A Photochromic Benzothiadiazole‐Diarylethene System with Tunable On/Off Fluorescence Modulation

Abstract

Organic molecules with photoswitchable emission properties are of interest in the optical devices field. We present herein in‐solution studies for two dimethoxydithienylethene‐fluorophore (DTE‐fluorophore) conjugates with a carboxylic acid anchor group attachable to semiconductor surfaces (DTE‐BODIPY and BTD‐DTE, where BTD=benzothiadiazole). Both conjugates show almost quantitative reversible photoisomerization between open (OF) and closed forms (CF). With excitation of the fluorophores, both conjugates emit fluorescence with highly solvent‐dependent OFs (BTD‐DTE>DTE‐BODIPY) and minor solvent‐dependent CFs. In the polar solvent MeCN for BTD‐DTE a TICT state is clearly observed, which will be located in the twisted conjugated structure of the benzoic acid‐BTD‐fluorophore‐methoxy‐thiophene unit. BTD‐DTE shows positive solvatofluorochromism with a decrease of fluorescence quantum yields by increasing the Lippert orientation polarizability function (Δf) verified in Lippert‐Mataga plots. This leads to solvent dependent on‐off/off‐on (CF‐OF) emission modulation by Förster resonance energy transfer (FRET) with well‐separated emission bands for BTD‐DTE.

Molecular photoswitches in aqueous environments

“…This altered p-conjugation is, on the one hand, responsible for the colour of the C isomer, and on the other hand allows for electronic communication between the two sides of the molecule. 373,374 In this way, a photoswitchable pyridoxal 5 0 -phosphate mimic was constructed (Fig. 25A).…”

Fluorescent Benzothiadiazole Derivatives as Fluorescence Imaging Dyes: A Decade of New Generation Probes

“…In this context, it is not rare for a deep solvatochromic dependence of the observed photoproperties of small organic fluorescent BTD derivatives. [47][48][49][50][51][52] The preferential orthoquinoid BTD nucleus and its permanent electric dipole moment [53] is capable of affecting the solubility, crystallinity, charge carrier mobility and, as a consequence, the photophysical properties of BTDs.…”

Unconventional Photoswitching Behavior of a Diarylethene‐Perylenediimide Dyad in Nanoparticles Emerging from Multiple Intermolecular Energy Transfer Processes

“…[9,15] This strategy has been successfully exploited, and many molecular devices based on this concept have been already described in the literature. [16][17][18][19][20] To take full advantage of energy transfer, gathering dyads into nanoparticles (NPs) or polymer matrices can be an excellent strategy. [6,[21][22][23][24][25][26][27][28] We recently discovered that molecular NPs made of DAE linked to a benzothiadiazole fluorophore displayed a "giant amplification of fluorescence photoswitching" (GAFP): NPs are strongly emissive when the dyad is in the OF and fluorescence is totally quenched even at low conversion yield.…”