| Research Abstract |
In this project, the belt-shaped large ring cyclophanes and the linear homologs in which the 1,2,4,5-positions of benzene rings are connected by disilane chains were synthesized, and their structures, the formation of inclusion compounds, and the electronic states were investigated.
These compounds were synthesized by the metathesis of benzo[1,2:4,5]bis(1,1,2,2-tetramethyl-1,2-disilacyclobut-3-ene) with the palladium complex. The linear dimer to pentamer and the cyclic tetramer and pentamer have been isolated so far.
The X-ray analysis showed that the cyclic tetramer has the belt-shaped rhombohedral structure with a cavity of 7.3 Å diameter, but it does not include a solvent molecule. The cyclic pentamer and the cyclic tetramer octaoxide include a benzene molecule in the cavity of 11.9 and 10.4 Å diameter, respectively. The benzene molecule is included in the parallel manner to the cyclophane ring. Although the benzene molecule easily escapes from the relatively large cavity of the cyclic pentamer in the air, the cyclic tetramer octaoxide holds the benzene molecule tightly and does not release it in the air and under reduced pressure. Therefore, benzene can be reversibly or irreversibly included by controlling the cavity size.
The linear trimer has the zigzag structure consisting of 1,2,4,5-tetrasilylbenzene units and includes two tetrahydrofuran molecules in the space formed by the zigzag structure. This inclusion way is rare and is regarded as the double-tweezers type.
The UV spectra of these compounds show the bathochromic shift and the increment of the extinction coefficient as the number of the 1,2,4,5-tetrasilylbenzene units increases. These results indicate that the σ-π conjugation between the silicon-silicon σ orbitals and the π orbitals of the benzene rings is extended all over the molecules.
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