Synthesis And Properties Of Organic Small Molecules Based On Aza-BODIPY

Aza-BODIPY fluorescent dyes have received extensive attention in the last two decades. As NIR dyes, they exhibit excellent photophysical properties,such as high fluorescence quantum yields,large absorption extinction coefficients, sharp fluorescence emissions,high photostability, etc. Aza-BODIPYs have been applied in Photodynamic therapy（PDT）, fluorescence imaging and chemical detection, the fluorescence probes based on Aza-BODIPY derivatives have been used to detect metal ions, anions and small molecular compounds, while the report on cyanide anion（CN^-） detection is still very rare. In this thesis, a series of new Aza-BODIPY fluorescent dyes were synthesized and their photophysical properties were investigated, more importantly, a new reaction mechanism between Aza-BODIPYs and CN^- was disclosed and investigated systematically.In Chapter 2, a new Aza-BODIPY derivative（L1） carrying two formyl groups was designed and synthesized. UV-Vis absorption and fluorescence spectra titration experiments were performed to study the sensing properties towards CN^-. The results indicated that L1 can be used as a colorimetric fluorescence sensor for CN^- in the detection system of DMSO/PBS（8/2, v/v）, the detection limit was calculated to be 7 μM. Based on the literature reports, we assumed the sensing behavior to be the reaction between CN^- and the formyl groups. However, the 1H NMR titration experiment clearly indicated that the formyl group wasn’t attacked even after the addition of large amount of CN^-. The phenomenon made us reconsider the reaction mechanism between AzaBODIPYs and CN^-.In chapter 3, the reaction mechanism between Aza-BODIPYs and CN^- was systematically investigated. By comparing the properties of the compounds without formyl groups, it turned out that the formyl group would not interfere with the detection of CN^-. Considering the large absorption changes after the addition of CN^-, we estimated that CN^- may attack one of the pyrrole rings to result in whole conjugation change of the Aza-BODIPYs. The possible reaction site was proposed based on the 1H NMR titration experiments and the theoretical calculations. Finally, the single crystal structure of the similar Aza-BODIPY-CN adduct intuitively suggested that the stoichiometry of AzaBODIPYs and CN^- was 1:1 and the reaction site was the 3-position of the Aza-BODIPYs’ core structure.In chapter 4, three Aza-BODIPY derivatives were designed and synthesized, we intended to study the effect of structure modification on the reaction property of Aza-BODIPYs with CN^-. Results demonstrated that the electron-withdrawing group BF2 would significantly affect the reaction between Aza-BODIPY derivatives and CN^-, and it could hardly occur if the BF2 group was not involved in the structure,this was due to the lack of an electron-withdrawing group BF2 which could make the N-substituted dipyrromethene structure more electron-deficient, the results of theoretical calculation also indicated that high energy was required for the reaction to take place. Meanwhile, the aldehyde group on the pyrrole rings still existed even in the presence of large amount of CN^-, this suggested that the core-structure was easier to be attacked compared with the aldehyde.In chapter 5,a TPE derivative M1 was designed, incorporating a nitrovinyl unit which is a strong Michael acceptor made it susceptible to some nucleophiles. The sensing properties of probe M1 toward HSO₃^- were studied through the UV-Vis absorption and fluorescence spectra titration experiments, the adduct of M1 and HSO₃^- was characterized by the HRMS. Results showed that this compound showed typical AIE properties, however, it showed response to HSO₃^- and thiolcontaining amino acids such as L-Cys, Hcy and GSH, the selectivity for HSO₃^- as a fluorescence probe needed to be improved.