Takafuji Makoto, Kawahara Tomoki, Sultana Nahid, Ryu Naoya, Yoshida Kyohei, Kuwahara Yutaka, Oda Reiko, Ihara Hirotaka
Department of Applied Chemistry and Biochemistry, Kumamoto University 2-39-1 Kurokami, Chuo-ku Kumamoto 860-8555 Japan
Materials Development Department, Kumamoto Industrial Research Institute 3-11-38 Higashimachi, Higashi-ku Kumamoto 862-0901 Japan.
RSC Adv. 2020 Aug 10;10(50):29627-29632. doi: 10.1039/d0ra05057a.
Aggregation-induced chirality is potentially useful in sensor technology applications. Herein we show extreme enhancement of secondary chirality through coordination-driven steric changes of terpyridyl ligand in molecular gels. The secondary chirality reflecting on enhancement of chiral signals (, circular dichroism (CD) and circularly polarised luminescence (CPL)) of the molecular gels formed from glutamide-attached terpyridine (-tpy) is extremely enhanced by the coordination of its terpyridyl groups to metal ions such as Cu, Zn and Ru, which is due to dramatic changes in the stacked structure of the chromophore groups through the formation of metal ion complex. Metal-free terpyridine exists in a non-planar geometry, which suppress π-π stacking interactions among aggregates. The planarity of the terpyridyl group is improved through metal-ion complexation, which induces the metal-ion-coordinated terpyridyl groups to stack. The thermal stabilities of the CD signals are strongly affected by the metal-ion species. CPL signal is generated in the molecular gel formed from -tpy-Zn complex accompanied by chelation-enhanced fluorescence. It is expected that large and sensitive coordination-driven secondary chirality signals (CD and CPL) are useful for sensing guest molecules and the surrounding environment.
聚集诱导手性在传感器技术应用中具有潜在的用途。在此，我们展示了通过分子凝胶中三联吡啶配体的配位驱动空间变化实现二级手性的极大增强。由连接谷氨酰胺的三联吡啶（-tpy）形成的分子凝胶中，反映手性信号（即圆二色性（CD）和圆偏振发光（CPL））增强的二级手性，通过其三联吡啶基团与铜、锌和钌等金属离子的配位而极大增强，这是由于通过形成金属离子配合物，发色团基团的堆积结构发生了显著变化。无金属的三联吡啶以非平面几何结构存在，这抑制了聚集体之间的π-π堆积相互作用。通过金属离子络合提高了三联吡啶基团的平面性，这促使金属离子配位的三联吡啶基团发生堆积。CD信号的热稳定性受到金属离子种类的强烈影响。在由-tpy-Zn配合物形成的分子凝胶中产生CPL信号，并伴有螯合增强荧光。预计大且灵敏的配位驱动二级手性信号（CD和CPL）可用于传感客体分子和周围环境。
