Su Xing, Wang Yi, Fang Xiaofeng, Zhang Yu-Mo, Zhang Ting, Li Minjie, Liu Yifei, Lin Tingting, Zhang Sean Xiao-An
College of Instrumentation and Electrical Engineering, Jilin University, Changchun, 130061, P. R. China.
College of Chemistry, Jilin University, 2699 Qianjin street, Changchun, 130012, P. R. China.
Chem Asian J. 2016 Nov 22;11(22):3205-3212. doi: 10.1002/asia.201601096. Epub 2016 Oct 20.
A high contrast tri-state fluorescent switch (FSPTPE) with both emission color change and on/off switching is achieved in a single molecular system by fusing the aggregation-induced emissive tetraphenylethene (TPE) with a molecular switch of spiropyran (SP). In contrast to most of the reported solid-state fluorescent switches, FSPTPE only exists in the amorphous phase in the ring-closed form owing to its highly asymmetric molecular geometry and weak intermolecular interactions, which leads to its grinding-inert stable cyan emission in the solid state. Such an amorphous phase facilitates the fast response of FSPTPE to acidic gases and induces the structural transition from the ring-closed form to ring-open form, accompanied with the "Off" state of the fluorescence. The structural transition leads to a planar molecular conformation and high dipole moment, which further results in strong intermolecular interactions and good crystallinity, so when the acid is added together with a solvent, both the ring-opening reaction and re-crystallization can be triggered to result in an orange emissive state. The reversible control between any two of the three states (cyan/orange/dark) can be achieved with acid/base or mechanical force/solvent treatment. Because of the stable initial state and high color contrast (Δλ=120 nm for cyan/orange switch, dark state Φ <0.01 %), the fluorescent switch is very promising for applications such as displays, chemical or mechanical sensing, and anti-counterfeiting.
通过将聚集诱导发光的四苯乙烯（TPE）与螺吡喃（SP）分子开关融合，在单个分子体系中实现了具有发射颜色变化和开/关切换功能的高对比度三态荧光开关（FSPTPE）。与大多数已报道的固态荧光开关不同，FSPTPE由于其高度不对称的分子几何结构和较弱的分子间相互作用，仅以闭环形式存在于非晶相中，这使其在固态下具有研磨惰性的稳定青色发射。这种非晶相促进了FSPTPE对酸性气体的快速响应，并诱导了从闭环形式到开环形式的结构转变，同时伴随着荧光的“关闭”状态。结构转变导致平面分子构象和高偶极矩，进而导致强分子间相互作用和良好的结晶性，因此当酸与溶剂一起加入时，开环反应和重结晶均可被触发，从而产生橙色发射状态。通过酸/碱或机械力/溶剂处理，可以实现三态（青色/橙色/暗态）中任意两种状态之间的可逆控制。由于初始状态稳定且颜色对比度高（青色/橙色开关的Δλ = 120 nm，暗态Φ <0.01 %），该荧光开关在显示、化学或机械传感以及防伪等应用方面极具前景。
