Synthesis And Properties Of New Pyridylimidazo[1,2-a]pyridine-BODIPY Derivatives

Imidazo[1,2-a]pyridine and its derivatives,as nitrogen-rich heterocycles,are generally adopted as important component with distinct biological activities in natural products or drugs.Due to the conjugated structure imidazo[1,2-a]pyridine,excellent optical properties are observed.BODIPYs have excellent photophysical and photochemical properities.Howevre,to the best our knowledge,there is few reported about the association combination of imidazo[1,2-a]pyridine and BODIPY.In this thesis,we report the design and synthesis pyridylimidazo[1,2-a]pyridine-BODIPY derivatives,as well as their attractive optical properties.One new molecular dyad 1 comprising imidazo[1,2-a]pyridine and borondipyrromethene subunits,has been synthesized starting from imidazo[1,2-a]pyridine derivative and fully characterized.The synthesis,optical properties of a series of imidazo[1,2-a]pyridine-BODIPY dyads 2-12 containing various functional groups at 2 or 2/6-position of the pyrrole,are described.Compound 2 were obtained from compound 1 with 4 equiv.of N-bromosuccinimide(NBS).Mono-and diiodo-substituted derivatives 3 and 4 were achieved with appropriate amounts usage of N-iodosuccinimide(NIS).The mono-and dual phenylations have been achieved by coupling reaction of respective iodinated BODIPY derivatives 3 and 4 with appropriate phenylboronic acid(Ar B(OH)2,Ar = C6H5-,4-OMe-C6H4-,4-NMe2-C6H4-,4-NPh2-C6H4-)in the presence of catalytic amounts of Pd(PPh3)4.Single crystal X-ray diffraction analyses of 1,2,4 and 6 revealed C-H···F interactions between molecules.Large effects of different electron-donating substituents on absorption and fluorescence were detected,and the emission colors were successfully tuned from green to NIR.Compounds 9 and 10 were not soluble in water,a purple red suspension was formed.But interestingly,after addition of HCl acid into the suspension,a clear orange-red solution appeared,and appeared emissive in orange-yellow color under UV-irradiation at 365 nm.Addition of base triethylamine(TEA)practically reverses the color changes indicating a reversible behavior.Later,1H NMR?absorption and fluorescence were detected for compounds 9 and 10.DFT and TDDFT calculations for all new compounds have been carried out for deep understanding their electronic transitions at ground states.Compound 7 was selected as an example for preliminary living cell imaging exploration.Both green and red fluorescence were observed when the images were collected from respective green and red channels.The results of cell imaging proved the good cellular uptake ability,and compound 7 may be applied as reagent.As evidenced by X-ray structural data,with metal cations binding to the vacant bidentate compound 1,five new luminescent transition metal complexes 13-17(dibromozinc(II),chlorocadmium(II),chlorotricarbonylrhenium(I),bis(2-phenylpyridine)iridium(III),dichloroplatinum(II)complexes)have been successfully formed.Absorption and emission spectral profiles are dominated by contribution of the BODIPY moiety.DFT and TDDFT calculations for all metal compounds have been carried out for deep understanding their electronic transitions at ground states.