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Dual bioorthogonal labeling enables the investigation and understanding of interactions in the biological environment that are not accessible by a single label. However, applying two bioorthogonal reactions in the same environment remains challenging due to cross‐reactivity. We developed a pair of differently modified 2′‐deoxynucleosides that solved this issue for dual and orthogonal labeling of DNA. Inverse‐electron demand Diels–Alder and photoclick reactions were combined to attach two different fluorogenic labels to genomic DNA in cells. Using a small synthetic library of 1‐ and 3‐methylcyclopropenyl‐modified 2′‐deoxynucleosides, two 2′‐deoxyuridines were identified to be the fastest‐reacting ones for each of the two bioorthogonal reactions. Their orthogonal reactivity could be evidenced in vitro. Primer extension experiments were performed with both 2′‐deoxyuridines investigating their replication properties as substitutes for thymidine and evaluating subsequent labeling reactions on the DNA level. Finally, dual, orthogonal and metabolic fluorescent labeling of genomic DNA was demonstrated in HeLa cells. An experimental procedure was developed combining intracellular transport and metabolic DNA incorporation of the two 2′‐deoxyuridines with the subsequent dual bioorthogonal labeling using a fluorogenic cyanine‐styryl tetrazine and a fluorogenic pyrene‐tetrazole. These results are fundamental for advanced metabolic labeling strategies for nucleic acids in the future, especially for live cell experiments. [ABSTRACT FROM AUTHOR]

The deployment of small‐molecule fluorescent agents plays an ever‐growing role in medicine and drug development. Herein, we complement the portfolio of powerful fluorophores, reporting the serendipitous discovery and development of a novel class with an imidazo[1,2‐a]pyridinium triflate core, which we term PyrAtes. These fluorophores are synthesized in a single step from readily available materials (>60 examples) and display Stokes shifts as large as 240 nm, while also reaching NIR−I emissions at λmax as long as 720 nm. Computational studies allow the development of a platform for the prediction of λmax and λEm. Furthermore, we demonstrate the compatibility of these novel fluorophores with live cell imaging in HEK293 cells, suggesting PyrAtes as potent intracellular markers. [ABSTRACT FROM AUTHOR]

Organic fluorophores are indispensable tools in cells, tissue and in vivo imaging, and have enabled much progress in the wide range of biological and biomedical fields. However, many available dyes suffer from insufficient performances, such as short absorption and emission wavelength, low brightness, poor stability, small Stokes shift, and unsuitable permeability, restricting their application in advanced imaging technology and complex imaging. Over the past two decades, many efforts have been made to improve these performances of fluorophores. Starting with the luminescence principle of fluorophores, this review clarifies the mechanisms of the insufficient performance for traditional fluorophores to a certain extent, systematically summarizes the modified approaches of optimizing properties, highlights the typical applications of the improved fluorophores in imaging and sensing, and indicates existing problems and challenges in this area. This progress not only proves the significance of improving fluorophores properties, but also provide a theoretical guidance for the development of high‐performance fluorophores. [ABSTRACT FROM AUTHOR]

Many microRNAs (miRNAs) are characteristically found in cancer cells, making miRNAs promising marker biomolecules for cancer diagnosis and therapeutics. However, it is challenging to use miRNA as a cancer signature because it is difficult to convert the nucleic acid sequence information into molecular functionality. To address this challenge, we realize nucleic acid‐to‐small molecule converters using hairpin DNA circuits. Harnessing a Staudinger reduction as a trigger for the conversion, we constructed hybridization chain reaction (HCR) and catalytic hairpin assembly (CHA) circuits that respond to oncogenic miR‐21. Fluorophore and dye molecules were released in response to miR‐21 through the HCR, providing fluorogenic and chromogenic readouts. Selective cytotoxicity in miR‐21‐abundant cells was realized by the CHA to release the anticancer drug SN‐38. This would be the first example of selective activation of a small‐molecule prodrug triggered by oncogenic miRNA in human living cells. [ABSTRACT FROM AUTHOR]

Heptamethine cyanine dyes enable deep tissue fluorescence imaging in the near infrared (NIR) window. Small molecule conjugates of the benchmark dye ZW800‐1 have been tested in humans. However, long‐term imaging protocols using ZW800‐1 conjugates are limited by their instability, primarily because the chemically labile C4′‐O‐aryl linker is susceptible to cleavage by biological nucleophiles. Here, we report a modular synthetic method that produces novel doubly strapped zwitterionic heptamethine cyanine dyes, including a structural analogue of ZW800‐1, with greatly enhanced dye stability. NIR‐I and NIR‐II versions of these doubly strapped dyes can be conjugated to proteins, including monoclonal antibodies, without causing undesired fluorophore degradation or dye stacking on the protein surface. The fluorescent antibody conjugates show excellent tumor‐targeting specificity in a xenograft mouse tumor model. The enhanced stability provided by doubly strapped molecular design will enable new classes of in vivo NIR fluorescence imaging experiments with possible translation to humans. [ABSTRACT FROM AUTHOR]

Herein we present a systematic study demonstrating to which extent exciton formation can amplify fluorescence based on a series of ethylene‐bridged oligo‐BODIPYs. A set of non‐ and weakly fluorescent BODIPY motifs was selected and transformed into discrete, chain‐like oligomers by linkage via a flexible ethylene tether. The prepared superstructures constitute excitonically active entities with non‐conjugated, Coulomb‐coupled oscillators. The non‐radiative deactivation channels of Internal Conversion (IC), also combined with an upstream reductive Photoelectron Transfer (rPET) and Intersystem Crossing (ISC) were addressed at the monomeric state and the evolution of fluorescence and (non‐)radiative decay rates studied along the oligomeric series. We demonstrate that a "masked" fluorescence can be fully reactivated irrespective of the imposed conformational rigidity. This work challenges the paradigm that a collective fluorescence enhancement is limited to sterically induced motional restrictions. [ABSTRACT FROM AUTHOR]

We present a second near‐infrared (NIR‐II) self‐checking molecule, LET‐1052, for acidic tumor microenvironment (TME) turn‐on photothermal therapy (PTT), followed by viscosity based therapeutic efficacy evaluation by itself in two independent channels, denoted as "self‐checking" strategy. In acidic TME, LET‐1052 was protonated and turned on NIR‐II absorption for PTT under 1064 nm laser irradiation. Subsequently, PTT‐induced cellular death increases intracellular viscosity, which inhibited the intramolecular rotation of LET‐1052, resulting in the enhancement of NIR‐I fluorescence for real‐time evaluation of PTT efficacy. After PTT of tumor‐bearing mice for different periods of NIR‐II laser irradiation, NIR‐I fluorescence in the tumor region showed positive correlation with tumor growth inhibition rate, demonstrating reliable and prompt prediction of PTT efficacy. The strategy may be expanded for instant evaluation of other therapeutic modalities for personalized medicine. [ABSTRACT FROM AUTHOR]

Examples from different research areas of Siegfried Hünig are displayed to remind us that organic chemistry owes much more than Hünig's base to this exceptionally versatile and creative chemist. The main research lines dealing with the synthesis and physical characterization of new dyes, multistage redox systems, and organic metals will be presented as well as his contributions to enamine chemistry, the discovery of diimine as a hydrogenation agent, and nucleophilic acylation with trimethylsilyl cyanide, which are less well‐known nowadays. In addition, exotic compounds with parallel C=C and N=N bonds were systematically studied in Hünig's group. Reflecting on the development of his research demonstrates both the importance of a systematic approach and how fruitful entirely unexpected results are if they meet a "well‐prepared mind". During Hünig's academic career, teaching played an indisputable role. His efforts in modernizing the chemistry institute at Würzburg and his support of young researchers in the academic system in Germany are also highlighted. [ABSTRACT FROM AUTHOR]

A range of unprocessed, reducing sugar substrates (mono‐, di‐, and trisaccharides) is shown to take part in a straightforward four‐step synthetic route to water‐soluble, uncharged BODIPY derivatives with unimpaired chiral integrity and high fluorescence efficiency. A wide compatibility with several postfunctionalizations is demonstrated, thus suggesting a universal utility of the multifunctional glycoconjugates, which we call GlycoBODIPYs. Knoevenagel condensations are able to promote a red‐shift in the spectra, thereby furnishing strongly fluorescent red and far‐red glycoconjugates of high hydrophilicity. The synthetic outcome was studied by X‐ray crystallography and by comprehensive photophysical investigations in several solvent systems. Furthermore, cell experiments illustrate efficient cell uptake and demonstrate differential cell targeting as a function of the integrated chiral information. [ABSTRACT FROM AUTHOR]

A strategy to implement four members of the classic coal‐tar dye family, Michler's ketone, methylene blue, rhodamine B, and crystal violet, into [Pd2L4] self‐assemblies is introduced. Chromophores were incorporated into bis‐monodentate ligands using piperazine linkers that allow to retain the auxochromic dialkyl amine functionalities required for intense colors deep in the visible spectrum. Upon palladium coordination, ligands with pyridine donors form lantern‐shaped dinuclear cages while quinoline donors lead to strongly twisted [Pd2L4] helicates in solution. In one case, single crystal X‐ray diffraction revealed rearrangement to a [Pd3L6] ring structure in the solid state. For nine examined derivatives, showing colors from yellow to deep violet, CD spectroscopy discloses different degrees of chiral induction by an enantiomerically pure guest. Ion mobility mass spectrometry allows to distinguish two binding modes. Self‐assemblies based on this new ligand class promise application in chiroptical recognition, photo‐redox catalysis and optical materials. [ABSTRACT FROM AUTHOR]

We present a straightforward, three‐step synthesis engaging an oligomerization and subsequent one‐pot oxidation step to form fully conjugated, benzene‐fused oligo‐BODIPYs from simple BODIPY precursors. FeCl3 serves as an efficient, bifunctional oxidant for a (multiple) cyclization/desaturation process, applied to ethylene‐bridged dimeric, trimeric and oligomeric species to transform linking ethano units into stiff benzene fusions between unsubstituted β‐positions of each BODIPY unit. The structural integrity was verified by X‐ray crystallography, and all target compounds were studied in detail by photophysical, electrochemical and computational means. The main S1 excited state gradually converges to a structure‐specific excitation limit, displaying a strong shift of the absorption event from about 500 nm (BODIPY monomer) to 955 nm (octamer) with attenuation coefficients up to ca. 500 000 M−1 cm−1. [ABSTRACT FROM AUTHOR]

The synthesis of organometallic complexes of modified 26π‐conjugated hexaphyrins with absorption and emission capabilities in the third near‐infrared region (NIR‐III) is described. Symmetry alteration of the frontier molecular orbitals (MOs) of bis‐PdII and bis‐PtII complexes of hexaphyrin via N‐confusion modification led to substantial metal dπ–pπ interactions. This MO mixing, in turn, resulted in a significantly narrower HOMO–LUMO energy gap. A remarkable long‐wavelength shift of the lowest S0→S1 absorption beyond 1700 nm was achieved with the bis‐PtII complex, t‐Pt2‐3. The emergence of photoacoustic (PA) signals maximized at 1700 nm makes t‐Pt2‐3 potentially useful as a NIR‐III PA contrast agent. The rigid bis‐PdII complexes, t‐Pd2‐3 and c‐Pd2‐3, are rare examples of NIR emitters beyond 1500 nm. The current study provides new insight into the design of stable, expanded porphyrinic dyes possessing NIR‐III‐emissive and photoacoustic‐response capabilities. [ABSTRACT FROM AUTHOR]

Perylene‐fused, aggregation‐free polycyclic aromatic hydrocarbons with partial zigzag periphery (ZY‐01, ZY‐02, and ZY‐03) were synthesized. X‐ray crystallographic analysis reveals that there is no intermolecular π–π stacking in any of the three molecules, and as a result, they show moderate‐to‐high photoluminescence quantum yield in both solution and in the solid state. They also display the characteristic absorption and emission spectra of perylene dyes. ZY‐01 and ZY‐02 with a nearly planar π‐conjugated skeleton exhibit amplified spontaneous emission (ASE) when dispersed in polystyrene thin films. Solution‐processed distributed feedback lasers have been fabricated using ZY‐01 and ZY‐02 as active gain materials, both showing narrow emission linewidth (<0.4 nm) at wavelengths around 515 and 570 nm, respectively. In contrast, ZY‐03 did not show ASE and lasing, presumably due to its highly twisted backbone, which facilitates nonradiative internal conversion and intersystem crossing. [ABSTRACT FROM AUTHOR]

We report the direct imidization of naphthalene and perylene dicarboxylic anhydrides/esters with bulky ortho,ortho‐diaryl‐ and ortho,ortho‐dialkynylaniline derivatives. This imidization method uses n‐butyllithium as a strong base to increase the reactivity of bulky amine derivatives, proceeds under mild reaction conditions, requires only stoichiometric amounts of reactants and gives straightforward access to new sterically crowded rylene dicarboximides. Mechanistic investigations suggest an isoimide as intermediary product, which was converted to the corresponding imide upon addition of an aqueous base. Single‐crystal X‐ray diffraction analyses reveal dimeric packing motifs for monoimides, while two‐side shielded bisimides crystallize in isolated molecules without close π–π‐interactions. Spectroscopic investigations disclose the influence of the bulky substituents on the optical properties in the solid state. [ABSTRACT FROM AUTHOR]

Helical carbazole‐based BODIPY analogues were readily synthesized via aza[7]helicenes. The structures of azahelicene‐incorporated BF2 dyes were elucidated by x‐ray diffraction analysis. DFT calculations revealed that the π‐conjugated system expanded from the helicene moiety to the BODIPY framework. The azahelicene‐fused boron complexes showed the Cotton effects and the circularly polarized luminescence (CPL) in the visible region. Furthermore, an axially chiral binaphthyl group was attached to the helically chiral dyes, which enhanced the chiroptical properties. [ABSTRACT FROM AUTHOR]

A new, transformative methodology for the preparation of diketopyrrolopyrroles from aldehydes, primary amines, nitriles, and diethyl oxalacetate has been developed. It is now possible to prepare diketopyrrolopyrroles bearing an ordered arrangement of three different substituents from abundant and commercially available materials, allowing the independent regulation of all desired physicochemical properties. For the first time very electron‐rich (carbazol‐3‐yl, dimethylaminophenyl, pyrrolo[3,2‐b]pyrrolyl), and sterically hindered substituents (naphthalen‐1‐yl, quinolin‐4‐yl, acridin‐9‐yl, imidazo[1,5‐a]pyridin‐1‐yl, 2‐bromophenyl etc.) can be appended to the diketopyrrolopyrrole core by condensation of an appropriate nitrile with a pyrrolidin‐2‐one intermediate. Even greater synthetic possibilities are related to the fact that such demanding substituents as 4‐dimethylaminophenyl, indol‐3‐yl, and 2‐methoxyphenyl can be incorporated from aldehyde precursors, bypassing problems with the nitriles reactivity. [ABSTRACT FROM AUTHOR]

Strongly emissive solid‐state materials are mandatory components for many emerging optoelectronic technologies, but fluorescence is often quenched in the solid state owing to strong intermolecular interactions. The design of new organic pigments, which retain their optical properties despite their high tendency to crystallize, could overcome such limitations. Herein, we show a new material with monomer‐like absorption and emission profiles as well as fluorescence quantum yields over 90 % in its crystalline solid state. The material was synthesized by attaching two bulky tris(4‐tert‐butylphenyl)phenoxy substituents at the perylene bisimide bay positions. These substituents direct a packing arrangement with full enwrapping of the chromophore and unidirectional chromophore alignment within the crystal lattice to afford optical properties that resemble those of their natural pigment counterparts, in which chromophores are rigidly embedded in protein environments. [ABSTRACT FROM AUTHOR]

The design of white‐light phosphors is attractive in solid‐state lighting (SSL) and related fields. A new strategy in obtaining white light emission (WLE) from dual‐way photon energy conversion in a series of dye@MOF (LIFM‐WZ‐6) systems is presented. Besides the traditional UV‐excited one‐photon absorption (OPA) pathway, white‐light modulation can also be gained from the combination of NIR‐excited green and red emissions of MOF backbone and encapsulated dyes via two‐photon absorption (TPA) pathway. As a result, down‐conversion OPA white light was obtained for RhB+@LIFM‐WZ‐6 (0.1 wt %), BR‐2+@LIFM‐WZ‐6 (2 wt %), and APFG+@LIFM‐WZ‐6 (0.1 wt %) samples under 365 nm excitation. RhB+@LIFM‐WZ‐6 (0.05 wt %), BR‐2+@LIFM‐WZ‐6 (1 wt %) and APFG+@LIFM‐WZ‐6 (0.05 wt %) exhibit up‐conversion TPA white light under the excitation of 800, 790, and 730 nm, respectively. This new WLE generation strategy combines different photon energy conversion mechanisms together. [ABSTRACT FROM AUTHOR]

Abstract: Through fusing isoindigo (IID) units at 6,7;6′,7′‐positions, a series of new near‐infrared (NIR) absorbing and stable ribbon‐like conjugated molecules, namely nIIDs in which n represents the number of IID units, have been synthesized. The optical band gaps of the molecules are lowered from 2.03 eV of 1IID to 1.12 eV of 6IID with the increase of the conjugation length. 3IID, 4IID, and 6IID have strong absorption in the NIR region and exhibit photothermal conversion efficiencies of greater than 50 % under laser irradiation at λ=808 nm. [ABSTRACT FROM AUTHOR]

Abstract: A small‐molecule fluorophore FD‐1080 with both excitation and emission in the NIR‐II region has been successfully synthesized for in vivo imaging. A heptamethine structure is designed to shift the absorption and emission into NIR‐II region. Sulphonic and cyclohexene groups are introduced to enhance its water solubility and stability. The quantum yield of FD‐1080 is 0.31 %, and can be increased to 5.94 % after combining with fetal bovine serum (FBS). Significantly, 1064 nm NIR‐II excitation was demonstrated with the high tissue penetration depth and superior imaging resolution compared to previously reported NIR excitation from 650 nm to 980 nm. FD‐1080 is not only capable of realizing non‐invasive high‐resolution deep‐tissue hindlimb vasculature and brain vessel bioimaging, but also quantifying the respiratory rate based on the dynamic imaging of respiratory craniocaudal motion of the liver for the awake and anaesthetized mouse. [ABSTRACT FROM AUTHOR]

Novel aqueous multiphase systems (MuPSs) formed by quaternary mixtures composed of cholinium-based ionic liquids (ILs), polymers, inorganic salts, and water are reported herein. The influence of several ILs, polymers, and salts was studied, demonstrating that a triple salting-out is a required phenomenon to prepare MuPSs. The respective phase diagrams and 'tie-surfaces' were determined, followed by the evaluation of the effect of temperature. Finally, the remarkable ability of IL-based MuPSs to selectively separate mixtures of textile dyes is shown. [ABSTRACT FROM AUTHOR]

The sequestration of luminophores within supramolecular polyhedral compartments of a crystalline zeolite-like hydrogen-bonded framework illustrates a unique approach to limiting the self-quenching ordinarily exhibited at the high concentrations achievable in this framework. A range of differently sized luminescent guests, namely coumarin 1, coumarin 4, fluorescein, [Ru(bpy)3]Cl2, and rhodamine B, can be encapsulated in amounts of up to one molecule per cage, equivalent to a concentration of 0.175 m, which is significantly higher than the concentration at which aggregation-induced quenching occurs in other media. The luminescence spectra of the encapsulated guests are consistent with the presence of isolated monomers and the absence of self-quenching. The emission color of the single crystals can be tuned readily from blue to red through the choice of guest molecules. These observations promise an approach to organic solid-state lasing compounds if crystals of sufficient size and quality can be prepared. [ABSTRACT FROM AUTHOR]

Polymethine bridges in cyanine dyes may be constrained by setting them into edge‐fused ring systems, or extended by conjugation with carefully chosen heterocycles. Recent studies have shown that modifications like these can give significantly brighter dyes with red‐shifted absorbance and emission maxima. [ABSTRACT FROM AUTHOR]

Microcapsules obtained by layer-by-layer assembly provide a good platform for biological analysis owing to their component diversity, multiple binding sites, and controllable wall thickness. Herein, different assembly species were obtained from two-photon dyes and traditional photosensitizers, and further assembled into microcapsules. Fluorescence resonance energy transfer (FRET) was shown to occur between the two-photon dyes and photosensitizers. Confocal laser scanning microscopy (CLSM) with one- and two-photon lasers, fluorescence lifetime imaging microscopy (FLIM), and time-resolved fluorescence spectroscopy were used to analyze the FRET effects in the microcapsules. The FRET efficiency could easily be controlled through changing the assembly sequence. Furthermore, the capsules are phototoxic upon one- or two-photon excitation. These materials are thus expected to be applicable in two-photon-activated photodynamic therapy for deep-tissue treatment. [ABSTRACT FROM AUTHOR]

A fundamental, highly fluorescent, and easily accessible scaffold derived from the BODIPY core is reported. The use of benzimidazole as a bridging ligand at the meso position enables the binding of two BF2 units to provide sufficient rigidity and enhanced electron-withdrawing strength. Absorption and emission events thus take place in the red ( λ≈600 nm); the fluorescence quantum yields can reach unity (0.96) and show little dependence on solvent polarity. The synthetic route was shortened to two steps starting from commercially available precursors while the preparation is modular and tolerates various pyrrole and benzimidazole moieties. Fluoride replacement by propynyl groups, various halogenations, as well as Knoevenagel-type condensations were applied to extend the versatility of these new photostable fluorophores, which we termed BOIMPYs. [ABSTRACT FROM AUTHOR]

Catalysts that can be regulated in terms of activity and selectivity by external stimuli may allow the efficient multistep synthesis of complex molecules and pharmaceuticals. Herein, we report the light-color regulation of the redox potential of a photocatalyst to control the activation of chemical bonds. Light-color control of the redox power of a photocatalyst introduces a new selectivity parameter to photoredox catalysis: Instead of changing the catalyst or ligand, alteration of the color of the visible-light irradiation adjusts the selectivity in catalytic transformations. By using this principle, the selective activation of aryl-halide bonds for C−H arylation and the sequential conversion of functional groups with different reduction potentials is possible by simply applying different colors of light for excitation of the photocatalyst. [ABSTRACT FROM AUTHOR]

A homologous series of donor-π-acceptor dyes was synthesized, differing only in the identity of the halogen substituents about the triphenylamine (TPA; donor) portion of each molecule. Each Dye-X (X=F, Cl, Br, and I) was immobilized on a TiO2 surface to investigate how the halogen substituents affect the reaction between the light-induced charge-separated state, TiO2(e−)/ Dye-X+, with iodide in solution. Transient absorption spectroscopy showed progressively faster reactivity towards nucleophilic iodide with more polarizable halogen substituents: Dye-F < Dye-Cl < Dye-Br < Dye-I. Given that all other structural and electronic properties for the series are held at parity, with the exception of an increasingly larger electropositive σ-hole on the heavier halogens, the differences in dye regeneration kinetics for Dye-Cl, Dye-Br, and Dye-I are ascribed to the extent of halogen bonding with the nucleophilic solution species. [ABSTRACT FROM AUTHOR]

Synergistic effects arising from the conjugation of organic dyes onto non-luminescent metal nanoparticles (NPs) have greatly broadened their applications in both imaging and sensing. Herein, we report that conjugation of a well-known pH-insensitive dye, tetramethyl-rhodamine (TAMRA), to pH-insensitive luminescent gold nanoparticles (AuNPs) can lead to an ultrasmall nanoindicator that can fluorescently report local pH in a ratiometric way. Such synergy originated from the dimerization of TAMRA on AuNPs, of which geometry was very sensitive to surface charges of the AuNPs and can be reversely modulated through protonation of surrounding glutathione ligands. Not limited to pH-insensitive dyes, this pH-dependent dimerization can also enhance the pH sensitivity of fluorescein, a well-known pH-sensitive dye, within a larger pH range, opening up a new pathway to design ultrasmall fluorescent ratiometric nanoindicators with tunable wavelengths and pH response ranges. [ABSTRACT FROM AUTHOR]

Unprecedented neutral perylene-3,4:9,10-tetracarboxylic acid bisimide (PBI) radicals and biradicals were synthesized by facile chemical oxidation of 4-hydroxyaryl-substituted PBIs. Subsequent characterization by optical and magnetic spectroscopic techniques, as well as quantum chemical calculations, revealed an open-shell singlet biradical ground state for the PBI biradical OS-2‥ (=1.2191) with a relatively small singlet-triplet energy gap of 0.041 eV and a large singlet biradical character of y=0.72. [ABSTRACT FROM AUTHOR]

Novel aza-diisoindolylmethene and their BF2-chelating complexes (benzo-fused aza-BODIPYs) were synthesized on a large scale and in a facile manner from phthalonitrile in tBuOK-DMF solution. The unique asymmetric donor-π-acceptor structure facilitates BN bond detachment in the presence of trifluoroacetic acid (TFA) in dichloromethane, resulting in sharp color change from red to colorless, with over 250 nm hypsochromic shift in the absorption maximum. This colorimetric process can be reversed by adding a very small amount of proton-accepting solvents or compounds. A 1H and 11B NMR spectroscopy study and also density functional theory (DFT) calculations suggest that TFA-induced BN bond cleavage may disrupt the whole π-conjugation of the BODIPY molecule, resulting in significant colorimetric behavior. [ABSTRACT FROM AUTHOR]

We describe herein the first radical CH arylation of BODIPY dyes. This novel, general, one-step synthetic procedure uses ferrocene to generate aryl radical species from aryldiazonium salts and allows the straightforward synthesis of brightly fluorescent ( Φ>0.85) 3,5-diarylated and 3-monoarylated boron dipyrrins in up to 86 % yield for a broad range of aryl substituents. In this way, new and complex dyes with red-shifted spectra can be easily prepared. [ABSTRACT FROM AUTHOR]

The unexpected introduction of a cationic imidazolium substituent in the 2-position of a tetrachloro-substituted perylene-3,4:9,10-tetracarboxylic acid bisimide (PBI) by the reaction of PBI-Cl4 1 with the N-heterocyclic carbene 1,3-di-iso-propyl-imidazolin-2-ylidene (iPr2Im 2) enables the isolation of an ambient stable zwitterionic radical. The remarkable stability of this unprecedented PBI-centered radical facilitates the complete characterization by several spectroscopic methods as well as single crystal structure analysis. Redox studies revealed that iPr2Im-PBI-Cl4 4 can be transferred reversibly to the corresponding anion and cation, respectively, even on a preparative scale. [ABSTRACT FROM AUTHOR]

Mitochondrial polarity strongly influences the intracellular transportation of proteins and interactions between biomacromolecules. The first fluorescent probe capable of the ratiometric imaging of mitochondrial polarity is reported. The probe, termed BOB, has two absorption maxima ( λabs=426 and 561 nm) and two emission maxima-a strong green emission ( λem=467 nm) and a weak red emission (642 nm in methanol)-when excited at 405 nm. However, only the green emission is markedly sensitive to polarity changes, thus providing a ratiometric fluorescence response with a good linear relationship in both extensive and narrow ranges of solution polarity. BOB possesses high specificity to mitochondria ( Rr=0.96) that is independent of the mitochondrial membrane potential. The mitochondrial polarity in cancer cells was found to be lower than that of normal cells by ratiometric fluorescence imaging with BOB. The difference in mitochondrial polarity might be used to distinguish cancer cells from normal cells. [ABSTRACT FROM AUTHOR]

A new method for the synthesis of industrially important azoimidazolium dyes is presented. The procedure is based on a reagent which is rarely used in the context of synthetic organic chemistry: nitrous oxide ('laughing gas'). N2O is first coupled to N-heterocyclic carbenes. Subsequent reaction with aromatic compounds through an AlCl3-induced CH activation process provides azoimidazolium dyes in good yields. [ABSTRACT FROM AUTHOR]

A photocatalytic formal [3+2] cycloaddition of 2 H-azirines with alkynes has been achieved under irradiation by visible light in the presence of organic dye photocatalysts. This transformation provides efficient access to highly functionalized pyrroles in good yields and has been applied to the synthesis of drug analogues. A primary trial of photocascade catalysis merging energy transfer and redox neutral reactions was shown to be successful. [ABSTRACT FROM AUTHOR]

Ternary complexes between the macrocyclic host cucurbit[8]uril, dicationic dyes, and chiral aromatic analytes afford strong induced circular dichroism (ICD) signals in the near-UV and visible regions. This allows for chirality sensing and peptide-sequence recognition in water at low micromolar analyte concentrations. The reversible and noncovalent mode of binding ensures an immediate response to concentration changes, which allows the real-time monitoring of chemical reactions. The introduced supramolecular method is likely to find applications in bioanalytical chemistry, especially enzyme assays, for drug-related analytical applications, and for continuous monitoring of enantioselective reactions, particularly asymmetric catalysis. [ABSTRACT FROM AUTHOR]

Porphyrins have drawn much attention as sensitizers owing to the large absorption coefficients of their Soret and Q bands in the visible region. In a donor and acceptor zinc porphyrin we applied a new strategy of introducing 2,1,3-benzothiadiazole (BTD) as a π-conjugated linker between the anchoring group and the porphyrin chromophore to broaden the absorption spectra to fill the valley between the Soret and Q bands. With this novel approach, we observed 12.75 % power-conversion efficiency under simulated one-sun illumination (AM1.5G, 100 mW cm−2). In this study, we showed the importance of introducing the phenyl group as a spacer between the BTD and the zinc porphyrin in achieving high power-conversion efficiencies. Time-resolved fluorescence, transient-photocurrent-decay, and transient-photovoltage-decay measurements were employed to determine the electron-injection dynamics and the lifetime of the photogenerated charge carriers. [ABSTRACT FROM AUTHOR]

Owing to their applications in biodetection and molecular bioimaging, near-infrared (NIR) fluorescent dyes are being extensively investigated. Most of the existing NIR dyes exhibit poor quantum yield, which hinders their translation to preclinical and clinical settings. Plasmonic nanostructures are known to act as tiny antennae for efficiently focusing the electromagnetic field into nanoscale volumes. The fluorescence emission from NIR dyes can be enhanced by more than thousand times by precisely placing them in proximity to gold nanorods. We have employed polyelectrolyte multilayers fabricated using layer-by-layer assembly as dielectric spacers for precisely tuning the distance between gold nanorods and NIR dyes. The aspect ratio of the gold nanorods was tuned to match the longitudinal localized surface plasmon resonance wavelength with the absorption maximum of the NIR dye to maximize the plasmonically enhanced fluorescence. The design criteria derived from this study lays the groundwork for ultrabright fluorescence bullets for in vitro and in vivo molecular bioimaging. [ABSTRACT FROM AUTHOR]

Feeling the field! The intensity of second harmonic generation (SHG) from a porphyrin in a lipid bilayer is exceptionally sensitive to electric field, thus indicating that these dyes may be useful probes for electrical signals in excitable cells such as neurons. The porphyrin‐based membrane probe (see picture, not to scale) gives a fast electro‐optic response which is about 5–10 times greater than those of conventional styryl dyes. [ABSTRACT FROM AUTHOR]

The article discusses a study on a novel thermosensing dye that comprises of a lanthanide coordination polymer. The synthesis of the thermosensing dye, which is called chameleon luminophore, is described. The study investigated the impact of TbIII ion and hexafluoro acetylacetonato (hfa) ligands on energy back transfer (BEnT) in the lanthanide coordination polymer. It also evaluated the coordination polymer's thermal stability and luminescence properties.

Nonlinear optics: A hemicyanine‐incorporating silicalite‐1 film with second‐order nonlinear optical properties supported on a glass plate was prepared. For the nonlinear optical properties of this material the number of hemicyanine dye moleclues included in the zeolite channels is important. Defects arising from Si deficiency along the channels prohibit the diffusion of the dyes into the interior of the zeolite film (see picture). [ABSTRACT FROM AUTHOR]

The article discusses a design strategy developed by Xie, Zhu and co-workers involving rational porphyrin dye structure optimization and cosensitization to obtain efficient dye-sensitized solar cells (DSSCs) using the traditional electrolyte. They developed a combined strategy involving molecular engineering and cosensitization to improve photovoltaic efficiency through targeted and syndergistic optimization of Voc and Jsc.

Organic solid‐state dye lasers promise versatility with respect to spectral tuning, but often face challenges owing to self‐quenching by aggregation. In their Communication on page 14003 ff., M. D. Ward et al. describe an approach to solid‐state lasing compounds in which isolated luminescent guest molecules, a range of well‐known laser dyes, are encapsulated in cages of a crystalline hydrogen‐bonded zeolite‐like framework. The luminescence of each compound is consistent with the absence of self‐quenching, and the emission color can be tuned from blue to red by the choice of guest molecule. [ABSTRACT FROM AUTHOR]

Microcapsules containing two‐photon dyes and traditional photosensitizers were obtained through layer‐by‐layer assembly, as described by M. J. Han, J. B. Li, and co‐workers in their Communication on page 13538 ff. These microcapsules were used for Förster resonance energy transfer (FRET) analysis and might find application in two‐photon‐activated photodynamic therapy for deep‐tissue treatment. [ABSTRACT FROM AUTHOR]

The article offers brief information on research related to chromoselective activation of redox-active chemical bonds.