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The fluorescent probe is constructed by incorporating an α, β-unsaturated pyridinium to a pyrene fluorophore. The chemodosimeter has shown a selective and sensitive response to sulfite anion over other various anions and biological thiol through a Michael addition of the sulfite to the alkene of the probe. Meanwhile, it can be easily observed that the color of the probe for sulfite changes from yellow to colorless by the naked eye, and from yellow to blue under UV lamp immediately after the sulfite is added.

G-quadruplex DNA plays a very important role in clinical diagnosis and fluorescence analysis has attracted extensive attention. A class of carbazole-based fluorescent probes for the detection of G-quadruplex DNA was established in this work. In this system, the installation of an oligo(ethylene glycol) chain on the scaffold will improve the water-solubility and biocompatibility. The presence of styrene-like different side groups could tune the selectivity toward G-quadruplex DNA binding. Results revealed that the substitution pattern and position gave a great influence on the ability for the discrimination of the G-quadruplex from other DNA structures. Especially, probe E1 bound to G-quadruplex DNA with superior selectivity, which exhibiting almost no fluorescence response in the presence of non-G-quadruplex DNA structures. Comprehensive analyses revealed that E1 could bind both ends of the G-quadruplex, resulting in a significant increase of fluorescence emission intensity. Cellular uptake assay suggested that E1 could pass through membrane and enter living cells with low cytotoxicity.

Herein we report simple pyridinium (1–3) and quinolinium (4) salts for the selective recognition of G-quadruplexes (G4s). Among them, the probe 1, interestingly, selectively discriminated parallel (c-KIT-1, c-KIT-2, c-MYC) G4s from anti-parallel/hybrid (22AG, HRAS-1, BOM-17, TBA) G4s at pH 7.2, through a switch on response in the far-red window. Significant changes in the absorption (broad 575 nm → sharp 505 nm) and emission of probe 1 at 620 nm, attributed to selective interaction with parallel G4s, resulted in complete disaggregation-induced monomer emission. Symmetrical push/pull molecular confinements across the styryl units in probe 1 enhanced the intramolecular charge transfer (ICT) by restricting the free rotation of C[dbnd]C units in the presence of sterically less hindered and highly accessible G4 surface/bottom tetrads in the parallel G4s, which is relatively lower extent in antiparallel/hybrid G4s. We confirm that the disaggregation of probe 1 was very effective in the presence of parallel G4–forming ODNs, due to the presence of highly available free surface area, resulting in additional π-stacking interactions. The selective sensing capabilities of probe 1 were analyzed using UV–Vis spectroscopy, fluorescence spectroscopy, molecular dynamics (MD)–based simulation studies, and 1H NMR spectroscopy. This study should afford insights for the future design of selective compounds targeting parallel G4s.

An efficient Pd-catalyzed arylation of alkylpyridine based on the pyridinium activation strategy has been developed for synthesis of mixed aryl alkylpyridines. It was found that (1) the N-methyl group in the pyridinium salts acted as a transient activator and could be automatically departed after the reaction, (2) CuBr was an indispensable additive for achieving the C6-selective arylation, (3) the α-branched alkyl chain on the alkylpyridine greatly increased the yield of the product. Deuterium labelling experiment revealed that in the case of the α-branched alkylpyridine, the presence of CuBr completely inhibited the H/D exchange at the benzylic position and thus enabled the selective arylation at the C6 position. This protocol demonstrates a broad substrate scope, and with respect to both the aryl iodides and the α-branched alkylpyridine, the desired mixed aryl alkylpyridines were obtained in generally good to excellent yields.

The first Pd/Cu catalyzed selective C2-alkenylation of pyridines with internal alkynes has been developed via the pyridinium salt activation strategy. Importantly, the configuration of the product alkenylpyridines could be tuned by the choice of the proper N-alkyl group of the pyridinium salts, thus allowing for both the Z- and E-alkenylpyridines synthesized with good regio- and stereoselectivity. A plausible mechanism was proposed based on the Hammett study and KIE experiment.

Activatable molecular probes hold great promise for targeted cancer imaging. However, the hydrophobic nature of most conventional probes makes them generate precipitated agglomerate in aqueous media, thereby annihilating their responsiveness to analytes a

Cyanine compounds have previously shown excellent in vitro and promising in vivo antileishmanial efficacy, but the potential toxicity of these agents is a concern. A series of 22 analogs of thiazole orange ((Z)-1-methyl-4-((3-methylbenzo[d]thiazol-2(3H)-ylidene)methyl)quinolin-1-ium salt), a commercial cyanine dye with antileishmanial activity, were synthesized in an effort to increase the selectivity of such compounds while maintaining efficacy. Cyanines possessing substitutions on the quinolinium ring system displayed potency against Leishmania donovani axenic amastigotes that differed little from the parent compound (IC50 12–42 nM), while ring disjunction analogs were both less potent and less toxic. Changes in DNA melting temperature were modest when synthetic oligonucleotides were incubated with selected analogs (ΔTm ≤ 5 °C), with ring disjunction analogs showing the least effect on this parameter. Despite the high antileishmanial potency of the target compounds, their toxicity and relatively flat SAR suggests that further information regarding the target(s) of these molecules is needed to aid their development as antileishmanials.

During a formation of four mixed hybrid halobismuthates (two of them have new structures) from solutions containing both Br? and I? ions, solid products enriched with iodine were isolated. Either oxidation or drying of mother liquors resulted in products with even higher iodine contents, up to pure iodobismuthates. All the compounds were characterized by a set of comprehensive methods (NMR, X-ray, DRS, etc.).

First anion···π contacts with quinoid rings have been described in novel co-crystals of tetrabromo- and tetrachloroquinone with iodide salts of substituted N-methylpyridinium cations. In seven crystal structures of these co-crystals, a centrosymmetric unit I-···quinone···I- is observed involving close contacts between iodide anions and electron-depleted carbon skeletons of the quinoid rings. However, the salt with N-methyl-4-methylcarboxypyridinium base crystallizes in two polymorphs characterized by O=C···quinone···C=O interaction instead of I-···quinone···I- one. A possible charge transfer, suggested by the black color of the crystals, is probed by solid-state NMR and IR spectroscopies and analyzed by DFT calculations.

Photochemical reactivity of a series of picolines and their N-methylated salts has been investigated by preparative irradiations and UV–vis spectroscopy. Understanding competing photochemical processes and knowledge of their relative efficiencies is important in the application of pyridines as photocages or in the synthesis of complex polycycles. Contrary to previous reports for the gas phase, picolines are not reactive in the phototransposition, presumably due to protonation of the pyridine nitrogen in the excited state. Deuterium exchange was observed upon irradiation in CD3CN–D2O, but it was rationalized by photoionization and radical formation. On the other hand, N-methylated picoline salts are not protonated upon excitation. They undergo photohydration and phototransposition (ΦR?=?0.01–0.06). Upon irradiation of iodides, azabicyclic [3.1.0] hydration products were obtained. A difference in product distribution was observed between iodides and perchlorates, due to photoelimination of perchloric acid leading to the thermal aziridine ring opening. Moreover, excitation of iodide derivatives gives rise to change transfer transition forming iodide radicals that eventually give I3 ? with the quantum efficiency ΦR?=?0.015–0.02.

A series of dimethine cyanine dyes, used as fluorescent probes, were synthesized under microwave irradiation, and identified by 1H NMR, IR, elemental analysis and HRMS. The investigation of their spectral properties in phosphate-buffer saline (PBS) showed that the absorption and emission maxima of the dyes were in the region 370-480 nm and 471-569 nm, respectively. The properties of the dyes as fluorescent probes for living cells imaging and flow cytometry were investigated. The results showed that dyes 1, 2, 8 or 9 could penetrate an intact cell membrane, stained the cell nuclear and exhibited bright fluorescence. Little background interference, low cell cytotoxicity and little photobleaching were showed during the imaging tests. The dyes 1, 8 and 9 could be applied in flow cytometry and dye 1/PI, dye 8/PI or dye 9/PI couple could be proposed as double staining agents to measure sperm cell viability. Thus the dyes represented the cell-permeant fluorescent probes.

Optically transparent crystal of the organic salt DEASI (2-[2-(4-Diethylamino-phenyl)-vinyl]-1-methyl-pyridinium iodide) has been synthesized by using knoevenagel condensation reaction method. The synthesized material has been purified by successfully recrystallization process. Single crystals of DEASI have been grown by slow evaporation technique at room temperature. The solubility of the title material has been determined at different temperature in acetonitrile/methanol mixture. The cell parameters and crystallinity of the title crystal were determined by single crystal XRD. The powder diffraction was carried out to study the reflection plane of the grown crystal and diffraction peaks were indexed. The presence of different functional groups in the crystal was confirmed by Fourier transform infrared (FTIR) analysis. 1H NMR spectrum was recorded to confirm the presence of hydrogen nuclei in the synthesized material. The optical property of the title crystal was studied by UV-Vis-NIR spectroscopic analysis. The melting point and thermal property of DEASI were studied using TGA/DSC technique. The Vicker's hardness (Hv) was carried out to know the category. The dielectric constant and dielectric loss of the compound decreases with an increase in frequencies. Chemical etching studies showed that the DEASI grows in the two dimensional growth mechanisms. The Kurtz-Perry powder second harmonic generation (SHG) test has done for title crystal.

Single crystals of organic optical material, 2-[2-(4-Diethylamino-phenyl)- vinyl]-1-methyl-pyridinium naphthalene-2-sulfonate (DESNS) (15 × 10 × 9 mm3) were grown by a slow evaporation technique at room temperature using methanol-acetonitrile (1:1) mixed solvent. The molecular structure of the grown crystal was confirmed by single crystal X-ray diffraction studies, and it belongs to orthorhombic system with space group Pbca and the unit cell dimentions are a = 11.5148(3) A?, b = 15.4352(4) A?, c = 27.2187(7) A?, Z = 8. The crystallinity of the title crystals was confirmed from the powder XRD pattern. The presence of functional groups of the title crystal was confirmed from the FTIR spectral studies. The transparent range and cut off wavelength of the grown crystal was studied by the UV-Vis-NIR spectroscopic analysis. The mechanical properties and thermal behavior of the grown crystals were studied from Vickers microhardness test and TG/DTA.

1-Alkyl-2-[4-(diethylamino)styryl]pyridinium salts showed fluorescence maxima at around 650 nm in the solid state depending on the alkyl group and counter anion. 1-Butyl-2-[4-(diethylamino)styryl]pyridinium bis(perfluorobutylsulfonyl)imide exhibited the fluorescence maximum at 652 nm with the highest quantum yield 0.16 in the crystalline form. The single X-ray crystallography suggests that this compound exhibits isolated dimer-type packing leading to fluorescence in the solid state.

The absorption and fluorescence spectroscopic responses of three pyridinium hemicyanine dyes to anions F-, Cl-, Br-, I-, H2PO4-, HSO4 - and OAc- were investigated. At lower concentrations of OAc- (less than 1 equiv.), both the absorption and the fluorescence intensities of 1-3 were more effectively changed than F- at identical concentrations. At higher concentrations of OAc- (more than 1 equiv.), the interaction was opposite for each compound. 1H NMR results indicated the interaction between 1, 2 or 3 and F- proceeded through hydrogen bonding. The results showed that these dyes are promising to develop dual fluorescence and chromogenic chemosensors toward F- and OAc- according to the subtle difference in the affinity of F - and OAc-. Pyridinium hemicyanine dyes bearing hydroxyl groups on the benzene ring provide a simple class of anion receptors which are capable of selectively reporting the presence of F- and OAc - in CH3CN by color changes. Copyright

A pyridylvinylene derivative containing piazselenole displayed high selectivity toward glutathione in the presence of other biorelevant analytes. The compound exhibited a 19?nm red-shift in absorption spectra and ～3-fold fluorescence intensity enhancement; in addition, it was possible to detect micromolar amounts of glutathione quantitatively using both red-shift absorbance and enhanced fluorescence. The mechanism of the reaction between the modified pyridylvinylene derivative and glutathione was confirmed using ESI-MS and absorption/fluorescence spectra.

Substituents on the pyridinium ring of N-methylpyridinium derivatives, especially those on the 2- or 4-position, have a large effect on the 1H and 13C NMR chemical shifts of the N-methyl group. Reasonable correlations between the chemical shift changes and the resonance substituent constants are observed. The dual substituent parameter approach provides an excellent correlation when a combination of polar and resonance substituent constants is employed.

We report here a synthesis of a new rhodacyanines 7X analogous to MKT-077 with quantitative yield using as starting material the thiazolinethione 1. Merocyanines 4 and their tosylates 5 have been prepared as intermediates for this class of compounds. The reactions leading to rhodacyanine 7X have been studied under microwave irradiation. Copyright Taylor & Francis Group, LLC.

The present invention relates to new styrylpyridinium-imine based dyes and their use in optical layers for optical data recording, preferably for optical data recording using a laser with a wavelength up to 500 nm. The invention further relates to a write

The present invention relates to the use of bis-styryl dyes in optical layers for optical data recording, preferably for optical data recording using a laser with a wavelength up to 450 nm. The invention further relates to a write only read many (WORM) ty

The first fluorescent styryl dye library with a broad color range was synthesized by combinatorial condensation of various aldehydes and methyl pyridinium compounds, and their applications as organelle specific staining probes were demonstrated. Copyright

A series of 1-methyl-2-(4-aminostyryl)pyridinium perchlorates and iodides were investigated as fluorescent probes for the monitoring of the progress of free radical polymerization. The study on the changes in the fluorescence intensity and spectroscopic shifts of studied compounds were carried out during thermally initiated polymerization of methyl methacrylate and during photoinitiated polymerization of a 2-ethyl-2-(hydroxymethyl)propane-1,3-diol triacrylate (TMPTA)-1-methylpyrrolidin-2-one (MP) mixture. The purpose of these studies was to find a relationship between the changes in the shape and intensity of probe fluorescence and degree of monomer conversion into polymer. The polymer formation was estimated gravimetrically or by the measurement of the degree of monomer double bond disappearance using FTIR spectroscopy.

The enamine-type methylene-N-heterocycles 1-5 react with cyclic 2-ethoxymethylene-1,3-dicarbonyl compounds 6 to give 2--1,3-dicarbonyl componds 7-14.The result of the reactions between 1,2-dihydro-1-methyl-2-methylene-quinoline (1a) and cyclic 1,3-dicarbonyl compounds depends on the nature of the dihydro intermediates A/B.Dehydrogenation of keton intermediates A results in 2-(1,2-dimethyl-4(1H)-quinolylidene)-1,3-dicarbonyl compounds 17-21.Enol intermediates B with 6-membered dicarbonyl ring form 6,12-methano-dibenzoxazocinones 22-25. 1H NMR spectra and X-ray structure analysis prove the structure of 23. - Keywords. 2--1,3-dicarbonyl compounds; 2-(1,2-Dimethyl-4(1H)-quinolylidene)-1,3-dicarbonyl compounds; 6,12-Methano-dibenzoxazocinones; X-ray analysis.

The synthesis of 1-aza-3-nitroso-2-phenylpyrrocoline (1) has been described.The unusual absorption data of the dyes derived from the condensation of 1-aza-3-nitroso-2-phenylpyrrocoline and N-phenacyl-2-methyl- and N-phenacyl-2-amino-pyridine have been explained as arising out of cyclisation of product during the reaction.The influence of quaternising groups on the absorption the dyes synthesised from the nitrosoazapyrrocoline (1) has been discussed.

The effects of the shape of a methyl group on reactivity, which cannot be accounted for by considering a methyl group as a spherical subtituent with the appropriate van der Waals radius, was considered in kinetics of alkylation of substituted pyridines and barriers to rotation and ground state conformations of an isopropyl group attached to a planar framework.The perturbation of a methyl group by an o-methyl group is accounted for by a unique conformational explanation which involves the polyhedral shape of the methyl group.

The synthesis and NMR spectroscopic properties of some methyl-substituted 1-methyl-1,4-dihydropyridines are described.

1-Substituted-2- and -4-methylpyridinium cations are converted by pentyl or ethyl nitrite and sodium methoxide into 1-substituted-2- and -4-pyridones respectively.

The base catalysed rearrangements of the cations (7), (17), (22), and (27) gave the enamines (9), (18), (23), and (28), which on hydrolysis yielded the aldehyde (10), (19), (24), and (29) respectively.The reactions are shown to be concerted sigmatropic rearrangements proceeding via a nine-membered transition state involving 10? electrons.The base catalysed rearrangements of the 3-phenylprop-2-ynyl (pentadienyl) ammonium cations (51), (52), (60), and (61), however yield only the products of , , and sigmatropic rearrangements.