Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543 (Singapore).
Angew Chem Int Ed Engl. 2014 Feb 17;53(8):2143-6. doi: 10.1002/anie.201306746. Epub 2014 Jan 23.
A [2+2] cycloaddition reaction has been observed in a number of solids. The cyclobutane ring in a photodimerized material can be cleaved into olefins by UV light and heat. The high thermal stability of the metal-organic salt K2SDC (H2SDC = 4,4'-stilbenedicarboxylic acid) has been successfully utilized to investigate the reversible cleavage of a cyclobutane ring. The two polymorphs of K2SDC undergo reversible cyclobutane formation by UV light and cleavage by heat in cycles. Of these, one polymorph retains its single-crystal nature during the reversible processes. Polymorphs are known to show different physical properties and chemical reactivities. This work reveals that the retention of single-crystal nature is strongly associated with the packing of molecules, which is controlled by kinetics and thermodynamics. The photoemissive nature of the products makes this as a promising material for photoswitches and optical data storage devices.
在许多固体中观察到了[2+2]环加成反应。光二聚化材料中的环丁烷环可以通过紫外光和热裂解为烯烃。金属有机盐 K2SDC（H2SDC=4,4'-联苯二甲酸）的高热稳定性已成功用于研究环丁烷环的可逆裂解。K2SDC 的两种多晶型物通过紫外光可逆地形成环丁烷，并通过热裂解循环进行。其中，一种多晶型物在可逆过程中保持其单晶性质。众所周知，多晶型物表现出不同的物理性质和化学反应性。这项工作表明，单晶性质的保留与分子的堆积密切相关，而分子的堆积受动力学和热力学控制。产物的光电发射性质使其成为光开关和光学数据存储设备的有前途的材料。
