Studies of complex systems and emerging properties to mimic biosystems are at the forefront of chemical research. Dynamic multistep cascades, especially those exhibiting allosteric regulation, are challenging. Herein, we demonstrate a versatile platform of photoswitchable covalent cascades toward remote and bidirectional control of reversible covalent bonds and ensuing assemblies. The relay of a photochromic switch, keto–enol equilibrium, and ring–chain equilibrium allows light-mediated reversible allosteric structural changes. The accompanying distinct reactivity further enables photoswitchable dynamic covalent bonding and release of substrates bidirectionally through alternating two wavelengths of light, essentially realizing light-mediated signaling cycles. The downfall of energy by covalent bond formation/scission upon photochemical reactions offers the driving force for the controlled direction of the cascade. To show the molecular diversity, photoswitchable on-demand assembly/disassembly of covalent polymers, including structurally reconfigurable polymers, was realized. This work achieves photoswitchable allosteric regulation of covalent architectures within dynamic multistep cascades, which has rarely been reported before. The results resemble allosteric control within biological signaling networks and should set the stage for many endeavors, such as dynamic assemblies, molecular motors, responsive polymers, and intelligent materials.

中文翻译：

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用于共价键和组件变构和双向控制的光开关级联

对复杂系统和模仿生物系统的新兴特性的研究处于化学研究的前沿。动态多步级联，尤其是那些表现出变构调节的级联，具有挑战性。在这里，我们展示了一个多功能的光可切换共价级联平台，用于远程和双向控制可逆共价键和随后的组装。光致变色开关、酮-烯醇平衡和环-链平衡的中继允许光介导的可逆变构结构变化。伴随的独特反应性进一步实现了光可切换的动态共价键合，并通过交替的两个波长的光双向释放底物，基本上实现了光介导的信号循环。光化学反应时共价键形成/断裂导致的能量下降为级联的受控方向提供了驱动力。为了显示分子多样性，实现了共价聚合物（包括结构可重构聚合物）的光切换按需组装/拆卸。这项工作实现了动态多步级联内共价结构的光可切换变构调节，这在以前很少有报道。结果类似于生物信号网络内的变构控制，并且应该为许多努力奠定基础，例如动态组装、分子马达、响应聚合物和智能材料。