Hemicyanine Dye Research Articles

The synthesis and spectroscopic investigation of dichromophoric hemicyanine dyes

Alkane α,γ-bis[4-methylpyridinium] diiodide and alkane α,γ-bis[4-methylquinolinium] diiodide were prepared and used as starting materials in the synthesis of dichromophoric cyanine dyes. Structural confirmation of the synthesized dyes was carried out by 1H NMR, MS spectroscopy and elemental analysis. The electronic absorption and the emission spectra for all the hemicyanines were measured in four organic solvents of varying polarity. All derivatives absorb in the region of about 500 nm and have molar absorptivity of about 10 4 M −1 cm −1. The absorption spectra of tested compounds are affected by their structure i.e. the structure of dialkyl(aryl)amino group, the electron acceptor part of the dye and the linker between two identical hemicyanine chromophores. The fluorescence bands' positions, in contrast to the absorption, are strongly affected by the solvent polarity.

Complex formation study of hemicyanine dyes with sodium dodecyl sulfate by differential spectroscopy

Complex formation of hemicyanine dyes within anionic surfactant sodium dodecyl sulfate is investigated using differential absorbance method. Micelle–water partition coefficients are calculated as a ratio of the mole fractions of dye in corresponding phases. The thermodynamic parameters highlight the energy efficiency of the process. Conductometric study is utilized to show the depression in critical micelle concentration of sodium dodecyl sulfate caused by each dye. In contrast to sodium dodecyl benzene sulfonate, where pyridinium nitrogen forms highly stable complexes with aromatic moiety of the surfactant, the dye bound to SDS through salt-like electrostatic interaction. More hydrophobic dyes are more efficiently solubilized as compared to their less hydrophobic homologs.

Amino(oligo)thiophene-Based Environmentally Sensitive Biomembrane Chromophores

There is a growing need for cellular imaging with fluorescent probes that emit at longer wavelengths to minimize the effects of absorption, autofluorescence, and scattering from biological tissue. In this paper a series of new environmentally sensitive hemicyanine dyes featuring amino(oligo)thiophene donors have been synthesized via aldol condensation between a 4-methylpyridinium salt and various amino(oligo)thiophene carboxaldehydes, which were, in turn, obtained from amination of bromo(oligo)thiophene carboxaldehyde. Side chains on these fluorophores impart a strong affinity for biological membranes. Compared with benzene analogues, these thiophene fluorophores show significant red shift in the absorption and emission spectra, offering compact red and near-infrared emitting fluorophores. More importantly, both the fluorescence quantum yields and the emission peaks are very sensitive to various environmental factors such as solvent polarity or viscosity, membrane potential, and membrane composition. These chromophores also exhibit strong nonlinear optical properties, including two-photon fluorescence and second harmonic generation, which are themselves environmentally sensitive. The combination of long wavelength fluorescence and nonlinear optical properties make these chromophores very suitable for applications that require sensing or imaging deep inside tissues.

Miniaturized setup for fluorescence sensing with optodes: Characterization of a new hemicyanine ion-selective-based membrane

A miniaturized and robust optical fluorosensor, designed as a portable instrumentation for the in situ analysis of ions in water samples by using optodes has been constructed with low cost discrete optical components. The chemical recognition element of the device consists of a plasticized PVC-based fluorescent optode, which includes a new hexamethine–hemicyanine dye as a fluorophore. The signal can be attributed to a certain analyte depending on the ionophore employed. In this work, a commercial potassium ionophore (valinomycin) has been used to formulate a model membrane selective to potassium. The sensor has been fully characterized using a simple flow injection analysis (FIA) system and analytical parameters such as sensitivity (0.71 mV dec −1 ), limit of detection (2.2 × 10 −5 M K + ), repeatability (R.S.D. = 4.2%), reproducibility, lifetime and ionic interferences have been determined. The developed miniaturized system has been applied to the potassium concentration determination in spiked tap water samples. The obtained results have been compared to those acquired by the ICP-OES reference method and the suitability of the experimental setup for the determination of ions in water samples by the miniaturized fluorescence proposal has been demonstrated.

Studies on an argon laser-induced photopolymerization employing both mono- and bischromophoric hemicyanine dye–borate complex as a photoinitiator: Part II

Several photoredox pairs containing dichromophoric hemicyanine dyes have been evaluated as novel photoinitiators for free radical polymerization induced with an argon-ion laser irradiation. The tested photoredox couples are the pairs composed of the hemicyanine dye cations acting as electron acceptors and n-butyltriphenyl borate anions being the electron donors. The photoinitiating abilities of the series of dimmeric dichromophoric stilbazolium borates; 1,2-; 1,3-; and 1,4-bis-[4-( p- N, N-dialkylaminostyryl)pyridinyl]xylene di- n-butyltriphenylborates, were compared to the photochemistry of structurally related, monochromophoric styrylpyridinium borates. The obtained results clearly documented that the dicationic photoinitiators exhibit a marked increase in the photoinitiation ability compared to the initiators consisting of a single charged hemicyanine dye. Our studies revealed also that the rate of photopolymerization depends on Δ G el of electron transfer between borate anion and styrylpyridinium cation. The latter value was estimated for all series of styrylpyridinium borate salts. The relationship between the rate of polymerization and the free energy of activation shows the dependence predicted by the classical theory of electron transfer.

Synthesis of Amphiphilic Dye-Self-Assembled Mesostructured Powder Silica with Enhanced Emission for Directional Random Laser

In this paper, we report a laser device application of dye-self-assembled mesostructured powder. Dye-assembled submicrometer-sized mesostrucutred silica with high luminescence was first synthesized at room temperature from a mixed-surfactant system comprising laboratory synthesized hemicyanine dye and cetyltrimethylammounium bromide (CTAB) as structure-directing agents. The fluorescence emission of the dye molecules was greatly enhanced when self-assembled into the mesostructred powder even though the dye concentration is very high. The highly luminescent powder was further used as gain media to fabricate a laser device. The laser device is a combination of planar microcavity with mesostructured powder random gain layer. Investigation of the laser performance employing the mesostructured powder with enhanced emission as gain media shows a directional output and a much lower threshold, which is 85 times lower than counterpart device using a mixture of silica sphere and dye molecules as gain media.

Diamine Catalyzed Hemicyanine Dye Formation from Nonfluorescent Precursors through DNA Programmed Chemistry

A hemicyanine fluorescent dye was generated by a diamine-catalyzed, DNA-templated, aldol-type condensation from nonfluorescent precursors. Studies of reaction rate and yield as a function of catalyst structure indicated the diamine catalyst operates in a concerted mechanism on both reaction components. Our findings expand the scope of reactions that can be performed by DPC and demonstrate that de novo chemical synthesis of labels can be coupled to biological recognition events in a homogeneous format with essentially no background.

The synthesis and characterization of novel coumarin-containing cyanine dyes via “Click” chemistry

Four novel cyanine dye derivatives (C-Cy(1–4)) in which a coumarin moiety is attached to benzoindole ring of asymmetric trimethine cyanine dyes or hemicyanine dye by 1,2,3-triazole have been successfully synthesized via “Click” reaction between the corresponding alkyl-end cyanine dyes and 3-azidocoumarin. Six reaction systems were employed to find the suitable “Click” conditions of cyanine dyes. It was found that the combination of DMF, CuI and di-i-propylethylamine (DIPEA) was the most excellent system for “Click” reaction. All of the compounds were characterized by 1H-NMR, MS, UV and FL.

Comparison of Photophysical Properties of the Hemicyanine Dyes in Ionic and Nonionic Solvents

The fluorescence properties of 4-[4-(dimethylamino)styryl]-1-n-alkylpyridinium bromide (hemicyanine) dissolved in solvents of different polarities and viscosities (methanol, ethylene glycol, tetra-ethylene glycol, glycerol, benzyl alcohol, pyridine, and two ionic liquids, 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIM]BF4, and 1-butyl-3-methylimidazolium hexafluorophosphate, [BMIM]PF6) were investigated. Significant increase in the fluorescence quantum yield and the fluorescence decay lifetime was observed with the increase in the viscosity of the solvent medium. It is because the intramolecular rotational motion of the molecule becomes more difficult in viscous liquid, which leads to a decrease in the nonradiative decay processes. The fluorescence quantum yields for all of the solutions followed a semiempirical law that depends only on the solvent viscosity. The correlation function C(t) was obtained for each solution by joining fluorescence decay curves measured at different wavelengths. From the fitted results of C(t), we observed the distinctive feature unique to the ionic liquids, in which the correlation functions for ionic liquid solutions are fitted to be biphasic, while they are monophasic for other solvents. The fluorescence maximum of hemicyanine dissolved in these ionic liquids red-shifted following the increase in the excitation wavelength.

Development of new heterobicationic monomethine dyes as effective photoinitiator of free radical polymerization in visible-light region

The dye initiators consisting of N-[3-(p-alkylpyridine)propyl]-2-[N-(3-bromopropyl)quinoline]-2-methylenebenzotiazolium diiodides as chromophores and n-butyltriphenylborate anion as electron donor were prepared to achieve an efficient photoinitiator of free radical polymerization in a visible-light region. The relative photoinitiating efficiencies of novel photoinitiators of vinyl monomers polymerization were evaluated. The results obtained clearly documented that the bicationic photoinitiators exhibit a marked increase in the photoinitiation ability compared to the initiators consisting of a single charged hemicyanine dye. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Determination of Absolute Orientations of Hemicyanine Dyes Incorporated into the Channels of Silicalite-1 Films

Hemicyanine dyes can be incorporated into silicalite-1 channels in uniform orientations.1 To find out the underlying mechanism, two different hemicyanine dyes having a long hydrophobic C18-alkyl chain on opposite ends of the dipolar nonlinear optical chromophore were adsorbed into the vertically oriented channels of silicalite-1 films supported on a glass plate. Second-harmonic phase measurement revealed that the above two molecules in the silicalite-1 channels were indeed oppositely oriented. A Langmuir monolayer of a hemicyanine was used as a reference sample to determine the absolute orientation of the dyes in the above samples, which allowed us to confirm that the hemicyanine dyes prefer to enter the zeolite channels with the hydrophobic tail part first.

Optical Dichroism of Hemicyanine-Incorporated Zeolite Monolayer Self-Assembled on Glass Plate

Hemicyanine dye molecules were put into the pores of a uniformly-oriented zeolite (silicalite-1) film self-assembled on a glass substrate. The anisotropy of the incorporated molecules in this film was studied by measuring the absorption with linearly polarized light. With 45 incidence, the absorption of p-polarized light was 9.3 times larger than that of s-polarized light, indicating the dye molecules were preferentially aligned normal to the plate along the vertical channel of the pore. On the other hand, the fluorescence anisotropy measured by using excitation on the edge of the film with linearly polarized light by confocal microscope was as much as 50. We propose that light scattering in an uneven silicalite film was the main cause of the discrepancy in observed anisotropy.

Studies on an argon laser-induced photopolymerization employing both mono- and bischromophoric hemicyanine dye–borate complex as a photoinitiator

Dye photoinitiators consisting of either 1,3-bis-[4-( p- N, N-dialkylaminostyryl)pyridinyl]propane (C1B2–C8B2) or 1,3-bis-[4-( p- N, N-dialkylaminostyryl)-pyridinyl]xylene (A1B2–A8B2) dications, acting both as light absorbers and as electron acceptors and n-butyltriphenylborate anions being electron donors were tested in order to reveal the effect of a dye structure on the efficiency of multiacrylate photoinitiated polymerization. The kinetic studies clearly demonstrated that the bischromophoric stilbazolium borate photoredox pairs exhibit a significant increase in the efficiency of TMPTA free radical polymerization in comparison to the pairs containing structurally related, monochromophoric styrylpyridinium borates (SP1B2–SP8B2). The efficiency of tested systems depends on the Δ G el of electron transfer between borate anion and styrypyridinium cation. The latter value was experimentally determined for 24 photoredox pairs. The relationship between the rate of polymerization and the free energy of activation of electron transfer reaction shows the dependence predicted by the classical theory of electron transfer phenomena. This relation is independently observed for mono- and bischromophoric hemicyanine borate salts.

X-ray and DFT studies of the structure and spectral property of 2-[2-(4-dimethylaminophenyl)ethenyl]-1-methyl-pyridinium iodide

A hemicyanine dye: 2-[2-(4-dimethylaminophenyl)ethenyl]-1-methyl-pyridinium iodide ( 1) was synthesized and characterized by X-ray diffraction, 1H NMR, MS, IR, UV–Vis spectra and elemental analysis. The crystals are monoclinic, space group P2 1/c, with a = 7.1231(8), b = 20.672(2), c = 10.9642(12) Å, V = 1605.7(3) Å 3, and Z = 4 (at 298(2) K). Crystal stacking scheme indicates the hydrogen bonds and intermolecular π⋯π interactions; the molecular planes arrange in a head-to-tail fashion along the ab plane due to the strong ‘push-pull’ electron system. Molecular geometries, frequencies and absorption properties were calculated at DFT/TD-DFT level using two hybrid exchange-correlation functionals, B3LYP and PBE1PBE. These calculations on ( 1) provide deep insight into its electronic structure and property.

ANNINE-6plus, a voltage-sensitive dye with good solubility, strong membrane binding and high sensitivity

We present a novel voltage-sensitive hemicyanine dye ANNINE-6plus and describe its synthesis, its properties and its voltage-sensitivity in neurons. The dye ANNINE-6plus is a salt with a double positively charged chromophore and two bromide counterions. It is derived from the zwitterionic dye ANNINE-6. While ANNINE-6 is insoluble in water, ANNINE-6plus exhibits a high solubility of around 1 mM. Nonetheless, it displays a strong binding to lipid membranes. In contrast to ANNINE-6, the novel dye can be used to stain cells from aqueous solution without surfactants or organic solvents. In neuronal membranes, ANNINE-6plus exhibits the same molecular Stark effect as ANNINE-6. As a consequence, a high voltage-sensitivity is achieved with illumination and detection in the red end of the excitation and emission spectra, respectively. ANNINE-6plus will be particularly useful for sensitive optical recording of neuronal excitation when organic solvents and surfactants must be avoided as with intracellular or extracellular staining of brain tissue.

Synthesis and Properties of Novel Hemicyanine Dye‐β‐Cyclodextrin

AbstractA series of novel hemicyanine dye‐β‐cyclodextrin compounds:mono‐6‐deoxy‐β‐cyclodextrin‐6‐[p‐(p‐substi‐ tuted styryl)pyridium] p‐totylfulfonates were synthesized by the condensation of mono‐6‐deoxy‐β‐ cyclodextrin‐6‐(p‐methyl pyridinium) p‐toluenesulfonate with (un)substituted benzaldehydes. Their structures were established by 1H NMR, IR, UV‐Vis and elemental analysis. The absorption and fluorescence properties of the novel compounds were measured in solution and the photostability of a selected hemicyanine dye‐β‐cyclodextrin compound was also investigated.

Colorimetric detection of fluoride in an aqueous solution using Zr(IV)–EDTA complex and a novel hemicyanine dye

A new highly sensitive and selective colorimetric method for fluoride determination in water is described. The novel reagent used is a hemicyanine dye ( HC), which forms a stable complex with Zr–EDTA, the fluoride-binding site, through the hydroxyl groups. The hemicyanine-chelating Zr–EDTA complex ( HC–Zr–EDTA) is ready to react with fluoride ion to release HC. This result in remarkable color change of the sensing solutions from red ( λ max = 513 nm) to yellow ( λ max = 427 nm) at pH 4.40. When applied to the colorimetric determination of fluoride ions, a linear range from 3.0 × 10 −6 to 5.0 × 10 −5 mol/L and a detection limit of 2.8 × 10 −6 mol/L with a correlation coefficient of 0.9993 can be achieved under the optimized conditions. Because of the specific affinity of fluorides for the [Zr–EDTA], there is little interference by other ions. This method has been successfully applied to the determination of fluorides in toothpaste samples.

Azido derivative of a hemicyanine dye with high sensitivity to visible light

Azido derivative of a hemicyanine dye with high sensitivity to visible light

Greater Fluorescence from Styrylpyridinium Dye upon Complexation with Cyclodextrin Derivatives through a π - π Interaction

The fluorescence of 4-(4'-dimethylamino)styryl-1-methylpyridinium (C1SP) was enhanced by more than 33-fold by complexation with beta-cyclodextrin (beta-CD) bearing a naphthalene, pyrene, or phenylboronic acid group. The great enhancement of the fluorescence of C1SP was due to a pi-pi stacking interaction, by which the bond rotation of C1SP was effectively suppressed. The results indicate that C1SP and structurally related hemicyanine dyes potentially become powerful fluorescent indicators for aromatic compounds through the pi-pi stacking interaction in water.

New hexamethine–hemicyanine dyes for the development of integrated optochemical sensors

New far-visible absorbing anilino-cyanine dyes have been synthesised for future application as chromoionophores in integrated waveguide absorbance optodes based on bulk optodes. The effect of the heterocycle, of the substitution of the heterocyclic nitrogen and of the type of heptamethine central ring on the pKa values (4.3-8.2 in ethanol-water solutions and 9.5-11.0 in plasticised PVC membranes), on the spectroscopic characteristics of the dye and on photostability is discussed. pH-selective bulk optodes have been formulated as a first approach to develop ion-selective optodes, and sensitivity, repeatability, lifetime and response time have been determined. The dyes show good analytical behaviour for use as chromoionophores for the development of ion-selective optodes. Reversible (80-87%), fast (tr90%=0.94-2.28 min) and pH-sensitive membranes (slopes of 0.09-0.23 DeltaAbs.pHdec-1, absorbance range 0.19-0.53) have been obtained. Moreover, they exhibit good spectroscopic features for employment with integrated optochemical sensors: absorption maxima of the acidic species in plasticised PVC membranes matched those of 650-670-nm LEDs, high molar absorption coefficients (epsilonacidic=3.5x10(4)-9.3x10(4) L mol-1 cm-1 and epsilonbasic=1.9x10(4)-6.7x10(4) L mol-1 cm-1) and fluorescence.