Propertiesof 1,1'-Binaphthyl Derivatives With Dual Fluorescence

As a most basic physical parameter,temperature involves almost all physical,chemical and biological processes.Rapid and accurate measurement of the temperature value in various environments is crucial for scientific research,technological development and even daily life.Among all kinds of thermometers,the ratio fluorescence thermometer is the most eye-catching.Ratio fluorescence temperature probe not only has the advantages of fast response and high spatial resolution of traditional fluorescence thermometer,but also can avoid the interference of background fluorescence,sample morphology and other factors.At present,the ratio fluorescence temperature detection mainly uses the doped polymer or nanoparticle system,which is complex to prepare and requires additional correction of the physical and chemical properties of two components,and sometimes leads to inaccurate temperature measurement due to the non-uniform doping disturbance.However,the fluorescence temperature probe based on single small organic molecule with temperature-dependent dual fluorescence can effectively solve the above problems.However,there are only a limited number of examples nowadays.In recent studies,our group has designed and synthesized a new molecule,2,2'-bis(dimethylamino)-6,6'-bis(dimesitylboryl)-1,1'-binaphthyl(BNMe2-BNaph).This compound exhibited dual fluorescence in polar solvents,and the positions of the two emission peaks were significantly different and easy to be distinguished.BNMe2-BNaph can be an ideal ratio fluorescent temperature probe because the intensity ratio of it's two emission peaks can change with temperature in linear relationship,and the fluorescence color can also change significantly at the same time.Unlike common molecular systems with D-?-A structures,this 1,1'binaphthyl derivatives are essentially composed of two independent D-?-A units connected by a single bond,and the potential electron interactions between the two units provide two possible pathways for intramolecular charge transfer.Preliminary speculation had been set that two fluorescence emission peaks of BNMe2-BNaph may come from the different excited state,namely the S1 and S2,respectively corresponding to inter-and intra-subunit charge transition through testing the emission spectrum and excitation spectrum and dynamic fluorescence spectrum of BNMe2-BNaph combined with the theoretical calculation results.Based on the preliminary research results,this paper mainly carried out the following two aspects:First,a reference compound MBNMe2-BNaph lacking an electron acceptor(-BMes2)was designed and synthesized.It was found that MBNMe2-BNaph had the same phenomenon of dual fluorescence emission,and was similar to BNMe2-BNaph.However,compared with BNMe2-BNaph,the sensitivity of MBNMe2-BNaph is lower and the linear range is narrower,indicating that the molecular structure of BNMe2-BNaph with double D-?-A units is very important for obtaining the high-sensitivity temperature-dependent dual fluorescence.On the other hand,we synthesized two other fluorescence compounds CHONMe2-BNaph and CNNMe2-BNaph by changing the electron acceptor with-CHO and-CN,so as to study the universality of our molecular design.The study found that these two compounds also have temperature-dependent dual fluorescence,which demonstrated that molecules with double D-?-A units can obtain this phenomenon.Moreover,the change of electron acceptor has a significant influence on the fluorescence intensity ratio and the separation of the two emission peaks,and the sensitivity.These results provide a theoretical basis for the further study of temperature-dependent dual fluorescence and the design of related ratio fluorescence thermometers.