Photophysical Properties Of BODIPY Dimers And Monobenzo-fused BODIPY

BODIPY compounds are one of the flourescent dyes widely studied in the last three decades, due to their promising application as ion detection, biological probes and labels, photosensitizers and energy conversion and so on, because of their many outstanding and desirable photophyscial properties by themselves, such as relatively high fluorescence quantum yields, larger molar extinction coefficients, wide spectral range and sharp fluorescence emission peak, insensitivity to acid and base, excellent heat and photo-stability, easy modification of the parent structure. In this paper we designed and synthesized three BODIPY dimers, studied the probability of a number of various sites-connected BODIPY dimers as photosensitizers in the photodynamic therapy. On the other hand, we studied the fluorescence properties of five long wavelength monobenzo-BODIPY dyes and quenching mechanism by quinones and phenol.Taking BODIPY monomer 1 as a template, we mainly designed and synthesized(2-2′) and(2-8′) positions covalently-linked BODIPY dimers by C-H activation and Vilsmeier-Haack reactions in the second chapter. The UV-vis absorption, fluorescence emission and excitation spectra, IR and MS of BODIPY monomers 1-4 and dimers5-12 were tested. The properties of excited singlet state, triplet state and singlet oxygen for dimers 5-12 were systematically studied, finding that each BODIPY unit in dimers and solvent polarity had significant effects on their photophysical properties.As the solvent polarity increased, the fluorescnece quantum yields of BODIPY dimers 6-12 markedly reduced. BODIPY dimers 6-12 had strong ability of singlet oxygen generated in the weak polar solvent-toluene, and were photosensitizers which possessed ideal results. The fluorescence lifetime of meso-meso directly-linked dimer12 was longest, with highest singlet oxygen quantum yield of 0.87.The fluorescence properties of five monobenzo-BODIPY compounds were measured in nonpolar and polar solvents in the third chapter. These monobenzo-BODIPY dyes emit bright red fluorescence(wavelength > 605 nm) with high fluorescence quantum yields(Φf ≥ 0.60), which are slightly affected by solventpolarity. The fluorescence lifetimes of these BODIPY compounds are also long(τf ~ 5ns) and not affected remarkably by solvent polarity. These fluorescence properties make them good fluorescent markers/probes in the red visible region. Quinones can efficiently quench the fluorescence of monobenzo-BODIPYs with the dynamic quenching rate constants in the order of 1010 M-1 s-1, suggesting that the BODIPY compounds can act as good electron donors for photoinduced electron transfer in artificial photosynthesis and organic solar cells.