Modulation of the spectroscopic property of Bodipy derivates through tuning the molecular configuration
作者:Yuting Chen、Liang Wan、Daopeng Zhang、Yongzhong Bian、Jianzhuang Jiang
DOI:10.1039/c1pp00001b
日期:2011.6
A series of six Bodipy derivatives, namely 4,4-difluoro-8-(4-amidophenyl)-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (1), 4,4-difluoro-8-(4-methylphenyl)-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (2), 4,4-difluoro-8-(4-nitrylphenyl)-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (3), 4,4-difluoro-8-(4-amidophenyl)-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene (4), 4,4-difluoro-8-(4-methylphenyl)-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene (5), and 4,4-difluoro-8-(4-nitrylphenyl)-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene (6) were structurally characterized by single crystal X-ray diffraction analysis. Two methyl substituents attached at C-1 and C-7 positions of boron-dipyrromethene (Bodipy) moiety in compounds 1–3 were revealed to prevent the free rotation of the benzene moiety, resulting in a molecular configuration with an almost orthogonal dihedral angle between the Bodipy and benzene moieties with the dihedral angle in the range of 81.14–88.56°. This is obviously different from that for 4–6 with a free-rotating benzene moiety relative to the Bodipy core due to the lack of two methyl substituents in the latter series of compounds, leading to an enhanced interaction between the Bodipy and benzene moieties for 4–6 in comparison with 1–3. The resulting larger HOMO–LUMO gap for 1–3 than 4–6 results in a blue-shifted absorption band for 1–3 relative to that for 4–6. Comparative studies over their fluorescence properties also disclose the blue-shifted fluorescence emission band and corresponding higher fluorescence quantum yield for 1–3 relative to those of 4–6, revealing the effect of molecular configuration on the spectroscopic properties of Bodipy derivatives. Comparison of the redox behaviors of these two series of Bodipy compounds provides additional support for this point. In addition, the electron-donating/withdrawing property of the para substituent of the benzene moiety was shown to exhibit a slight influence on the electronic absorption and fluorescence emission properties of the Bodipy compounds.
一系列六种Bodipy衍生物,即4,4-二氟-8-(4-酰氨基苯基)-1,3,5,7-四甲基-4-硼-3a,4a-二氮- s-茚烯 (1)、4,4-二氟-8-(4-甲基苯基)-1,3,5,7-四甲基-4-硼-3a,4a-二氮- s-茚烯 (2)、4,4-二氟-8-(4-硝基苯基)-1,3,5,7-四甲基-4-硼-3a,4a-二氮- s-茚烯 (3)、4,4-二氟-8-(4-酰氨基苯基)-3,5-二甲基-4-硼-3a,4a-二氮- s-茚烯 (4)、4,4-二氟-8-(4-甲基苯基)-3,5-二甲基-4-硼-3a,4a-二氮- s-茚烯 (5)和4,4-二氟-8-(4-硝基苯基)-3,5-二甲基-4-硼-3a,4a-二氮- s-茚烯 (6)通过单晶X射线衍射分析进行了结构表征。化合物1-3中位于硼-二吡咯美烯(Bodipy)结构单元C-1和C-7位置的两个甲基取代基被发现防止了苯基部分的自由旋转,导致Bodipy和苯基部分之间几乎正交的分子构型,二面角范围为81.14-88.56°。这显然与4-6的情况不同,后者的苯基部分相对于Bodipy核心具有自由旋转性,因为后者系列化合物缺乏两个甲基取代基,导致相较于1-3,4-6之间Bodipy和苯基部分的相互作用增强。1-3的较大HOMO-LUMO间隙使其吸收带相对于4-6发生蓝移。对其荧光特性的比较研究也揭示了1-3的荧光发射带蓝移以及对应的较高荧光量子产率,相对于4-6,显示出分子构型对Bodipy衍生物光谱特性的影响。对这两系列Bodipy化合物的氧化还原行为的比较进一步支持了这一点。此外,苯基部分对位取代基的电 donating/withdrawal特性对Bodipy化合物的电子吸收和荧光发射性质也显示出轻微影响。