Derivatives of 2,3-(1,4-dialkoxyaceno)norbornadiene 1-4 underwent ring-opening metathesis polymerization (ROMP) reactions with a ruthenium carbene complex Cl 2 (PCy 3 ) 2 -RudCHPh to afford the corresponding polymers P1-P4 with narrow polydispersity. These materials exhibited luminescence both in solution and as films, whereas P3 and P4 were used successfully for the fabrication of light emitting diodes (LED). The device ITO/P4/Ca/ Al, made of a spin-coated layer of P3 or P4, displayed white light that can be turned on at 7 V with a maximum intensity of 427 cd/m 2 at 15 V. The white electroluminescence is composed of a blue emission band from the aromatic chromophore and a red component derived from solid aggregates. The performance of devices can be improved by insertion of an additional electron-transporting layer, i.e., 1,3,5-tris(2′-(1′-phenyl-1′-H-benzimidazole)benzene (TPBI). The device ITO/P4/TPBI/Mg:Ag displayed blue light with a turn-on voltage of 5 V and maximal intensity of 930 cd/m 2 at 15 V. The change of chromaticity can be ascribed to a shift of charge recombination sites in the bulk of P4 film. The phenomenon was verified by adjusting the thickness of TPBI layer, whereas a continuous variation in color was observed upon changing bias.
The cycloadducts 2A‐5A obtained from the Diels‐Alder cycloadditions of 1,2,3,4‐tetrachloro‐4,5‐dimethoxycyclopentadiene (1) with p‐benzoquinone (2), 1,4‐naphthoquinone (3), 1,4‐anthraquinone (4), and 2,3‐dicyano‐1,4‐benzoquinone (5) were subjected to the reaction with triethylamine in dichloromethane at room temperature. Cycloadducts 2A and 5A enolized to give the corresponding hydroquinones 2B and 5B, which were oxidized with DDQ to afford naphthoquinone ester 2D and anthraquinone ester 5D, respectively. In the cases of cycloadducts 3A and 4A, the enolization occurred concurrently with oxidation and fragmentation to produce directly the polyacenoquinone esters 3D and 4D, respectively. Under the same reaction condition, the unsymmetrical cycloadduct 6A derived from naphthoquinone ester 2D and 1 yielded isomeric polyacenoquinone esters 6Da and 6Db in a ratio of about 8:1.
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