Pyridinium Dyes Research Articles

Labeling Hair Cells and Afferent Neurons in the Posterior Lateral-Line System of Zebrafish

The lateral line is a mechanosensory system that comprises a set of discrete sense organs called neuromasts, which are arranged in reproducible patterns on the surface of fish and amphibians. The posterior component of the system, the posterior lateral line, comprises the neuromasts on the body and tail. Each neuromast has a core of mechanosensory hair cells, each of which is depolarized by water motion in one direction and hyperpolarized by motion in the other direction, thereby enabling fish to extract information from the movements of water around their body. Neuromasts are innervated by a few afferent neurons (usually two, but sometimes more), which have their cell bodies clustered in cranial ganglia and project their central axons to the hindbrain, where they extend longitudinally along all rhombomeres. Hair cells are readily labeled by small cationic styryl pyridinium dyes such as DiASP. Afferent fibers are also progressively labeled with this dye, presumably by trans-synaptic uptake. Adjusting the dye concentration and incubation time can lead to the labeling of the entire afferent system, thereby providing a fast and easy method for visualizing the central projection in the hindbrain of live fish. The simplicity of the method makes it potentially useful for screens based on forward or reverse genetic approaches. Here we present protocols for labeling hair cells in live zebrafish and for labeling afferent neurons in zebrafish embryos.

Ultrafast Excited-State Dynamics of Donor–Acceptor Biaryls: Comparison between Pyridinium and Pyrylium Phenolates

The excited-state dynamics of two donor-acceptor biaryls that differ by the strength of the acceptor, a pyridinium or a pyrylium moiety, have been investigated using a combination of steady-state solvatochromic absorption, ultrafast fluorescence, as well as visible and infrared transient absorption spectroscopies. The negative solvatochromic behavior of pyridinium phenolate indicates that the permanent electric dipole moment experiences a decrease upon S1 ← S0 excitation, implying that the ground state possesses more zwitterionic character than the excited state. In contrast, pyrylium phenolate exhibits a weakly positive solvatochromic behavior corresponding to a small increase in the dipole moment upon excitation, implying more zwitterionic character in the excited than the ground state. Both compounds are therefore situated at different sides of the cyanine-limit structure, which has equally polar ground and excited states. Despite these differences, both molecules exhibit qualitatively similar excited-state properties. They are characterized by a very short fluorescence lifetime, increasing from about 1 to 20 ps, when varying solvent viscosity from 0.4 to 11 cP. There are, however, characteristic differences between the two compounds: The excited-state lifetimes of the pyrylium dye are shorter and also depend somewhat on polarity. The ensemble of spectroscopic data can be explained with a model where the emitting Franck-Condon excited state relaxes upon twisting around the single bond between the aryl units to a point where the excited- and ground-state surfaces are very close or intersect. After internal conversion to the ground state, the distorted molecule relaxes back to its equilibrium planar configuration, again largely dependent upon solvent viscosity. However, in this case, the kinetics for the pyrylium dye are slower than for the pyridinium dye and the polar solvent-induced acceleration is significantly stronger than in the excited state. This difference of kinetic behavior between the two compounds is a direct consequence of the change of the electronic structure from a normal to an overcritical merocyanine evidenced by steady-state spectroscopy.

Synthesis of Specific Solvatochromic D‐π‐A Dyes with Pyridinium Ring as Electron‐Withdrawing Group for Dye‐Sensitized Solar Cells

AbstractSpecific solvatochromic D‐π‐A‐type pyridinium dyes were designed and developed as photosensitizers for dye‐sensitized solar cells (DSSCs). The dyes have N‐sulfobutylpyridinium or N‐(carboxybutyl)pyridinium bromide as an electron‐withdrawing anchoring group. The two dyes show specific solvatochromism, leading to a large bathochromic shift of the absorption band in halogenated solvents. Moreover, a dye‐adsorbed TiO2 film immersed into halogenated solvents exhibits specific solvatochromism, as does a dye solution of halogenated solvents. DSSCs based on specific solvatochromic D‐π‐A‐type pyridinium dyes and halogenated solvents as electrolyte solvent were prepared and their photovoltaic performance investigated. It was found that the appropriate combination of solvatochromic dyes with electrolyte solution and the effective interaction between solvatochromic dyes and TiO2 surface can lead to not only an enhancement of light‐harvesting efficiency (LHE), but also efficient electron injection from the dye to the conduction band (CB) of TiO2. This work demonstrates that the solvatochromism of organic dyes is a key consideration for high‐performance DSSCs based on organic dye sensitizers.

Solid-state fluorescence properties and mechanofluorochromism of D–π-A pyridinium dyes bearing various counter anions

A pronounced bathochromic shift-type mechanofluorochromism (MFC) is found for D–π-A pyridinium dyes OD1–OD3 having diphenylamino group as an electron donor and pyridinium ring as an electron acceptor linked by carbazole as a π-conjugated bridge, and bearing various counter anions (X−=Cl−, Br−, or I−). Interestingly, both absorption and fluorescence peaks of as-recrystallized dyes show bathochromic shift by grinding, and the degrees of the bathochromic shift depend on the type of counter anion of OD1–OD3. We propose that the use of various counter anions for D–π-A pyridinium dyes can be one of the most effective strategies, not only to express a pronounced MFC, but also to control changes of fluorescence properties by the grinding and heating, resulting in fine-tuning of fluorescent color change by the MFC.

APP+, a fluorescent analogue of the neurotoxin MPP+, is a marker of catecholamine neurons in brain tissue, but not a fluorescent false neurotransmitter.

We have previously introduced fluorescent false neurotransmitters (FFNs) as optical reporters that enable visualization of individual dopaminergic presynaptic terminals and their activity in the brain. In this context, we examined the fluorescent pyridinium dye 4-(4-dimethylamino)phenyl-1-methylpyridinium (APP+), a fluorescent analogue of the dopaminergic neurotoxin MPP+, in acute mouse brain tissue. APP+ is a substrate for the dopamine transporter (DAT), norepinephrine transporter (NET), and serotonin transporter (SERT), and as such represented a candidate for the development of new FFN probes. Here we report that APP+ labels cell bodies of catecholaminergic neurons in the midbrain in a DAT- and NET-dependent manner, as well as fine dopaminergic axonal processes in the dorsal striatum. APP+ destaining from presynaptic terminals in the dorsal striatum was also examined under the conditions inducing depolarization and exocytotic neurotransmitter release. Application of KCl led to a small but significant degree of destaining (approximately 15% compared to control), which stands in contrast to a nearly complete destaining of the new generation FFN agent, FFN102. Electrical stimulation of brain slices at 10 Hz afforded no significant change in the APP+ signal. These results indicate that the majority of the APP+ signal in axonal processes originates from labeled organelles including mitochondria, whereas only a minor component of the APP+ signal represents the releasable synaptic vesicular pool. These results also show that APP+ may serve as a useful probe for identifying catecholaminergic innervations in the brain, although it is a poor candidate for the development of FFNs.

Development of Dye-Sensitized Solar Cells Based on D-^|^pi;-A Pyridinium Dye without Carboxylic Acid Moiety as Anchoring Group

Development of Dye-Sensitized Solar Cells Based on D-^|^pi;-A Pyridinium Dye without Carboxylic Acid Moiety as Anchoring Group

Specific solvatochromism of D–π-A type pyridinium dyes bearing various counter anions in halogenated solvents

Donor–π-acceptor type pyridinium dyes OD1–OD4 bearing various counter anions (X−=Cl−, Br−, I−, or BPh4−) have been designed and developed to gain greater insight into the influences of the electronic structures of D–π-A type pyridinium dye on the specific solvatochromism in halogenated solvents: the intramolecular charge transfer absorption bands of the dyes OD1–OD4 in halogenated solvents show a large bathochromic shift compared with those in the non-halogenated solvents. This study revealed that the halogenated solvents can significantly enhance the intramolecular charge transfer characteristics of D–π-A type pyridinium dye with soft counter anion, leading to large bathochromic shift of absorption band in halogenated solvents, which is in good agreement with an increase in the energy of halogen–halide anion interaction for the type of the halogen atom of halogenated solvents.

Organic photosensitizers with N-carboxymethyl pyridinium acceptor/anchoring group for dye-sensitized solar cells

Four new organic dyes with N-carboxymethyl pyridinium as electron acceptors/anchoring groups were designed and synthesized. The optical and electrochemical properties were characterized by UV–vis, fluorescence spectroscopy and cyclic voltammetry. The absorption spectra of the four pyridinium dyes were in the range of 450–650nm. The dye with triphenylamine as the electron donor shows a solar-energy-to-electricity conversion efficiency (η) of 2.33% in comparison with the reference Ru-complex (N719 dye) with a η value of 5.45% under the same experimental conditions. The dye with phenoxazine as the electron donor gives broad IPCE spectra in the range of 400–750nm. All these new dyes are simple in structure, very easy to synthesize, and gives high Voc.

Effect of NaCl on the binding constant of styryl pyridinium dyes in anionic surfactant system

Perturbation of micelle structure by salt plays a vital role in micellar growth. Cationic alkyl styryl pyridinium dyes are found to interact differently with anionic surfactant systems according to their structural differences. In this work the binding constant of some tailor made styryl pyridinium dyes (1) in ground state and excited state has been studied in anionic sodium dodecyl sulfate (SDS) in the presence and absence of NaCl using absorption and steady state fluorescence spectroscopy. Larger binding constant of the dyes in the excited state compared to the ground state has been explained in terms of flexibility of dyes in excited state. The highest binding constant value for C12 is attributed to the compatibility of the hydrophobic chain of both the surfactant and the dye.

Synthesis and photophysical properties of two novel branched pyridinium inner salt dyes

Two new branched pyridinium inner salt dyes, 2,6-di[2-( N -ethyl-carbazole-3-yl)vinyl]- N -(3-sulfonatepropyl)pyridinium, inner salt ( 2 ) and 2,4,6-tri[2-( N -ethyl-carbazole-3-yl)vinyl]- N -(3-sulfonatepropyl)pyridinium, inner salt ( 3 ), with N -ethyl-carbazolyl as electron donor group and pyridine cation as electron acceptor group have been synthesized. Their single- and two-photon related fluorescence properties in various solvents have also been examined. These dyes exhibit stronger fluorescence emission relative to the corresponding linear counterpart and common pyridinium dyes with discrete cation and anion components. Three-branched organic dye 3 has a high fluorescence quantum yield as 0.12 and exhibits strong orange two-photon excited fluorescence at 608 nm in THF with large two-photon absorption cross-section being 606 GM. Two new branched pyridinium inner salt dyes with N -ethyl-carbazolyl as electron donor group have been synthesized. Three-branched organic dye has a high fluorescence quantum yield as 0.12 and exhibits strong orange two-photon excited fluorescence at 608 nm in THF with two-photon absorption cross-section being 606 GM. ► Two new branched pyridinium inner salt dyes were synthesized. ► The dyes exhibit strong yellow or orange fluorescence emission. ► Three-branched organic dye exhibits strong orange two-photon excited fluorescence in THF.

Azadithiacrown ether based ditopic receptors capable of simultaneous multi-ionic recognition of Ag+ and Hg2+

Abstract Novel azadithiacrown ether containing bis(styryl)pyridinium dyes were synthesized and their complexation with different transition metal cations was investigated. It was found that the compounds give a selective ratiometric optical response in the presence of silver (I) and mercury (II) cations. Evidence was given for the occurrence of two stoichiometries: LM and LM 2 . Moreover, the formation of a mixed complex [Ag + · L ·Hg 2+ ] containing both Ag + and Hg 2+ cations simultaneously was demonstrated. Optical spectroscopy was used to estimate stability constant values of the complexes, NMR spectroscopy data allowed us to offer a model of spatial arrangement of the obtained species.

Synthesis and specific solvatochromism of D–π–A type pyridinium dye

Donor–π–acceptor (D–π–A) type pyridinium dye bearing an iodide ion as the counter anion that has been newly synthesized showed specific solvatochromism, leading to large bathochromic shift of absorption band in halogenated solvents: the bathochromic shifts of the D–π–A type pyridinium dye in halogenated solvents are larger than those of the non-halogenated solvents of low ɛr values. Investigation of absorption spectral measurement, 1H NMR measurements, and semi-empirical molecular calculations (AM1 and INDO/S using the SCRF Onsager Model) revealed that the intramolecular charge transfer (ICT) characteristics of the D–π–A type pyridinium dye became stronger in the halogenated solvents. On the basis of the experimental results and the theoretical calculations, the influences of halogenated solvent on the large bathochromic shift of D–π–A type pyridinium dye are discussed. ©2012 Elsevier Science. All rights reserved.

Eggshell Particles (ESP) as Potential Adsorbent for Styryl Pyridinium Dyes—A Kinetic and Thermodynamic Study

Eggshell particles (ESP) of a definite mesh size have been prepared and characterized through infrared and scanning electron microscopy. Adsorption of some styryl pyridinium dyes (SP-1 and SP-2) has been studied on ESP surface from water-ESP interface and the effects of adsorbate concentration, adsorbent dosage, temperature, salts, and the contact time have been examined. A first time study of the effect of water-structure making salt (kosmotroph) such as NaCl and structure breaking salt (chaotroph) such as KCl and NH4SCN on the adsorption process on ESP has been reported. Both types of salts have opposing effects on the adsorption of SP-1 dye; however, in case of SP-2 dye both of them show similar effects. The adsorption process is found to follow a second order kinetics. Thermodynamic studies show the occurrence of a physical adsorption with exothermic energetic. The adsorption follows Langmuir isotherm model and the area of coverage has been calculated to show the impact of hydrogen bonding on the adsorption phenomenon.

A Pyridinium Dye as Chromogenic Probe for DNA Molecule

A pyridinium dye with N-butyl-carbazole as an electron donor group and pyridinium cation as electron acceptor group has been synthesized. The crystal structure and photophysical properties of the dye in different solvents are researched. The interaction between the dye and DNA is also researched. The results reveal that the dye can be used as a DNA probe.

Temperature Induced Emulsification and Demulsification of Pseudoternary Mixtures of Tween80–Butanol–Kerosene–Water System

The phase diagrams of pseudoternary mixtures of Tween80–butanol–kerosene–water system were constructed by visual titration. The major three domains, i.e., oil in water, bicontinuous, and water in oil microemulsions were demarcated through conductivity measurement. A sharp increase in specific conductance in increasing water content in the bicontinuous domain has been ascribed to the percolation of ions through water continuum. Temperature induced clouding behavior of the mixtures in the Winsor IV domains was investigated to find out the effect of composition on the clouding temperature. A generalized regression model was proposed considering the cloud point to be a function of surfactant/cosurfactant ratio and oil and emulsifier contents. The increase in all these parameters increases the cloud points of the mixture. In the turbid Winsor III domain, temperature has an emulsifying effect. With increase in temperature, the turbid phase separates to three different phases, which experience transparent, translucent, and turbid characteristics due to mass transfer from one phase to another. The mass transfer phenomenon was well visualized by using nickel as water-soluble and N-alkyl 4-(p-N,N-dimethylaminostyryl)pyridinium dyes as oil-soluble probes.

Synthesis, Photophysical Properties and Aggregates of a New Pyridinium Dye

A new pyridinium dye, 2-{2-[9-ethyl-carbazole-3-yl]vinyl}-N-(3-sulfooxypropyl) pyridinium inner salt, has been synthesized. The photophysical properties of the dye in DMF were investigated. The dye exhibits strong orange fluorescence with quantum yield Φ = 0.1. The particles are nano-scale after 30minutes, but it will accumulate to micron-scale after 4h.

Novel Pyridinium Dyes That Enable Investigations of Peptoids at the Single-Molecule Level

Single-molecule microscopy is a powerful tool for investigating various uptake mechanisms of cell-penetrating biomolecules. A particularly interesting class of potential transporter molecules are peptoids. Fluorescence labels for such experiments need to comply with several physical, chemical, and biological requirements. Herein, we report the synthesis and photophysical investigation of new fluorescent pyridinium derived dyes. These fluorescent labels have advantageous structural variations and spacer units in order to avoid undesirable interactions with the labeled molecule and are able to easily functionalize biomolecules. In our case, cell-penetrating peptoids are successfully labeled on solid supports, and in ensemble measurements the photophysical properties of the dyes and the fluorescently labeled peptoids are investigated. Both fluorophores and peptoids are imaged at the single-molecule level in thin polymer gels. With respect to bleaching times and fluorescence lifetimes the dye molecules and the peptoids show only slightly perturbed optical behaviors. These investigations indicate that the new fluorophores fulfill well single-molecule microscopy and solid-phase synthesis requirements.

ChemInform Abstract: Synthesis and Characterization of Mono-, Bis-, and Trissubstituted Pyridinium and Pyrylium Dyes.

A series of mono-, bis-, and trissubstituted pyridinium and pyrylium dyes have been synthesized by the condensation of methylpyridinium and methylpyrylium salts with aldehydes or nitroso compound. Large bathochromic shifts were observed in the following order, both in substituted azomethine pyridinium and pyrylium dyes, mono < bis < tris. The magnitude of the shift appeared in the order of multiple bonds, –CH=CH– < –CH=CH–CH=CH– < –CH=N–.

FM dyes enter via a store-operated calcium channel and modify calcium signaling of cultured astrocytes

The amphiphilic fluorescent styryl pyridinium dyes FM1-43 and FM4-64 are used to probe activity-dependent synaptic vesicle cycling in neurons. Cultured astrocytes can internalize FM1-43 and FM4-64 inside vesicles but their uptake is insensitive to the elevation of cytosolic calcium (Ca(2+)) concentration and the underlying mechanism remains unclear. Here we used total internal reflection fluorescence microscopy and pharmacological tools to study the mechanisms of FM4-64 uptake into cultured astrocytes from mouse neocortex. Our data show that: (i) endocytosis is not a major route for FM4-64 uptake into astrocytes; (ii) FM4-64 enters astrocytes through an aqueous pore and strongly affects Ca(2+) homeostasis; (iii) partitioning of FM4-64 into the outer leaflet of the plasma membrane results in a facilitation of store-operated Ca(2+) entry (SOCE) channel gating; (iv) FM4-64 permeates and competes with Ca(2+) for entry through a SOCE channel; (v) intracellular FM4-64 mobilizes Ca(2+) from the endoplasmic reticulum stores, conveying a positive feedback to activate SOCE and to sustain dye uptake into astrocytes. Our study demonstrates that FM dyes are not markers of cycling vesicles in astrocytes and calls for a careful interpretation of FM fluorescence.

Dye‐Sensitized Solar Cells Based on a Novel Fluorescent Dye with a Pyridine Ring and a Pyridinium Dye with the Pyridinium Ring Forming Strong Interactions with Nanocrystalline TiO2 Films

AbstractAs new‐type donor–acceptor π‐conjugated dyes capable of forming a strong interaction between the electron‐acceptor moiety of the sensitizers and a TiO2 surface, fluorescent dye OH11 and pyridinum dye OH12 with a pyridine and pyridinium ring as the electron‐accepting group, respectively, have been designed and synthesized as photosensitizers for use in dye‐sensitized solar cells (DSSCs). The fluorescent dye OH11 exhibits an absorption band at around 410 nm and a fluorescence band at around 530 nm. On the other hand, the pyridinum dye OH12 shows an absorption maximum at around 560 nm, assigned to a strong intramolecular charge‐transfer excitation from the dibutylamino group to the pyridinium ring. The short‐circuit photocurrent densities of the DSSCs prepared by using OH11 and OH12 are 4.33 and 1.74mA cm–2, and the solar energy‐to‐electricity conversion yields are 1.33 and 0.51 %, respectively, under simulated solar light [AM (air mass) 1.5, 100 mW cm–2]. The open‐circuit photovoltage for OH11 (525 mV) is higher than that of OH12 (444 mV). The effects of the configuration of the dyes on the TiO2 surface and of their chemical structures on the photovoltaic performances are discussed on the basis of semi‐empirical molecular orbital calculations (AM1 and INDO/S), spectral analyses and cyclic voltammetry.