Environment‐Sensitive Fluorophores with Benzothiadiazole and Benzoselenadiazole Structures as Candidate Components of a Fluorescent Polymeric Thermometer

Abstract

An environment-sensitive fluorophore can change its maximum emission wavelength (λ(em)), fluorescence quantum yield (Φ(f)), and fluorescence lifetime in response to the surrounding environment. We have developed two new intramolecular charge-transfer-type environment-sensitive fluorophores, DBThD-IA and DBSeD-IA, in which the oxygen atom of a well-established 2,1,3-benzoxadiazole environment-sensitive fluorophore, DBD-IA, has been replaced by a sulfur and selenium atom, respectively. DBThD-IA is highly fluorescent in n-hexane (Φ(f) =0.81, λ(em) =537 nm) with excitation at 449 nm, but is almost nonfluorescent in water (Φ(f) =0.037, λ(em) =616 nm), similarly to DBD-IA (Φ(f) =0.91, λ(em) =520 nm in n-hexane; Φ(f) =0.027, λ(em) =616 nm in water). A similar variation in fluorescence properties was also observed for DBSeD-IA (Φ(f) =0.24, λ(em) =591 nm in n-hexane; Φ(f) =0.0046, λ(em) =672 nm in water). An intensive study of the solvent effects on the fluorescence properties of these fluorophores revealed that both the polarity of the environment and hydrogen bonding with solvent molecules accelerate the nonradiative relaxation of the excited fluorophores. Time-resolved optoacoustic and phosphorescence measurements clarified that both intersystem crossing and internal conversion are involved in the nonradiative relaxation processes of DBThD-IA and DBSeD-IA. In addition, DBThD-IA exhibits a 10-fold higher photostability in aqueous solution than the original fluorophore DBD-IA, which allowed us to create a new robust molecular nanogel thermometer for intracellular thermometry.

Saccharide-induced modulation of photoluminescence lifetime in microgels

“…The response can then be tracked using various transducing methods including mass-sensitive, electrochemical, electrical or optical outputs, such as luminescence. This was achieved through various processes: (1) modulation of the polarity of the environment, affecting the luminescence of polarity-sensitive luminophores linked to the matrix; 9,10 (2) modulation of the distance between adjacent fluorophores bound to the polymer chain, affecting the Förster resonance energy transfer (FRET) efficiency between the donor and the acceptor; [11][12][13][14][15][16][17] (3) elastic tension exerted by the network on the surface of quantum dots or noble metal nanoparticles, which creates interfacial states that quench the photoluminescence (PL); [18][19][20] (4) stretching tension on a dye molecule, such as Bordeaux Red, which affects the p-p stacking of the fluorophores assembled into dye domains; [21][22][23] and (5) dielectric environment changes which modulate the PL of graphene sheets. 5,6 Moreover, the hydrophilic nature and the high water content of the hydrogels, similar to the extracellular matrix, make them intrinsically biocompatible.…”

Supramolecular guest relay using host-protein nanocavities: an application of host-induced guest protonation

“…14,43,[45][46][47] The structural understanding of these environment sensitive fluorophores reveal that these dyes have intramolecular charge transfer (ICT) properties and called ICT dyes. 14,43,47,49,51 which is acting as an acceptor part. 4 Similarly, by introducing a donor and an acceptor group into a molecule separated by πconjugated spacer, one can design novel ICT dye.…”

Recent Developments in the Synthesis and Applications of 1,2,5-Thia- and Selenadiazoles. A Review

“…153,279 Fluorophores with benzothiadiazole and benzoselenadiazole cores 234 showed environmentally sensitive fluorescence that was efficient in apolar and aprotic solvents and good photostability, which allowed investigators to develop these compounds as fluorescent nanogel thermometers. 212 Polymers containing the benzothiadiazole unit 235, obtained by electropolymerization of corresponding monomers, are processible and low band gap electrochromes, exhibiting high redox stability, high coloration efficiency, high transmittance, and low response time ( Figure 18). Furthermore, these polymers reflect various hues of blue and green pallets of the Red-Green-Blue color-space in the neutral state.…”

“…Reaction of aromatic and heteroaromatic ortho-diamines and selenium dioxide was conducted in solid state, 204,205 in ethanol, 20,[206][207][208][209][210][211][212] in acetic anhydride, 213 and even in water. [214][215][216] Typical examples of fused 1,2,5-selenadiazoles prepared are given in Figure 6 (solvents used and yields of selenadiazoles are shown below the formulae).…”