To create lowb and-gap,f luorescent, and elastic organic crystal emitters,w ef ocused on an extended pconjugated system based on:a )aplanar conformation,b) arigid structure,and c) controlled intermolecular interactions. Herein, we report on two fluorescent and highly flexible organic crystals (1 and 2)whichcould bend under an applied stress.T he bent crystals rapidly recover their straight shape upon release of the stress.C rystal 1 with at etrafluoropyridyl terminal unit and al ower band-gap energy (orange emission, l em = 573 nm, F F = 0.50), showed no bending mechanofluorochromism and had superior performance as an optical waveguide with reddish orange emission. The waveguide performance of the crystal did not decrease under bending stress.F or crystal 2 with ap entafluorophenyl terminal unit (green emission, l em = 500 nm, F F = 0.38), the original waveguide performance decreased under an applied bending stress; however,this crystal showed aunique bending mechanofluorochromism.

Highly selective tail-to-tail dimerization of methyl methacrylate has been realized by an N-heterocyclic carbene catalyst, giving dimethyl 2,5-dimethyl-2-hexenedioate with an E/Z ratio of 95:5 in 86% isolated yield. The umpolung mechanism is proposed on the basis of interception of the intermediates using ESI-MS analyses and deuterium-labeling experiments.

Coordination polymerizations of para-substituted phenylallenes (2a−2e) were carried out by using [(π-allyl)NiOCOCF3]2 (1) as an initiator. The polymerizations were found to proceed through a living mechanism to yield polymers exclusively composed of 2,3-polymerized units in high yields, where the resulting polymers have predictable molecular weights and narrow molecular weight distributions. From kinetic studies, the polymerization rate was found to increase with the electron-donating character of the para substituent in 2. The coordination polymerizations of α-methylphenylallene (2f) and γ-methylphenylallene (2g) were also carried out to produce soluble polymers. In these cases, the methyl substituent on the allene moiety (especially at the γ-position) was found to reduce the polymerizability. A plausible polymerization mechanism was also discussed based on the results obtained in the study.

A coordination polymerization of alkoxyallenes (2a-2f) by the [q3-(allyl)NiOCOCF3] (1) /PPh, system was carried out to obtain a polymer (3) bearing exomethylenes on the main chain. The structure of the obtained polymer was confirmed by 'H-, "C-NMR and IR spectra, and was revealed to consist of two units, one bearing an exomethylene side chain and the other an end ether side chain as a result of 1,2-and 2,3-~olymerization. In the case of methoxyallene, the ratio was estimated as 32:68. The number average molecular weight (M&f t& resulting polymer varied linearly with increasing ratio of monomer to initiator. The molecular weight distributions (MJM,,) of the polymers obtained here were always approximately 1.1.These results may strongly support that the present polymerization proceeds bya living mechanism. Under an inert atmosphere, the propagating end of the polymer was quite stable and could be kept without any decrease in activity for more than a week. The proportion of 1,2-and 2,3-polymerization was a little affected by the substituents on the alkoxyallenes, as the steric bulkiness of the substituents increased the content of 2,3-polymerization units.

No abstract