Organic Red And Near-infrared Fluorescent Materials Based On Boron Difluoride ?-diketone

In recent years,red and near-infrared fluorescent dyes have shown application prospects in bioimaging,photoelectronic display,fluorescent probe,information security and encryption transmission,etc.Organic fluorescent dyes have attracted wide attention because of their unique advantages such as good biocompatibility,diverse molecular structures,and low price.However,some organic red and near-infrared fluorescent dyes suffer from low luminescence efficiency,which limits their application.Therefore,it is of great significance to develop efficient organic red and near-infrared fluorescent dyes.In this thesis,with carbazole as the electron donor,boron difluoride dione group as the electron acceptor,phenyl,vinyl or vinyl phenyl as the?bridge,D-?-A and A-?-D-?-A typed red/near-infrared organic fluorescent dyes were synthesized by altering the structure and the substituted position of the?bridge.The bandgap of the molecules,the luminescence properties of the fluorescent dyes in solution and aggregation state were analyzed by means of UV-vis absorption spectra,photoluminescence spectra,transient fluorescence spectra and X-ray diffraction patterns.The results are listed as follows:(1)Aggregation induced luminescence/fluorescence quenching propertiesIn DMSO/H₂O or THF/H₂O mixtures solvents,molecules BF₂PNCZ,BF₂VPNCZ,DBF₂VPCZ and SBF₂VPCZ with moderated structures exhibited aggregation-induced fluorescence enhancement behaviors.Molecules DBF₂VCZ and SBF₂VCZ with planar skeletons exhibited aggregation induced fluorescence quenching behaviors.(2)Luminescence properties in the aggregate stateWith the decrease of molecular bandgaps,solid-state luminescence of the dyes was tuned from red to near-infrared emission.In addition,all of the fluorescent dyes showed stimuli-responsive luminescence properties.Upon mechanical grinding,BF₂PNCZ,BF₂VPNCZ with the N-substituted?bridge showed redshift mechanoresponsive luminescence.On the other hand,DBF₂VCZ?SBF₂VCZ?DBF₂VPCZ?SBF₂VPCZ with the 3,6-or 3-substituted?bridge exhibited blueshifted mechanoresponsive and thermoresponsive luminescence.