| Summary: | 碩士 === 臺灣大學 === 化學研究所 === 98 === Because of its unique rigid, bulky and three-dimensional structure, pentiptycene is a potential scaffold for the construction of molecular machines. This thesis reports the synthesis and properties of new pentiptycene derivatives as molecular gear and molecular brake systems.
The target molecular gear system IBI/IBI-OMe was prepared from compound 6/9 by the Sonogashira reaction. Compound IBI serves as a model compound. The precursor of IBI-OMe is racemic mixture and thus IBI-OMe is a mixture of stereoisomers including diastereomers and phase isomers. On the basis of experimental and simulated variable temperature (VT) NMR spectra and DFT (B3LYP/6-31G*//AM1) calculations, we concluded that the pentiptycene rotation in IBI-OMe is correlated at room temperature, and we also observed the swing motion of one pentiptycene rotor in the U-shaped cavities of the other pentiptycene rotor. The experimental free energies ΔG‡ for gear slippage is 18 kcal mol-1 at 298 K.
For the molecular brake system, middle-ring disubstituted pentiptycenes 12(s)/12(a), 13(s)/13(a), 14(s)/14(a), 15(s)/15(a), 16(s)/16(a) from the tetramethoxypentiptycene quinone 11(s)/11(a) have been prepared. They are the precursors for the target compound B-OH and B-CO.
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