Photomodulation of fluoride ion binding through anion-π interactions using a photoswitchable azobenzene system

Abstract

The discovery of photoswitchable azobenzene-systems that undergo trans-to-cis photoisomerisation was a milestone in supramolecular chemistry. Such photoswitches have possible applications in data storage, stimuli responsive delivery systems, and molecular machines due to fast and selective switching. However, the light induced cis isomer of azobenzene is rather unstable and reverts thermally and photochemically to the thermodynamically stable trans configuration. We report, for the first time, controlled photoswitching of an azo-naphthalenediimide (azo-NDI) which can be achieved upon binding of fluoride ions through anion-π interaction. This NDI-F–NDI “sandwich” stabilises the cis configuration through the generation of an NDI•− radical anion, and a dianionic, NDI2− species that becomes unusually stable in the cis form. The sandwiched cis form reverts to the trans form only upon decomplexation of F−. A model pollutant was successfully degraded using the photogenerated NDI-F–NDI sandwich. This opens a wide range of applications in molecular and supramolecular nanotechnology.

Dynamic multistimuli-responsive reversible chiral transformation in supramolecular helices

“…The proposed NDI-L-Glu complex mimics the natural supramolecular chiral self-assembly of TMV. The NDI molecule offers a compact, planar and aromatic, π-conjugated system that has found numerous applications in particularly organic electronics due to their excellent n-type conductivity, stability and ability to self-assemble into supramolecular structures 36 – 40 . On the other hand, the chosen appendage L-Glu offers one of the most fascinating entity to achieve chiral supramolecular assemblies with inherent reversibility.…”

Light triggered encapsulation and release of C60 with a photoswitchable TPE-based supramolecular tweezers

“…Stimuli-responsive supramolecular host for fullerenes can open up the possibilities for handling the bucky balls and other carbon-based frameworks with superior controls using the stimuli such as pH, electrical or magnetic fields, electrochemical and photonic signals 17–21 . Light is one of the most extensively used stimuli because of its non-invasive nature and easy regulation by the precise focus of its exposure area, and adjustment of its wavelength and intensity 22,23 . Several light-triggered and redox-triggered release of guest molecules have been reported in recent years 24–27 .…”

A π‐Conjugated Chromophore Dye and Its Functional Paper Strips for Visually On‐Site Sensing F− and Its Reaction Mechanism

“…For fluoride ion (F − ), the smallest size and highest charge density, any chronic deficiency of F − will lead to gastric and kidney disorder or osteoporosis, while excess F − would induce dental and skeletal fluorosis and other serious diseases including collagen breakdown, bone disorders and immune system disruption . Great efforts have been devoted for F − detection, such as chromatography, electrochemistry, photoluminescence, mass spectrometry,, fluorescent spectrophotometry and colorimetric spectrophotometry . For example, Bhosale, et al .…”