Construction Of Tripod BODIPYs Via Low Temperature Nucleophilic Substitution

In recent years, Boron dipyrromethene dyes(BODIPY) structures have got rapid development among abundant fluorescent dyes. The BODIPY dyes show many excellent properties, such as high molar extinction coefficients, high fluorescence quantum yield, excellent photostability, less sensitivity to solvent polarity and p H, and narrower spectrum in absorption and emission which can be tuned easily etc. Ten novel tripod BODIPY fluorescent compounds bearing phenolic and amine derivatives were synthesized via nucleophilic substitution of cyanuric chloride at low temperatures. All the seven compounds were characterized by MS, 1HNMR, 13 CNMR, IR, and they haven’t been reported so far.First,the appropriate reaction conditions were found through exploring the reaction temperatures and the reaction time.The optimized reaction conditions was obtained as follows:The third chlorine of the aldehyde-containing intermediates were substituted by nucleophilic reagent at low temperature ahead of the complexation with BF3×Et2O. DIEA was chose as acid-binder during substitution of the third chlorine and the coordination process with boron trifluoride. The two steps can be performed in a one-reactor result in the simplified process and the less reaction time.Next, the reaction temperature, reaction mechanism, reactivity between the different structure of the intermediates and nucleophilic reagent were investigated:(1) The temperature of the third chlorine of the triazine substituted by amine nucleophilic reagent would be lower than phenolic nucleophilic reagent: the temperature of substitution by amine was below room temperature and phenol was 45 oC.(2) The yield of the third chlorine of the triazine substituted by amine nucleophilic reagent was lower than phenolic nucleophilic reagent.(3) The activity of third chlorine was enhanced at enough temperature: the displacement of the third chlorine of the triazine with amines were conducted immediately at the enough temperature(25 oC), reaction time would be prolonged at the lower temperature(-5oC);the displacement of the third chlorine of the triazine with phenols were conducted completely at the enough temperature(45 oC), the displacement was conducted partly at the lower temperature(30 oC).(4) The third chlorine of intermediates with more electron-withdrawing groups would easier be replaced(5) A proposed mechanism about the active chloride was discussed.Last, the UV-Vis and fluorescence spectra of the dyes obtained in this paper showed that :(1) The different kinds of phenolic and amine moieties used in the auxiliary part affected the maximum emission wavelength and the maximum absorption wavelength of the dyes slightly.(2) The fluorescence quantum yields of all compounds were 29.55%(2b-Ⅴ)~67.33%(2b-Ⅰ).