A stiff-stilbene strapped calix[4]pyrrole receptor can be reversibly switched by light between a strong chloride-binding Z-isomer and a very weakly binding E-isomer. The light-induced switching process is monitored by UV-Vis and ¹H NMR spectroscopy and chloride binding is studied in detail using both ¹H NMR and ITC titrations in DMSO and MeCN. In DMSO, at millimolar concentrations, switching from a fully bound to an almost fully unbound state can be triggered. Quantification of the binding constants in MeCN reveals an extraordinary 8000-fold affinity difference between the Z- and E-isomer. Single crystal X-ray crystallographic analysis gives insight into the structure of the photogenerated E-isomer and the geometry of the chloride-bound receptors is optimized by DFT calculations. The highly effective control of binding affinity demonstrated in this work opens up new prospects for on demand binding and release in extractions and photocontrol of membrane transport processes, among other applications.

中文翻译：

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光开关捆扎杯[4]吡咯受体：高效氯离子的结合和释放

硬二苯乙烯键合的杯[4]吡咯受体可通过光在强氯离子结合的Z-异构体和极弱氯离子的E-异构体之间逆转。通过UV-Vis和¹ H NMR光谱监测光诱导的转换过程，并使用DMSO和MeCN中的¹ H NMR和ITC滴定法详细研究了氯离子的结合。在DMSO中，在毫摩尔浓度下，可以触发从完全结合状态到几乎完全未结合状态的转换。MeCN中结合常数的定量揭示了Z-和E之间的8000倍亲和力差异-异构体。单晶X射线晶体学分析可深入了解光生E异构体的结构，并且通过DFT计算可优化结合氯的受体的几何形状。这项工作中证明的对结合亲和力的有效控制为膜运输过程的萃取和光控制中的按需结合和释放开辟了新的前景。