Theoretical Study of the Electronic Structure of 2,2′-Bisilole in Comparison with 1,1′-Bi-1,3-cyclopentadiene: σ*-π* Conjugation and a Low-Lying LUMO as the Origin of the Unusual Optical Properties of 3,3′ ,4,4′-Tetraphenyl-2,2′-bisilole1

Bulletin of the Chemical Society of Japan

Volumn 69, Issue 8, 1996, Pages 2327-2334

  Yamaguchi, Shigehiro ^a   Tamao, Kohei ^a  

^a KYOTO UNIVERSITY   (Japan)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0000383676     PISSN: 00092673     EISSN: None     Source Type: Journal    
DOI: 10.1246/bcsj.69.2327     Document Type: Review

References (33)

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24. The PM3 level calculations have also shown that the LUMO level of silole 5 is lower by 0.15 eV than that of cyclopentadiene 6, while the HOMO levels are comparable to each other.
25. Similar σ*-π* conjugation has quite recently been reported to be seen in 2,2′,5,5′-tetrasila-1,1′-bicyclopentylidene: M. Ichinohe, A. Sekiguchi, H. Sakurai, "69th Annual Meetings of the Chemical Society of Japan," Kyoto, March 1995, Abstr., 3C808.
26. A. R. Bassindale and P. G. Taylor, in "The Chemistry of Organic Silicon Compounds," ed by S. Patai and Z. Rappoport, Wiley, New York (1991), pp. 893-963.
27. Similarly, if 5,5-dimethyl-1,3-cyclopentadiene is divided into the butadiene moiety and dimethylcarbene moiety (propane), the corresponding σ* orbital (4.04 eV) of propane lies at 2.57 eV higher level than that of dimethylsilylene moiety.
28. The final result (Table 2, Entry 7), however, does not completely reproduce the calculation results based on the X-ray structure (Table 2, Entry 1); the latter has a lower LUMO by 0.05 eV and a higher HOMO by 0.1 eV than the distorted model system. These differences are probably due to the total strain of other parts of the rings.
29. The reduction potential difference between 10 and 11 is slightly larger than that between 2a and 4a. This is inconsistent with the calculation results, probably due to the different substituent patterns between these two series.
30. As only one example for silole-containing (on 2,5-positions) fully π-conjugated polymers so far, thiophene-silole copolymers have been prepared by us: K. Tamao, S. Yamaguchi, M. Shiozaki, Y. Nakagawa, and Y. Ito, J. Am. Chem. Soc., 114, 5867 (1992), and Ref. 12e.
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