5-[4-(Dimethylamino)phenyl]-2-benzamidopyrazines: fluorescent dyes based on Cypridina oxyluciferin
作者:Takashi Hirano、Tatsuki Nakagawa、Ai Kodaka、Shojiro Maki、Haruki Niwa、Minoru Yamaji
DOI:10.1007/s11164-012-0645-3
日期:2013.1
To clarify the acyl substitution effect on the fluorescent property of Cypridina oxyluciferin analogs, which have the 4-(dimethylamino)phenyl group at C5, we compared the spectroscopic properties of benzamide 1b and its 2,6-dimethylphenyl derivative 1c in various solvents with those of acetamide 1a. Similarity of the fluorescence wavelengths of 1a–c indicates that the π-electronic conjugation in the excited singlet (S1) state is terminated at the acyl group and that the benzamide moiety in 1b has little effect on modulating the florescence color. The similar fluorescence solvatochromism of 1a–c reveals that their S1 states have a similar intramolecular charge transfer character. The fact that 1a–c have various fluorescence quantum yields and lifetimes depending on solvent polarity and hydrogen bonding interactions in solutions provides information about the decay processes competing with the fluorescence process in the S1 states. Among 1a–c, benzamide 1b exhibits the most sensitive variation of the fluorescence intensity depending on the solvent used. Similarity of the fluorescence spectra of 1a–c adsorbed in NaY zeolites was also observed, which indicates that the S1 states of 1a–c give mobile conformers in the NaY supercages. The relationship between the molecular structures of 1a–c and their spectroscopic properties will provide a guide for designing a new fluorophore based on Cypridina oxyluciferin.
为了弄清酰基取代对 Cypridina 氧荧光素类似物荧光特性的影响,我们比较了苯甲酰胺 1b 及其 2,6-二甲基苯基衍生物 1c 与乙酰胺 1a 在不同溶剂中的光谱特性。1a-c 的荧光波长相似,表明激发态单线态(S1)的π-电子共轭终止于酰基,1b 中的苯甲酰胺分子对荧光颜色的调节作用很小。1a-c 类似的荧光溶解色度表明,它们的 S1 态具有类似的分子内电荷转移特性。根据溶液中溶剂极性和氢键相互作用的不同,1a-c 具有不同的荧光量子产率和寿命,这一事实提供了有关与 S1 态荧光过程竞争的衰变过程的信息。在 1a-c 中,苯甲酰胺 1b 的荧光强度随所用溶剂的变化最为敏感。在 NaY 沸石中吸附的 1a-c 的荧光光谱也具有相似性,这表明 1a-c 的 S1 态在 NaY 超级包裹体中具有可移动的构象。1a-c 的分子结构与其光谱特性之间的关系将为设计基于 Cypridina oxyluciferin 的新型荧光团提供指导。