Synthesis And Properties Of Fluoroboron Fluorescent Dyes Based On Imidazo[1,2-a]Pyridine

Imidazo[1,2-a]pyridine and their derivatives can be used as precursors for a variety of drugs,and have been widely used in the pharmaceutical field.Because of their ?-conjugated structure,they also have excellent fluorescence properties.BODIPY compounds have been investigated in many fields due to their excellent photophysical and photochemical properties.It is anticipated the combination of two chromophores may possesses the advantage of each other.However,to the best our knowledge,there is no report about the association of imidazo[1,2,a]pyridine and BODIPY.In this paper,a series of BODIPY derivatives based on imidazo[1,2-a]pyridine and the synthesis of fluoroboron compounds were introduced,and their optical properties were studied.Our main results are summarized as follows:A series of imidazo[1,2-a]pyridine derivatives HLa-HLe,formyl compounds 2a/b,intermediates of BODIPY 3a/b and mononuclear(single B center)and binuclear(two B centers)imidazo[1,2-a]pyridine-BODIPY derivatives,la-le,4a,b,and 5a b have been synthesized through simple reaction steps They were characterized by,HNMR,13CNMR,and MS.The crystal structures of 1b,4a,4b(mononuclear)and 5b(dinuclear)were characterized by X-ray single crystal diffractionand,and the intermolecular hydrogen bonds(C-H…F)were observed in the crystals of these compounds.The optical properties of these fluoroboron compounds are also excellent;they all have a high absorption coefficient,strong fluorescence and light stability.DFT and TD-DFT studies reveal efficient electronic interactions between the imidazo[1,2-a]pyridine moiety and BODIPY plane for dyads 4a,b,and 5a,b.Since compound 4a has a very excellent emission intensity and quantum yield,we have extended the potential application.Firstly,compound 4a is very sensitive to TFA solution;with the increment of TFA concentration,the absorption and emission of 4a have a great change,indicating that 4a may be have potential application in pH sensors.Secondly,the potential use of 4a in cell imaging has been explored,to show good cellular uptake ability.Therefore,compound 4a may have potential application in cell imaging.