Synthesis Of β-phenolic O-phenanthroline Boron Complexes And Their Application In Fluorescent Thermometers

In daily production and life or scientific research,the accurate control of temperature is very meaningful.The accurate measurement of temperature is inseparable from the thermometer.Non-contact fluorescent temperature sensors can play an important role in many special fields,such as revealing cell life activities and measuring temperature in strong magnetic and electric environments.With the development and application of fluorescent temperature sensors,a variety of temperature sensors with different response modes have been formed.Among them,the single-molecule dual emission fluorescence temperature sensor has become a research hotspot as a new type of temperature sensor.In this paper,three kinds of N,O-chelated boride and one N,N-chelated boride were synthesized.The photophysical properties and single crystal structure of the four ligands and the photophysical properties and temperature response properties of the complexes were studied.The research contents are as follows:（1）Through the Suzuki coupling reaction and the deprotection reaction of the protective group,the corresponding bis（β-phenoloxy）phenanthroline（H-OH,Bu-OH and F-OH）ligand and a 5,9-dipyrrophenothiazine（N-NH）ligand were obtained.The photophysical behaviors of the four ligands were studied by absorption spectroscopy and emission spectroscopy.H-OH and Bu-OH in the large polar solvents（tetrahydrofuran,ethyl acetate and acetonitrile）have observed large Stokes shift and monoenol-monoketo fluorescence emission at long wavelengths,indicating that the molecule has an Excited-State Intramolecular Proton Transfer（ESIPT）process in the strong-polar solvent.The excitation spectrum also confirms this view.However,in the compounds F-OH and N-NH,due to the strong electron withdrawing effect of fluorine and the weak acidity of pyrrole,the process of ESIPT was not observed.（2）Under the action of alkali,BF₃·Et₂O is complexed with ligand to obtain the corresponding boron-complexed N,O-chelates（H-BF₂,Bu-BF₂ and F-BF₂）and boron-complexed N,N-chelate（N-BF₂）.Through the absorption and emission spectra,the four chelates show huge differences in different solvents.The reason is that solvent molecules containing heteroatoms partially dissociated the boride.By spin-coating H-BF₂ on a quartz wafer,the temperature response properties of H-BF₂were studied.The H-BF₂ solid film exhibits a dual-emitting phenomenon.The relationship between the intensity ratio of the double fluorescence peak and the temperature conforms to a polynomial function relationship,and the standard deviation R² value reaches 0.980.Further structural simulations show that the response mechanism of H-BF₂ is derived from the vibration-induced emission mechanism.