Understanding the dynamic structural changes accompanying radical formation provides detailed insights into the design of stimuli-responsive redox-active materials. In this study, we develop a metal-organic framework (MOF) comprising a π-acidic 1,4,5,8-naphthalenediimide (NDI)-based ligand and Nd³⁺, viz. X-DGIST-4 (X = synthesis temperature in °C, DGIST = Daegu Gyeongbuk Institute of Science and Technology). The reduction of the NDI moieties to the radical-anionic state (NDI^·−) in 75-DGIST-4 can be triggered by various stimuli (heat, X-rays, and ultraviolet, visible, and infrared light), indicating the presence of structure-guided multiple electron transfer pathways. The single-crystal-to-single-crystal transformation of 75-DGIST-4 upon X-ray-induced radical formation reveals sequential structural changes. The solvothermally synthesized radical-anionic MOF, viz. 150-DGIST-4, offers a more complete structural understanding of the radical-anionic state. Importantly, the stabilization of radical-anionic NDI^·− by adjacent benzoates allows this state to be visualized by single-crystal X-ray diffractometry; the pendant benzoate is twisted to optimize the electrostatic interaction between NDI^·− and the benzoate phenyl group.

了解伴随自由基形成的动态结构变化为刺激响应氧化还原活性材料的设计提供了详细的见解。在这项研究中，我们开发了一种金属有机框架 (MOF)，它包含 π-酸性 1,4,5,8-萘二亚胺 (NDI) 基配体和 Nd ³⁺，即。X-DGIST-4（X = 合成温度，单位为°C，DGIST = 大邱庆北科学技术研究院）。NDI部分还原为自由基阴离子状态（NDI ^-) 在 75-DGIST-4 中可以被各种刺激（热、X 射线和紫外线、可见光和红外线）触发，表明存在结构引导的多个电子转移途径。X 射线诱导自由基形成后 75-DGIST-4 的单晶到单晶转变揭示了连续的结构变化。溶剂热合成的自由基阴离子 MOF，即。150-DGIST-4，提供了对自由基阴离子状态的更完整的结构理解。重要的是，相邻苯甲酸盐对自由基阴离子 NDI ^·-的稳定作用使得这种状态可以通过单晶 X 射线衍射法进行可视化。^{侧基苯甲酸酯被扭曲以优化 NDI ·-}和苯甲酸酯苯基之间的静电相互作用。