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2-(5-Arylpyridine-2-yl)-6-(het)arylquinoline-based "push-pull" fluorophores were synthesized by means of the heterocyclization reaction between the corresponding isonitrosoacetophenone hydrazones and 6-bromoquinoline-2-carboxaldehyde followed by an aza-Diels-Alder/Suzuki cross-coupling reaction sequence. The optical properties of the obtained fluorophores were studied and the non-linear optic behavior for the two most representative ones were confirmed based on the solvatochromic experiments. • 2-(5-Arylpyridin-2-yl)-quinolines were synthesized as "push-pull" fluorophores. • "1,2,4-Triazine methodology" was used for synthesis of the fluorophores. • Photophysical properties were studied. • The UV/Vis absorption and fluorescence spectra were investigated. [ABSTRACT FROM AUTHOR]

Abstract It is an effective and precise strategy to design the fluorescence probe for Hg2+ based on a new specific reaction. A novel turn-on fluorescent probe, 4-{2-[4-(2-Mercapto-benzoyloxy)-phenyl]-vinyl}-1-methyl-pyridinium[ e ]iodide (MBPVP) for Hg2+ was developed. The mechanism was based on Hg2+-mediated ester hydrolysis to release the fluorophore, 4-[2-(4-Hydroxy-phenyl)-vinyl]-1-methyl-pyridinium[ e ]iodide, which showed outstanding intramolecular charge transfer (ICT) and the yellow-green fluorescence were observed. The turn-on probe showed rapid response time, outstanding selectivity and sensitivity for Hg2+ over other metal ions in 100% PBS buffer (pH = 7.4). The linear range was 2–16 µM and the detection limit was 6.5 nM. Furthermore, MBPVP was used to determine Hg2+ in real samples and in the solid state. Graphical abstract fx1 Highlights • A turn-on fluorescence probe (MBPVP) for Hg2+ based on new specific reaction was developed. • MBPVP showed rapid response time, high selectivity and sensitivity in 100% aqueous solution. • The probe was applied in water samples and in the solid state. [ABSTRACT FROM AUTHOR]

Abstract Low-cost and nontoxic fluorescent reagents are important for on-site analysis performed by non-professionals. In this work, a cheap and widely available food additive, caramel was used as an effective fluorescence reagent for the sensitive detection of 2,4,6-trinitrophenol (TNP), 2,4-dinitrophenol (DNP) and 4-nitrophenol (4-NP). Through a simple dialysis, fluorescent components of a commercial caramel were harvested with a yield as high as 60%. The structural characterization demonstrated that the fluorescent components were dehydrated oligomers of carbohydrates. Their fluorescence can be quenched by these nitrophenols. The quenching mechanism was speculated as inner filter effect. At pH 8, a linear range of 0.2–22 μM and a detection limit of 90 nM could be achieved for TNP. Based on the difference of their quenching efficiency at different pHs, TNP, DNP and 4-NP can be simultaneously determined by solving the linear equations obtained at pH 3, 5 and 8. Successful detection of these nitrophenols in the water and soil samples was performed with relative standard deviations of 1.1–5.9% and recoveries of 95–108% of spiked standards. Graphical abstract fx1 Highlights • Fluorescent components were isolated from caramel through dialysis in high yield. • The fluorescent components are dehydrated oligomers of carbohydrates. • Simultaneous detection of nitrophenols in water and soil samples was achieved. [ABSTRACT FROM AUTHOR]

Abstract A dual-functional fluorescent probe based on coumarin fluorophore for monitoring ClO− and Cu2+ was synthesized and characterized. The identification mechanisms for ClO− and Cu2+ induced different colorimetric and ratiometric changes. ClO− caused a colorimetric change from yellow to colorless and 120 nm blue-shifted emission spectra from red to blue. Besides, Cu2+ induced a remarkable fluorescence quenching behavior and 36 nm blue-shifted absorption spectra accompanied by the color change from yellow to luminous yellow. As expected, Probe 1 displayed excellent selectivity and sensitivity for detecting ClO− and Cu2+ over other competing ions in their respective systems. The limits of detection for ClO− and Cu2+ were 24.62 nM and 0.39 nM, respectively. The recognition mechanisms were proved by 1H NMR, mass spectrum and theoretical calculations. More importantly, the reversibility of Cu2+ could be applicable to rapid quantification for ClO−/Cu2+. Thus, the strategy for sensing ClO−/Cu2+ was carried out, which revealed broad applications of Probe 1 in multiple actual water and biology. Graphical abstract Unlabelled Image Highlights • A novel coumarin-based fluorescent probe for multiple ions was achieved. • The probe can distinguish ClO− and Cu2+ in different mixed solutions by adjusting the cyclic reversibility of Cu2+. • The probe showed rapid responses for ClO− and Cu2+ in multiple real water with high sensitivity and selectivity. • The probe can be used to monitor exogenous ClO− and Cu2+ in organisms. [ABSTRACT FROM AUTHOR]

In this study, we report on the syntheses of novel angular fused azaacenes. For this purpose, the synthesis of the bis-diamine 2 (TABEF) could be shortened and optimized. The condensation reaction of 2 with different types of 1,2-diketones yielded new azaacene derivatives of types 10, 11 and 12. Analogously, 2 was cyclized with thionyl chloride to give the piazthiol derivative 13. The optical and electrochemical properties of all new compounds were investigated by UV/Vis absorption, fluorescence emission spectroscopy and cyclovoltammetric measurements. [ABSTRACT FROM AUTHOR]

A fluorescent probe for protease sensing and based on the “covalent-assembly” principle is reported. The basic rational for this unusual class of chemodosimeters proposed by the Anslyn and Yang groups entails the synthesis of non-fluorophore caged precursors full-stable and reactive towards the targeted analyte. Unlike the first generation of protease-sensitive “covalent-assembly” type probes recently published by ourselves ( Org. Biomol. Chem. 2017 , 15 , 2575–2584), the availability of dicyanomethylidenyl and enzyme-labile phenylacetamide moieties within the core structure of mixed bis-aryl ether 2 enables its rapid conversion into a fluorescent pyronin dye at physiological pH and upon activation with penicillin G acylase (PGA). This is real progress towards the practical implementation of this ingenious activation mechanism to the detection of enzymes in their native environment ( in cellulo or in vivo ). [ABSTRACT FROM AUTHOR]

A set of new oxazol-5-one fluorophores incorporating ethylene glycol chains terminated with an aldehyde unit has been synthesized and characterized structurally. Two pairs of compounds can be distinguished according to the substitution on the oxazol-5-one moiety: one pair bears a tolyl unit and the other a nitrophenyl unit. The difference within the pairs is the length of the ethylene glycol chain. The evaluation of absorption and emission properties of the new oxazol-5-one derivatives was carried out in seven different solvents of varying polarity, which showed intense absorption maxima at 384–418 nm and emission maxima at 430–607 nm, respectively. The solvatofluorism study of 3a and 3c revealed that their emission wavelengths are very sensitive to solvent polarity and are red shifted in polar solvents. 3a and 3c fluorophores exhibited high Stokes shift values between 4158 and 7921 cm − 1 . [ABSTRACT FROM AUTHOR]

Two novel organic fluorophores, containing bis-naphthylamide and quinoline motifs, have been designed and synthesized. One of the fluorophores contains an isobutylene unit and exhibits a significant aggregation-induced emission (AIE) and a remarkable highly selective ratiometric fluorescence response towards Zn2+ in solution as well as in human liver cancer cells. The AIE behavior of this fluorophore was fully verified by fluorescence and UV/Vis spectroscopy, quantum yield calculations, and single-crystal X-ray diffraction, which revealed an intricate crystal packing system. Conversely, a fluorophore that lacks the isobutylene moiety did not exhibit any significant fluorescent properties as a result of its more flexible molecular structure that presumably allows free intramolecular rotational processes to occur. [ABSTRACT FROM AUTHOR]

Four acenaphtho[1,2-k]fluoranthene-cored fluorophores 1-4 attached by a variety of N-containing electron-donating groups have been designed and synthesized. The appending N-containing moieties and the central acenaphtho[1,2-k]fluoranthene core form twisted molecular configurations and lead to separated HOMO and LUMO frontier molecular orbitals. X-ray crystallographic analysis demonstrates that the substituted aromatic amines separate the luminescent π-conjugated cores in the solid state. These compounds display excellent thermal and amorphous stabilities, high solid-state fluorescence quantum efficiencies, and ambipolar charge transporting properties, indicating that they are ideal candidates for fabricating non-doped organic light-emitting diodes (OLEDs). The device based on compound 4 exhibits the best electroluminescent performance with an external efficiency of 2.82% and brightness of 45800 cdm-2, demonstrating the potential applications of this compound for OLED displays and lighting. [ABSTRACT FROM AUTHOR]

Unimolecular submersible nanomachines (USNs) bearing light-driven motors and fluorophores are synthesized. NMR experiments demonstrate that the rotation of the motor is not quenched by the fluorophore and that the motor behaves in the same manner as the corresponding motor without attached fluorophores. No photo or thermal decomposition is observed. Through careful design of control molecules with no motor and with a slow motor, we found using single molecule fluorescence correlation spectroscopy that only the molecules with fast rotating speed (MHz range) show an enhancement in diffusion by 26% when the motor is fully activated by UV light. This suggests that the USN molecules give ~9 nm steps upon each motor actuation. A non-unidirectional rotating motor also results in a smaller, 10%, increase in diffusion. This study gives new insight into the light actuation of motorized molecules in solution. [ABSTRACT FROM AUTHOR]

Carboxylic acid substituted fluorescein derivatives were synthesized from 2,4-dihydroxy carboxylic acid and phthalic anhydride or trimellitic anhydride. The photophysical properties like absorption, emission and fluorescence quantum yields of these fluorophores were studied. The conjugation studies of these fluorophores with different proteins at different concentrations were carried out. The effect of pH on photophysical properties was studied at different pH ranges from 5 to 12. The change in the absorption and emission with respect to viscosity of medium was also studied. The changes in the electronic transition, energy levels, and orbital diagram of the fluorescein derivatives were computed using the TD-DFT computations and co-related with experimental photophysical data. [ABSTRACT FROM AUTHOR]

A series of electronically dissymmetric all-organic macrocycles were synthesized using straightforward synthetic procedures. These macrocycles vary in the nature of the substituents, the geometry of the linkage that connects the electron-deficient aromatic ring, the type of linkage, and the presence or absence of a heteroaromatic ring. These small structural variations impart significant differences in the performance of these macrocycles in binding benzo[ a]pyrene, with binding constants up to 2.5 × 104 M-1 obtained. They also lead to significant differences in their ability to promote non-covalent energy transfer from benzo[ a]pyrene to a BODIPY fluorophore, with energy transfer efficiencies ranging from 32 % to 398 %. These differences can be explained using a variety of computational investigative techniques, which highlight the flexibility of the macrocycle architectures to accommodate benzo[ a]pyrene and to promote close donor-acceptor interactions. [ABSTRACT FROM AUTHOR]

The endoplasmic reticulum (ER) plays critical roles in the processing of secreted and transmembrane proteins. To deliver small molecules to this organelle, we synthesized fluorinated hydrophobic analogues of the fluorophore rhodol. These cell-permeable fluorophores are exceptionally bright, with quantum yields of around 0.8, and they were found to specifically accumulate in the ER of living HeLa cells, as imaged by confocal laser scanning microscopy. To target a biological pathway controlled by the ER, we linked a fluorinated hydrophobic rhodol to 5-nitrofuran-2-acrylaldehyde. In contrast to an untargeted nitrofuran warhead, delivery of this electrophilic nitrofuran to the ER by the rhodol resulted in cytotoxicity comparable to the ER-targeted cytotoxin eeyarestatin I, and specifically inhibited protein processing by the ubiquitin-proteasome system. Fluorinated hydrophobic rhodols are outstanding fluorophores that enable the delivery of small molecules for targeting ER-associated proteins and pathways. [ABSTRACT FROM AUTHOR]

Light-activatable drugs offer the promise of controlled release with exquisite temporal and spatial resolution. However, light-sensitive prodrugs are typically converted to their active forms using short-wavelength irradiation, which displays poor tissue penetrance. We report herein erythrocyte-mediated assembly of long-wavelength-sensitive phototherapeutics. The activating wavelength of the constructs is readily preassigned by using fluorophores with the desired excitation wavelength λex. Drug release from the erythrocyte carrier was confirmed by standard analytical tools and by the expected biological consequences of the liberated drugs in cell culture: methotrexate, binding to intracellular dihydrofolate reductase; colchicine, inhibition of microtubule polymerization; dexamethasone, induced nuclear migration of the glucocorticoid receptor. [ABSTRACT FROM AUTHOR]

Herein we report on the synthesis and acid-responsive emission properties of donor-acceptor (D-A) molecules that contain a thienothiophene unit. 2-Arylthieno[3,2-b]thiophenes were conjugated with an N-methylbenzimidazole unit to form acidresponsive D-A-type fluorophores. The D-A-conjugated fluorophores showed intense intramolecular chargetransfer (ICT) emission in response to acid. The effect of the substitution on their photophysical properties as well as their solvent-dependence indicated non-twisting ICT emission in protonated D-A molecules. The quinoidal character of 2-arylthienothiophene as a donor part is discussed, as it is assumed that it contributes to suppression of the molecular twisting in the excited state, therefore decreasing the nonradiative rate constant, thereby resulting in the intense ICT emission. Acid-base-sensitive triple-color emission was also achieved by the introduction of a base-responsive phenol group in the donor part. [ABSTRACT FROM AUTHOR]

Lactosyl ceramide analogues carrying novel bifunctional BODIPY-based fluorescent tags were designed and synthesised for live cell imaging. Addition of azide functionality on the fluorophore facilitated isobaric tagging for quantitative multiplexed analysis of biomolecules based on tandem mass spectrometry. [ABSTRACT FROM AUTHOR]

Nine L-shaped benzimidazole fluorophores have been synthesized, computationally evaluated and spectroscopically characterized. These “half-cruciform” fluorophores respond to bases, acids and anions through changes in fluorescence that vary from moderate to dramatic. [ABSTRACT FROM AUTHOR]

Review: [48 refs. [ABSTRACT FROM AUTHOR]