Flapping motion as a fluorescent probe for assembly process involving highly viscous liquid-like cluster intermediates during evaporative crystallization
Flapping motion as a fluorescent probe for assembly process involving highly viscous liquid-like cluster intermediates during evaporative crystallization
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拍打运动作为荧光探针，用于蒸发结晶过程中涉及高粘度液体状簇中间体的组装过程
DOI：
10.1007/s43630-022-00321-0
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Fuyuki Ito
中科院分区：
文献类型：
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作者：
Shiho Katsumi;Hiroyuki Tanaka;Ryota Kotani;Shohei Saito;Fuyuki Ito
荧光探针广泛用于基于其光物理性质的分子环境评估。其中，柔性芳香光功能体系（FLAP）由于蒽翼的激发态平坦化而成为独特的粘度探针。我们以前曾应用荧光光谱监测溶剂的蒸发结晶。取决于聚集形式的荧光颜色和光谱变化使得在蒸发结晶期间能够直接荧光可视化。实现了两步成核模型中提出的类液体团簇中间体的荧光可视化。然而，这些团簇的物理性质，特别是粘度，分子运动和分子间相互作用，仍然不清楚。在这项研究中，FLAPs被用作探针的局部粘度变化和空间限制的液体状团簇状态在蒸发结晶过程中，通过观察荧光光谱的变化，并使用高光谱相机（HSC）成像。绿色发射来源于溶液中的单体，由于自由拍动运动。在拥挤条件下，随着粘度的增加，荧光颜色变成蓝色。如果类液体簇状态的存活时间足够，则结晶相（R相）形成经由V形分子的2倍π堆叠阵列进行。在类液团簇状态区域中难以形成V形堆叠柱状结构，导致首尾相连的二聚体结构的沉积，例如黄色发射相（Y相）。在FLAP的情况下，堆叠中间体不会在溶剂蒸发过程中形成液体状簇;相反，它以无定形形式沉积，表现出蓝光发射（B相）。这些结果表明，组织和重新排列堆积形式对维持类液团簇态的存活时间是重要的。我们首次实现了在溶剂蒸发过程中溶剂耗尽时局部分子运动时粘度变化的荧光探测。图形摘要
Fluorescence probes are widely used to assess the molecular environment based on their photo-physical properties. Specifically, flexible and aromatic photo-functional system (FLAP) is unique viscosity probe owing to the excited-state planarization of anthracene wings. We have previously applied fluorescence spectroscopy to monitor the evaporative crystallization of solvents. The fluorescence color and spectral changes, which depend on the aggregation form, enable direct fluorescence visualization during evaporative crystallization. The fluorescence visualization of the liquid-like cluster intermediate proposed in the two-step nucleation model for the nucleation process has been achieved. However, the physical properties of these clusters, especially the viscosity, molecular motion, and intermolecular interactions, are still unclear. In this study, FLAPs are used as probes for local-viscosity changes and space limitations of the liquid-like cluster state during evaporative crystallization by observing the fluorescence–spectral changes and using hyperspectral-camera (HSC) imaging. Green emission originates from the monomer in the solution owing to the free-flapping motion. The fluorescence color turns blue with increasing viscosity under crowding conditions. If the survival time of the liquid-like cluster state is sufficient, crystalline phase (R-phase) formation proceeds via a 2-fold π-stacked array of the V-shaped molecules. It is difficult to form the V-shaped stacked columnar structures in the liquid-like cluster state region, resulting in the deposition of head-to-tail dimer structures, such as the yellow-emissive phase (Y-phase). In the case of the FLAP, the stacking intermediate does not form during solvent evaporation in the liquid-like cluster; rather, it is deposited in an amorphous form that exhibits blue emission (B-phase). These findings suggest that it is important to the maintenance of the survival time of the liquid-like cluster states to organize and rearrange the stacking forms. We have achieved the fluorescence probing of viscosity changes at local molecular motion with solvent depletion during solvent evaporation for the first time.Graphical Abstract