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Herein, a new water soluble Ca 2+ fluorescence chemosensor based on aggregation-induced emission (AIE) characteristics has been developed, combining the AIE effect of tetraphenylethylene (TPE) and the complexation capability of bidentate pyridine carboxylate. The bidentate pyridine carboxylate group provides the chemosensor with good water-solubility which is important for detection in biological systems. This chemosensor L showed high selectivity for Ca 2+ by a turn-on response in almost pure aqueous solution with a detection limit of 51.2 nM. L can be used as a recyclable Ca 2+ fluorescent chemosensor in the presence of EDTA. Moreover, the chemosensor L was successfully applied to imaging detection and real-time monitoring of Ca 2+ in living cells with low toxicity and good membrane permeability. [ABSTRACT FROM AUTHOR]

A series of boronic acid derived salicylidenehydrazinopyridine complexes have been synthesized from the condensation of 2-hydrazinopyridine or 2-hydrazinoquinoline and salicylaldehyde then followed by complexation with various boronic acids. Their X-ray structures demonstrate that the boron atoms adopt a tetrahedral geometry and the aryl substituents from arylboric acids along the vertical axis gave the molecule stereotactic structure and induced molecular chirality. These dyes have good solubility on organic solvents due to the nonplanar curved structure and the presence of axial-substituted groups that provide steric protection. They have strong visible-light absorption, weak emission and large Stoke shifts in organic solvents. Interestingly, molecular aggregates of these new boron complexes experienced the transformation from H -type aggregation to J- type aggregation and exhibited strong aggregation-induced emission (AIE) activities. These novel AIE dyes showed great potential as bioimaging dyes, and two complexes were mainly distributed in lipid droplets of cells in colocalization experiments. [Display omitted] • New boron complexed fluorophore (BOSPY) has been developed from various arylboric acids. • Molecular chirality of these dyes after boron complexation was confirmed by X-ray structures. • These dyes exhibit strong aggregation-induced emission (AIE). • These AIE dyes are suitable for fluorescence imaging and two dyes can specifically localize in lipid droplets of cells. [ABSTRACT FROM AUTHOR]

Abstract: A turn-on fluorescent probe DNBS-CSA is reported here with selective detection of thiols over other amino acids. Probe DNBS-CSA possesses the widely-used thiol-selective 2,4-dinitrobenzenesulfonyl (DNBS) group to react with thiols and release the fluorescent salicylaldehyde azine with aggregation-induced emission (AIE) characteristics. The use of AIE dye prevented the sensor from aggregation-induced fluorescence quenching which is challenging for other thiols sensors. Upon the addition of cysteine (Cys) to DNBS-CSA in aqueous solution (10 mM PBS buffer at pH 7.4 containing 30% DMSO), an intense fluorescence enhancement was observed at 558 nm with a large stokes shift of ∼170 nm. Under the optimal condition, the fluorescence intensity linearly increased with the concentration of Cys in the range of 8–18 μM with a correlation coefficient of R 2 = 0.991. The fluorescence enhancement of DNBS-CSA upon addition of Cys on test paper was also observed, enabling DNBS-CSA function as solid materials (such as test papers) for thiols detection. The detection of thiols in serum samples was successfully performed. With good cell permeability, the probe was applied to the imaging of thiols in HEK 293T cells. [Copyright &y& Elsevier]

Organic materials with strong solid-state fluorescence and sensitive stimuli responsiveness are highly desired for both fundamental research and practical applications. We report herein an azabenz-annulated perylenediimide (AzaBPDI)-based dye, AzaBP-TPE, which contains tetraphenylethene units in the planar aromatic structure. AzaBP-TPE undergoes typical intramolecular charge transfer, aggregation-induced emission, and mechanochromic fluorescence. In the solid state, AzaBP-TPE emits bright-yellow light with a photoluminescence quantum yield of 27%, and this emission becomes red fluorescence when MCF is induced, by using mechanical force to collapse the crystalline structure. Moreover, bright-yellow fluorescence can be recovered by exposing AzaBP-TPE powder to chloroform vapor. Notably, AzaBP-TPE nanoparticles can penetrate live cells and emit red light and, therefore, can be applied as a functional dye in bio-imaging. [Display omitted] • A novel azabenz-annulated perylenediimide-based dye, AzaBP-TPE was developed. • AzaBP-TPE exhibits typical AIE and reversible MCF in the solid state. • Good biocompatibility indicates AzaBP-TPE a potential functional dye for cell-imaging. [ABSTRACT FROM AUTHOR]

Various aggregation-induced emission luminogen (AIEgen) derivatives based on TPE (tetraphenylethylene) containing the electron-donating moiety (–NMe 2 , –OMe) and bromine (–Br) moiety were prepared, which are key intermediates for tuning the emission wavelength of TPE; Type 1: dimethylamine (NMe 2)-substituted derivatives, Type 2: methoxy (OMe)-substituted derivatives, Type 3: bromine (Br)-substituted derivatives, and Type 4: mixed formulation derivatives. We systematically analyzed the synthesis, AIE properties, photophysical properties, and biological applicability of 16 types of TPE-based AIEgen. We expect that our investigation, especially the donor-substitution effect of TPE, could serve as a guide to developing a new TPE-based AIEgen series as well as fluorescent probes. [Display omitted] • Donor-substitution effect of tetraphenylethylene (TPE) AIEgens was systematically identified. • Synthesis and photophysical property of 16 derivatives of TPE was disclosed. • CLSM imaging of cells using the TPE derivatives was demonstrated. [ABSTRACT FROM AUTHOR]

In the paper, a novel aggregation-induced emission (AIE) target molecule derived from rhodamine 6G hydrazine and tetrastyrene carbaldehyde was synthesized and characterized. And the single crystal was obtained by high boiling solvent volatilization (DMF/H 2 O) method, which is the first reported analogous compound single crystal. Inside the crystal structure, the limited benzene ring spinning was observed. By the change of pH, the special spiro structure opened, simultaneously, the fluorescence resonance energy transfer process (blue to orange yellow fluorescence, colorless to pink) between tetrastyrene and rhodamine 6G occurred. So the AIE target molecule can be used as an effective fluorescence and color probe for detecting H+ (pH). Additionally, the cell fluorescence imaging experiment proved potentially that the AIE target molecule could detect the change of pH in organism. Moreover, the FRET sensing mechanism was concluded by fluorescence spectra and DFT calculation. Such studies provided important ideas for pH sensor based on AIE molecule. • A novel aggregation-induced emission (AIE) target molecule derived from rhodamine 6G group was synthesized. • The AIE molecule exhibited color and fluorescence sensing property for H+. • The fluorescence sensing mechanism was concluded by DFT calculation. [ABSTRACT FROM AUTHOR]

Four novel yellow-to red-emitting fluorophores with a 1-(2-hydroxyethyl) pyridinium core and different electron-donating terminal moieties (N -methylcarbazole, N , N -dibutylbenzenamine, N -methylpyrrole, and 2-methylfuran) were designed and facilely synthesized via the one-step Knoevenagel condensation. All these compounds (HPs) were characterized by 1H NMR, 13C NMR, and HRMS. Their photophysical properties including linear absorption, one-photon excited fluorescence, two-photon absorption, and two-photon excited fluorescence, were systematically investigated in various solvents. And the density functional theory calculations were conducted to analyze the electronic structures of HPs. The two-photon absorption cross-sections (δ) values of HPs measured by the Z-scan technique were determined to be as large as 1354 (1HP-CZ), 4462 (2HP-BA), 836 (3HP-PR), and 2944 GM (4HP-FU) in DMSO. The two-photon action cross-sections (Φ × δ) values of 1HP-CZ and 2HP-BA in H 2 O measured by the two-photon induced fluorescence method were about 50 GM. 1HP-CZ , 3HP-PR , and 4HP-FU also exhibited good water solubility. Meanwhile, it was found that 2HP-BA exhibited notable aggregation-induced emission characteristic in DMSO/H 2 O mixture. The aggregate particle size distribution of 2HP-BA was measured by the dynamic light scattering method, and the aggregation characteristic of 2HP-BA was observed by the transmission electron microscopy. Besides, 2HP-BA also exhibited red emission. Then, HPs with relatively low cytotoxicity were used for one- and two-photon excited fluorescence imaging in living HepG2 cells. The results indicate that HPs are potential candidates in the bioimaging field due to their photophysical properties and biocompatibility. Image 1 • Four novel fluorophores with pyridinium core were synthesized and characterized. • Their TPA cross-sections values in DMSO range from 836 to 4462 GM. • 2HP-BA exhibits AIE characteristic and red emission. • Their two-photon action cross-sections values in H 2 O range from 11 to 54 GM. • They have been successfully applied for OPEF and TPEF imaging in living cells. [ABSTRACT FROM AUTHOR]