Highly Efficient Förster Resonance Energy Transfer Modulations of Dual-AIEgens between a Tetraphenylethylene Donor and a Merocyanine Acceptor in Photo-Switchable [2]Rotaxanes and Reversible Photo-Patterning Applications

Abstract

A series of novel photo-switchable [2]­rotaxanes (i.e., Rot-A-SP and Rot-B-SP before and after shuttling controlled by acid–base, respectively) containing one spiropyran (SP) unit (as a photochromic stopper) on the axle and two tetraphenylethylene (TPE) units on the macrocycle were synthesized via click reaction. Upon UV/visible light exposure, both mono-fluorophoric rotaxanes Rot-A-SP and Rot-B-SP with the closed form (i.e., non-emissive SP unit) could be transformed into the open form (i.e., red-emissive merocyanine (MC) unit) to acquire their respective bi-fluorophoric Rot-A-MC and Rot-B-MC reversibly. The aggregation-induced emission (AIE) properties of bi-fluorophoric TPE combined with MC AIEgens of these designed rotaxanes and mixtures in semi-aqueous solutions induced interesting ratiometric photoluminescence (PL) and Förster resonance energy transfer (FRET) behaviors, which were further investigated and verified by dynamic light scattering (DLS), X-ray diffraction (XRD), and time-resolved photoluminescence (TRPL) measurements along with theoretical studies. Accordingly, in contrast to the model axle (Axle-MC) and the analogous mixture (Mixture-MC, containing the axle and macrocycle components in a 1:1 molar ratio), more efficient FRET behaviors and stronger red PL emissions were obtained from dual-AIEgens between a blue-emissive TPE donor (PL emission at 468 nm) and a red-emissive MC acceptor (PL emission at 668 nm) in both novel photo-switchable [2]­rotaxanes Rot-A-MC and Rot-B-MC under various external modulations, including water content, UV/Vis irradiation, pH value, and temperature. Furthermore, the reversible fluorescent photo-patterning applications of Rot-A-SP in a powder form and a solid film with excellent photochromic and fluorescent behaviors are first investigated in this report.

Self‐assembly and tunable optical properties of intramolecular charge transfer molecules

“…A large variety of molecules such as π-conjugated small molecules, small organometallics, intramolecular/intermolecular charge transfer compounds, and π-conjugated polymers have been synthesized to achieve desirable AIE properties. [6] Particularly, intramolecular charge transfer (ICT) molecules, [7,8] with electron delocalized and transferred in a single molecule, are good candidates for light emitters. They usually consist of electron donor moiety and electron acceptor moiety, which are linked by π-conjugated core to make a donor-acceptor (D-A) system.…”

Multi-stimuli programmable FRET based RGB absorbing antennae towards ratiometric temperature, pH and multiple metal ion sensing

“…The tunability of spectral properties of model antennae RB 6, GB 12 and nal RGB antenna 1 with different stimuli inspired us to utilize these antennae as switchable uorescent inks. [72][73][74][75][76][77][78][79] Firstly, antenna-poly(methyl methacrylate (PMMA) composites were prepared by dissolving RB 6, GB 12 and RGB 1 (c $ 10 À3 M) and PMMA (1 wt%) in chloroform. Filter paper with text written with RB 6-PMMA composite appeared yellowish green under normal light which on exposure to TFA changed to an olive green colour and comes back to the original colour aer $5 minutes (Fig.…”

Dynamic Photochromic Polymer Nanoparticles Based on Matrix-Dependent Förster Resonance Energy Transfer and Aggregation-Induced Emission Properties

“…With special molecular design, self-assembled supramolecular PNPs combining FRET and photochromic switching exhibited chameleon fluorescent colors . As has been demonstrated, the efficiency of FRET determines the rate and extent of the color shift . Nevertheless, most of the studies as described above focus on the improvement of the energy transfer efficiency either by varying the donor–acceptor ratios, which were usually required to prepare a series of PNPs with gradient ratios, or the implementation of multiple environmental stimuli (e.g., thermal, photo, and vapor).…”