| Budget Amount *help |
¥12,800,000 (Direct Cost: ¥12,800,000)
Fiscal Year 2003: ¥5,000,000 (Direct Cost: ¥5,000,000)
Fiscal Year 2002: ¥7,800,000 (Direct Cost: ¥7,800,000)
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| Research Abstract |
New carbon allotropes having a carved conjugated system such as fullerenes and carbon nanotubes have been extensively studied from physical and chemical viewpoints. However, the supramolecular properties of the hollow of these materials have not been known well. We have recently synthesized a series of [n]CPPAs (cyclic paraphenylacetylenes) la-d (n = 6〜9) as relatively stable compounds. These compounds have smooth belt-shaped structure similar to a cut piece of carbon nanotube, and thus may be termed "carbon nanorings". They can be regarded as good model compounds for investigating the supramolecular properties of inner space of carved conjugated systems.
In the period of this grant, we have found interesting host properties of CPPAs as the following.
1)The belt-shaped π-conjugated [6]-and [8]CPPA exhibit nanosizecl cavities, and act as host molecules in crystalline inclusion complexes with hexamethylbenzene and toluene, respectively. The concave side of the cavities appears to possess a negative electronic potential.
2)Unusually stable complexes are formed between [6]CPPA and fullerenes (either C60 or bis(ethoxy-carbonyl)methanofullerene), Crystallographic analysis reveals that; a major driving force for the formation of such complexes is the existence of a novel concave-convex π-π interaction.
3)Carbon nanorings are structurally tuned to optimize their complexation with fullerenes (C_<60> and C_<70>). The affinity of carbon nanorings with fullerenes correlates with the width of the contact area. As the intence fluorescence emission of the CPPA host is quenched by the complexation of a fullerene, this effect can be used as a basis of a fullerene sensor.
4)Multi-inclusion structure, reminiscent of Russian Matrioshka dolls, have been constructed in nonpolar organic solvents from carbon nanorings and a C_<60> molecule. A study of these structures show there is a substantial difference between the electronic properties of planar and curved conjugated systems.
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