Directed nickel-catalyzed regio- and diastereoselective arylamination of unactivated alkenes.

Few methods have been reported for intermolecular arylamination of alkenes, which could provide direct access to important arylethylamine scaffolds. Herein, we report an intermolecular syn-1,2-arylamination of unactivated alkenes with arylboronic acids and O-benzoylhydroxylamine electrophiles with Ni(II) catalyst. The cleavable bidentate picolinamide directing group facilitates formation of stabilized 4-, 5- or 6-membered nickelacycles and enables the difunctionalization of diverse alkenyl amines with high levels of regio-, chemo- and diastereocontrol. This general and practical protocol is compatible with broad substrate scope and high functional group tolerance. The utility of this method is further demonstrated by the site-selective modification of pharmaceutical agents.

A mesogenic triphenylene-perylene-triphenylene triad.

A straightforward synthesis of triphenylene-perylene-triphenylene triad structures has been achieved by using versatile triphenylene intermediates bearing a single oxyalkyl amine side chain. Among these, PBITP(10) showed a stable columnar mesophase implying favorably matched core-core separations in the structure. Importantly, the triad can be used as a vehicle for doping columnar triphenylene matrices with functional but incompatible perylene units and a mixture of hexahexyloxytriphenylene matrix doped with 0.1% PBITP(10) is homogeneous and liquid crystalline.

Exploring reversible quenching of fluorescence from a pyrazolo[3,4-b]quinoline derivative by protonation.

Pyrazolo[3,4-b]quinoline derivatives are reported to be highly efficient organic fluorescent materials suitable for applications in light-emitting devices. Although their fluorescence remains stable in organic solvents or in aqueous solution even in the presence of H(2)O, halide salts (LiCl), alkali (NaOH) and weak acid (acetic acid), it suffers an efficient quenching process in the presence of protic acid (HCl) in aqueous or ethanolic solution. This quenching process is accompanied by a change in the UV spectrum, but it is reversible and can be fully recovered. Both steady-state and transient fluorescence spectra of 1-phenyl-3,4-dimethyl-1H-pyrazolo-[3,4-b]quinoline (PAQ5) during quenching are measured and analyzed. It is found that a combined dynamic and static quenching mechanism is responsible for the quenching processes. The ground-state proton-transfer complex [PAQ5H(+)] is responsible for static quenching. It changes linearly with proton concentration [H(+)] with a bimolecular association constant K(S)=1.95 M(-1) controlled by the equilibrium dissociation of HCl in ethanol. A dynamic quenching constant K(D)=22.4 M(-1) is obtained by fitting to the Stern-Volmer equation, with a bimolecular dynamic quenching rate constant k(d)=1.03x10(9) s(-1) M(-1) under ambient conditions. A change in electron distribution is simulated and explains the experiment results.

[Photoluminescence from bis-t-butylbenzoxazolylthiophene doped silica films].

Thin nano-porous silica films doped with high concentrations of fluorescent material, 2, 5-bis (5-tert-butyl-2-benzoxazolyl)-thiophene (BBOT) were prepared via a sol-gel process. Uniform and bright blue fluorescence was observed. Light emission properties of these organic molecule doped inorganic silica films, i.e., hybrid films, were measured using ultraviolet-visible (UV-Vis) absorption spectroscopy, steady and time-resolved fluorescence spectroscopy as well as optical microscopy. Features of these materials were revealed in this investigation: Firstly, photoluminescence intensity from BBOT doped silica films increased linearly as the concentrations of BBOT increased if the dopant concentration was relatively low and below 6 x 10(-3) mol x L(-1); Secondly, no molecular aggregation or phase separation was observed using optical microscopy when the BBOT concentration was below 6 x 10(-3) mol x L(-1) in BBOT doped silica films. Thirdly, the fluorescence lifetimes of BBOT in the doped silica films were longer than that in a dilute dioxane solution (1.957 ns), which was contradicted to our general understanding that the fluorescence lifetime may be reduced in a condensed matter due to molecular interactions or quenching. It was further found that the fluorescence lifetime also varied with the gelation conditions. Taking a BBOT concentration of 6 x 10(-3) mol x L(-1) for an example, the lifetime of BBOT in doped silica films was about 2.45 ns for a specimen polymerized at 50 degrees C; while the lifetime was increased to 3.04 ns for a specimen polymerized at 90 degrees C. This work demonstrates no concentration quenching when the BBOT dopant concentrations increased to as high as 6 x 10(-3) mol x L(-1) in the silica matrix. In comparison with the changes in time-resolved photoluminescence of BBOT in dioxane solution and that of the BBOT doped nano-porous silica in relation to their concentration dependence and the gelation conditions, it was found that concentration quenching can be effectively suppressed by the nano-porous silica matrix. A stable fluorescent organic-inorganic hybrid material is thus obtained.

Photoluminescence and electroluminescence from a hybrid of lumogen red in nanoporous-silica.

In this paper white electroluminescence from a lumogen red-doped nanoporous silica matrix is presented. The matrix was prepared using a sol-gel process, and lumogen red--a perylene derivative--was doped at a number of concentrations. The photoluminescence and electroluminescence of the lumogen red-doped nanoporous-silica composite were investigated in detail. The structures, surface morphology, and optical properties of the nanoporous silica composites were investigated. The average pore size of the nanoporous-silica matrix was approximately 5 nm. The absorption spectra of the lumogen red in the nanoporous-silica matrix were broader than those from solution specimens. The photoluminescence of the lumogen red-doped nanoporous-silica matrix depended strongly on the excitation wavelengths. When excited at relatively longer wavelengths, e.g., 467 nm, the emissions peaked at constant positions (approximately 608 nm) for all cases, except a small shift to the red from its solution 601 nm. However, if excited at a shorter wavelength in the range of 200-400 nm, additional blue emissions were observed, which were particularly strong and suggested defect centers of the nanoporous-silica matrix. The electroluminescence from a single-layered sandwich device consisting of the lumogen red-doped nanoporous-silica was interesting. When driving with an AC electric field, electroluminescence spectra covered a whole spectral range, consisting of the red emission from lumogen red and the blue and green emission from the nanoporous silica matrix. In this way, we actually achieved a white electroluminescence from this hybrid organic and silica device with a color coordinate, CIE [x, y] = [0.30, 0.35] at a driving electric field of 3.0 x 10(6) V/cm. This was a first attempt to investigate electroluminescence from an organic dye-doped nanoporous silica matrix.