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Five novel dual-state emissive imidazo[1,2- α ]pyridine-based luminogens IP1-5 were rationally designed and prepared by varying the conjugation length and the nature of donor-acceptor (D-A) units. These D-A chromophores displayed cyan, green, yellow, and red fluorescence in the solid state, with full-color emission achieved for the first time through modification of imidazo[1,2- α ]pyridine core. Interestingly, IP1 and IP5 in the solid state exhibited an abnormal remarkable blue-shift emission compared with those in THF, probably due to the highly twisted molecular conformations and solvent effect by theoretical calculations as well as crystal structure analyses. Importantly, IP1-5 revealed remarkable reversible acid-induced acidichromism, accompanied with dual change of colorimetric and fluorometric determination. Viscosity-dependent fluorescence was next conducted, indicting IP1-3 can be utilized for local viscosity detection. Moreover, IP1-5 served as promising candidates for multicolor bioimaging with low cell toxicity and good biocompatibility. Five asymmetric donor-acceptor dual-state emissive imidazo[1,2- ɑ ]pyridines have been synthesized with full color emission acidichromism, viscosity-dependent fluorescence, and biological imaging. [Display omitted] • Five DSE fluorophores IP1-5 based on carbonyl-substituted imidazo[1,2- α ]pyridine have been synthesized and characterized. • IP1-5 exhibited full color solid emission through manipulation of D-A electronic structures and conjugation length. • IP1-5 displayed reversible acidochromism and bioimaging applications with excellent biocompatibility and cell permeability. • IP1-3 showed viscosity-dependent fluorescence with application as potential viscosity sensors. [ABSTRACT FROM AUTHOR]

It is highly demanded and challenging to develop small-molecular fluorescent sensors for the ratiometric detection of pH fluctuation. A ratiometric fluorescent pH sensor was constructed by integrating a pH-sensitive fluorophore with a pH-insensitive hemicyanine group. Its linear and reversible ratiometric fluorescent response from pH 7.0 to 8.8 and 6.0 to 9.0 respectively makes this sensor suitable for the practical tracking of pH fluctuation in live cells. With this sensor, stimulated pH fluctuation has been successfully tracked in a ratiometric manner via fluorescence imaging with low dark toxicity. [ABSTRACT FROM AUTHOR]

Triphenylphosphonium (TPP) cations endow fluorophores with improved hydrophilicities and mitochondria targeting abilities. Evidently, the number of cationic moieties can influence the behavior of fluorophores in different environments. Two water-soluble BODIPY fluorophores, 3TPP and 5TPP , were constructed with three and five TPP groups, respectively, in their structure. Both showed maximum absorption and emission at 640–700 nm wavelengths; however, 5TPP showed a fluorescence quantum yield 10 times higher than that of 3TPP in an aqueous medium, highlighting the beneficial effect of two additional TPP groups on the photophysical properties. While both fluorophores showed excellent stabilities and mitochondrial imaging abilities with low cytotoxicities in HeLa and MCF-7 cells, 5TPP permeated into the mitochondria better than 3TPP. Interestingly, 5TPP demonstrated a 90-fold increase in "turn-on" fluorescence in the presence of bovine serum albumin (BSA) in relation to that of four other proteins (i.e., lysozyme, esterase, transferrin, and fibrinogen). Notably, the fluorescence intensity of 5TPP increased with increasing BSA concentration. The present work is the first report on BODIPY sensors with multiple bulky cationic moieties and provides insights on the applicability of 5TPP as a novel biomaterial for mitochondrion tracking and light-up fluorescence protein sensing. • BODIPY-based fluorophores, 3TPP and 5TPP , were conjugated with three and five (triphenylphosphonium) TPP groups, respectively. • Both fluorophores showed excellent photostabilities and mitochondrial imaging abilities with low cytotoxicities in HeLa and MCF-7 cells. • 5TPP exhibited a 90-fold increase in "turn-on" fluorescence in the presence of bovine serum albumin (BSA) with respect to that of four other proteins (i.e., lysozyme, esterase, transferrin, and fibrinogen). [ABSTRACT FROM AUTHOR]

A new highly selective and sensitive chemosensor 1 for both Al 3+ and F − was designed and synthesized. 1 could detect both Al 3+ and F − with turn-on fluorescence behavior in a nearly perfect aqueous solution. The binding stoichiometry of receptor 1 with Al 3+ and F − was proposed to be 1:1, respectively, based on Job plot, 1 H NMR titration and ESI-mass spectrometry analysis. The detection limits (1.12 μM for Al 3+ and 7.01 μM for F − ) of 1 for Al 3+ and F − were lower than the World Health Organization guidelines (7.41 μM for Al 3+ and 79 μM for F − ) for drinking water. Chemosensor 1 was also successfully applied to living cells for simultaneous detection and quantification of both Al 3+ and F − . Moreover, the sensing mechanisms of 1 toward Al 3+ and F − were explained by theoretical calculations. [ABSTRACT FROM AUTHOR]

In this work, two new hybrid benzothiadiazole-coumarin derivatives have been designed and applied as selective live cell fluorescence imaging probes. The developed dyes had their photoproperties evaluated and proved to be stable emitters. DFT calculations have been used to shed some light on the photophysical properties observed for both fluorophores and explained the obtained data. The lipophilic structures selectively stained the plasma membrane of both live and fixed cells of several tumoral and healthy lineages. Comparison of the novel hybrid fluorogenic dyes with the commercially available CellMask proved the preference for plasma membrane staining of the dyes. Finally, zebrafish embryos have been used as complexes models and these embryos were selectively stained, thus indicating the advantages of the hybrid dyes also for multicellular staining in comparison with the commercial dye. Image 1 • Hybrid benzothiadiazole-coumarin based fluorophores were synthesized. • DFT calculations shed light over the photophysical properties of the compounds. • Fluorescent bioprobes were developed and tested at cellular level. • Multicellular staining tests were performed. • Selective for plasma membrane staining assays. [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]