A new synthetic route to mononitrated oligothiophenes is described, as well as the preparation of halogenated derivatives (Br, I) thereof. An unusual deep red colour is observed and explained, with the aid of DFT calculations, as arising from a significant quinoidal contribution to the molecular structure. The crystal structures of two compounds, H(C4H2S)3NO2 and Br(C4H2S)3NO2, are presented. Both compounds have planar sheets held together by intermolecular short contacts (hydrogen bonds and, for the latter, NO2···Br interactions); the sheets do not directly superimpose, so the effect of the π-stacking is not maximized. Solid-state fluorescence and extended-Hückel band-structure calculations are also presented for these materials.
介绍了单硝化低聚噻吩的新合成路线,以及其卤代衍生物(Br、I)的制备方法。在 DFT 计算的帮助下,观察到了一种不寻常的深红色,并解释了这种深红色是由于分子结构中存在大量的醌基。文中展示了 H(C4H2S)3NO2 和 Br(C4H2S)3NO2 这两种化合物的晶体结构。这两种化合物都具有通过分子间短接触(氢键以及后者的 NO2-Br 相互作用)固定在一起的平面片层;片层并不直接叠加,因此π堆叠的效果并没有最大化。此外,还介绍了这些材料的固态荧光和扩展胡克尔带状结构计算结果。