2002 Fiscal Year Final Research Report Summary
Elongation and Contraction of Molecular Springs. Synthesis, Structures, and Properties of Bridged [7]Thiaheterohelicenes
| Project/Area Number |
12440179
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Organic chemistry
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| Research Institution | Wakayama University |
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Principal Investigator |
TANAKA Kazuhiko Wakayama University, Systems Engineering, Professor, システム工学部, 教授 (00025446)
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| Co-Investigator(Kenkyū-buntansha) |
OSUGA Hideji Wakayama University, Systems Engineering, Lecturer, システム工学部, 教授 (50304184)
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| Project Period (FY) |
2000 – 2002
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| Keywords | thiaheterohelicene / helical pitch / X-ray crystallography / inclusion / circular dichroism / absorption spectra / bridged helicene / unbridged helicene |
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| Research Abstract |
A series of bridged [7]thiaheterohelicenes 3a-c and 4 with a variety of helical pitches have been prepared from racemic and optical pure 2, 13-bis(hydroxymethyl)dithieno[3, 2-e: 3', 2'-e']benzo[1, 2-b: 4, 3-b']bis[1]benzothiophene (1) in order to investigate the helical structures in solution. Recrystallizations of (PM)-3a, (PM)-3b, (PM)-3c, and (P)-4 from hexane-dichloromethane gave crystals suitable for X-ray crystallography, while recrystallization of (PM)-4 with benzene gave an inclusion complex with a stoichiometry of (PM-4)_4【O!R】 (C_6H_6). X-ray analyses of (PM)-3a-c, (PM-4)_4【O!R】 (C_6H_6), and (P)-4 indicate that the dihedral angles between terminal thiophene rings of the helical framework significantly vary from 22^o for 4 to 59^o for 3c. This represents as increase of 37^o or 168%. Although the ^<13>C-NMR and UV absorption spectra of bridged helicenes 3a-c and unbridged helicene 5 are essentially the same, the molar rotation of 5 is very large compared with those of 3a-c and 4. A red-shift (15nm) in the circular dichroism (CD) spectrum is observed for 4, suggesting that this compound is more planar than 3a-c in solution. In the series of [7]thiaheterohelicenes studied, the minimum helical pitch is 2.70 A^^o for 4.
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