电子等排体的噻吩多烯与苯多烯同系递变的比较Ⅱ

为了比较噻吩多烯和苯多烯三岔共轭体系的性能,合成了三个系列带两个拉电子基团的噻吩多烯三岔化合物(TDn,TEn,TFn),测定了它们在环已烷和乙醇中的电子吸收光谱。实验表明,带两个拉电子基团的噻吩多烯三岔共轭化合物的电子吸收光谱频率也都遵守同系线性规律,相关系数Υ>0.99。与相应的苯多烯化合物的电子光谱相比,吸收峰普遍地红移一个插烯双键所引起的红移数值。相应的同系直线相距很近。△λ_(th)/△λ_E值为0.83-1.10。第一个拉电子基团的引入,化合物的电子吸收峰红移30nm左右,但当第二个拉电子基团引入时,电子吸收峰仅红移3—17nm,其作用只相当于一个取代基。

A COMPARISON OF HOMOLOGOUS GRADATION FOR ISOSTREIC THIENYL- AND PHENYL-POLYENE SERIES II

Three series of 2-thienyl polyenic forked compounds(TDn, TEn,TFn) with two electron-attracting groups have been synthesized. In the following, every new compound is marked with an asterisk.The electronic absorption spectra of these compounds have been measured in cyclohexane and ethanol. It has been found that all the their absorption peaks show red shift about 30nm as compared with those of the corresponding phenyl compounds, and that the wave number of absorption peaks of all the 2-thienyl polyenic forked compounds conform to the rule of homologous linearity with correlation coefficients γ>0.99. The homologous line of the thienyl series lies very close to that of the phenyl series. The average △λth/△λE values is 0 .83--1.10, slightly greater than that of the linear chain series. This shows that, when the first electron-attracting group is introduced in 2-thienyl polyene chain, its effect is equvelent to about one chain unit of the molecular trunk , while-the introduction of the second electron-attracting group causes a red shift of only 3-17nm. This indicates that the second forked group plays the role of a substituent group.