Synthesis of Ultrahighly Electron-Deficient Pyrrolo[3,4‑d]pyridazine-5,7-dione by Inverse Electron Demand Diels–Alder Reaction and Its Application as Electrochromic Materials

A new electron acceptor 6-alkylpyrrolo­[3,4-d]­pyridazine-5,7-dione (PPD) with a very low LUMO level has been synthesized via a challenging inverse electron demand Diels–Alder reaction between thiophene and furan-decorated tetrazine substrates and an electron-deficient 1-alkyl-1H-pyrrole-2,5-dione unit. The PPD monomer has been incorporated into a series of donor–acceptor-type conjugated polymers as electrochromic materials with good optical contrast, fast switching speed, and high coloration efficiency.

本研究通过噻吩（thiophene）与呋喃（furan）修饰的四嗪（tetrazine）底物和缺电子1-烷基-1H-吡咯-2,5-二酮单元之间的极具挑战性的逆电子需求狄尔斯-阿尔德（inverse electron demand Diels–Alder）反应，合成了一种具有极低最低未占据分子轨道（Lowest Unoccupied Molecular Orbital, LUMO）能级的新型电子受体（electron acceptor）6-烷基吡咯并[3,4-d]哒嗪-5,7-二酮（PPD）。将该PPD单体掺入一系列给体-受体型共轭聚合物中，此类聚合物作为电致变色材料时，展现出优良的光学对比度、快速的开关切换速度以及较高的着色效率。