An Intelligent AIEgen with Nonmonotonic Multiresponses to Multistimuli

Abstract

Intelligent stimulus-response (S/R) systems are the basis of natural process and machine control, which are intensively explored in biomimetic design and analytical/biological applications. However, nonmonotonic multi-S/R systems are still rarely studied so far. In this work, a rational design strategy is proposed to achieve such a unique S/R system by integrating opposite luminescence behaviors in one molecule. When solvent polarity increases, many heterocyclic or carbonyl-containing compounds often become more emissive due to the suppression of the proximity effect, whereas molecules with donor-acceptor (D-A) structures tend to be less emissive because of the twisted intramolecular charge transfer. Meanwhile, protonation on D/A moieties will weaken/strengthen the D-A interaction to result in blue/redshifted emissions. By combining a protonatable heterocyclic acceptor and a protonatable donor together in one molecule, nonmonotonic brightness responses to polarity stimuli and nonmonotonic color responses to pH stimuli can be achieved. The design strategy is successfully verified by a simple molecule named 4-(dimethylamino)styryl)quinoxalin-2(1H)-one (ASQ). ASQ exhibits nonmonotonic responses to polarity and pH stimuli, and aggregation-induced emission (AIE) with a nonmonotonic AIE curve. Meanwhile, ASQ can be adjusted to emit white light in an acidic environment, and it shows multivalent functionalities including albumin protein sensing, ratiometric pH sensing, and amine gas sensing.

Mechanistic connotations of restriction of intramolecular motions (RIM)

“…[ 7 ], Copyright, American Chemical Society), (C) dark state (adapted with permission from Ref. [ 8 , 9 ], Copyright Wiley-VCH and Ref. [ 10 ], Copyright ChemRxiv) and (D) photochemical reaction (adapted with permission from Ref.…”

How to Manipulate Through-Space Conjugation and Clusterolumi-nescence of Simple AIEgens with Isolated Phenyl Rings?

“…29 At fw of less than 50%, the enhancement of TBC emission was due to the increased polarity of the solvent mixture. 31 However, aggregates merely formed at high water fraction whose internal polarity was less affected by the surrounding environment. Meanwhile, a portion of the TBC emission was reabsorbed by the TSC species via the Förster resonance energy transfer (FRET) process, which decreased the emission from TBC but increased the emission from TSC.…”

Intermolecular hydrogen bonds induce restriction of access to the dark state for triggering aggregation-induced emission

“…To reverse the transition from the dark to bright state, researchers have proposed several strategies, including intermolecular interactions by the formation of aggregates, the formation of complexes with guest molecules, or changing the polarity of solvents (Scheme 1a). 16,30,31 However, broadening the RADS mechanism by designing fluorescent molecules with AIE behaviors is still a great challenge.…”