Key Laboratory of Green Chemistry and Technology of Ministry of Education, College of Chemistry, Sichuan University, 29 Wangjiang Road, Chengdu 610064, People's Republic of China.
Mater Horiz. 2021 May 1;8(5):1499-1508. doi: 10.1039/d0mh02032j. Epub 2021 Mar 10.
Described herein is the first example of mechanically induced single-molecule white-light emission based on excited-state intramolecular proton transfer (ESIPT) materials. The mechanism of mechanochromism is clearly disclosed by powder and single crystal X-ray diffraction (XRD) data, infrared spectroscopy, and fluorescence up-conversion measurement, etc. 2-(2'-Hydroxyphenyl)oxazole (6b) with a herringbone packing motif exhibits a predominant keto-form emission, giving off yellowish-green fluorescence. Mechanical grinding transforms the herringbone packing motif into a brickwork packing motif, decreases the intermolecular distances, which results in an enhanced intermolecular charge-transfer interaction, and therefore changes the ESIPT dynamics, leading to an enhanced enol-form emission and white fluorescence. Herringbone-packing 6b is thermodynamically more stable than brickwork-packing 6b. Thus, the latter can convert to the former by solvent fuming or thermal annealing.
本文首次报道了基于激发态分子内质子转移（ESIPT）材料的机械诱导单分子白光发射。通过粉末和单晶 X 射线衍射（XRD）数据、红外光谱和荧光上转换测量等手段，清楚地揭示了机械变色的机制。具有鱼骨堆积模式的 2-(2'-羟基苯基)恶唑（6b）表现出主要的酮式发射，发出淡黄色荧光。机械研磨将鱼骨堆积模式转变为砖式堆积模式，减小了分子间距离，增强了分子间电荷转移相互作用，从而改变了 ESIPT 动力学，导致增强的烯醇式发射和白色荧光。鱼骨堆积的 6b 在热力学上比砖式堆积的 6b 更稳定。因此，后者可以通过溶剂冒烟或热退火转化为前者。
