Novel Fluorine Boron Complex Contain N^N Or N^O:Synthesis And The Fluorescence Properties

Fluorine boron complex represents a family of extremely versatile fluorophores which are currently attracting increasing interest among various research areas including electrochromic display systems,solar cells,liquid crystals,optical storage devices,laser dyes,etc,owing to their remarkable photophysical features,such as high fluorescence quantum yield,excellent photo-stability,and sharp fluorescence spectra.Despite all these advancements,low emission wavelength and the small Stokes shift have been the two major drawbacks which limit the actual applications of this class of fluoresce complexes.Furthermore,aggregation-caused quenching is another common hurdle that turns away most fluorine boron complexes from their practical application.To circumvent this problem,novel fluorine boron complexes were developed which with long emission,large Stokes shift and the solid fluoresce.Herein we report three new types of the fluorine boron complexes which exhibit excellent optical properties.Part 1: 4,4-Difluoro-4-bora-3a,4a-diaza-s-indacene?BODIPY?derivatives were efficiently synthesized by a three-step reaction starting from 3-methylindole and the substituted benzaldehyde.The fluorescence properties of the BODIPY derivatives were investigated in different organic solvents.These fluorescent dyes exhibited no fluorescent intensity in most common solution but a high fluorescent intensity with a long-wavelength?ca.600 nm?emission in some special solution.The novel solvatochromic of the BODIPY derivatives maybe is due to the interplay with these special solvents.Information supporting this inference was supported by 1H NMR and density functional theory calculations.Part 2: Isatin-phenylhydrazone derivatives and their corresponding BF2-complexes were efficiently synthesised by a three-step reaction starting from isatin and phenylhydrazine hydrochloride.The fluorescence properties of the isatin-phenylhydrazone derivatives and derived BF2 complexes were investigated in different organic solvents,in the solid state and in mixed solvent solutions of THF and H₂ O.These fluorescent dyes exhibited low fluorescent intensity in solution but a high fluorescent intensity as aggregates and in their sol id state due to the interesting aggregation-induced emission enhancement characteristics which were caused by the inhibiti on of intramolecular rotation in the single molecule state.Information supporting this inference was supported by single crystal X-ray analysis.The Stokes shift of these dyes can be achieved 95¹98 nm vs the typical BF2-complexes?ca.15 nm?in the solid-state which were caused by the remarkable geometry relaxation upon photoexcitation and its substantial effect on the energy levels of molecular orbitals.Information supporting this inference was supported by the density functional theory calculations.Part 3: Condensation of 4-?diethylamino?salicylaldehyde with aqueous hydrazine,followed by complexation with BF3·OEt2 gives a fluorescent indicator highly selective for copper.The indicator forms a 2: 1 complex with Cu^{2+} and displays a highly sensitive and selective fluorescent quenching action with Cu^{2+} upon excitation at 440 nm in water/THF?7: 3,v/v?solution.This action is pH-independent over the range 4.5 < pH < 9.5.