Studies Of The Synthesis And Fluorescence Properties Of Novel N-N,N-O Fluoroboron Fluorescent Dyes

Fluorescent dyes are very important tools in many fields,in which fluoroboron fluorescent dyes are widely used for biological cell imaging,fluorescent probes,organic light emitting diodes(OLEDs)and solar energy conversion due to their excellent photochemical properties.So it has great significance to constantly design new structures to explore new fluorescent properties.In this paper,a total of 19 compounds of N-N and N-O fluoroboron complexes were designed and synthesized,and their fluorescence properties were tested and studied.4-hydroxy coumarin and aniline served as raw materials with diazotization and fluorideboron complexation,we synthesized five compounds 3a-3e with yield21-84%.The fluorescence properties were investigated,it was found that the fluorescence was quenched in the strong polar solvent,but the fluorescence was obviously enhanced in DMF,and the wavelengths of the excitation and emission were obviously blue-shift.The effect of the strong donating electron-donating groups on the fluorescence are very obvious.The absence of substituents and the strong electron-withdrawing groups have little effect on the fluorescence.The compounds are good solid fluorescence materials,which has a large Stokes Shift of 150-180 nm with liquid fluorescence.2-hydroxy naphthalene formaldehyde and aniline served as raw materials with the aromatic amination and fluoride boron complexation,we got five compounds.Precursor of complexations yield 95-98% and complexation yield 40-80%.The fluorescence properties were tested and precursors 5 were found to have good solid fluorescence but have no liquid fluorescence but exhibiting good AIE properties.The complex product 6 exhibits good solid and liquid fluorescence,where the electron-withdrawing group significantly enhances the fluorescence and the Stokes Shift reaches 70-100 nm.Tryptamine and 2-pyridinecarboxaldehyde were prepared by the Pictet-Spengler(P-S)reaction.Reacted with oxidation and fluoroboron complexation,we obtain two compounds 9a and 9b in yields of 50.4% and 48.7%.The fluorescence properties ofthe two compounds were tested with strong yellow-green liquid fluorescence and yellow solid fluorescence.The Stokes Shift 60-110 nm,fluorescence quantum yield up to 0.95.Meanwhile,the two compounds are very stable under acidic and alkaline conditions.Upon pH ? 1,the fluorescence of the unsubstituted compound get obviously weakened and almost quenched.1,4-dihydroxyanthraquinone and aniline served as raw materials wieh the double amination and fluoride boron complexation,seven compounds 11a-11 g got in the yield of 60.1%-69.2%.The fluorescence properties were measured,and the compounds in solution sate had red fluorescence but the solid had no fluorescence.The electron-withdrawing group enhances the fluorescence,and the electron-donating group weakened the fluorescence,and the strong electron-donating group(-OCH3)maked the fluorescence almost quenched.In addition,the heavy atom effect significantly affected the fluorescence intensity and weakened it.The datas showed that when the concentration were 3x10-5mol·L-1,the fluorescence intensity increased to the strongest and reached 4x10-4mol·L-1,almost close to quenching.