Team of academician Tian He of Huali and Professor Ma Xiang: host guest assembly to realize visible light excited organic room temperature phosphorescence emission in aqueous phase

Article author: academician Tian He and Professor Ma Yu's team recently made important progress in the field of room temperature phosphorescence Relevant research results were published in angel Chem Int Ed （ Angew Chem Int Ed   2019 , DOI: 10.1002/anie.201914513 ） 。 Room temperature phosphorescence (RTP), as a special kind of long-life photoluminescence, has been widely used in organic light-emitting diodes, sensor detection and anti-counterfeiting materials due to its large Stokes displacement and multiple response to environmental factors The reported pure organic room temperature phosphorescence is mostly based on solid systems such as crystals, polymers, small molecules, etc., while the pure organic room temperature phosphorescence in liquid or solution state is often difficult to achieve On the one hand, due to the irregular movement of molecules in the solution, the energy of excited states in the three-wire state is mostly dissipated in the form of non radiative transitions, on the other hand, quenching factors such as oxygen in the solution are also greatly The emission of phosphorescence is limited Although supramolecular macrocyclic host molecules, including cyclodextrin and cucurbit [7] urea, have been used to realize room temperature phosphorescence emission in water phase, their short excitation wavelength and low phosphorescence quantum yield limit their application in biological field To solve this problem, academician Tian He and Professor Ma Hui's research team first realized the visible light excited pure organic room temperature phosphorescence based on host guest assembly by using the common supramolecular macrocyclic host molecule Hulu [8] urea and simple dye guest molecule The aqueous solution of guest molecules presents blue fluorescence emission, while the simple mixing of Cucurbit [8] urea and the aqueous solution of guest molecules in 1:1 molar ratio can realize bright yellow phosphorescence emission, so changing the ratio of host guest molecules or competitive objects can realize the regulation of polychromatic fluorescence / phosphorescence Based on the analysis of the single crystal structure of the assembly, the assembly characterization of the solution state and the photophysical properties test, the author concludes that the assembly structure of phosphorescence is a 2:2 complex formed by two Hulu [8] urea molecules and two guest molecules On the one hand, the cavity of Cucurbit [8] urea effectively insulates part of the dissolved oxygen and limits the vibration of the guest molecules; on the other hand, the two guest molecules assembled by the claddings generate a new charge transfer state due to the close parallel arrangement, which makes the absorption red of the assembly move to the visible light area, and realizes the room temperature phosphorescence emission excited by the visible light This special host guest complex is also used in the Hela cell imaging and the preparation of polychromatic light-emitting hydrogel, which has potential biological application value This strategy, which realizes pure organic room temperature phosphorescence by assembly induced emission, breaks the limitation of solution phosphorescence quenching in previous work, and is expected to achieve a new breakthrough in the field of time-resolved imaging combined with the long-life characteristics of phosphorescence, providing a new idea for the construction of room temperature phosphorescence in water phase (source: angelw Chem Int ed.) the research work was mainly completed by Wang Jie, a doctoral candidate, under the guidance of academician Tian He and Professor Ma Hui He was greatly helped by Professor Yongshu, a graduate student of Hubei University, Luo Xiaopeng and Yan Zile, an engineer of Japanese science company, in the analysis of single crystal test The research results are supported by the NSFC basic science center project, Youqing project, Shanghai dawn plan and other projects.