Qiao Di, Wang Jin-Yun, Zhang Li-Yi, Dai Feng-Rong, Chen Zhong-Ning
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, China.
Dalton Trans. 2019 Aug 7;48(29):11045-11051. doi: 10.1039/c9dt02177a. Epub 2019 Jun 26.
Three quinoline-based zinc(ii)-Schiff base complexes were synthesized and characterized by X-ray crystallography. They exhibit remarkable aggregation-induced emission enhancement (AIEE) in acetonitrile/diethyl ether mixtures due to the conversion of weak luminescence in homogeneous solution into strong emission in the nano-aggregated phase after increasing the fractions of diethyl ether. Interestingly, the AIEE performance can be significantly promoted by joining the two quinoline units through an alkoxy chain. Moreover, they show reversible mechanochromic luminescence behavior between dark and bright states during the grinding-fuming cycles, due to the modulation of morphologies between amorphous and crystalline states. Introducing an electron donating group in the para-position of aniline significantly improves the mechanochromic luminescence effect with a more accessible and distinct emission colour contrast. The molecular packing in the crystalline phase and time-dependent density functional theory (TD-DFT) calculations demonstrate that multiple intermolecular C-Hπ and π-π interactions significantly strengthen the molecular rigidity and enhance the intramolecular charge-transfer (ICT) characteristics, leading to the effective emission enhancement in crystalline/nano-aggregated states. The novel AIEE and reversible mechanochromic luminescence properties point to the promising potential applications of these complexes in smart fluorescent materials.
合成了三种喹啉基锌（II）-席夫碱配合物，并通过X射线晶体学对其进行了表征。由于在增加乙醚比例后，均相溶液中的弱发光转变为纳米聚集相中的强发射，它们在乙腈/乙醚混合物中表现出显著的聚集诱导发光增强（AIEE）。有趣的是，通过烷氧基链连接两个喹啉单元可以显著提高AIEE性能。此外，由于在研磨-熏蒸循环中无定形和结晶态之间的形态调制，它们在暗态和亮态之间表现出可逆的机械变色发光行为。在苯胺的对位引入供电子基团，通过更易获得且明显的发射颜色对比，显著改善了机械变色发光效果。结晶相中的分子堆积和含时密度泛函理论（TD-DFT）计算表明，多个分子间C-Hπ和π-π相互作用显著增强了分子刚性并增强了分子内电荷转移（ICT）特性，导致在结晶/纳米聚集态下有效发射增强。这些新颖的AIEE和可逆机械变色发光特性表明这些配合物在智能荧光材料中具有广阔的潜在应用前景。
