| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1996: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1995: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Research Abstract |
We have successfully synthesized 1,2-cyclopentenylene-ethynylene and 3,4-thienylene-ethynylene oligomers. The well-documented palladium-caralyzed coupling reaction of terminal alkynes and alkenyl or aryl halides was repeatedly applied to the synthesis of these oligomers, which were fully characterized by spectroscopic and elemental analyzes. Electronic absorption spectra of 1,2-cyclopentenylene-ethynylene oligomers showed bathochromic shifts with increasing chain length, indicating increasing conjugation of the pi-electrons. On the other hand, electronic spectra of 3,4-thienylene-ethynylene oligomers showed a characteristic pi-pi^<**> transition with almost identical absorption maximum, suggesting a favorable twist conformation of the thienyl-ethynyl moieties, which decreases conjugation of the pi-electrons. The solid-state conformations of 3,4-thienylene-ethynylene oligomers were elucidated by an X-ray crystallographic analysis, and they take a totally heilcal conformation. A detailed comparison of the ^1H NMR spectra of the oligomers revealed high-field shifts of the thienyl protons, supporting that the helical conformation with intramolecular stacking of the thiophene moieties also dominates in solution. A tandem cyclization reaction of the 1,2-cyclopentenylene-ethynylene system was induced at above 200ﾟC in a solution. Although the 3,4-thienylene-ethynylene systems were thermally stable, they were cyclized under the influence of tellurium tetrachloride to afford novel thiophene-fused pentalene system. These oligomers showed intense fluorescence in a visible region, suggesting potential materials as optoelectronic devices.
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