Abstract：
Generally, the potential reactive \"olefin pairs\" in the molecular crystals satisfying Schmidt\'s criteria could undergo topological [2+2] cycloaddition. In this study, another factor that affects the photodimerization reactivity of chalcone analogues was found. The cyclic chalcone analogues of (E)-2-(2,4-dichlorobenzylidene)-2,3-dihydro-1H-inden-1-one (BIO), (E)-2-(naphthalen-2-ylmethylene)-2,3-dihydro-1H-inden-1-one (NIO), (Z)-2-(2,4-dichlorobenzylidene)benzofuran-3(2H)-one (BFO), and (Z)-2-(2,4-dichlorobenzylidene)benzo[b]thiophen-3(2H)-one (BTO) have been synthesized. While the geometrical parameters for the molecular packing of the above four compounds did not exceed Schmidt\'s criteria, [2+2] cycloaddition did not occur in the crystals of BIO and BTO. The single crystal structures and Hirshfeld surface analyses revealed that interactions of C=O⋅⋅⋅H (CH2 ) existed between adjacent molecules in the crystal of BIO. Therefore, the carbonyl and methylene groups linked with one carbon atom in carbon-carbon double bond were tightly confined in the lattice, acting as a tweezer to inhibit free movement of the double bond and suppressing [2+2] cycloaddition. In the crystal of BTO, similar interactions of Cl⋅⋅⋅S and C=O⋅⋅⋅H (C6 H4 ) prevented free movement of the double bond. In contrast, the intermolecular interaction of C=O⋅⋅⋅H only exists around the carbonyl group in the crystals of BFO and NIO, leaving the C=C double bonds to move freely and allowing the occurrence of [2+2] cycloaddition. Driven by photodimerization, the needle-like crystals of BFO and NIO displayed evident photo-induced bending behavior. This work demonstrates that the intermolecular interactions around carbon-carbon double bond affect the [2+2] cycloaddition reactivity except for Schmidt\'s criteria. These findings provide valuable insights into the design of photomechanical molecular crystalline materials.
摘要：
（E）-2-（2,4-二氯亚苄基）-2,3-二氢-1H-inden-1-酮（BIO）的环状查耳酮类似物，(E)-2-(萘-2-基亚甲基)-2,3-二氢-1H-茚-1-酮(NIO)，(Z)-2-(2,4-二氯亚苄基)苯并呋喃-3(2H)-酮(BFO),合成了(Z)-2-(2,4-二氯亚苄基)苯并[b]噻吩-3(2H)-酮(BTO)。虽然上述四种化合物的分子堆积的几何参数没有超过施密特的标准，[2+2]环加成在BIO和BTO中未发生。单晶结构和Hirshfeld表面分析表明，BIO中相邻分子之间存在C=O‧H（CH2）的相互作用。因此,与碳-碳双键中的一个碳原子连接的羰基和亚甲基被紧密地限制在晶格中，作为镊子，以抑制双键的自由运动和抑制[2+2]环加成。在BTO,Cl.S和C=O.H（C6H4）的相似相互作用阻止了双键的自由运动。相比之下,在BFO和NIO中,C=O.H的分子间相互作用只存在于羰基周围,使C=C双键自由移动，并允许[22]环加成的发生。由光二聚化驱动，BFO和NIO的针状晶体表现出明显的光致弯曲行为。这项工作表明，碳-碳双键周围的分子间相互作用会影响[22]环加成反应性，除了施密特的标准。这些发现为光机械分子晶体材料的设计提供了有价值的见解。
