Tunable spectroscopic and electrochemical properties of conjugated push–push, push–pull and pull–pull thiopheno azomethines
作者:Stéphane Dufresne、Marie Bourgeaux、W. G. Skene
DOI:10.1039/b616379c
日期:——
Novel azomethines consisting uniquely of thiophene units were examined. The highly conjugated compounds were prepared by condensing air stable aminothiophenes with 2-thiophene aldehydes, which were substituted with various electronic groups. The resulting azomethines are highly conjugated and are both reductively and hydrolytically resistant. Various electron donating and accepting groups placed in the 2-position of 5-thiophene carboxaldehyde lead to electronically delocalized pushâpush, pullâpull, and pushâpullazomethines. These electronic groups affect both the HOMO and the LUMO levels, which influence the absorption and emission spectra. Colors spanning the entire visible spectrum ranging from yellow to blue are possible with these nitrogen containing conjugated compounds. Excited state deactivation of the singlet excited state occurs predominately by internal conversion while only a small amount of energy is dissipated by intersystem crossing to the triplet state and by fluorescence. The ensuing fluorescence and phosphorescence of the thiopheno azomethines are similar to those of their thiophene analogues currently used in functional devices, but with the advantage of a low triplet state and tunable HOMOâLUMO energy levels extending from 3.0 to 1.9 eV. Quasi-reversible electrochemical radical cation formation is possible while the oxidation potential is dependent on the nature of the electronic group appended to the thiophene. The crystallographic data of the electronic pushâpush system show the azomethine bonds are planar and linear and they adopt the E isomer.
我们研究了仅由噻吩单元组成的新型偶氮甲烷。这些高度共轭的化合物是通过将空气稳定的氨基噻吩与 2-噻吩醛缩合而制备的,后者被各种电子基团取代。所制备的偶氮甲烷具有高度共轭性,并具有抗还原性和抗水解性。在 5-噻吩醛的 2 位上放置了各种电子供体和受体,从而产生了电子分散的推推、拉拉和推拉偶氮甲烷。这些电子基团会影响 HOMO 和 LUMO 水平,从而影响吸收和发射光谱。这些含氮共轭化合物的颜色横跨从黄色到蓝色的整个可见光谱。单重激发态的激发态失活主要是通过内部转换实现的,只有少量能量是通过系统间转换到三重态和荧光而耗散的。噻吩偶氮甲烷随之产生的荧光和磷光与目前用于功能器件的噻吩类似物相似,但其优点是三重态较低,HOMOâLUMO 能级可调,从 3.0 到 1.9 eV。这种化合物可以形成准可逆的电化学自由基阳离子,而氧化电位则取决于噻吩所附电子基团的性质。电子推挽系统的晶体学数据显示,偶氮甲基键是平面和线性的,它们采用 E 异构体。