Study group of Professor Liu Yu, Nankai University: luminescence behavior of lanthanide elements in aqueous solution extended by pseudorotaxane mediated by cucurbit [8] urea

Introduction rare earth luminescent materials (such as EU and TB) have been the focus of current research due to their unique luminescent properties, such as long-lived excited states, large Stokes shifts, visible light emission, long luminescent life and narrow emission bandwidth However, its luminescent properties in aqueous solution will be severely quenched by O-H groups of proton solvents (such as H 2O and CH 3OH), which greatly limits its application Recently, Professor Liu Yu's research group of Nankai University has made new progress in this field through supramolecular technology, effectively expanding the fluorescence lifetime and quantum yield of supramolecular / rare earth assemblies in aqueous solution (org Lett., 2019, DOI: 10.1021/acs.orglett 9b03597) Liu Yu, Ph.D., Professor of Nankai University, is mainly engaged in the research of organic supramolecular chemistry He was awarded the trans century talents by the Ministry of education in 1994, supported by the National Science Fund for Distinguished Young Scholars in 1996, awarded the title of expert in Tianjin in 1997, and awarded the title of expert by the Ministry of education in 2000 The distinguished professor of "Yangtze River scholars Award Program" was selected into the "one million talents project" of the Ministry of human resources In 2010, he won the contribution award of Chinese overseas Chinese community In 2012, he was awarded the national excellent scientific and technological worker In 2006 and 2011, he served as the chief scientist of national 973 major research program More than 450 papers have been published in core journals at home and abroad, including 46 papers with influence factors greater than 10.0, 13000 papers cited by SCI, and H-index of 61 He has edited 3 monographs and participated in editing 8 monographs It has won 1 second prize of National Natural Science Award, 3 first and second prizes of provincial and ministerial natural science awards, 1 special prize of Baosteel outstanding teachers and outstanding contribution award of national science and technology plan implementation during the 11th five year plan At present, he is the deputy editor in chief of China Chemical express and the editorial board member of seven magazines, such as Asian J org Chem The front research results of the project portfolio: the luminescence behavior of lanthanide elements in aqueous solution mediated by cucurbit [8] urea Liu Yu, Professor of Nankai University, has done a series of work on the controllable luminescence behavior of lanthanide rare earth ions through the construction of organic supramolecular system (nano lett., 2006, 6, 2196-2200; org Lett., 2008, 10 , 5557 - 5560 ; J Org Chem   2011 , 76 , 1910 - 1913 ; J Am Chem Soc   2013 , 135 , 10190 - 10193 ; J Am Chem Soc   2017 , 139 , 7168 - 7171 ;
Chem Sci , 2019 , 10 , 3346 - 3352）。 Recently, based on the previous work of our group, the pseudorotaxane constructed by using the pseudorotaxane mediated by cucurbit [8] urea macrocycle can effectively enhance the fluorescence lifetime and quantum yield of Tb 3 + and EU 3 + in aqueous solution It is significant that the CB [8] @ G1 2 @ Tb 3 + pseudorotaxane with long life and high quantum yield is constructed by this supramolecular technology It showed good specific response to antibiotics in aqueous solution and solid membrane (Figure 1, Org Lett., 2019, DOI: 10.1021/acs.orglett.9b03597) Fig 1 Schematic diagram of lanthanide rare earth luminescent supramolecular pseudorotaxane (source: org Lett.) after CB [8] was added to G1 aqueous solution, the UV-Vis absorption band of naphthalene decreased gradually at 250-300 nm, and two isoabsorption points appeared at 260 nm and 280 nm (Fig 2a), with the increase of emission at 405 nm, 335 The fluorescence emission of naphthalene decreases gradually at nm (Fig 2b) These phenomena confirm the formation of CB [8] @ G1 2 pseudo [3] rotaxane in CB [8] cavity Fig 2 Host guest fluorescence ultraviolet (source: org Lett.) by adding Tb 3 + cation to pseudo [3] rotaxane CB [8] @ G1 2 solution, the absorption of G1 and CB [8] @ G1 2 increases at 275 nm, indicating that TB 3 + cation is coordinated with the carboxyl group of G1 (Fig 3a) It is found that the fluorescence emission intensity of CB [8] @ G1 2 @ Tb 3 + is twice as strong as that of G1 @ Tb 3 +, which indicates that the binding of CB [8] can enhance the fluorescence of G1 @ Tb 3 + Fig 3 UV fluorescence of the coordination between the assembly and the rare earth and the coordination map of the single object and the rare earth (source: org Lett.) interestingly, the excited state lifetime (τ = 1.33 MS) and quantum yield (Ф = 7.81%) of CB [8] @ G1 2 @ Tb 3 + are 29.1 and 8.7 times of the corresponding values of G1 @ Tb 3 + (τ = 45.76 μ s, Ф = 0.89%), and it is also observed that CB [8] is 29.1 and 8.7 times of the corresponding values of G1 @ EU 3 ++ The excited state lifetime and quantum yield of the complex also have enhancement effects Fig 4 Life comparison chart (source: org Lett.) to sum up, cucurbit [8] urea mediated pseudorotaxane CB [8] @ G1 2 can further coordinate with TB 3 + to construct pseudorotaxane, which shows specific fluorescence response to antibiotics in aqueous solution and solid membrane This supramolecular assembly method provides a new way to improve the special physical and chemical properties of rare earth luminescence in aqueous solution Figure 5 Detection of antibiotics in solution and film by assembly (source: org Lett.)