Herein, we present a strategy to access a novel class of pH-responsive, dual-state emissive (DSE), highly fluorescent pyrrole-based chromophores via diformylation of dipyrroethenes (DPE) followed by condensation with various anilines derivatives. The DPE-based chromophores exhibit a large Stokes’ shift and maintain good fluorescent quantum yields. Remarkably, these chromophores demonstrate reversible colourimetric changes and a fluorometric 'on-off-on' switch in response to pH variations. Various spectroscopic techniques, optical microscopy, X-ray crystallography, and computational studies revealed that the synthesized molecules adopt a two-dimensional conformation due to the presence of strong π···π stacking and hydrogen bonding interactions, allowing them to function as flexible molecular hosts. Under acidic conditions, selective protonation of imine bonds and subsequent complexation with counter anion enhance the host-guest interactions, resulting in a stable three-dimensional supramolecular structure. Notably, the reversibility of these molecules under basic conditions showcases the robustness and potential applications of these chromophores in various fields, ranging from the design of finely tuned pH-responsive degradable polymers to self-healing materials, sensing, and molecular devices.

中文翻译：

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合理设计的二辉硝基发色团的 pH 响应超分子开关


在本文中，我们提出了一种策略，通过二吡咯乙烯 （DPE） 的二甲酰化，然后与各种苯胺衍生物缩合，获得一类新型的 pH 响应、双态发射 （DSE）、高荧光吡咯基发色团。基于 DPE 的发色团表现出较大的斯托克斯位移并保持良好的荧光量子产率。值得注意的是，这些发色团表现出可逆的比色变化和响应 pH 变化的荧光“开-关-开”开关。各种光谱技术、光学显微镜、X 射线晶体学和计算研究表明，由于存在强π···π堆叠和氢键相互作用，使它们能够作为灵活的分子宿主发挥作用。在酸性条件下，亚胺键的选择性质子化和随后与反阴离子的络合增强了主客体相互作用，从而产生稳定的三维超分子结构。值得注意的是，这些分子在基本条件下的可逆性展示了这些发色团在各个领域的稳健性和潜在应用，从精细调整的 pH 响应可降解聚合物的设计到自修复材料、传感和分子装置。