Research On The Synthesis, Properties And Application Of Novel BODIPY Fluorescence Dyes

Over the past twenty years, boradiazaindacenes (difluoro-bora-dipyrromethenes, boron-dipyrromethene, BODIPYs or BDPs) as fluorescent dyes have attracted considerable attention, for they present many advantageous spectral properties, such as high molar extinction coefficients (ε), high fluorescence quantum yields (Φ_f), excellent photostability, less sensitivity to solvent polarity and pH, and narrower spectrum in absorption and emission at visible light which can be tuned easily etc.One portion of the research work focused on the synthesis of suitable and typical BODIPY derivatives which can be applied for X-ray analysis. Six BODIPY derivatives were synthesized and their single crystal structures were determined in order to disclose their molecular arrangement, spatial stacking and possible hydrogen bonds in microscopic scale. From the results we found that: The main skeleton composed of three fused heterocyclic rings is close to planar and conjugated, and the positive charge in nitrogen atoms should be delocated, although the boron atom affected by fluorine atoms. The existence of phenyl ring in C8 postion influence both the formation of the C—H---F hydrogen bonds and the quantum yield of fluorescence, which are the results of the spatial hindrance. The dihedral angel between the phenyl ring and BODIPY main core is relative to the different substitute groups. The styrene part can enlarge the conjugated degree of BODIPY skeleton and red-shifted the spectra so that afford the dyes with long wavelength.Furthermore, in recent years, BODIPY derivatives had been widely used in fluorescent sensors, biolabels, pharmacological and pathological analyzing for their special photophysical and photochemical properties, while the prerequisite of their applications is how to synthesize the BODIPY derivatives with special functional groups, such as amino, carboxyl and hydroxyl group. BODIPY dyes with carboxyl can be used in many fields, such as protein detection, DNA sequencing and nucleotide analyzing etc. So, another part of the research work aimed at exploring this kind of dyes, which arise from pyrroles and dicarboxylic anhydrides in one pot reactions, and free carboxyl can be released during the reaction directly by the open-ring reaction of the dicarboxylic anhydrides. The molecular structures of the six derivatives are symmetrical, and the strategy of the method is effective and convenient which avoided the complicated synthesis of starting materials compared with asymmetrical methods reported before. This BODIPY derivatives own good spectral properties, the methyl groups on BODIPY skeleton benefit to the fluorescence quantum yields and molar extinction coefficient but affect on the photostability of the dyes. The photofading experiments indicated that the dyes with carboxyalkyl groups in C8 positions own higher photostability than those with 2-carboxy -phenyl groups, and dye la and 2a own excellent photostability in water. All of these are the synergy effect of the electron cloud density, the special hindrance and their capacities to generate ¹O₂ and probability of reaction with ¹O₂.On the other hand, the activated dye 1c and 2c derivated from dye la and 2a respectively were verified by NMR and X-ray (for 2c). BSA labeling experiments of dye 1c shows that the dye is suitable for protein detection and analyzing. The limit of detection (LOD) is up to 2 ng by SDS-PAGE and gel image analysis. This work should act as a basic and instructive role for the applications of this kind of dyes in biology.