Conducting a reaction in the solid state eliminates the usage of solvents. If such reactions are conducted in a single-crystal to single-crystal (SCSC) fashion, then structural characterization by single-crystal X-ray crystallography (SCXRD) techniques provides unequivocal structural details. Although topochemical principles govern, getting single crystals at the end of a SCSC reaction purely depends on the experimental skills of the researchers. SCSC reactions are common among solid-state [2 + 2] cycloaddition reactions (hereafter “photoreaction”) after the classical work of Schmidt and co-workers in 1960s. Synthons and tectons in the crystal engineering box can be exploited to bring the functional groups into the required alignment and packing to achieve the desired chemical reactivities and physical properties, respectively. Bringing a pair of alkenes closer together in the organic molecules provides an effective starting point to achieve the goal of crystal engineering.

中文翻译：

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表现出 [2 + 2] 光环加成反应和动态效应的光反应晶体

在固态下进行反应消除了溶剂的使用。如果此类反应以单晶到单晶 (SCSC) 方式进行，那么通过单晶 X 射线晶体学 (SCXRD) 技术进行的结构表征可以提供明确的结构细节。尽管拓扑化学原则支配，但在 SCSC 反应结束时获得单晶完全取决于研究人员的实验技能。在 1960 年代 Schmidt 及其同事的经典工作之后，SCSC 反应在固态 [2 + 2] 环加成反应（以下简称“光反应”）中很常见。可以利用晶体工程盒中的合成子和构造子将官能团带入所需的排列和堆积，以分别实现所需的化学反应性和物理性质。