二芳基乙烯类酸致变色材料的光机械效应

Photomechanical effects of acidochromic diarylethene derivatives

本文合成了氟代萘乙烯基苯并唑BO1N4F和氟代萘乙烯基苯并噻唑BT1N4F,二者在紫外光照下可发生拓扑[2+2]环加成反应,生成的主产物为β-型二聚体.由于前者的光化学反应效率高于后者,因此,BO1N4F的光二聚反应导致晶体内部产生较大的张力.当累积在棒状晶体中的张力快速释放时,晶体发生爆裂,产生的碎片跳离原位置;当累积在针状晶体中的张力缓慢释放时,晶体发生显著的背光弯曲.此外,光二聚反应将平面形二芳基乙烯分子转化为蝴蝶形环丁烷衍生物,共轭分子的去平面化导致基于二聚体D-BO1N4F的薄膜对三氟乙酸蒸气的检测限低于薄膜BO1N4F.可见,光诱导[2+2]环加成反应不仅能改善二芳基乙烯衍生物在薄膜中的荧光传感性能,而且是分子晶体产生光机械效应的驱动力.

Naphthalenylvinylbenzoxazol BO1 N4 F and naphthalenylvinylbenzothiazole BT1 N4 F have been synthesized,and led to topo-photochemical reactions.Compared with BT1 N4 F,the dimerization efficiency of BO1 N4 F is so high that more stress is yielded in the crystals during[2+2]cycloaddition reaction.When the accumulated strain is released rapidly,the rod-like crystals BO1 N4 F are burst and the fragments jump away.The needle-like crystal BO1 N4 F bend away from UV light source since the accumulated strain during dimerization is released slowly.Cracks are observed in the slice-like crystal BT1 N4 F under UV light on account of low efficiency of dimerization.In addition,the planar-like diarylethene molecules BO1 N4 F and BT1 N4 F can be transformed into butterfly-like cyclobutanes via topochemical reactions,which improves the fluorescent response abilities of the films in the detection of TFA vapor.Therefore,the light-induced[2+2]cycloaddition reaction of diarylethene not only enhances the performance in sensory property of the film,but also becomes the driving force for the photomechanical effects.