Research On The Solvent-free Synthesis And Spectrum Property Of Aza-BODIPY NIR Fluorescence Compounds

Aza-BODIPY(Aza-boron-dipyrromethene)is a new NIR fluorescence compound which was developed in recent years.Because of excellent fluorescent properties,such as longer absorption and emission wavelength,sharp half peak width and high fluorescent quantum yield,it has been widely noted and used to chemical sensors,mental ion detection,biological probe,photodynamic therapy,solar cells and fluorescent switch,etc.Small modifications to the Aza-BODIPY framework enable turning of its fluorescence characteristics.The main work of this paper includes the following three parts.Part 1:The solvent-free process for prepared Azadipyrromrthene in high-pressure reactor was studied.Azadipyrromethene were synthesized from aromatic ketones and aromatic aldehydes via three-step reactions.At first,a series of chalcone analogues were obtained by the reaction of Aldo 1-condensation.Then intermediates 2 were synthesized through Michael addition reaction of chalcone with nitromethane.Azadipyrromethene chromophores were obtained with intermediates 2 and ammonium acetate.But according to the references,the yields of Azadipyrromethene chromophores were very low.The highest one is only 47%.Therefore,the Synthetic routes need to be optimized.In this study,the concept of green chemistry has been considered.The method of solid phase without solvent is tried to the synthesis of Azadipyrromethene.The optimum process was selected as follows:the moles ratio of intermediates 2a and ammonium acetate as 1:20,at 160? reacted 1 h,producted Azadipyrromethene chromophore 3a in 89%yield.Further another thirteen Azadipyrromethene derivatives were obtained in high yields.Compared to the previous conditions,this way not only simplifies the experimental operation but also greatly decreases the reaction time and increases the reaction yield.What's more,the method of solid phase without solvent in high-pressure reactor avoids the harm to human from organic solvent,reduces the waste of organic solvents and achieves the greening of reaction.The structures of all synthesized compounds were characterized by 'H NMR spectra.Part 2:The new process for synthesized ?-nitro-Aza-BODIPY was studied.Aza-BODIPY derivatives were obtained by the reaction Azadipyrromethene derivatives with Boron trifluoride diethyl ether(BF3·Et2O).Starting from Aza-BODIPY and ceric ammonium nitrate(CAN),the optimum process was selected as follows:the moles ratio of Aza-BODIPY 4a and ceric ammonium nitrate as 1:1.4,at 0 ? reacted 4 h,producted ?-nitro-Aza-BODIPY derivatives 5a in 85%yield.Further another four ?-nitro-Aza-BODIPY derivatives were obtained in high yields.This new process of synthesis ?-nitro-Aza-BODIPY has the advantages such as convenient operation,low energy consumption and high reaction efficiency,etc.The structures of all synthesized compounds were characterized by 1H NMR spectra.Part 3:The ultraviolet-visible absorption spectrum and fluorescence spectrum of four Aza-BODIPY derivatives and four ?-nitro-Aza-BODIPY derivatives were measured.Then fluorescent quantum yield were calculated.All the compounds have a larger molar absorptivity in the long wavelength region.Most of the compounds have good performance in fluorescent quantum yield,up to 0.55.On this basis,the relation between the photophysical properties and the structure of the dyes were investigated.