Cao Chen, Xue Xin-Ran, Ge Yu, Liu Dong, Braunstein Pierre, Lang Jian-Ping
College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, Jiangsu, China.
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, P. R. China.
J Am Chem Soc. 2024 Sep 11;146(36):25028-25034. doi: 10.1021/jacs.4c07453. Epub 2024 Aug 30.
Controlling the packing of olefinic molecules in crystals is essential for triggering solid-state [2 + 2] photocycloaddition reactions and the synthesis of photocontrolled smart materials. Herein, we report the stepwise photodimerization-triggered photopolymerization of two triene coordination polymers (CPs), {[Zn(2-BBA)(tpeb)]·0.5CHCN} (, 2-HBBA = 2-bromobenzoic acid, tpeb = 1,3,5-tri-4-pyridyl-1,2-ethenylbenzene) and {[Zn(3-BBA)(tpeb)]·CHCN)} (, 3-HBBA = 3-bromobenzoic acid). Upon irradiation with 420 nm light, each pair of closely packed and parallel olefinic bonds in undergoes a [2 + 2] cycloaddition reaction, which connects two adjacent -shaped chains into a ladder-like coordination chain [Zn(2-BBA)(bpbdpvpcb)] (, bpbdpvpcb = 1,3-bis(4-pyridyl)-2,4-bis(3,5-di(2-(4-pyridyl)vinyl)phenyl]cyclobutene) through single-crystal to single-crystal (SCSC) transformation. After photodimerization from to has occurred, the olefinic bonds that were initially distant are brought in close enough proximity to meet the requirements for a subsequent [2 + 2] cycloaddition reaction. Upon further light irradiation, the neighboring bpbdpvpcb ligands in experience a SCSC photopolymerization based on [2 + 2] photocycloaddition and transform into poly-3b,4,5,5a,8b,9,10a-octahydro-4,5,9,10-tetrapyridyl-2,7-di(2-(4-pyridyl)vinyl)dicyclobuta[,]-pyren (poly-otpdpvdcbp). showed similar structural changes under UV light illumination. Under light exposure, single crystals of and with different morphologies exhibit bending, cracking, and jumping photomechanical motions. The composite film () engineered by dispersing crystalline particles of in poly(vinyl alcohol) (PVA) displays interesting light-wavelength-dependent photomechanical motions and can perform photodriven swimming on a liquid surface. This work provides a useful and promising approach to enable photodimerization of those photoinactive olefin pairs embedded in CPs and opens a new route to synthesize organic polymers by using olefinic CP platforms.
控制烯烃分子在晶体中的堆积对于引发固态[2 + 2]光环加成反应和光控智能材料的合成至关重要。在此，我们报道了两种三烯配位聚合物（CPs），{[Zn(2 - BBA)(tpeb)]·0.5CHCN}（，2 - HBBA = 2 - 溴苯甲酸，tpeb = 1,3,5 - 三 - 4 - 吡啶基 - 1,2 - 乙烯基苯）和{[Zn(3 - BBA)(tpeb)]·CHCN)}（，3 - HBBA = 3 - 溴苯甲酸）的逐步光二聚引发的光聚合反应。用420 nm光照射时，中的每一对紧密堆积且平行的烯烃键会发生[2 + 2]环加成反应，通过单晶到单晶（SCSC）转变将两条相邻的 - 形链连接成梯状配位链[Zn(2 - BBA)(bpbdpvpcb)]（，bpbdpvpcb = 1,3 - 双（4 - 吡啶基） - 2,4 - 双（3,5 - 二（2 - （4 - 吡啶基）乙烯基）苯基]环丁烯）。从到发生光二聚反应后，最初相距较远的烯烃键被拉近到足够近的距离，以满足后续[2 + 2]环加成反应的要求。进一步光照后，中的相邻bpbdpvpcb配体基于[2 + 2]光环加成经历SCSC光聚合反应，并转变为聚 - 3b,4,5,5a,8b,9,10a - 八氢 - 4,5,9,10 - 四吡啶基 - 2,7 - 二（2 - （4 - 吡啶基）乙烯基）二环丁烷[，]芘（聚 - otpdpvdcbp）。在紫外光照射下表现出类似的结构变化。在光照下，具有不同形态的和的单晶表现出弯曲、开裂和跳跃的光机械运动。通过将的结晶颗粒分散在聚乙烯醇（PVA）中设计的复合膜（）表现出有趣的依赖于光波长的光机械运动，并且可以在液体表面进行光驱动游泳。这项工作提供了一种有用且有前景的方法，使嵌入CPs中的那些光惰性烯烃对能够发生光二聚反应，并开辟了一条利用烯烃CP平台合成有机聚合物的新途径。
