization of glycosylation in single-chain plasminogen activator initial results

Preliminary results are presented using a combination of affinity chromatography, reversed-phase HPLC and electrospray ionization mass spectrometry to produced peptide maps for N-linked, O-linked and non-glycosylated peptides from an endoproteinase LysC digest of DSPA1, a recombinant DNA derived glycoprotein. Although the system was used to identify a number of major N-linked structures, notably complex biantennary structures attached to asparagine 362, no O-linked glycopeptides from the possible 4 attachment sites were identified. The system did, however, demonstrate the feasibility of the approach and the applicability of the instrumental system.     

Multi-sweep asynchronous parallel successive overrelaxation for the nonsymmetric linear complementarity problem

Convergence is established for themulti-sweep asynchronous parallel successive overrelaxation (SOR) algorithm for thenonsymmetric linear complementarity problem. The algorithm was originally introduced in [4] for the symmetric linear complementarity problem. Computational tests show the superiority of the multi-sweep asynchronous SOR algorithm over its single-sweep counterpart on both symmetric and nonsymmetric linear complementarity problems.This material is based on research supported by National Science Foundation Grants CCR-8723091 and DCR-8521228, and Air Force Office of Scientific Research Grants AFOSR-86-0172 and AFOSR-86-0124.     

Synthesis, structure, aggregation-induced emission, self-assembly, and electron mobility of 2,5-bis(triphenylsilylethynyl)-3,4-diphenylsiloles

2,5-Bis(triphenylsilylethynyl)-3,4-diphenylsiloles with different 1,1-substituents [XYSi(CPh)(2) (C-C≡C-SiPh(3))(2)] (Ph=phenyl) were synthesized in high yields by the Sonogashira coupling of 2,5-dibromo-3,4-diphenylsiloles with triphenylsilylacetylene, and two of these were characterized crystallographically. Crystal structures and theoretical calculations showed that the new silole molecules had higher conjugation than 2,5-diarylsiloles. They possessed low HOMO and LUMO energy levels due to the electron-withdrawing effect of the triphenylsilylethynyl groups. Cyclic voltammetry analysis revealed low electron affinities, which were comparable to those of perfluoroarylsiloles. B3LYP/6-31* calculations demonstrated that the new siloles possessed large reorganization energies for electron and hole transfers and high electron mobilities. A mobility of up to 1.2×10(-5) cm(2) V(-1) s(-1) was obtained by the transient electroluminescence method, which was about fivefold higher than that of tris(8-hydroxyquinolinato)aluminum, a widely used electron-transport material, under the same conditions. All of the silole molecules possessed high thermal stability. Although, their solutions were weakly emissive, their nanoparticle suspensions and thin films emitted intense blue-green light upon photoexcitation, demonstrating a novel feature of aggregation-induced emission (AIE). Polarized emissions were observed in the silole crystals. The addition of solvents, which did not dissolve the silole molecules, into silole-containing solutions caused self-assembly of the molecules, which produced macroscopic fibrils with strong light emissions.     

Comparison of the Nucleation Kinetics Obtained from the Cumulative Distributions of the Metastable Zone Width and Induction Time Data

A linearized integral model based on classical nucleation theory is applied in this work to determine the interfacial energy and pre-exponential factor using a linear plot from the cumulative distributions of the metastable zone width (MSZW) data for some systems reported in the literature, including isonicotinamide, butyl paraben, dicyandiamide, and salicylic acid. Based on the same criterion for the nucleation point, the interfacial energy and pre-exponential factor are determined using the conventional linear regression method from the cumulative distributions of the induction time data for the same systems. The results indicate that the interfacial energy and pre-exponential factor calculated from the MSZW data are consistent with those calculated from the induction time for the studied systems.     

Aggregation and chiroptical behavior of a high molecular weight chirally substituted dialkylpoly(p‐phenyleneethynylene)

The solvent and temperature dependent aggregation of high molecular weight bis[S‐(+)‐3,7‐dimethyloctyl)] substituted poly(p‐phenyleneethynylene) (PPE, 2 ) was examined by absorption, emission and circular dichroism spectroscopy. All herein employed methods strongly support the view that 2 forms ordered aggregates in the solid state and in solvent mixtures. This is the first case in which a chiral high molecular weight PPE displays its aggregation by both optical and chiroptical methods.