Molecular Motions in AIEgen Crystals: Turning on Photoluminescence by Force-Induced Filament Sliding

Abstract

Life process is amazing, and it proceeds against the eternal law of entropy increase through molecular motion and takes energy from the environment to build high-order complexity from chaos to achieve evolution with more sophisticated architectures. Inspired from the elegance of life process and also to effectively exploit the undeveloped solid-state molecular motion, two unique chiral Au­(I) complexes were elaborately developed in this study, in which their powders could realize a dramatic transformation from nonemissive isolated crystallites to emissive well-defined microcrystals under the stimulation of mechanical force. Such an unusual crystallization was presumed to be caused by molecular motions driven by the formation of strong aurophilic interactions as well as multiple C–H···F and π–π interactions. Such a prominent macroscopic off/on luminescent switching could also be achieved through extremely subtle molecular motions in the crystal state and presented a filament sliding that occurred in a layer-by-layer molecular stacking fashion with no involvement of any crystal phase transition. Additionally, it had been demonstrated that the manipulation of the solid-state molecular motions could result in the generation of circularly polarized luminescence.

BioAIEgens Derived from Rosin: How Does Molecular Motion Affect Their Photophysical Processes in Solid State?

“…Simultaneous regulation and visualization of the solid-state molecular motion is a challenge although it is significant to understand the structural design of molecular machines or photo-responsive smart materials. [47][48][49][50][51] Herein, the active molecular motion of AB-SA and the conformational rigidification effect of alicyclic moiety enable the regulation of the solid-state molecular motion of the generated BioAIEgens. Superior to the monitoring of structural variation from enol to keto under UV light by infrared absorption (Fig.…”

“…The fully understanding and regulation of the molecular motions on the excited state is thus of great significance for the rational and accurate design of new luminescent materials. [47][48][49][50][51] Herein, we have succeeded a series of alicycle-fused Schiff bases as a new class of BioAIEgens derived from natural rosin. The alicyclic moieties help to rigidify the flexible structure of the non-emissive Schiff base to light up its fluorescence.…”

Film Electrochemiluminescence Controlled by Interfacial Reactions Along with Aggregation‐, Matrix‐Coordination‐, and Crystallization‐Induced Emissions

“…Interestingly, these factors can provide orders of magnitude light intensity enhancements if developed properly, [14,15] where these phenomena have been thoroughly studied and incorporated into most luminophore research. [16][17][18][19][20] To summarize, AIE provides photoluminescence (PL) enhancements when brought from a solution to a solid by the restriction of intramolecular motion (RIM) that can cause nonradiative relaxations of excited states. [21] In fact, Tang and coworkers in 2001 noticed a 333 times PL enhancement between solution and solid state organic silole compounds, and then coined the term AIE.…”

“…The complementary information is represented as relative radical stabilities of luminophores in films and light enhancement factors, like aggregation induced emission (AIE), crystallization induced emission (CIE), matrix coordination induced emissions (MCIE) and interfacial reactions. Interestingly, these factors can provide orders of magnitude light intensity enhancements if developed properly, [14,15] where these phenomena have been thoroughly studied and incorporated into most luminophore research [16–20] …”

Lighting up solid states using a rubber

“…However, most of these stimuli-responsive processes tend to be slow and incomplete, fostering generally mild changes in material properties. By contrast, chemical reactiondriven stimuli responses, such as pH change, redox reactions, and coordination effects, are usually rapid and sufficiently extensive because of direct contact between the interacting species [22][23][24][25][26][27][28][29] . Nonetheless, this type of stimuli-responsive behavior is generally only effective in solutions.…”