Synthesis,Structure,Spectral Properties And Theory Of Novel N,O-Coordinating 1,8-Naphthyridine Fluoroboron Compounds

1,8-naphthalidine derivatives are widely found in many medicinal plants,and their naphthalidine rings have strong rigidity,excellent photophysical properties,coordination ability and biological activity,so these compounds have been applied in the fields of organic luminescent materials,fluorescence sensors and medicine.In recent years,more and more 1,8-naphthalidine derivatives with different substituents have been synthesized and widely used.The N,O-coordinating fluoroboron compounds were synthesized by introducing a-BF₂ group to the 1,8-naphthyridine ring,which improved the fluorescence properties of the 1,8-naphthyridine derivatives,which were beneficial to them in terms of fluorescent probes applications.Based on their advantages,nine novel N-（5,7-disubstituted-1,8-naphthyridin-2-yl）amide derivatives and their seven novel fluoroboron compounds were designed and synthesized.The spectral properties of the 16 compounds and the responses to acid and base for the 7 fluoroboron compounds were determined by UV absorption spectroscopy and fluorescence emission spectroscopy.The research results are as follows:1.The nine novel N-（5,7-disubstituted-1,8-naphthyridin-2-yl）amide derivatives were synthesized and their structures were confirmed by nuclear magnetic resonance,mass spectrometry and X-ray single crystal diffraction.Their spectral properties in different polar solvents were tested.The results show that the maximum absorption wavelengths of the nine compounds are around 340-360 nm,the maximum emission wavelengths are around 370-410 nm,and the solvent polarity has little effect on their spectral properties.The introduction of the-BF₂ group increases theπelectron delocalization,which reduces the energy of the electron transition.2.The seven novel N,O-coordinating fluoroboron compounds with N-（5,7-disubstituted-1,8-naphthyridin-2-yl）amide derivatives as ligands were synthesized.The structure was determined by mass spectrometry and X-ray single crystal diffraction,and their spectral properties in different polar solvents and their response to acid and base for their spectra were tested.The results show that the compounds have good luminescence properties and are sensitive to acid-base reactions.They have potential applications in pH probes,and solvent polarity has little effect on their spectral properties.3.The crystals of the 12 compounds were cultured by ether diffusion at room temperature,and their structures were determined by X-ray single crystal diffractometry.4.Theoretical infrared spectrum,electron absorption spectrum,frontier molecular orbital and energy of the 16 compounds were investigated by using the density functional theory.The properties of electron transfer for the compounds were shown by analyzing the frontier molecular orbital and energy gap.Their theoretical infrared spectrum and electron absorption spectra were assigned,and the theoretical results were consistent with the experimental results.