摘要/Abstract

通过Pd催化的Sonogashira偶联合成了三个以4，4'-二甲氧基三苯胺基团为氧化还原中心的偶氮苯化合物4～6，电化学和光谱电化学的研究表明，该类化合物具有优秀的氧化还原可逆性.光致异构的实验表明，三苯胺基团在偶氮苯上的取代位置对该类化合物的光化学性质有显著的影响.化合物4不仅可以通过光照实现顺式到反式的异构化，也可仅通过改变三苯胺基团的价态高效地实现.
关键词: 三苯胺, 偶氮苯, 光致异构, 氧化还原
Three azobenzenes 4~6 conjugated with 4,4'-dimethoxy-triphenylamine redox center have been synthesized by palladium-catalyzed Sonogashira coupling reactions in moderate yield after column chromatographic purification. They are all stable when exposed in air and moisture in both the solid and solution state. The ¹H NMR spectra of 4~6 showned that the azobenzene groups are in the trans configuration. The UV/Vis spectra of the target molecule were studied. The UV/Vis absorption bands of 4~6 are less clearly separated, which is similar to those for aminoazobenzen or pseudostilbene. The absorption bands at the π→π^* band of 4 and 6 are redshifted, due to the strong electronic interaction between the azobenzene unit and the para-triphenylamine unit, which results in the formation of a longer conjugation system than the corresponding meta isomers. Electrochemical and spectroelectrochemical studies indicate excellent redox reversibility of these compounds. Significant spectra change upon the process of redox makes these compounds have potential applications of electrochemical switching. Among the derivatives, compound 4 exhibits the highest cis form (45%) in the photostationary state (PSS) upon light irradiation at 435 nm. The photoisomerization studies indicate that the photochemistry properties is strongly influenced by the substituted position of the triphenylamine moiety. Photoisomerization studies showed that these compounds have fast photoisomerization rate due to the higher photoisomerization quantum yield, which is an order of magnitude larger than that of ferrocenyl (ethynyl) azobenzenes. Both compounds 4 and 6 exhibit excellent fatigue resistance and reversibility under several repeated reversible isomerization cycles. The cis-to-trans photoisomerization of 4 can be not only achieved by irradiation at UV lignt, but also realized by a more efficient way of change the state of redox center. Our study will provide a good basis for research in design new type of multiple-response molecular switches.
Key words: triphenylamine, azobenzene, photoisomerization, redox


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