Institut für Organische Chemie und Makromolekulare Chemie, Heinrich-Heine-Universität Düsseldorf, Universitätsstrasse 1, D-40225 Düsseldorf, Germany.
Institut für Physikalische Chemie, Heinrich-Heine-Universität Düsseldorf, Universitätsstrasse 1, D-40225 Düsseldorf, Germany.
Molecules. 2022 Apr 6;27(7):2354. doi: 10.3390/molecules27072354.
A versatile amphiphilic pyrano[2,3-]indole for halochromic turn-ON luminescence in acidic or basic media is accessed by an insertion-coupling-cycloisomerization and adjusting solubilizing and phenolic functionalities. While almost non-emissive in neutral solutions, treatment with acids or bases like trifluoroacetic acid (TFA) or 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) reveals distinct luminescence at wavelengths of 540 nm or 630 nm in propan-2-ol, respectively. Turn-ON emission can be detected at pH values as mild as pH = 5.31 or 8.70. Quantum yields in propan-2-ol are substantial for protonated ( = 0.058) and deprotonated ( = 0.059) species. Photometrically, p of 3.5 and p of 10.5 were determined in propan-2-ol. With lipophilic polyether sidechains and hydrophilic protonation and deprotonation sites the molecule can be regarded as amphipolar, which results in good solubility properties for different organic solvents. In aqueous media, an organic co-solvent like propan-2-ol (35%) or tetrahydrofuran (25%) is needed, and the solution can be diluted with pure water without precipitation of the compound. At higher concentrations of water, a turbid solution is formed, which indicates the formation of micellar structures or clusters. With dynamic light scattering we could show that these clusters increase in size with increasing water content.
一种多功能的两亲性吡喃并[2,3-]吲哚，通过插入-偶联-环化异构化反应，并调节增溶和酚官能团，可在酸性或碱性介质中实现对变色开-关荧光的调控。在中性溶液中几乎不发光，而用三氟乙酸（TFA）或 1,8-二氮杂二环[5.4.0]十一-7-烯（DBU）等酸或碱处理时，分别在异丙醇中于 540nm 或 630nm 处显示出明显的发光。在 pH 值低至 5.31 或 8.70 时即可检测到开-关发射。在异丙醇中，质子化（ = 0.058）和去质子化（ = 0.059）物种的量子产率都很高。在异丙醇中，通过光度法确定了 p 值为 3.5 和 p 值为 10.5。该分子具有亲脂性聚醚侧链和亲水性质子化和去质子化位点，因此可以被视为两性分子，这使得它在不同有机溶剂中具有良好的溶解性。在水介质中，需要添加有机溶剂如异丙醇（35%）或四氢呋喃（25%）作为共溶剂，并且可以用纯水稀释溶液而不会导致化合物沉淀。在水的浓度较高时，会形成混浊溶液，这表明形成了胶束结构或聚集体。通过动态光散射，我们可以证明这些聚集体的尺寸随着含水量的增加而增加。
