A series of naphthalimide (NAI)-based red-emissive thermally activated delayed fluorescence (TADF) acrylic monomers has been designed and synthesized. When copolymerized with a host material by Cu(0)-reversible deactivation radical polymerization (Cu(0)-RDRP), polymers exhibiting orange to deep-red TADF were obtained with quantum yields of up to 58% in solution and 31% in the solid state. These emitters exhibit dual emission consisting of high-energy prompt fluorescence from the NAI acceptor (λ max = 340 nm in toluene) and red-delayed fluorescence from the charge-transfer process (λ max = 633−711 nm in toluene). This dual emissive property was utilized to create redto-blue temperature-responsive polymers by copolymerization of NAI−DMAC with N-isopropylacrylamide and a blue fluorescent dopant. These polymers exhibit red TADF at room temperature and blue fluorescence at 70 °C, with a high ratiometric fluorescent thermal response of 32 ± 4% K −1 . Such systems are anticipated to have utility in bioimaging, drug delivery, and temperature sensing, further expanding the range of applications for red TADF materials.
s‐Heptazines are emerging as strong electron acceptors for efficient thermally activated delayed fluorescent (TADF) materials, yet the difficulties in synthesizing them have limited their practical use. Here, three novel s‐heptazine TADF materials with green to deep‐red emission (λmax = 525–664 nm) and high photoluminescence quantum yields, synthesized by either pseudoelectrophilic substitution or Negishi coupling routes, are described. These materials also demonstrate strong nonlinear optical absorption, with two‐photon cross sections up to 1260 GM. With deep‐red fluorescence, strong two‐photon absorption, high quantum yield, and delayed fluorescence, the emitter HAP‐3MeOTPA is ideally suited for use in nanoparticle‐based bioimaging experiments. The two kinds of luminescent nanoparticle are prepared, namely hostless, aggregate‐based organic dots (a‐Odots) and rigid, glassy Odots (g‐Odots) as biocompatible and water‐dispersible TADF probes. The g‐Odots are shown to retain the nonlinear optical properties, high photoluminescence quantum yield, and TADF observed in the constituent heptazine dye. These g‐Odots are then used as biological imaging probes with immortalized human kidney cancer (HEK293) cells, and single and multi‐photon‐excited microscopy coupled with time‐gated luminescence measurements are demonstrated. This work not only describes new routes to efficient heptazine‐based TADF materials, but also demonstrates their potential as nanoparticle‐based bioimaging probes combining several advanced optical functions.
Diaryl selenides containing o-hydroxymethylene substituents function as peroxide-destroying mimetics of the antioxidant selenoenzyme glutathione peroxidase (GPx), via oxidation to the corresponding spirodioxyselenuranes with hydrogen peroxide and subsequent reduction back to the original selenides with glutathione. Parent selenides with 3-hydroxypropyl or 2,3-dihydroxypropyl groups produced the novel compounds 10 and 11, respectively, with greatly improved aqueous solubility and catalytic activity. The phenolic derivative 28 displayed similarly ameliorated properties and also modest radical-inhibiting antioxidant activity, as evidenced by an assay based on phenolic hydrogen atom transfer to the stable free radical DPPH. In contrast, several selenides that afford pincer selenuranes (e.g., 20 and 21) instead of spiroselenuranes upon oxidation showed inferior catalytic activity. Several selenide analogues were attached to polyethylene glycol (PEG) oligomers, as PEG substituents can improve water solubility and bioavailability, while retarding clearance. Again, the PEG derivatives afforded remarkable activity when oxidation generated spirodioxyselenuranes and diminished activity when pincer compounds were produced. Several such compounds proved to be ca. 10- to 100-fold catalytically superior to the diaryl selenides and their spirodioxyselenurane counterparts investigated previously. Finally, an NMR-based assay employing glutathione in D2O was designed to accommodate the faster reacting water-soluble mimetics and to more closely duplicate in vivo conditions.
Energy transfer (EnT) is a fundamental activation process in visible-light-promoted photocycloaddition reactions. This work describes the performance of imidazoacridine-based TADF materials for visible-light mediated triplet-triplet EnT photocatalysis. The TADF material...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.