A straightforward route to 1,4-dihydropyrrolo[3,2-b]pyrroles comprised of two electron-withdrawing quinoline or tetrazolo[1,5-a]quinoline scaffolds has been developed. The versatile multicomponent reaction affording 1,4-dihydropyrrolo[3,2-b]pyrroles combined with intramolecular direct arylation enables assembly of these products in just three steps from anilines with overall yields exceeding 30%. The planarized, ladder-type heteroacenes possess up to 14 conjugated rings. These nominally quadrupolar materials exhibit efficient fluorescence with wavelengths spanning most of the visible spectrum from green–yellow for the dyes possessing biaryl bridges and orange–red for the fully fused systems. In many cases, the fluorescence quantum yields are large, the solvatofluorochromic effects are strong, and the fluorescence is maintained even in crystalline state. Analysis of the electronic structure of these molecular architectures using quantum chemical methods suggests that the character and position of the flanking heterocycle determine the shape of HOMO and LUMO and their extension to N-aryl substituents, influencing the values of molar absorption coefficient. An experimental study of the two-photon absorption (2PA) properties has revealed that it occurs in the 700–800 nm range with apparent deviation from the Laporte parity selection rule, which may be attributed to Hertzberg–Teller contribution to vibronically allowed 2PA transition.

中文翻译：

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强极化 π-延伸 1,4-二氢吡咯并[3,2-b]吡咯与四唑并[1,5-a]喹啉稠合

已经开发出一种由两个吸电子喹啉或四唑并[1,5- a ]喹啉支架组成的1,4-二氢吡咯并[3,2- b ]吡咯的直接途径。提供 1,4-二氢吡咯并[3,2- b ]吡咯的多功能多组分反应与分子内直接芳基化相结合，只需三个步骤即可从苯胺组装这些产物，总产率超过 30%。平面化梯型杂并苯拥有多达 14 个共轭环。这些名义上的四极材料表现出高效的荧光，波长跨越大部分可见光谱，从绿-黄（对于具有联芳基桥的染料）到橙-红色（对于完全融合的系统）。在许多情况下，荧光量子产率大，溶剂化荧光变色效应强，并且即使在结晶状态下也能保持荧光。使用量子化学方法对这些分子结构的电子结构进行分析表明，侧翼杂环的特征和位置决定了HOMO和LUMO的形状及其向N-芳基取代基的延伸，从而影响摩尔吸收系数的值。对双光子吸收 (2PA) 特性的实验研究表明，它发生在 700–800 nm 范围内，明显偏离拉波特宇称选择规则，这可能归因于赫茨伯格-泰勒对振动允许的 2PA 跃迁的贡献。