Research On The Synthesis And Property Of Novel BODIPY Dyes

Boron-dipyrromethene (BODIPY) fluorophores have attracted a lot of attention in thedesign of fluorescence labels and biomolecule sensors, because they present many excellentphotospectral properties, such as high extinction coefficients(ε), high fluorescence quantumyields(φ_f) and good photostability. This kind of dyes is comparatively easy to be oxidizedand reduced, which triggers BODIPY fluorophores' application in photo-switches based onthe theory of electron or charge transfer (CT). In this thesis, based on the rescent references,many novel Boron-dipyrromethene dyes with active substituents have been synthesized forconvenient applications in biological labeling fields, and two series of BODIPY dyes presentstrong fluorescence and Near-inferd Absorption.At the beginning, two kinds of BODIPY dyes 1 and 2 with short spectral wavelengthswere synthesized, and different active groups were introduced to the dyes by usingsubstituented benzenealdehydes as reagents. The spectral properties of these dyes weredetected in various solvents, and the quantum yields of 2 are more than 10 times larger thanthose of the corresponding 1. Combined with the crystal structures of 1 and 2, a conclusioncan be drawn that both the electronic "push-pull" effect and the steric effect result in thedistinct quantum yields of 1 and 2 dyes. The dye 2d with amino group shows photo-inducedelectronic transfer(PET) phenomenon in strong polar solvent, however, the PET effection canbe forbaden by the acylation of amino. The four methyl groups in dyes 2 will increase theelectron cloud density of dye molecules and make dyes 2 easier to be oxidized and lessphoto-stable than dyes 1. Different p-substituent phenyls also affect the photostability of thesedyes. When an electron-donating group is at the p-position of phenyl moiety, thephotostability will decrease.The second, in view of developing longwavelength BODIPY dyes, the dyes 3 with apyrrole group at 5 position were synthesized, and the five-member cycle will avoid the spacejam between the aromatic group and BODIPY frame. The absorption and emission spectra of3 show large red-shift (more than 80nm compared with dyes 1) and reach about 600nm. Thisphenomenon suggests that the pyrrole group conjugated with BODIPY skeleton very well.The last, series dyes 4 and 5 with styryl groups were synthesized, and the phenyl wereseparated with BODIPY skeleton by carbon-carbon double bonds. The X-ray results of 5bshow that the double bond in the molecule is in trans form, and the two styryl groupsconjugates with BODIPY framework very well. This is the most important reason for the longspectral wavelength of these series of dyes. The spectral properties of 4 and 5 were detected indetail, and these dyes without amino groups present high fluorescence quantum yields.Dimethylamino dyes in 4 and 5 are intensively sensitive to solvents, and photo-induced ICT (intra-molecular charge transfer) process may happen in these molecules. However, the ICTcould be stopped by the protonation of the N, N-dimethylamino group. The red shift of 5c·H~+can be attributed to the formation of push-pull electronic system: one protonated amino groupas "pull" and another non-protonated amino group as "push" group in 5c.