School of Chemical Engineering and Technology, Tianjin University, 300072, Tianjin, China.
Chemistry. 2023 Jul 11;29(39):e202300906. doi: 10.1002/chem.202300906. Epub 2023 May 22.
New chiral and achiral dyes were synthesized by using clean, highly efficient Diels-Alder 'click' reactions. We prepared pure endo- and exo- stereoisomers and blue-light-emitting single crystal of an exo-isomer. H NMR spectroscopy and single-crystal X-ray diffraction reveal the precise spatial configurations of endo- and exo-dye stereoisomers. Single-crystal X-ray diffraction results reveal the dynamic nature of Diels-Alder covalent bonds. By reversible formation and cleavage of dynamic covalent bonds, an achiral dye was converted to a chiral dye, where achiral dansyl dye moiety was replaced by chiral moiety. Before achiral-to-chiral dye conversion, the dye system displayed dansyl acceptor green light-emitting color due to intramolecular fluorescence resonance energy transfer, where the blue emission of pyrene donor fluorophore was not observed. After achiral-to-chiral dye conversion, light-emitting colors of dye system change from green to blue, where the pyrene-to-dansyl fluorophore energy transfer was suppressed, and pyrene fluorophore blue emission was restored. Chiral transfer occurs in a chiral dye solid from non-chromophore alky chirality to pyrene chromophore. Thus, the chiral dye solid displayed chiral optical behaviors, i. e., circular dichroism and circularly polarized luminescence.
我们使用清洁、高效的 Diels-Alder“点击”反应合成了新的手性和非手性染料。我们制备了纯内型和外型立体异构体以及外型异构体的蓝光发射单晶。1 H NMR 光谱和单晶 X 射线衍射揭示了内型和外型染料立体异构体的精确空间构型。单晶 X 射线衍射结果揭示了 Diels-Alder 共价键的动态性质。通过可逆形成和动态共价键的断裂，将非手性丹磺酰染料转化为手性染料，其中非手性丹磺酰部分被手性部分取代。在手性染料转化之前，由于分子内荧光共振能量转移，染料体系显示丹磺酰供体绿光发射颜色，其中未观察到芘给体荧光团的蓝色发射。在手性染料转化之后，染料体系的发光颜色从绿色变为蓝色，其中芘到丹磺酰荧光团的能量转移被抑制，并且恢复了芘荧光团的蓝色发射。手性转移在手性染料固体中从非发色团烷基手性到手性发色团芘发生。因此，手性染料固体表现出手性光学行为，即圆二色性和圆偏振发光。
