Organic polymorphic crystals with multi-stimuli response:excellent mechanical elasticity,novel two-stage heterotropic photochromism and self-reversible acidichromism

多刺激响应多晶型有机晶体:出色的机械弹性、全新的二段折返光致变色和自可逆酸致变色

Smart multi-stimuli responsive organic materials have become increasingly favored due to their advantages of high stability and easy regulation.In this study,a cyanostilbene derivative((αZ)-2-chloro-α-[(4-methoxyphenyl)methylene]-5-pyridinehyde,TAR)was successfully synthesized,and its polymorphs(TAR-1 and TAR-2)exhibited multiple responsive behaviors under different stimulus conditions.TAR-1 is supposed to have excellent mechanical properties,while TAR-2 shows fascinating heterotropic photochromism(green-cyan-yellow)under different intensities of ultraviolet(UV)irradiation,which has never been reported in previous studies.Further investigation revealed that this was attributed to different degrees of[2+2]cycloaddition induced by UV light.In addition,both polymorphs could be protonated during Trifluoroacetic acid fuming and deprotonate automatically after fuming,accompanied by the significant variation in fluorescence.Finally,two scenarios were designed based on their unique stimuli-responsive properties,which proved their promising potential in fields of information security and anti-counterfeiting encryption.

智能多刺激响应有机材料因其稳定性高、易于调控等优点而越来越受到人们的青睐.本研究成功合成了一种氰基苯乙烯衍生物((αZ)-2-氯-α-[(4-甲氧基苯基)亚甲基]-5-吡啶,TAR),其多晶型(TAR-1和TAR-2)在不同刺激条件下表现出多种响应行为.TAR-1具有优异的力学性能,而TAR-2在不同强度的紫外线照射下表现出迷人的二段折返光致变色(绿-青-黄),这在以往的研究中从未报道过.进一步的研究表明,这是由于紫外光诱导的不同程度的[2+2]环加成所致.此外,这两种多晶型都能在三氟乙酸发烟过程中发生质子化,发烟后能自动去质子化,并伴有显著的荧光变化.最后,基于其独特的刺激响应特性设计了两种场景,证明了其在信息安全和防伪加密领域的巨大潜力.