In view of increasing interest in light-emitting materials, we have investigated the light-emitting characteristics and occurrence of conjugation between arms of star-shaped rigid molecules that comprise a 1,3,5-triethynylbenzene core and methoxy group-substituted oligo(p-phenylethynylene) arms. Consequently, we achieved the ultimate goal (Phif approximately 1.0, log epsilon > 5) for organic molecules with respect to light-emitting ability by creating very intense violet-blue (8, Phif = 0.97, log epsilon = 5.11) and blue (9, Phif = 0.98, log epsilon = 5.29) bright light-emitters. Also, pi conjugation was found to occur between the arms of 9 despite the meta-substituted system. We found a linear relationship of kr (with positive slope) and kd (with negative slope) with the number of dimethoxyphenyleneethynylene units for MMPT (4, 6, 8) and DMPT (5, 7, 9) homologues and the contrasting solvent effect on lambdaem of 8 and 9. It is also interesting that lambdaabs, epsilon, lambdaem, and Phif of 9 are greater than those of the corresponding banana- and rod-shaped molecules.

In view of the increasing importance of highly efficient light-emitting materials in chemistry, biological science, and materials science, we investigated the light-emitting efficiency tuning of rod-shaped oligo(p-phenylene ethynylene)s (OPEs, trimeric to pentameric systems) by donor and acceptor groups, so that they emit the very intense fluorescence (Phif approximately 1.0, log epsilon approximately 5) at 460 nm as the desired wavelength region. This goal was achieved by side modification by MeO (donor) groups and end modification by a CN-substituted benzene ring or CF3-substituted pyridine ring (acceptor) of tetrameric p-phenylene ethynylene rod-shaped molecules (Phif = 0.96, lambdaem = 458 nm, log epsilon = 4.96 for the former and Phif = 0.99, lambdaem = 459 nm, log epsilon = 4.92 for the latter). The high Phif values for 11 and 12 are interpreted in terms of kr (radiative rate constant) and kd (radiationless rate constant). The linear relationship with a positive slope between Phif and the Hammett sigma constant was found for the first time. It is found that kd rather than kr varies with sigmap-X. The photophysical properties (Phif, lambdaem, lambdaabs, log epsilon) were not so altered with the solvent polarity, which could be explained by the dipole moments in the excited and ground states. The results would be valuable for the molecular design of highly efficient light-emitting materials.

A series of 3-(3,5-di-tert-butyl-4-hydroxybenzylidene)pyrrolidin-2-ones was synthesized and evaluated as candidate antiinflammatory/analgesic agents as well as dual inhibitors of prostaglandin and leukotriene synthesis. Some compounds that showed dual inhibitory activity were found to possess equipotent antiinflammatory activities to indomethacin, with reduced ulcerogenic effects. One of the compounds, N-methoxy-3-(3,5-di-tert-butyl-4-hydroxybenzylidene)pyrrolidin-2-o ne, was found to have a wider safety margin than indomethacin or piroxicam, and was selected for detailed evaluation as a candidate drug for clinical application.

Doughnut‐shaped fluorescent molecules: Highly symmetrical, functionally and structurally interesting octakis‐m‐cyclynes 1 and octakis‐p‐cyclynes 2 are shown to be a new class of light‐emitting materials (see scheme). A pentacoordinate CuII complex of 1 exhibits remarkably intense fluorescence, contrary to the behavior expected for CuII complexes, which suggests that other transition‐metal complexes of 1 may also function as luminescent materials.

Pick of the bunch: Banana‐shaped molecules 1 and 2 containing dimethoxybenzene and pyridine units are highly efficient emitters of violet light despite the interruption of the π conjugation because of meta substitution. The contrasting solvent dependencies of the fluorescence quantum yield values of 1 and 2 are explained by the disparity between the difference density distributions in the excited states of the molecules.