Handbook of Aggregation-Induced Emission, Volume 2. Группа авторов

Handbook of Aggregation-Induced Emission, Volume 2 - Группа авторов


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two crystals. In addition, according to differential scanning calorimetry (DSC) and powder X‐ray diffraction (PXRD), it is known that 68‐Crys. (G) undergoes phase transformation to the aggregate of 68‐Crys. (YG) by annealing at 231 °C, and 68‐Crys. (YG) converted to 68‐Crys. (G) by ablation treatment at 236 °C. During multiple annealing/ablation treatments, reversible switching of solid fluorescent color was obtained (Figure 3.28c).

Image described by caption.

      Source: Reprinted from Ref. [74] (Copyright 2013 American Chemical Society).

      (d) Molecular structure of 69. (e) Photographs of polymorphous single crystals of 69 (69(G), 69 (YG), and 69(Y)). (f) Schematic illustration of the relationship between slip‐stacking modes and an emission wavelength of 69. (g) Reversible vapor‐ and thermo‐responsive fluorescence printing and erasing by using 69.

      Source: Reprinted from Ref. [75] (Copyright 2015 John Wiley and Sons).

      By introducing rotary benzene rings into the symmetric positions of salicylaldehyde azine to increase the conformational flexibility thus achieving thermochromic switch provides a new idea for the design of stimulus‐responsive AIE materials. Based on this design principle, Tong's group modified 68 with long alkyl chains and reported the single crystals of 69 exhibiting three different fluorescence colors (Figure 3.28e), which also showed reversible stimuli‐responsive fluorescence switching (Figure 3.28d) [75]. X‐ray crystal structure analysis shows that the great differences existed in the molecular conformation and arrangement of the three crystals due to the presence of long alkyl chains, especially the small interplanar spacing of 69 (Y) with intermolecular p–p interactions, which resulted in a red‐shift in emission wavelength (Figure 3.28f). In addition, under the solvent fumigation of dichloromethane, the yellow form of 69 (Y) changed to its green form 69 (G) due to the molecular rearrangement from relatively close interplanar spacing and intermolecular p–p interaction therein to “monomer”‐like packing evidenced by DSC, polarized light microscopy, and PXRD. Annealing operations recovered an orange fluorescence from the green form with molecular arrangements similar to “dimers” (Figure 3.28f). Such reversibly stimuli‐responsive characteristics of molecule 69 were further applied to fluorescence printing and erasing in response to organic vapor and thermal stimuli (Figure 3.28g).

Schematic illustration of the molecular structure of 70 and its mechanical/thermal stimulus response.

      Source: Adapted with permission from Ref. [76] (Copyright 2011 American Chemical Society).

Image described by caption.

      Source: Reprinted from Ref. [31] (Copyright 2016 Elsevier B.V.).

      (d) Molecular structure of 72. (e) Luminescence images of 72 under various conditions (λex = 365 nm). (f) Luminescence images of the as‐synthesized and ground samples of 72 (photographs taken under a 365‐nm UV illumination). (g) (a and c) Packing diagrams of 72 at room temperature, and (b and d) packing diagrams of 72 at liquid N2 temperature (interactions shown in the


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