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Regulation of fluorescence and self‐assembly of a salicylaldehyde azine‐containing amphiphile by a water‐soluble pillar[5]arene via host–guest recognition in water was realized. The fluorescence and the self‐assembled aggregates of the bola‐type amphiphile G can be tailored by adding different amounts of water‐soluble pillar[5]arene (WP5). In addition, the emission property and self‐assembly behavior of G and WP5 are responsive to pH conditions. Furthermore, the fluorescence emission property of G and the regulation by WP5 or pH conditions was applied as information encryption material, rewritable paper, and erasable ink. We believe that this fluorescence regulation strategy is promising for the construction of advanced fluorescent organic materials. [ABSTRACT FROM AUTHOR]

Distyrylbenzenes (DSBs) are well‐known for their strong multicolour fluorescence. Fluorescence tuning of DSB via further functionalization/arylation, on the other hand, is uncommon. This paper reports a Pd‐catalysed direct arylation approach for introducing different aryl groups onto fluorobenzene‐containing DSB moiety (7) in high yields (67–72 %). The versatile methodology allows the substitution of neutral [tolyl (1)], electron‐deficient [p‐formyl benzene (2), p‐acetyl benzene (3), p‐nitrobenzene (4)] and electron‐rich [carbazole (5), triphenylamine (6)] aryl groups. The electron‐deficient aryls render mono‐substitution, while the electron‐rich counterparts promote di‐substitution. The compounds (1–6) show blue, green, and yellow fluorescence in both the solution and solid states; the fluorescence quantum yields reach >98 % and the peak maxima span from 425 to 560 nm. The mono‐carbazole DSB (5) exhibit white light emission (WLM) in polar solvents (acetone, DMF, CH3CN, DMSO and NMP) with very high fluorescence quantum yields (φf) of 60–80 %. For WLM, such high efficiency (φf) is somewhat uncommon. Moreover, visible‐to‐NIR reversible electrochromism is demonstrated by the TPA‐integrated DSB (6). The colour of 6 changes from pristine light yellow to orange, and the absorption maxima shifts from 372 to 1500 nm when a positive potential of 1.0 V vs Ag/Ag+ is applied. Moreover, the system shows high colouration efficiency in the NIR region with fast switching speeds for colouration and decolouration as fast as 0.98 s and 1.05 s. [ABSTRACT FROM AUTHOR]

Stimulus‐responsive organic materials with luminescence switching properties have attracted considerable attention for their practical applications in sensing, security, and display devices. In this paper, bent‐type bisbenzofuropyrazine derivatives, Bent‐H and Bent‐sBu, with good solubilities were synthesized, and their physical and optical properties were investigated in detail. Bent‐H gave three crystalline polymorphs, and they showed different luminescence properties depending on their crystal packing structures. In addition, Bent‐H exhibited mechanochromic luminescence in spite of its rigid skeleton. Bent‐sBu exhibited unique concentration‐dependent vapochromic luminescence. Ground Bent‐sBu was converted to blue‐emissive, green‐emissive, and green‐emissive high‐viscosity solution states at low, moderate, and high concentrations of CHCl3 vapor, respectively. This finding represents a concentration‐dependent multi‐phase transition with an organic solvent, which is of potent interest for application in sensing systems. [ABSTRACT FROM AUTHOR]

There is growing interest in developing printable paper sensors to enable rapid testing of analytes for environmental, food safety, and clinical applications. A major challenge is to find suitable bioinks that are amenable to high-speed printing and remain functional after printing. We report on a simple and effective approach wherein an aqueous ink composed of megadalton-sized tandem repeating structure-switching DNA aptamers (concatemeric aptamers) is used to rapidly create patterned paper sensors on filter paper by inkjet printing. These concatemeric aptamer reporters remain immobilized at the point of printing through strong adsorption but retain sufficient segmental mobility to undergo structure switching and fluorescence signaling to provide both qualitative and quantitative detection of small molecules and protein targets. The convenience of inkjet printing allows for the patterning of internally referenced sensors with multiplexed detection, and provides a generic platform for on-demand printing of sensors even in remote locations. [ABSTRACT FROM AUTHOR]

Intermolecular [2+2] photodimerization provides a distinctive approach to construct photoresponsive fluorescent materials in a manner of switching on solid‐state fluorescence. Herein, we report efficient photoactivation of bright solid‐state fluorescence based on controllable intermolecular [2+2] photodimerization reaction of benzo[b]thiophene 1,1‐dioxide (BTO) derivatives, which provides a simple and effective way to construct smart photoresponsive solid‐state fluorescent materials. Rational choice of substituents in BTO molecular skeleton enables them to efficiently undergo photodimerization through regulating molecular stacking in crystal, and also leads to photoactivation of solid‐state fluorescence due to the generation of brightly fluorescent photodimers. This intermolecular photodimerization reaction also offers an effective method to synthesize photostable AIEgens with purely through‐space conjugation. [ABSTRACT FROM AUTHOR]

We report the synthesis and late‐stage diversification of a new class of hetero‐buckybowl, BN‐embedded dibenzocorannulenes (B2N2‐DBCs). The synthesis is achieved via one‐shot halogenative borylation, comprising the nitrogen‐directed haloboration of alkyne and an intramolecular bora‐Friedel‐Crafts reaction, which provides BN‐embedded dibenzocorannulene possessing two bromo substituents (B2N2‐DBC‐Br). B2N2‐DBC‐Br undergoes diversification via coupling reactions to provide a variety of arylated derivatives (B2N2‐DBC‐R), exhibiting strong blue fluorescence. An organic light‐emitting diode (OLED) employing one of the derivatives as an emitter exhibited a high external quantum efficiency of 6.6 % and long operational lifetime of 907 h at an initial luminance of 1000 cd m−2, indicating the significant potential for the development of efficient and stable hetero‐buckybowl‐based OLED materials. [ABSTRACT FROM AUTHOR]

Herein, we propose a rational design strategy by introducing photoactive thienyl and pyridyl groups into an AIE‐active tetraarylethene skeleton to achieve highly efficient photochemistry‐activated fluorescence enhancement from dominantly photo‐physical aggregation‐induced emission behavior, and prove that such photoactivated fluorescence enhancement is perfectly suited for superstable photocontrollable dual‐mode patterning applications in both solution and solid matrix. It is found that the photoactivated fluorescence of designed AIEgen is attributed to the irreversible cyclized‐dehydrogenation reaction under UV irradiation, and the oxidation product has a brighter fluorescence in both solution and solid states owning to its rigid and planar structure. The overall transformation rate of the AIEgen from its opened form to dehydrogenated form is up to nearly 100 % in a short period of UV irradiation, and the fast transformation and the stable product of this photochemical reaction guarantees super stability of photocontrolled patterning, which can be applied in photoactivated dual‐mode patterning and advanced anti‐counterfeiting. [ABSTRACT FROM AUTHOR]

Melanin‐like nanomaterials have found application in a large variety of high economic and social impact fields as medicine, energy conversion and storage, photothermal catalysis and environmental remediation. These materials have been used mostly for their optical and electronic properties, but also for their high biocompatibility and simplicity and versatility of preparation. Beside this, their chemistry is complex and it yields structures with different molecular weight and composition ranging from oligomers, to polymers as well as nanoparticles (NP). The comprehension of the correlation of the different compositions and morphologies to the optical properties of melanin is still incomplete and challenging, even if it is fundamental also from a technological point of view. In this minireview we focus on scientific papers, mostly recent ones, that indeed examine the link between composition and structural feature and photophysical and photochemical properties proposing this approach as a general one for future research. [ABSTRACT FROM AUTHOR]

The reaction of tetra(o‐tolyl)diborane(4) with organic azides afforded three different compounds, diborylamines, diboryltriazenes, and B2‐hexazenes having a bicyclic B2N6 ring system. The reaction with aryl azides gave diborylamines, while the reaction with 1 equiv. of alkyl azides furnished diboryltriazenes. In the case of the reaction with an excess amount of primary alkyl azide, a new heterocyclic B2‐hexazenes were obtained. The formation of the B2N6 structure could be explained by one general reaction mechanism via the diboryltriazene intermediate according to the control experiments and DFT calculations. The B2‐hexazenes exhibited a strong fluorescence with a remarkably high fluorescent quantum yield of up to 96 %. [ABSTRACT FROM AUTHOR]

An exceptional level of control over the direction of the (2,3)‐sigmatropic rearrangement between N‐oxides and alkoxylamine is achieved by simply changing the solvent in which they are dissolved. Protic solvents like water, methanol and hexafluoroisopropanol favour the N‐oxide form, while other solvents like acetone, acetonitrile and benzene favour the alkoxylamine. The reaction temperature and nature of the substituents on the alkene affect the rate of rearrangement. A N‐oxide fragment was attached to two fluorescent molecules and acted as an on/off switch for their fluorescence. The conversion of alkoxylamines into the corresponding N‐oxides has not previously been described and is here termed the 'Reverse Meisenheimer Rearrangement'. [ABSTRACT FROM AUTHOR]

Sensing of low‐pressure signals is of great importance for cutting‐edge technologies. Organic piezochromic molecules offer a promising library of pressure sensitive materials which can be tailor‐designed toward specific requirements. However, very few examples of low‐pressure sensitive piezochromic fluorescent molecules have been obtained till date, and the underlying mechanisms are still in its infancy. Herein, we report highly sensitive piezochromic fluorescent switching under low‐pressure regimes (∼60 kPa) of tetraphenylethylene‐anthraquinone (TPE‐AQ) based on the controlled molecular design and polymorphic phase strategy. The influence of both intramolecular conformation effect and variations of intermolecular stacking modes on the piezochromic property of TPE‐AQ is investigated. The underlying mechanism of the low‐pressure sensitive piezochromic fluorescence switching is demonstrated to be closely related to the loosely packed molecular orientation, as confirmed by X‐ray diffraction measurements combined with simulations. This work provides a way to design highly efficient pressure sensors based on organic molecular systems. [ABSTRACT FROM AUTHOR]

A series of substituted derivatives of tetraaza[7]helicenes were synthesized and the influence of the substitution on their photophysical and photoredox‐catalytic properties was studied. The combination of their high fluorescence quantum yields of up to 0.65 and their circularly polarized luminescence (CPL) activity results in CPL brightness values (BCPL) that are among the highest recorded for [7]helicenes so far. A sulfonylation/hetarylation reaction using cyanopyridines as substrates for photoinduced electron transfer (PET) from the excited helicenes was conducted to test for viability in photoredox catalysis. DFT calculations predict the introduction of electron withdrawing substituents to yield more oxidizing catalysts. [ABSTRACT FROM AUTHOR]

Fluorescent isocoumarin‐fused cycloalkynes, which are reactive in SPAAC and give fluorescent triazoles regardless of the azide nature, have been developed. The key structural feature that converts the non‐fluorescent cycloalkyne/triazole pair to its fluorescent counterpart is the pi‐acceptor group (COOMe, CN) at the C6 position of the isocoumarin ring. The design of the fluorescent cycloalkyne/triazole pairs is based on the theoretical study of the S1 state deactivation mechanism of the non‐fluorescent isocoumarin‐fused cycloalkyne IC9O using multi‐configurational ab initio and DFT methodologies. The calculations revealed that deactivation proceeds through the electrocyclic ring opening of the α‐pyrone cycle and is accompanied by a redistribution of electron density in the fused benzene ring. We proposed that the S1 excited state deactivation barrier could be increased by introducing a pi‐acceptor group into a position that is in direct conjugation with the formed C=O group and has a reduced electron density in the transition state. As a proof of concept, we designed and synthesized two fluorescent isocoumarin‐fused cycloalkynes IC9O‐COOMe and IC9O‐CN bearing pi‐acceptors at the C6 position. The importance of the nature of a pi‐acceptor group was shown by the example of much less fluorescent CF3‐substituted cycloalkyne IC9O‐CF3. [ABSTRACT FROM AUTHOR]

Chiral fluorescent macrocycles consisting of two to four units of dimethyl 2,5‐diaminoterephthalate can be readily synthesized in a one‐pot manner from inexpensive building blocks. Depending on the concentration, either a paracyclophane‐like dimer with closely stacked benzene rings or a triangular trimer is the main product of the reaction. The macrocycles exhibit fluorescence in solution as well as in the solid state with maxima that are red‐shifted with decreasing size of the macrocyclic ring and are observed at wavelengths from 590 (tetramer in solution) to 700 nm (dimer in the solid state). Chirality dictates the differential absorption and emission of circularly polarized light by these molecules. The ECD and CPL effects are particularly strong for the trimer, which is characterized by relatively large dissymmetry factors gabs=±2.8×10−3 at 531 nm and glum=±2.3×10−3 at 580 nm in n‐hexane, being at the same time highly luminescent (Φfl=13.7 %). Despite the small chromophore, the circularly polarized brightness BCPL of 2.3 dm3 mol−1 cm−1 is comparable to values reported for other classes of established CPL emitters in the visible region, such as expanded helicenes or larger π‐conjugated systems. [ABSTRACT FROM AUTHOR]

Phosphonium‐based compounds gain attention as promising photofunctional materials. As a contribution to the emerging field, we present a series of donor‐acceptor ionic dyes, which were constructed by tailoring phosphonium (A) and extended π‐NR2 (D) fragments to an anthracene framework. The alteration of the π‐spacer of electron‐donating substituents in species with terminal −+PPh2Me groups exhibits a long absorption wavelength up to λabs=527 nm in dichloromethane and shifted the emission to the near‐infrared (NIR) region (λ=805 nm for thienyl aniline donor), although at low quantum yield (Φ<0.01). In turn, the introduction of a P‐heterocyclic acceptor substantially narrowed the optical bandgap and improved the efficiency of fluorescence. In particular, the phospha‐spiro moiety allowed to attain NIR emission (797 nm in dichloromethane) with fluorescence efficiency as high as Φ=0.12. The electron‐accepting property of the phospha‐spiro constituent outperformed that of the monocyclic and terminal phosphonium counterparts, illustrating a promising direction in the design of novel charge‐transfer chromophores. [ABSTRACT FROM AUTHOR]

Breaking the centrosymmetry of [n]cycloparaphenylenes ([n]CPPs) by one meta connection, leads to bright emission in the typically non‐fluorescent smaller derivatives, conserving their size dependent emissive properties. Using the building block strategy for [n]CPPs, different nitrile substituted meta[n]CPPs (n=6, 8, 10) have been prepared. The nitrile substituent offers a convenient handle for functional group conversions (e.g. carboxylic acid, amide, aldehyde, as well as 1H‐tetrazole). Besides the synthetic work, the photophysical properties of these novel m[n]CPP derivatives have been characterized. Additionally, the host–guest ability of cyano‐m[10]CPP has been explored by studying its complexation with fullerene C60. These insights open new applications of meta[n]CPPs as fluorophore in synthetic organic chemistry, material sciences as well as biomedical research. [ABSTRACT FROM AUTHOR]

New chiral and achiral dyes were synthesized by using clean, highly efficient Diels–Alder 'click' reactions. We prepared pure endo‐ and exo‐ stereoisomers and blue‐light‐emitting single crystal of an exo‐isomer. 1H NMR spectroscopy and single‐crystal X‐ray diffraction reveal the precise spatial configurations of endo‐ and exo‐dye stereoisomers. Single‐crystal X‐ray diffraction results reveal the dynamic nature of Diels–Alder covalent bonds. By reversible formation and cleavage of dynamic covalent bonds, an achiral dye was converted to a chiral dye, where achiral dansyl dye moiety was replaced by chiral moiety. Before achiral‐to‐chiral dye conversion, the dye system displayed dansyl acceptor green light‐emitting color due to intramolecular fluorescence resonance energy transfer, where the blue emission of pyrene donor fluorophore was not observed. After achiral‐to‐chiral dye conversion, light‐emitting colors of dye system change from green to blue, where the pyrene‐to‐dansyl fluorophore energy transfer was suppressed, and pyrene fluorophore blue emission was restored. Chiral transfer occurs in a chiral dye solid from non‐chromophore alky chirality to pyrene chromophore. Thus, the chiral dye solid displayed chiral optical behaviors, i. e. circular dichroism and circularly polarized luminescence. [ABSTRACT FROM AUTHOR]

A series of luminescent, neutral pentacoordinate dithieno[3,2‐b:2',3'‐d]phosphole compounds was synthesized by [4+1] cycloaddition of o‐quinones with the corresponding trivalent phospholes. The electronic and geometrical modification of the π‐conjugated scaffold implemented here impacts the aggregation behavior of the species in solution. It proved successful in generating species with improved Lewis acidity of the phosphorus center that was then leveraged for small‐molecule activation. Hydride abstraction from an external substrate involving the hypervalent species is followed by an intriguing P‐mediated umpolung from the hydride to a proton and supports the catalytic potential of this class of main‐group Lewis acids for organic chemistry. This study is a comprehensive investigation into various methods, including electronic, chemical, geometric modifications (and sometimes combinations of these approaches) to systematically improve the Lewis acidity of neutral and stable main‐group Lewis acids with practical value for a range of chemical transformations. [ABSTRACT FROM AUTHOR]

The target mono‐BF2 complex is weakly emissive in fluid solution because radiationless decay of the excited‐singlet state is promoted through an intramolecular N⋅⋅⋅H−N hydrogen bond. The lack of mirror symmetry for this compound is attributed to vibronic effects, as reported previously for the bis‐BF2 complex (BOPHY). Red‐shifted fluorescence is observed from single crystals, the emission quantum yield approaching 30 % with a fluorescence lifetime of 2 ns. The large Stokes shift of 5,700 cm−1 helps minimize self‐absorption. Crystallography indicates that the internal fold and twist angles are increased substantially in the crystal, but the hydrogen bond is weakened relative to solution. The crystal structure is compiled from pairs of head‐to‐tail molecules having a shift of ca. 4.1 Å and closest approach of ca. 3.5 Å. These molecular pairs are arranged in columns, which, in turn, assemble into sheets. The proximity favors excitonic coupling between individual molecules, with the coupling strength obtained by analysis of the absorption spectrum reaching ca. 1,000 cm−1. Both the ideal dipole approximation and the extended dipole methodology seriously overestimate the coupling strength, but the atomic transition charge density procedure leads to good agreement with experiment. Emission is attributed to the closely coupled molecular pair functioning in an excimer‐like manner with the exciton trapped in a local minimum. Increasing temperature causes a slight blue shift and loss of fluorescence. [ABSTRACT FROM AUTHOR]

Four series of isostructural derivatives of 3‐ring liquid crystalline derivatives containing p‐carboranes (12‐vertex A, and 10‐vertex B), bicyclo[2.2.2]octane (C), or benzene (D) as the variable structural element were investigated for their mesogenic behavior and electronic interactions. Comparative studies demonstrated that the effectiveness of elements A–D in stabilization of the mesophase typically increases in the order: B

Chlordecone (CLD), a Persistent Organic Pollutant, is still present in water and food chain of the French West Indies (FWI), leading to dramatical public health problems. One of the major issues is the lack of an easy, non‐expensive, sensitive and robust method for the detection of chlordecone to ensure chlordecone‐free water and foods for the residents of the FWI. This study reports on the development of a fluorescent molecular cage that allows a simple and convenient detection of chlordecone in water at environmental concentration. The specific structural features of chlordecone prompted the choice of hemicryptophanes as receptor. First, the size, shape of the cavity, as well as the recognition units, were optimized to identify the most efficient non fluorescent host for CLD complexation. Then, this selected compound was equipped with fluorophores at different positions in order to find the most efficient system for CLD detection by fluorescence. Among the two most promising fluorescent cages, the newly synthesized hemicryptophane with biphenyl moieties allowed the development of a fast, easy, reproducible and cheap procedure to detect CLD in water. Based on its sensitivity and scalability, with modulation of hemicryptophane, concentration, CLD concentrations were estimated over five orders of magnitude (10−2–103 μg/L) including the environmental levels of contamination and the permissible limit for drinking water in the FWI. [ABSTRACT FROM AUTHOR]

The development of dual‐state emissive (DSE) fluorophores, i. e. organic molecules showing balanced emission in both solution and as molecular solids, has recently become an emerging approach in material science, biology, sensing, and optoelectronics. However, the majority of existing DSE fluorophores represents structural modifications of the scaffolds known for their aggregation‐induced emission (AIE) properties, e. g. tetraphenylethylenes (TFE), triphenylamines (TFA), and others. In this study, we introduce aurones as an easily accessible scaffold for the construction of DSE fluorophores and describe the main design principles allowing to achieve the balanced emission in both solution and solid state. Herein, we present the solid‐state fluorescence in a systematic series of aurone derivatives for the first time. We propose that the newly found DSE properties of aurones in combination with their established biological activity can be applied efficiently in biomedical studies and diagnostic tools. [ABSTRACT FROM AUTHOR]

Most organic thermochromic fluorescent materials exhibit thermo‐induced hypsochromic emission due to the formation of excimers in ordered molecular solids; however, it is still a challenge to endow them with bathochromic emission despite its significance in making up the field of thermochromism. Here, a thermo‐induced bathochromic emission in columnar discotic liquid crystals is reported realized by intramolecular planarization of the mesogenic fluorophores. A three‐armed discotic molecule of dialkylamino‐tricyanotristyrylbenzene was synthesized, which preferred to twist out of the core plane to accommodate ordered molecular stacking in hexagonal columnar mesophases, giving rise to bright green monomer emission. However, intramolecular planarization of the mesogenic fluorophores occurred in isotropic liquid increasing the conjugation length, and as a result led to thermo‐induced bathochromic emission from green to yellow light. This work reports a new concept in the thermochromic field and provides a novel strategy to achieve fluorescence tuning from intramolecular actions. [ABSTRACT FROM AUTHOR]

Although remarkable progresses are achieved in the design and development of the mono‐shift in photoluminescence for mechanofluorochromic materials, it is still a severe challenge to explore the opposite mechanofluorochromic materials with both blue‐ and red‐shifted photoluminescence. Herein, two unprecedented 4,5‐bis(TPE)‐1H‐imidazole fused pyridine or quinoline‐based fluorophores X‐1 and X‐2 were designed and synthesized, and X‐1 and X‐2, exhibit completely opposite mechanofluorochromic behavior. Under UV lamp, the color of pristine X‐1 changed from blue to green with reversible redshifted 27 nm in fluorescence emission spectra after ground, while the color of pristine X‐2 changed from red to yellow with reversible blue‐shifted 74 nm after ground. The detailed characterizations (including PXRD, SEM and DSC) confirmed that this opposite mechanofluorochromism was attributed to the transformation of order‐crystalline and amorphous states. The crystal structure analysis and theoretical calculation further explain that opposite mechanofluorochromic behavior take into account different π–π stacking mode by induced π‐extended systems. In addition, these TPE‐based fluorophores (X‐1 and X‐2) exhibited excellent bio‐compatibility and fluorescence properties for bio‐imaging, writable data storage and anti‐counterfeiting materials. [ABSTRACT FROM AUTHOR]

Dual‐state emission luminogens (DSEgens) are receiving research interest in the construction of multifunctional materials due to their inherent advantage of high emission efficiency in both the molecularly dispersed solution state and the solid state. However, it remains challenging in synthesizing DSEgens via a delicate manipulation of the molecular structures. This work presents an example of bright DSEgen synthesis by tuning the molecular electronic structures and conformations. Three coumarin‐tetraphenylethylene (TPE) molecules with a donor‐acceptor electronic structure and highly twisting conformations have been synthesized. While compound resulting from direct conjugation of coumarin with a TPE unit shows aggregation‐induced emission, compound with an N,N‐diaminoethyl modification on the 7‐position of coumarin and compound with a further phenyl linker between coumarin and TPE units feature strong dual‐state emission. Benefiting from their strong solid emission and twisting conformations, these fluorophores display reversible mechanofluorochromism. Finally, applications for rewritable information storage in the solid state and live‐cell imaging in the solution state were demonstrated. [ABSTRACT FROM AUTHOR]

Stimuli‐induced structural transformation of supramolecular cages has drawn increasing attention because of their sensitive feature to external variations as model systems to simulate biological processes. However, combining structural transformation and useful functions has remained a difficult task. This study reports the solvato‐controlled self‐assembly of two unique topologies with different emission characteristics, a water‐soluble Ag8L4 cage (A) and an Ag4L2 cage (B), produced from the same sulfonate‐pendant tetraphenylethene (TPE) bridged tetrakis‐(1,2,4‐triazolium) ligand. Both cages show interesting solvent‐responsive reversible structural transformation, and the change of fluorescence signals can efficiently track the process. Additionally, water‐soluble cage A exhibits unique properties in thermochromism, thiol amino acid sensing, and subcellular imaging in aqueous media. [ABSTRACT FROM AUTHOR]

Two new 2,3‐dicyanopyrazinophenanthrene‐based acceptors (A) p‐QCN and m‐QCN were synthesized to blend with a donor (D) CPTBF for the exciplex formation. The energy levels of p‐QCN and m‐QCN are modulated by the peripheral substituents 4‐ and 3‐benzonitrile, respectively. Exciplex‐forming blends were identified by the observation of the red‐shifted emissions from various D : A blends with higher ratios of donor for suppressing the aggregation of acceptor. The two‐component relaxation processes observed by time‐resolved photoluminescence support the thermally activated delayed fluorescence (TADF) character of the exciplex‐forming blends. The device employing CPTBF : p‐QCN and (2 : 1) and CPTBF : m‐QCN (2 : 1) blend as the emitting layer (EML) gave EQEmax of 1.76 % and 5.12 %, and electroluminescence (EL) λmax of 629 nm and 618 nm, respectively. The device efficiency can be further improved to 4.32 % and 5.57 % with CPTBF : p‐QCN and (4 : 1) and CPTBF : m‐QCN (4 : 1) as the EML, which is consistent with their improved photoluminescence quantum yields (PLQYs). A new fluorescent emitter BPBBT with photoluminescence (PL) λmax of 726 nm and a high PLQY of 67 % was synthesized and utilized as the dopant of CPTBF : m‐QCN (4 : 1) cohost system. The device employing CPTBF : m‐QCN (4 : 1): 5 wt.% BPBBT as the EML gave an EQEmax of 5.02 % and EL λmax centered at 735 nm, however, the weak residual exciplex emission remains. By reducing the donor ratio, the exciplex emission can be completely transferred to BPBBT and the corresponding device with CPTBF : m‐QCN (2 : 1): 5 wt.% BPBBT as the EML can achieve EL λmax of 743 nm and EQEmax of 4.79 %. This work manifests the high efficiency near infrared (NIR) OLED can be realized by triplet excitons harvesting of exciplex‐forming cohost system, followed by the effective energy transfer to an NIR fluorescent dopant. [ABSTRACT FROM AUTHOR]

Through McMurry coupling reaction, three meso‐position functionalized pillar[5]arene derivatives (H‐1, H‐2, and H‐3) have been successfully prepared by embedding aggregation‐induced emission luminogens (AIEgens, diphenyldibenzofulvene (DPDBF) and tetraphenylethylene (TPE)) into the skeleton of supramolecular macrocycles. H‐1, bearing [15]paracyclophane ([15]PCP) and DPDBF moiety, exhibits yellow emission and demonstrates obvious AIE effect. In order to further improve the host‐guest properties of this type of structure, H‐2 and H‐3 are prepared by replacing the [15]PCP moiety with pillar[5]arene backbone, both of which show significant AIE effect and excellent host‐guest complexation properties with pyrazine salt guest G‐1 and 1,4‐dicyanobutane G‐2. Our findings indicate that G‐1 can decrease the fluorescence intensity of the AIE macrocycles, while G‐2 can increase their fluorescence intensity in solution. [ABSTRACT FROM AUTHOR]

Specifically amplifying the emission signals of optical probes in tumors is an effective way to improve the tumor‐imaging sensitivity and contrast. In this paper, the first case of dendron‐based fluorescence turn‐on probes mediated by a Förster resonance energy transfer (FRET) mechanism is reported. Dendrons up to the fourth generation with a hydrophilic oligo(ethylene glycol) scaffold are synthesized by a solid‐phase synthesis strategy, and show precise and defect‐free chemical structures. To construct the fluorescence turn‐on probe, one Cy5.5 molecule is conjugated to the focal of a G3 dendron through a robust linkage and eight Black Hole Quencher 3 (BHQ‐3) molecules are conjugated to its periphery through a PEG chain bearing a reductively cleavable disulfide linkage. By in vitro and in vivo experiments, it is demonstrated that the fluorescence of the dendron‐based probe can be activated effectively and rapidly in the reductive environments of tumor cells and tissues, and the probe thus exhibits amplified tumor signals and weak normal tissue signals. Compared with the reported nanoscale turn‐on probes, the dendron‐based probe has several significant advantages, such as well‐defined chemical structure, precisely controllable fluorophore/quencher conjugation sites and ratio, desirable chemical stability, and reproducible pharmacokinetic and pharmacological profiles, and is very promising in tumor detection. [ABSTRACT FROM AUTHOR]

The reversible modulation of fluorescence signals by light is of high interest for applications in super‐resolution microscopy, especially on the DNA level. In this article we describe the systematic variation of the core structure in nucleoside‐based diarylethenes (DAEs), in order to generate intrinsically fluorescent photochromes. The introduction of aromatic bridging units resulted in a bathochromic shift of the visible absorption maximum of the closed‐ring form, but caused reduced thermal stability and switching efficiency. The replacement of the thiophene aryl unit by thiazol improved the thermal stability, whereas the introduction of a benzothiophene unit led to inherent and modulatable turn‐off fluorescence. This feature was further optimized by introducing a fluorescent indole nucleobase into the DAE core, resulting in an effective photoswitch with a fluorescence quantum yield of 0.0166 and a fluorescence turn‐off factor of 3.2. The site‐specific incorporation into an oligonucleotide resulted in fluorescence‐switchable DNA with high cyclization quantum yields and switching efficiency, which may facilitate future applications. [ABSTRACT FROM AUTHOR]

We report the synthesis, gelation abilities and aggregation‐induced, blue‐shifted emission (AIBSE) properties of two minimalistic diketopiperazine‐based gelators. Despite containing a highly insoluble luminophore that makes up more than half of their respective molecular masses, efficient hydrogelation by multiple stimuli for one and efficient organogelation for the other compound are reported. Insights into the aggregation and gelation properties were gained through examination of the photophysical and material properties of selected gels, which are representative of the different modes of gelation. The synthesis of the gelators is highly modular and based on readily available amino acid building blocks, allowing the efficient and rapid diversification of these core structures and fine‐tuning of gel properties. [ABSTRACT FROM AUTHOR]

The assembly of two tripyridinium‐tricarboxylate ligands and different metal ions leads to seven isostructural MOFs, which show novel 2D→2D supramolecular entanglement featuring catenane‐like interlocking of tricyclic cages. The MOFs show tripyridinium‐afforded and metal‐modulated photoresponsive properties. The MOFs with d10 metal centers (1‐Cd, 1‐Zn, 2‐Cd, 2‐Zn) show fast and reversible photochromism and concomitant fluorescence quenching, 1‐Ni displays slower photochromism but does not fluoresce, and 1‐Co and 2‐Co are neither photochromic nor fluorescent. It is shown here that the network entanglement dictates donor‐acceptor close contacts, which enable fluorescence originated from interligand charge transfer. The contacts also allow photoinduced electron transfer, which underlies photochromism and concomitant fluorescence response. The metal dependence in fluorescence and photochromism can be related to energy transfer through metal‐centered d‐d transitions. In addition, 1‐Cd is demonstrated to be a potential fluorescence sensor for sensitive and selective detection of UO22+ in water. [ABSTRACT FROM AUTHOR]

Acquiring desirable device performance with deep‐blue color purity that fulfills practical application requirements is still a challenge. Bipolar fluorescent emitters with hybrid local and charge transfer (HLCT) state may serve to address this issue. Herein, by inserting anthracene core in the deep‐blue building blocks, the authors successfully developed two highly twisted D‐π‐A fluorescent emitters, ICz‐An‐PPI and IP‐An‐PPI, featuring different acceptor groups. Both exhibited superb thermal stabilities, high photo luminescent quantum yields and excellent bipolar transport capabilities. The non‐doped OLEDs using ICz‐An‐PPI and IP‐An‐PPI as the emitting layers showed efficient blue emission with an external quantum efficiency (EQEmax) of 4.32 % and 5.41 %, and the CIE coordinates of (0.147, 0.180) and (0.149, 0.150), respectively. In addition, the deep blue doped device based on ICz‐An‐PPI was achieved with an excellent CEmax of 5.83 cd A−1, EQEmax of 4.6 % and the CIE coordinate of (0.148, 0.078), which is extremely close to the National Television Standards Committee (NTSC) standard. Particularly, IP‐An‐PPI‐based doped device had better performance, with an EQEmax of 7.51 % and the CIE coordinate of (0.150, 0.118), which was very impressive among the recently reported deep‐blue OLEDs with the CIEy <0.12. Such high performance may be attributed to the hot exciton HLCT mechanism via T7 to S2. Our work may provide a new approach for designing high‐efficiency deep‐blue materials. [ABSTRACT FROM AUTHOR]

Three new zinc(II) coordination units [Zn(1–3)] based on planar‐directing tetradentate Schiff base‐like ligands H2(1–3) were synthesized. Their solid‐state structures were investigated by single crystal X‐ray diffraction, showing the tendency to overcome the square‐planar coordination sphere by axial ligation. Affinity in solution towards axial ligation has been tested by extended spectroscopic studies, both in the absorption and emission mode. The electronic spectrum of the pyridine complex [Zn(1)(py)] has been characterized by MC‐PDFT to validate the results of extended TD‐DFT studies. Green emission of non‐emissive solutions of [Zn(1–3)] in chloroform could be switched on in the presence of potent Lewis‐bases. While interpretation in terms of an equilibrium of stacked/non‐fluorescent and destacked/fluorescent species is in line with precedents from literature, the sensitivity of [Zn(1–3)] was greatly reduced. Results of a computation‐based structure search allow to trace the hidden Lewis acidity of [Zn(1–3)] to a new stacking motif, resulting in a strongly enhanced stability of the dimers. [ABSTRACT FROM AUTHOR]

We report a generalizable strategy for biosensing that takes advantage of the resistance of DNA aptamers against nuclease digestion when bound with their targets, coupled with toehold mediated strand displacement (TMSD) and rolling circle amplification (RCA). A DNA aptamer containing a toehold extension at its 5′‐end protects it from 3′‐exonuclease digestion by phi29 DNA polymerase (phi29 DP) in a concentration‐dependent manner. The protected aptamer can participate in RCA in the presence of a circular template that is designed to free the aptamer from its target via TMSD. The absence of the target leads to aptamer digestion, and thus no RCA product is produced, resulting in a turn‐on sensor. Using two different DNA aptamers, we demonstrate rapid and quantitative real‐time fluorescence detection of two human proteins: platelet‐derived growth factor (PDGF) and thrombin. Sensitive detection of PDGF was also achieved in human serum and human plasma, demonstrating the selectivity of the assay. [ABSTRACT FROM AUTHOR]

Organic small‐molecule fluorophores with near‐infrared IIa (NIR‐IIa) emission have great potential in pre‐clinical detection and inoperative imaging due to the high‐spatial resolution and deep penetration. However, developments of the NIR‐IIa fluorophores are still facing considerable challenges. In this work, a series of diketopyrrolopyrrole (DPP)‐based fluorophores were designed and synthesized. Subsequently, nanomaterial T25@F127 with significant NIR‐IIa emission properties was rationally prepared by encapsulating DPP‐based fluorophore T25, and was selected for fluorescence angiography and cerebral vascular microscopic imaging with nearly 800 μm penetrating depth and excellent signal‐background ratio of 4.07 and 2.26 (at 250 and 400 μm), respectively. Furthermore, the nanomaterial T25@cRGD with tumor targeting ability can image tiny metastatic tumor on intestine with a small size of 0.3 mm×1.0 mm and high‐spatial resolution (SBR=3.84). This study demonstrates that the nanomaterials which encapsulated T25 behave as excellent NIR‐IIa fluorescence imaging agents and have a great potential for in vivo biological application. [ABSTRACT FROM AUTHOR]

Peptides and nucleic acids can self‐assemble to give supramolecular structures that find application in different fields, ranging from the delivery of drugs to the obtainment of materials endowed with optical properties. Forces that stabilize the "suprastructures" typically are hydrogen bonds or aromatic interactions; in case of nucleic acids, Watson‐Crick pairing drives self‐assembly while, in case of peptides, backbone hydrogen bonds and interactions between aromatic side chains trigger the formation of structures, such as nanotubes or ribbons. Molecules containing both aromatic peptides and nucleic acids could in principle exploit different forces to self‐assemble. In this work we meant to investigate the self‐assembly of mixed systems, with the aim to understand which forces play a major role and determine formation/structure of aggregates. We therefore synthesized conjugates of the peptide FF to the peptide nucleic acid dimer "gc" and characterized their aggregates by different spectroscopic techniques, including NMR, CD and fluorescence. [ABSTRACT FROM AUTHOR]

A strongly twisted benzo‐fused tris‐cycloheptenylene, containing three dibenzosuberenone units fused to a common benzene ring, was subjected to Ramirez olefination and subsequent palladium‐catalyzed Suzuki‐Miyaura cross‐coupling with 4‐substituted phenylboronic acids. The high steric demand within the overcrowded, benzene‐rich benzo‐fused tris‐cycloheptenylenes enforced an unprecedented 1,2‐rearrangement upon π‐extension during the Suzuki coupling reaction. According to crystal structure analysis, the resulting negatively curved polycyclic aromatic hydrocarbons consist of two heptagons and one octagon surrounding a central benzene ring as a result of strain release. In the solid state, the materials exhibit a blue to blue‐green fluorescence with increased quantum yields and a hypsochromic shift of the emission maxima compared to their respective solutions. [ABSTRACT FROM AUTHOR]

The two‐step synthesis, structural, and photophysical properties of a series of heteroaryl‐substituted bis‐anil derivatives presenting aggregation‐induced emission (AIE) coupled with an excited‐state intramolecular proton transfer (ESIPT) process is described. The fluorescence color of the aggregates can be fine tuned by changing the electronic nature of the peripheral substitution, leading to a wide range of emission wavelengths (from green to the near infra‐red). Moreover, upon introduction of strong electron‐withdrawing groups such as cyano (CN), a competition between ESIPT and deprotonation is observed leading to the emission of the anionic species at low water percentage. This observation led to the synthesis of an additional mixed AIE fluorophore, functionalized by methoxy groups on one side and cyano groups on the other side. Upon addition of water, this dye displays first anionic emission, followed by typical AIE/ESIPT red fluorescence upon formation of the aggregates. TD‐DFT calculations on selected AIE dyes were performed to rationalize the nature of the emissive transitions in these derivatives. [ABSTRACT FROM AUTHOR]

A novel enantiopure π‐allylruthenium(IV) precatalyst allowed the enantioselective and stereospecific allylations of indoles and gave access to indolin‐3‐ones, containing vicinal stereogenic centers. Facile separation of diastereoisomers exhibiting opposite circularly polarized luminescence (CPL) activities in diverse solvents, including water, demonstrated the potential of these sustainable transformations and of the newly prepared molecules. [ABSTRACT FROM AUTHOR]

Organic donor‐acceptor complexes as new organic semiconductor class have attracted wide attention, due to their potential applications in functional optoelectronics. Herein, we present two new charge transfer cocrystals of di‐cyanodiazafluorene ‐perylene (DCPE) and di‐cyanodiazaflfluorene‐pyrene (DCPY) through a rational cocrystal‐engineering strategy. Although they are both 1 : 1 mixed stacking cocrystals with similar chemical structures, the DCPE cocrystal possesses a non‐centrosymmetric space group and narrower band gap compared to DCPY cocrystal, because of the non‐covalent bonding variation. The electrostatic potential accumulated in the lateral facets leads to highly twisted DCPE nanobelts, and the small band gap causes near infrared fluorescence. Meanwhile, the DCPY crystals with centrosymmetric space groups and weaker intermolecular interactions exhibited an untwisted morphology and red emission. This study will be helpful for the design and understanding of functional cocrystal materials that can be used in flexible micro/nano‐mechanics, mechanical energy, and optical devices. [ABSTRACT FROM AUTHOR]

Multistimuli‐responsive chromism was observed for vinylene‐linked bisflavin 1 a with an extended π‐conjugated platform. The yellow emission of a dilute solution of 1 a in CHCl3 (0.2 mM) observed at 298 K under UV excitation was changed to orange or red emission upon (1) an increase of concentration, (2) a decrease of temperature, and (3) variation of the solvent. This is in contrast to the almost non stimuli‐responsive chromism of the N‐methylated bisflavin analogue 1 b and monoflavin 2 a. Mechanistic investigation by 1H NMR analysis under various conditions revealed that the extended π‐conjugation platform and imide moiety of 1 a generate controllability in the formation of lower‐ and higher‐ordered aggregates, which induce variation of the emission color upon change. Bisflavin 1 a also exhibited redox‐induced chromism, where the orange emission of 1 a was quenched by the addition of hydrazine under anaerobic conditions, and changed back to the original emission upon subsequent bubbling of O2 gas. [ABSTRACT FROM AUTHOR]

Core‐fluorescent cavitands based on 2‐(2′‐resorcinol)benzimidazole fluorophores (RBIs) merged with the resorcin[4]arene skeleton were designed and synthesized. The cavitands, due to the presence of intramolecular hydrogen bonds and increased acidity, show excited state intramolecular proton transfer (ESIPT) and readily undergo deprotonation to form dianionic cavitands, capable of strong binding to organic cations. The changes in fluorescence are induced by deprotonation and binding events and involve huge Stokes shifts (due to emission from anionic double keto tautomers) and cation‐selective enhancement of emission originating from the restriction of intramolecular motion (RIR) upon recognition in the cavity. Ab initio calculations indicate that the macrocyclic scaffold stabilizes the ground state tautomeric forms of the fluorophores that are not observed for non‐macrocyclic analogs. In the excited state, the emitting forms for both macrocyclic scaffolds and non‐macrocyclic analogs are anionic double keto tautomers, which are the result of excited state intramolecular proton transfer (ESIPT) or excited state double proton transfer (ESDPT). [ABSTRACT FROM AUTHOR]

Naphthalenediimides (NDIs) have been extensively studied due to their tunable luminescent properties. However, generally, the monomers or aggregates of non‐core substituted NDIs exhibit low fluorescence quantum yields (ΦFL<10 %) in the solid state, which limit their applications as light‐emitting materials and render their chiral species unsuitable for circularly polarized luminescence (CPL). Herein, a series of non‐core substituted chiral NDIs that exhibit high luminous efficiencies (ΦFL up to 56.8 % for racemate and 36.5 % for enantiomer) and a strong CPL behavior in the solid state is reported. These significant improvements are attributed to the unique molecular conformation of the chiral NDIs and the formation of distinctive discrete dimers. The structures of the NDIs were significantly simpler and more accessible than those of other NDIs. The findings evidence that non‐core substituted NDIs can exhibit strong fluorescence in the solid state and provide a new pathway to improve photophysical properties of NDIs. [ABSTRACT FROM AUTHOR]

Easily synthesizable, fluorescent, organic nanoaggregates have been utilized, for the first time, in the selective recognition of d-(−)-ribose at pH 5.5 in water. In the self-assembled form, the reactive sites of the monomer units can be properly organized to form an effective 'recognition cleft' for ribose (limit of detection ≈23 μ m), in which binding mainly occurs through a combination of hydrogen-bonding and CH⋅⋅⋅π interactions. The degree of agglomeration shows a profound influence on the extent of ribose sensing. A reduction in the optical response (≈1.8-fold) is observed when ribose is allowed to interact with nanoaggregates of smaller dimensions (a decrease in the hydrodynamic diameter from (≈212.7±10.2) to (≈44.6±3.5) nm). The protocol is also utilized for the estimation of ribose in human urine samples and oral supplements. Low-cost paper strips have also been developed for rapid, on-site detection of ribose without involving any sophisticated instruments or skilled personnel. [ABSTRACT FROM AUTHOR]

Aroyl‐S,N‐ketene acetal‐based bichromophores can be readily synthesized in a consecutive three‐component synthesis in good to excellent yields by condensation of aroyl chlorides and an N‐(p‐bromobenzyl) 2‐methyl benzothiazolium salt followed by a Suzuki coupling, yielding a library of 31 bichromophoric fluorophores with substitution pattern‐tunable emission properties. Varying both chromophores enables different communication pathways between the chromophores, exploiting aggregation‐induced emission (AIE) and energy transfer (ET) properties, and thus, furnishing aggregation‐based fluorescence switches. Possible applications range from fluorometric analysis of alcoholic beverages to pH sensors. [ABSTRACT FROM AUTHOR]

Novel electron donor–acceptor–donor (D‐A‐D) compounds comprising dibenzo[a,j]phenazine as the central acceptor core and two 7‐membered diarylamines (iminodibenzyl and iminostilbene) as the donors have been designed and synthesized. Investigation of their physicochemical properties revealed the impact of C2 insertion into well‐known carbazole electron donors on the properties of previously reported twisted dibenzo[a,j]phenazine‐core D‐A‐D triads. Slight structural modification caused a drastic change in conformational preference, allowing unique photophysical behavior of dual emission derived from room‐temperature phosphorescence and triplet–triplet annihilation. Furthermore, electrochemical analysis suggested sigma‐dimer formation and electrochemical polymerization on the electrode. Quantum chemical calculations also rationalized the experimental results. [ABSTRACT FROM AUTHOR]

The effects of defect states on the fluorescence (FL) and electrochemiluminescence (ECL) properties of graphite phase carbon nitride (g‐CN) are systematically investigated for the first time. The g‐CN nanosheets (CNNSs) obtained at different condensation temperatures are used as the study models. It can be found that all the CNNSs have two kinds of defect states, one is originated from the edge of CNNSs (labeled as CN‐defect) and the other is attributed to the partially carbonization regions (labeled as C‐defect). Both two kinds of defect states substantially affect the luminescent properties of CNNSs. Both the FL and ECL signals of CNNSs contain a band gap emission and two defect emissions. For the FL of CNNSs, decreasing the density of defect states can increase efficiently the FL quantum yield, while increasing the density of defect states can make the FL spectra red shift. For the ECL of CNNSs, increasing the density of CN‐defect states and decreasing the density of C‐defect states are greatly important to improve the ECL activity. This work provides a deep insight into the FL and ECL mechanisms of g‐CN, and is of significance in tuning the FL and ECL properties of g‐CN. Also, it will greatly promote the applications of CNNSs based on the FL and ECL properties. [ABSTRACT FROM AUTHOR]

Mono‐ and di‐boranil‐substituted helicenes were prepared by BF2‐borylation of the corresponding anils, readily synthesized by condensation of 2‐amino‐ and 2,15‐diamino‐helicenes with 4‐(diethylamino)salicylaldehyde. After enantiomeric resolution using HPLC, their chiroptical properties including circularly polarized fluorescence in solution and in PMMA films were investigated and rationalized with the help of NMR, X‐ray and quantum‐chemical calculations. [ABSTRACT FROM AUTHOR]

High‐performance deep‐blue emitters with external quantum efficiencies (EQEs) exceeding 5 % are still scarce in organic light‐emitting diodes (OLEDs). In this work, by introducing a [1,2,4]triazolo[1,5‐a] pyridine (TP) unit at the N1 position of phenanthroimidazole (PI), two luminescent materials, PTPTPA and PTPTPA, were obtained. Systematic photophysical analysis showed that the TP block is suitable for constructing hybridized local and charge‐transfer (HLCT) emitters. Its moderate electron‐withdrawing ability and rigid planar structure can enhance the CT component while ensuring color purity. In addition, compared with PTPTPA, the additional phenyl ring of PTPBPTA not only increased the oscillator strength, but also decreased the Stokes shift. TDDFT calculations pointed out facile reverse intersystem crossing processes in PTPTPA from high‐lying triplet states to the singlet excited state. A nondoped device based on PTPTPA as emitter showed impressive performance with EQEmax of 7.11 % and CIE coordinates of (0.15, 0.09). At the same time, it was also an efficient host for yellow and red phosphorescent OLEDs. By doping yellow (PPYBA) and red (BTPG) phosphorescent dyes into PTPTPA, a white OLED with a high EQE of 23.85 % was achieved. The successful design of PTPTPA not only provided an optimization choice for OLED emitters, but also demonstrated the empirical rules for the design of multifunctional deep‐blue emitters. [ABSTRACT FROM AUTHOR]