Studies On The Synthesis And Spectral Properties Of(hydroxyl/aminophenyl)benzozoles-BODIPY Dyads

Proton transfer compounds and boron fluoride pyrrole(BODIPY)have been widely used and promoted in recent years.The synthesis of dyads can provide new ideas for the construction of fluorescence recognition system and the design of novel luminescent materials.In this paper,five energy donor-acceptor dyads of 2-(2-hydroxyl/aminophenyl)benzoazole and BODIPY divalent groups were synthesized by the method of amide synthesis.Their structures were characterized by ¹H NMR and high resolution mass spectrometry.The spectral properties of these dyads were studied by UV-vis absorption spectrum,fluorescence emission spectrum,fluorescence titration and quantum chemistry calculation.Effects of aromatic substituents on proton transfer in excited state and spectral properties of 2-(2-hydroxyphenyl)benzimidazole(HBI)was studied by density functional(DFT)and time-dependent density functional(TD DFT)theory.1.The dyads HBT-BODIPY and HBT-BODIPY¹were synthesized.The spectra showed that the maximum absorption wavelength of HBT-BODIPY was about 500 nm,and there was an emission peak near 513 nm.Because HBT-BODIPY¹has a large degree of conjugation,the absorption and emission of the latter are redshifted by about 14 nm compared with the former.The solvent effect indicated that the dyads are not sensitive to solvents.The cationic response results showed that Cu²⁺and Ni²⁺had fluorescence quenching effect on HBT-BODIPY and HBT-BODIPY¹.When pH=11?14,the fluorescence intensity of HBT-BODIPY was significantly reduced,and the molecular structure of HBT-BODIPY¹was destroyed under the condition of pH=12?14.2.It was found that the stable configurations of the ground and excited states of HBI and HBI-R were alcohol-type and ketone type.The substitution group reduced the proton transfer energy barrier in both the ground state and excited state of HBI,and ESIPT was more likely to occur than GSIPT.Aromatic ring substituents cause obvious redshift in both absorption and emission peaks.In DMSO solvent,the fluorescence intensity of HBI-BODIPY decreased as the concentration of Cu²⁺and Ni²⁺increased,and the molar binding ratio was 1:1 and 1:2,respectively.HBI-BODIPY has strong anti-interference performance in recognizing Cu²⁺and Ni²⁺.When pH=11?14,the amide bond of HBI-BODIPY was broken,the fluorescence peak at 515 nm was reduced,and a new emission peak appeared at 448 nm.3.The dyad HBO-BODIPY was synthesized and the absorption and emission spectra in different solvents were measured.In acetonitrile solvent,a fluorescence resonance energy transfer(FRET)system with HBO-NH₂as the energy donor and compound 2a as the energy receptor was constructed.The effect of donor and aceptor concentration on FRET was studied.Ion response and anti-interference experiments show that HBO-BODIPY can recognize Cu²⁺and Ni²⁺and has strong anti-interference.When pH was 11?14,the fluorescence peak of HBO-BODIPY at 515 nm was reduced and a new emission peak appeared at 472 nm.4.Experiments and theoretical calculations showed that different solvents have little effect on the absorption and emission spectra of APBT-BODIPY.It was found that APBT-BODIPY had intramolecular fluorescence resonance energy transfer from energy donor APBT-COOH to energy receptor 3a in THF.And construct a FRET pair between the two molecules.With the increase of H⁺concentration,the absorption peak of APBT-BODIPY shifted blue at short wave strength,and the fluorescence peak decreased at 514 nm.APBT-BODIPY showed good specificity to Cu²⁺,and its fluorescence intensity decreased as the concentration of Cu²⁺increased.