新型BODIPY荧光染料的合成及光谱性质研究

传统的BODIPY荧光染料具有荧光量子效率高、摩尔消光系数大、紫外吸收和荧光发射峰窄等优点，然而这类荧光染料普遍存在荧光发射波长短和Stokes位移小的缺点，因而限制了它们在体内生物传感及成像方面的广泛应用。为了得到荧光发射波长较长和Stokes位移大的BODIPY荧光染料，以BODIPY母核为基本结构，通过在它的8位连接吸电子性质的酯基来增加分子内电荷转移程度，同时在其3,5位引入供电子的芳香取代基增加分子的π共轭结构，合成得到了一类8位酯基取代的新型BODIPY荧光染料。所得到的新型BODIPY荧光染料的化学结构经过1H NMR, 13C NMR和HR-MS得以确认。光谱测试结果表明，这类染料的紫外吸收光谱(λ_abs=536 nm)和荧光发射光谱(λ_em=592 nm)与普通的BODIPY相比都发生显著红移(80 nm)，并且保持了较高的荧光量子效率(Ф=0.43)。此外，这类BODIPY荧光染料的紫外可见吸收光谱和荧光发射光谱几乎完全分开，Stokes位移长达60 nm，可以有效地避免自吸收和生物样品的背景干扰。密度泛函理论计算结果表明，这种相对较大的Stokes位移主要是由于染料分子在基态和激发态下不同的几何构型所造成的。该类化合物的光物理性能受溶剂的影响小，是一类性能优良的新型荧光染料。细胞成像结果表明，染料1具有良好的细胞渗透性和光稳定性，可以实现对细胞的荧光成像。

Synthesis and Spectroscopic Properties of Some Novel BODIPY Dyes

BODIPY dyes have some unique properties including high fluorescence quantum yield, large extinction coefficiency, narrow absorption and emission band. However, most of BODIPY dyes display short emission wavelength and small Stokes shift, which limits their applications in biosensing and bioimaging in vivo. For bioimaging application, a fluorescent dye with long emission wavelength and large Stokes shift is highly desired. To push the absorption and emission spectrum of BODIPY to red and even far-red region, a COOEt group was introduced to the meso position, and some aromatic group was attached to the 3,5 position of BODIPY core. The structure of resulting compounds were comfirmed by 1H NMR, 13C NMR and HR-MS. Dye-1 displays a strong UV-Vis absorption band centered at 536 nm and a sharp emission band is located at 592 nm, which is significantly red-shifted (80 nm) compared to ordinary BODIPY analogs. In addition, the meso-COOEt substituted BODIPYs exhibit high quantum yield and red to far-red emission. Notably surprisingly, the meso-COOEt substituted BODIPYs display almost separated UV-Vis absorption and emission spectra with a large Stokes shift (~60 nm). Time-dependent density functional theory calculations were conducted to understand the structure-optical properties relationship, and it was revealed that the large Stokes shift was resulted from the geometric change from the ground state to the first excited singlet state. The spectroscopic properties of these BODIPY dyes display very subtle solvent-dependence effect. Furthermore, BODIPY was tested for its ability of imaging in living cells. The results indicate that Dye-1 is a water-soluble and membrane-permeable probe. Therefore, these BODIPYs are a new family dyes with excellent spectroscopic properties and can be good candidates for bioimaging in living cells.