A newly prepared photoresponsive material, specifically a naphthalene diimide molecule containing alkylamino groups, was found to exhibit a structural phase transition in the crystalline state. The phase transition dramatically altered the molecular arrangement from orthogonal π‐π stacking to parallel π‐π stacking. The photomechanical response of each crystal was also changed before and after the phase transition. While the as‐prepared crystal immediately responded to light irradiation (λ=370 nm), the responsiveness of the crystal became slower after heat treatment. Upon light irradiation, radical species, such as the radical anion, radical anion dimer, and mixed valence species, were formed, which have nearly the same distribution in both phases. However, the spin system and the structure of the radical anion were quite different from each other and were found to be sensitive to the molecular arrangement. The photo‐responsiveness of the crystals was corroborated by evaluating the relaxation of the radical anion.

中文翻译：

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在萘二酰亚胺衍生物中通过结构相变切换光机械响应

发现新制备的光敏材料，特别是含有烷基氨基的萘二酰亚胺分子，在结晶状态下显示出结构相变。相转变显着地改变从正交分子排列π - π堆叠成平行π - π堆叠。在相变之前和之后，每个晶体的光机械响应也发生了变化。所制备的晶体立即对光辐照做出反应（λ＝ 370nm），热处理后晶体的响应性变慢。在光照射下，形成了自由基物种，例如自由基阴离子，自由基阴离子二聚体和混合化合价物种，它们在两个相中具有几乎相同的分布。然而，自旋系统和自由基阴离子的结构彼此完全不同，并且发现它们对分子排列敏感。通过评估自由基阴离子的弛豫，证实了晶体的光响应性。