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Designing photoluminescence sensing devices for gaseous oxygen that combine ease of acquisition with efficient performance is a critical yet challenging task. Herein, a novel oxygen‐sensing probe based on zeolite Y confined silver clusters prepared via a simple approach, is proposed. The large Ag6 clusters formed after hydrogenation exhibit a bright orange emission. They are characterized by a high photoluminescence quantum yield (≈31%) and a long luminescence decay time (>500 µs). A possible formation mechanism of these clusters, which are for the first time observed in Faujasite zeolites, is proposed. Luminescence switching‐off, triggered by oxygen, can be detected in a dual‐channel combination of linear emission‐quenching and lifetime‐reduction, enabling a visual and ultrasensitive (limit of detection of 58 Pa) quantitative detection of oxygen in a wide pressure range (0–100 kPa) with fast response (<1 s), reversibility and reproducibility. A more detailed analysis shows that this high sensitivity is due to the long decay time of the orange emission and the high affinity of the zeolite for O2 adsorption rather than to a high rate constant for quenching. This work contributes to the development of optical oxygen sensing technology and lays the foundation for the design of silver cluster‐based zeolites for photo‐functional applications. [ABSTRACT FROM AUTHOR]

A new family of unsymmetrical boron chromophores chelated with two BF2 units, named BOPAM, has been developed via a one‐pot, three‐step reaction starting from commercially available thioamides via i) conversion to amidrazones, ii) condensation with pyrrole aldehydes, and iii) boron chelation. This synthetic pathway has been proven to be highly efficient, having a broad substrate tolerance and giving the BOPAM products high yield. Notably, some of the BOPAM dyes show interesting photophysical properties with fluorescence quantum yields up to 0.98 in toluene. A fine‐tuning of their emissive properties has been attained through tailored molecular design strategies guided by in‐depth computational investigations. Tailored substitution with electron‐donating groups at the BOPAM ring leads to the opening of a non‐radiative decay channel involving a dark state and consequently a significant quenching of the fluorescence. The study is complemented by exhaustive steady‐state and time‐resolved spectroscopic measurements. [ABSTRACT FROM AUTHOR]

In this paper we revisit the fluorescent properties of two fluorophores, namely N‐butyl‐7‐(4‐ methoxyphenyl)‐2,1,3‐benzothiadiazole‐4‐amine (1) and 4‐[[7‐(4‐methoxyphenyl)‐2,1,3‐ benzothiadiazole‐4‐yl]amino]‐benzonitrile (2), whose emissive and fluorescent sensing properties were recently investigated by Peng et al. in Ref. [1]. Experimentally, these two fluorophores were reported to show excitation wavelength‐dependent emission properties, especially 1, which is a dual emitter. The authors of the original manuscript ascribed the excitation‐wavelength‐dependent emission properties to an emission from a higher‐lying excited state (i. e. anti‐Kasha emission). Our investigations, including steady‐state spectroscopy, lifetime measurements and time‐dependent density functional theory and second‐order algebraic diagrammatic construction [ADC(2)] calculations, unambiguously highlight that the fluorophores do not violate Kasha's rule but reveal instead that a protonated species is responsible for the higher‐lying emissive band. In addition, we have elucidated the actual fluorescent pH sensing mechanisms. More and more molecular systems are reported to violate Kasha's rule; sometimes without compelling proof. This study highlights the need to i) exhaustively investigate apparent anomalous cases reported in the literature that seemingly violate Kasha's rule and ii) propose good scientific practices to correctly assign anomalous photochemical events. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) can provide a variety of nanocompartments for the confinement of guest molecules. Furthermore, the emissions of fluorescent molecules can be tuned by confinement. In this study, a solvent‐free "bottle‐around‐ship" method is used to encapsulate perylene and 9,10‐dimethylanthracene, two polycyclic aromatic hydrocarbons, in the MOF ZIF‐8. Luminescence color tuning is achieved, including white‐light emission, when controlling the loading of only a single type of guest. Photophysical analysis suggests that the variations in luminescence result from various guest arrangements in the nanocompartments, as well as host–guest interactions. Because of the tight confinement of the guests, this host–guest system displays excellent luminescence thermal stability. [ABSTRACT FROM AUTHOR]

Light‐emitting diodes (LEDs) are an efficient source of lighting, with many commercial applications like general illumination, camera flashes, phone or laptop displays, and TV screens. However, they present certain limitations, including low‐quality color rendition, and the use of expensive/toxic rare‐earth elements. There is therefore an urgent need for the development of improved luminescent materials free of rare earths. Luminescent metal–organic framework (LMOF) materials are promising candidates for photonics devices. Most MOF‐LEDs reported are of the down‐converter type, where UV or blue LED are coated with LMOFs, however there is limited progress in the development of LED using LMOFs as the electroluminescent layer. Herein, it is reported a novel Guest@MOF composite synthesized by encapsulating a semiconducting Gaq3 metal complex [gallium(III) tris(8‐hydroxyquinolinato)], into the ZIF‐8 pore [Zn (2‐methylimidazolate)2], yielding a green‐yellowish luminescent material exhibiting a relatively high quantum yield of 15% upon photoexcitation. Subsequently, a down‐converter LED comprising 405‐nm violet LED coated with Gaq3@ZIF‐8, yielding a white MOF‐LED is shown. Then the use of Gaq3@ZIF‐8 as an electroluminescent layer in a hybrid‐LED, achieving an orange‐yellowish light emitting device is demonstrated. This work reveals the potential of LMOFs for next‐generation LED technology, by exploiting the Guest@MOF concept to enable electroluminescent applications. [ABSTRACT FROM AUTHOR]

Nucleosides with a bi(hetero)aryl nucleobase have unique potential applications as antiviral drugs and molecular probes. The need for transition metal catalysis to synthesize these nucleosides from pre‐functionalized building blocks and the use of nucleobase protection groups results in expensive and tedious syntheses. Herein we report that 5‐imidazolyl‐uracil can be obtained by scalable Van Leusen imidazole synthesis and regioselectively introduced on ribose to obtain the desired nucleoside in a 5 step synthesis (total yield 55 %). The 5‐imidazolyl moiety leads to improved fluorescence properties. The only side‐product formed was characterized by 2D‐NMR and X‐ray crystallography and could be suppressed during synthesis in favor of the desired product. [ABSTRACT FROM AUTHOR]

Only a few straightforward procedures for the preparation of indolo[2,3‐c]carbazoles are known, despite promising features for material applications. Herein we present a convenient synthesis of 5,10‐dihydrobenzo[a]indolo[2,3‐c]carbazoles using an oxidative cyclization of 1,2‐bis(1H‐indol‐2‐yl)benzenes prepared from readily accessible starting materials. Functionalization through electrophilic aromatic substitution reactions and palladium‐catalyzed cross‐coupling reactions were investigated, which lead to the isolation of new functionalized 5,10‐dihydrobenzo[a]indolo[2,3‐c]carbazoles, whose steady state electronic spectroscopy has been examined. [ABSTRACT FROM AUTHOR]

Abstract: Localization‐based super‐resolution microscopy has become an indispensable tool in biology to study features smaller than the diffraction limit of light. In a multicolor approach, adequate spectral separation of the different photoswitchable probes is required. A far‐red emitting dye is often one of the labels of choice. However, irradiation with high laser intensity can induce photo‐conversion of some of the most frequently used fluorophores. Herein we show that upon intense irradiation with a 561 nm laser line, far‐red organic dyes photoconvert to blue‐shifted emissive species. In the case of Alexa Fluor 647, the most commonly used fluorescent label in super‐resolution microscopy, this derivative is created over time in an intramolecular, irreversible photoinduced chemical reaction. The dynamics of this reaction are altered by the presence of reducing agents. Importantly, the blue‐shifted derivatives emit in the spectral range of the red fluorescent proteins (e. g. PAmCherry and converted mEos3.2), severely implicating multicolor super‐resolution imaging. [ABSTRACT FROM AUTHOR]

Abstract: The search for new smart‐materials in solid‐state light‐emitting applications, like hybrid organic–inorganic light‐emitting devices (OLEDs), has seen an intense growth in the recent years. Among all the possibilities, metal‐organic frameworks (MOFs) have emerged as promising smart materials due to their chemical and structural properties. Herein, for the first time, the use of a Zr‐based MOF (Zr‐NDC, NDC = dimethyl 2,6‐naphthalenedicarboxylate) as electroluminescent active material in OLED devices is reported. The results indicate that, independently of the properties of the polymer used to form the emissive layer, the OLED emission is due to radiative electron and hole recombination in the MOF. A tuning of the optoelectronic properties of the device by incorporating Coumarin 153, (C153) and 4‐(Dicyanomethylene)‐2‐methyl‐6‐(4‐dimethylaminostyryl)‐4H‐pyran, into the MOF pores is demonstrated. Using different MOFLED architectures, and MOF composition, it is possible to elucidate the photoluminescence and electroluminescence mechanisms, providing the clues for further improvements. It is observed that the current density as well as the electroluminescent behavior depends on the dopant fluorophores. It is also shown that defects within the Zr‐MOF play a role in the OLED optoelectronic properties. The results clearly demonstrate the potential of MOFs as new tunable electroluminescent materials for OLED applications. [ABSTRACT FROM AUTHOR]

This study reports on the use of a self-assembling organogel, 5-(4-nonylphenyl)-7-azaindole ( 1), as a new emitter in small-molecule organic light emitting devices (OLEDs). The theoretical calculations along with the photophysical characterization studies suggest the coexistence of the monomer and dimer species at high concentration of compound 1. The presence of this type of dimer (formed via H-bonding) is responsible for the increased emission. However, the most notable feature is the 3D network of vastly interconnected fibers formed in the organogel that modifies the photophysical properties. Based on this, several OLED architectures are made in order to understand the mechanism involved in the electroluminescence (EL) behavior of 1. Although the position of the EL spectra differs from that of the photoluminescence (PL) spectra, the trends observed in the device properties perfectly match with dimer formation. In this framework a better device performance is associated to a higher efficiency of dimer formation, which optimizes in the OLED prepared from the organogel. Therefore, these results show that the rational combination of a moiety showing a strong PL intensity increased upon aggregation with organogel properties is an efficient strategy to create alternative emitters for OLED devices. [ABSTRACT FROM AUTHOR]

Silver clusters incorporated in a zeolite matrix represent a promising alternative for rare earth phosphors, organic dyes, and quantum dots as emitters in organic and hybrid organic/inorganic light-emitting diodes (OLEDs). Compared to other existing types of emitters, they combine an excellent stability to oxygen and humidity with a high luminescence quantum yield and color tunability. This study reports on the first use of these silver exchanged zeolites embedded in polyvinyl carbazole (PVK), which is expected to act as a conducting matrix, as emitters in a single-layer OLED. It is demonstrated that the introduction of these Ag zeolites leads to electroluminescence bands that clearly differ from pristine PVK OLEDs as well as from the photoluminescence spectra of the Ag zeolites. The current density and the spectral properties observed in these devices are strongly influenced by the zeolite silver loading, paving the way for a new type of easily tunable hybrid and cost-effective OLEDs. [ABSTRACT FROM AUTHOR]

A novel palladium-catalyzed direct C(sp3)−H arylation of the methyl group at the 8-position of BODIPY by bromoarenes was established. A deprotonative cross-coupling process was supposed to be involved in the reaction. This approach allowed us to attach electron-donating/withdrawing, halogen substituted aryls and a heteroaryl with a yield running from 55 to 99 %. Novel pH sensors, which in the absence of acid showed the occurrence of photoinduced electron transfer, were synthesized by attaching dimethylaniline to the methyl at the C8-position of BODIPY. The reference compounds with dimethylaniline directly attached to the C8-position were also synthesized and besides photoinduced electron transfer also showed a charge-transfer emission. Their photophysical properties were investigated by steady-state fluorescence, time-correlated single-photon counting and femtosecond fluorescence up-conversion. Time-dependent density functional (TD-DFT) electronic-structure calculations on the properties of the excited states corresponding to local excitation of the BODIPY core and to charge transfer were conducted. Upon addition of trifluoroacetic acid in toluene and ethanol, the partial fluorescence intensity recovery was at least an order of magnitude more efficient with the newly synthesized sensors compared to the traditional reference sensors. The improved sensitivity of these novel BODIPY-based pH sensors was attributed to less efficient proton-coupled electron transfer of the protonated species. [ABSTRACT FROM AUTHOR]

Abstract: Controlling the morphology of organolead halide perovskite crystals is crucial to a fundamental understanding of the materials and to tune their properties for device applications. Here, we report a facile solution‐based method for morphology‐controlled synthesis of rod‐like and plate‐like organolead halide perovskite nanocrystals using binary capping agents. The morphology control is likely due to an interplay between surface binding kinetics of the two capping agents at different crystal facets. By high‐resolution scanning transmission electron microscopy, we show that the obtained nanocrystals are monocrystalline. Moreover, long photoluminescence decay times of the nanocrystals indicate long charge diffusion lengths and low trap/defect densities. Our results pave the way for large‐scale solution synthesis of organolead halide perovskite nanocrystals with controlled morphology for future device applications. [ABSTRACT FROM AUTHOR]

A novel π-conjugated triad and a polymer incorporating indolo[3,2- b]-carbazole ( ICZ) and 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene ( BODIPY) were synthesized via a Sonogashira coupling. Compared to the parent BODIPY the absorption and fluorescence spectrum were for both compounds broader and redshifted. The redshift of the fluorescence and the decrease of the fluorescence quantum yield and decay time upon increasing solvent polarity were attributed to the formation of a partial charge-transfer state. Upon excitation in the ICZ absorption band the ICZ fluorescence was quenched in both compounds mainly due to energy transfer to the BODIPY moiety. In a similar ICZ- π- DPP polymer (where DPP is diketopyrrolopyrrole), a smaller redshift of the absorption and fluorescence spectra compared to the parent DPP was observed. A less efficient quenching of the ICZ fluorescence in the ICZ- π- DPP polymer could be related to the unfavorable orientation of the transition dipoles of ICZ and DPP. The rate constant for energy transfer was for all compounds an order of magnitude smaller than predicted by Förster theory. While in a solid film of the triad a further redshift of the absorption maximum of nearly 100 nm was observed, no such shift was observed for the ICZ- π- BODIPY polymer. [ABSTRACT FROM AUTHOR]

Diazadithia[7]helicenes were synthesized from the readily available building block ethyl 7-chloro-8-formylthieno[3,2- f]quinoline-2-carboxylate by a Wittig reaction-photocyclization strategy. The helicene core was functionalized by nucleophilic aromatic substitution with a variety of nucleophiles (e.g., O-, N-, and C-centered) and palladium-catalyzed reactions such as Suzuki coupling and Buchwald-Hartwig amination. Racemization studies confirmed that the enantiopure forms of these [7]helicenes are conformationally stable compared to their lower analogues. The solid-state structures of the novel diazadithia[7]helicenes were determined by single-crystal X-ray diffraction. The crystal structures of these azathia[7]helicenes show columnar stacking in antiparallel fashion. The HOMO-LUMO gaps of the new compounds were determined on the basis of electrochemical and optical measurements. [ABSTRACT FROM AUTHOR]