| Summary: | 碩士 === 國立臺灣大學 === 化學研究所 === 95 === In recent years, scientists have devoted to developing molecular machines by chemical synthesis. A variety of molecular machines, including motors, shuttles, switches, and elevators, has been reported.
In this thesis, we report on a new “ light-controlled molecular rotary ” system, which consists of two main components: a four-bladed pentiptycene and substituted styrene. The substituent in the styryl group is 3,5-dinitro (1), 4-nitro (2), 3,5-dimethoxy (4), 4-methoxy (5).The pentiptycene and substituted styrene are connected by a single bond that functions as an axle. When the molecule is in the trans form, the pentiptycene group rotates freely at room temperature. Upon irradiation, the double bond isomerizes and the substituted styryl group inserts to the cavity of pentiptycene, which blocks its rotation. According to variable-temperature 1H-NMR, the rotational barrier（kcal/mol）of single bond is cis-1 ( 17.16 )＞cis-2 ( 15.07 )＞cis-5 ( 15.04 )＞cis-4 ( 14.69 )＞cis-3 ( 12.63 ).
The photostationary state of compound 1 in CH2Cl2 is cis-1/trans-1=75/25（λ=306 nm） and trans-1/cis-1=45/55（λ=254 nm）. This, the constitution of compound 1 can be switched by light by about 20 %. The switching percentage is longer for compound 3~5, which is about 40 %, from cis/trans=95/5（306 nm）to trans/cis=55/45（λ=254 nm）
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