Odom Susan A, Lancaster Kelly, Beverina Luca, Lefler Kelly M, Thompson Natalie J, Coropceanu Veaceslav, Brédas Jean-Luc, Marder Seth R, Barlow Stephen
School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA 30332-0400, USA.
Chemistry. 2007;13(34):9637-46. doi: 10.1002/chem.200700668.
Five diamines with thiophene-based bridges--(E)-1,2-bis{5-[bis(4-butoxyphenyl)amino]-2-thienyl}ethylene (1), 5,5'-bis[bis(4-methoxyphenyl)amino]-2,2'-bithiophene (2), 2,6-bis[bis(4-butoxyphenyl)amino]dithieno[3,2-b:2',3'-d]thiophene (3), N-(4-tert-butylphenyl)-2,6-bis[bis(4-methoxyphenyl)amino]dithieno[3,2-b:2',3'-d]pyrrole (4 a) and N-tert-butyl-2,6-bis[bis(4-methoxyphenyl)amino]dithieno[3,2-b:2',3'-d]pyrrole (4 b)--have been synthesised. The syntheses make use of the palladium(0)-catalysed coupling of brominated thiophene species with diarylamines, in some cases accelerated by microwave irradiation. The molecules all undergo facile oxidation, 4 b being the most readily oxidised at about -0.4 V versus ferrocenium/ferrocene, and solutions of the corresponding radical cations were generated by addition of tris(4-bromophenyl)aminium hexachloroantimonate to the neutral species. The near-IR spectra of the radical cations show absorptions characteristic of symmetrical delocalised species (that is, class III mixed-valence species); analysis of these absorptions in the framework of Hush theory indicates strong coupling between the two amine redox centres, stronger than that observed in species with phenylene-based bridging groups of comparable length. The strong coupling can be attributed to high-lying orbitals of the thiophene-based bridging units. ESR spectroscopy indicates that the coupling constant to the amino nitrogen atoms is somewhat reduced relative to that in a stilbene-bridged analogue. The neutral species and the corresponding radical cations have been studied with the aid of density functional theory and time-dependent density functional theory. The DFT-calculated ESR parameters are in good agreement with experiment, while calculated spin densities suggest increased bridge character to the oxidation in these species relative to that in comparable species with phenylene-based bridges.
已合成了五种带有噻吩基桥连的二胺——（E）-1,2-双{5-[双（4-丁氧基苯基）氨基]-2-噻吩基}乙烯（1）、5,5'-双[双（4-甲氧基苯基）氨基]-2,2'-联噻吩（2）、2,6-双[双（4-丁氧基苯基）氨基]二噻吩并[3,2-b:2',3'-d]噻吩（3）、N-（4-叔丁基苯基）-2,6-双[双（4-甲氧基苯基）氨基]二噻吩并[3,2-b:2',3'-d]吡咯（4a）和N-叔丁基-2,6-双[双（4-甲氧基苯基）氨基]二噻吩并[3,2-b:2',3'-d]吡咯（4b）。这些合成反应利用了钯（0）催化的溴代噻吩物种与二芳基胺的偶联反应，在某些情况下通过微波辐射加速反应。这些分子都易于氧化，相对于二茂铁鎓/二茂铁，4b在约-0.4V时最容易被氧化，通过向中性物种中加入三（4-溴苯基）铵六氯锑酸盐生成了相应自由基阳离子的溶液。自由基阳离子的近红外光谱显示出对称离域物种（即III类混合价物种）的特征吸收；在Hush理论框架内对这些吸收进行分析表明，两个胺氧化还原中心之间存在强耦合，比在具有类似长度的亚苯基桥连基团的物种中观察到的耦合更强。这种强耦合可归因于噻吩基桥连单元的高能轨道。电子顺磁共振光谱表明，相对于芪桥连类似物，与氨基氮原子的耦合常数有所降低。借助密度泛函理论和含时密度泛函理论对中性物种和相应的自由基阳离子进行了研究。密度泛函理论计算的电子顺磁共振参数与实验结果吻合良好，而计算得到的自旋密度表明，相对于具有亚苯基桥的类似物种，这些物种氧化时桥的特征增加。
