π‑Extended Thiadiazoles Fused with Thienopyrrole or Indole Moieties: Synthesis, Structures, and Properties

We report the syntheses, structures, photophysical properties,
and redox characteristics of donor–acceptor-fused π-systems,
namely π-extended thiadiazoles 1–5 fused with thienopyrrole or indole moieties. They were synthesized
by the Stille coupling reactions followed by the PPh3-mediated
reductive cyclizations as key steps. X-Ray crystallographic studies
showed that isomeric 1b and 2b form significantly
different packing from each other, and 1a and 4a afford supramolecular networks via multiple hydrogen bonding with
water molecules. Thienopyrrole-fused compounds 1b and 2b displayed bathochromically shifted intramolecular charge-transfer
(CT) bands and low oxidation potentials as compared to indole-fused
analog 3b and showed moderate to good fluorescence quantum
yields (Φf) up to 0.73. In 3b–5b, the introduction of electron-donating substituents in
the indole moieties substantially shifts the intramolecular CT absorption
maxima bathochromically and leads to the elevation of the HOMO levels.
The Φf values of 3–5 (0.04–0.50) were found to be significantly dependent on the
substituents in the indole moieties. The OFET properties with 1b and 2b as an active layer were also disclosed.

本报告阐述了π-扩展硫二唑类化合物1-5的合成、结构、光物理性质及氧化还原特性，其中这些化合物通过π-共轭体系与噻二唑或吲哚基团融合而成。其合成过程以Stille偶联反应为基础，辅以三苯基膦介导的还原性环化反应作为关键步骤。X射线晶体学研究表明，异构体1b和2b呈现出显著不同的分子堆积方式，而1a和4a则通过多重氢键与水分子相互作用，形成超分子网络。噻二唑融合化合物1b和2b相较于吲哚融合类似物3b，表现出向红移的分子内电荷转移(CT)带和较低的氧化电位，并显示出中等到良好的荧光量子产率（Φf）高达0.73。在3b-5b中，引入电子供体取代基至吲哚基团，显著将分子内CT吸收最大值向红移，并导致最高占据分子轨道(HOMO)能级的提升。3-5（0.04-0.50）的Φf值被发现与吲哚基团中的取代基有显著相关性。此外，以1b和2b作为活性层的有机发光电场效应晶体管（OFET）特性亦被揭示。