Switching Monomer‐to‐Excimer Fluorescence by Noncovalent Interaction Competition Strategy

Abstract

Noncovalent fluorescence switching materials with specific molecular packing motifs for desired performance are difficult to design accurately due to the complexity of intermolecular interactions. Herein, a noncovalent interaction competition strategy to design fluorescence-switching materials by fine-modulating hydrogen-bond and π-π interactions is proposed. Hydrogen bonds are generated by nitrogen/oxygen-containing units while π-π interactions are generated between polycyclic aromatic hydrocarbons. After these two interactions are balanced in strength, they attempt to induce the formation of respective molecule assemblies stably under controllable conditions. Through thermal stimulus produced by a laser, a reversible assembly transition with high-contrast monomer-to-excimer fluorescence switching is achieved, which demonstrates promising applications in rewritable optical recording and time-dependent anti-counterfeiting. This strategy provides a crucial step toward the controllable switching of supramolecular assembly for information handling.

Stimuli-fluorochromic smart organic materials

“…Among the common anti-counterfeiting technologies, advanced stimuli-fluorochromic materials provide a much higher level of security, which is because the encrypted information can only be identified when external stimuli is applied. 16,98,105 Here, a representative example of anti-counterfeiting based on stimuli-fluorochromic smart materials will be detailed. 16 A fluorescence-switchable material based on fine-modulating π–π interaction and hydrogen bonds exhibits promising application in time-dependent anti-counterfeiting, 16 which is attributed to the reversible assembly conversion with high-contrast monomer-to-excimer fluorescence-switching induced by the laser-produced thermal stimulus.…”

“…1–12 Among them, stimuli-fluorochromic smart materials (SFSMs), whose photoluminescence properties can be switched by applying different external stimuli, have attracted tremendous attention due to their highly sensitive response and easy visualization. 13–31 As an example of advanced functional materials, stimuli-fluorochromic smart materials exhibit great application potential for applications such as sensors, 22,26,32–43 information storage, 44–47 bioimaging, 48–50 information encryption and smart displays, 27,31,51–76 green printing, 13,55,77–89 smart optoelectronic devices, 90–93 and anti-counterfeiting. 20,24,94–110 During the past few decades, there have been numerous reports on the design and synthesis of various emission color-switching SFSMs in both solution and the solid state, including conformation-dependent organic π-conjugated molecules (π-conjugated and non-conjugated), 81,111–117 organometallic compounds, 118 and host–guest complexes.…”

Constructing a pyrene-based dimer in a crystal by adjusting the steric hindrance over the pyrene plane

“…26 In the crystal form, two pyrene molecules in a dimeric stacking structure show face-to-face π–π stacking; 23 however, chemical modification of the pyrene at the molecular level always results in the loss of the pyrene dimer stacking due to multiple factors, such as electrostatic potential (ESP), steric hindrance, and intermolecular interaction. 27–33 Research specializing in the pyrene-based dimer stacking is actually reported less. 32–38 Some approaches to the construction of the pyrene-based dimer stacking have been demonstrated to be effective, including molecular crystal engineering, 31–34 cocrystal engineering, 39 intramolecular chemical modification, 40,41 and supramolecular assembly in cavity host.…”

“…27–33 Research specializing in the pyrene-based dimer stacking is actually reported less. 32–38 Some approaches to the construction of the pyrene-based dimer stacking have been demonstrated to be effective, including molecular crystal engineering, 31–34 cocrystal engineering, 39 intramolecular chemical modification, 40,41 and supramolecular assembly in cavity host. 42 Thereinto, the molecular packing structures achieved using molecular crystal engineering are suitable for practical applications; however, they are unpredictable, and their construction is more challenging.…”

“…In the research reported here, to access the pyrene-based dimer stacking, steric hindrance is considered as a main factor that dominates the molecular packing motifs. Meanwhile, because benzo[ d ]thiazole (BZT) has been demonstrated to obviously affect the molecular packing structures by chemical modification, 33,38,39 it was used as the substituent to adjust the steric hindrance around the pyrene. Three pyrene derivatives were designed and synthesized by incorporating BZT with pyrene.…”