Dyes In Various Solvents Research Articles

A STUDY ON TAUTOMERIC EQUILIBRIA OF SOME NEW 3-CRHLORO-4- FLUOROAMLINEMONOAZO DISPERSE DYE DERIVATIVES

A series of new monoazo disperse dyes derived from 3-chloro-4-fluoroaniline have been synthesized The six novel monoazo disperse dyes were synthesized by diazotisation of 3- chloro-4-fluoroaniline and coupling with 1 -naphthylamine, 6-methoxy-2-naphthol, Nphenylnaphthylamine, 3-aminophenol, 1,3-dihydroxybenzene and 2-naphthol. The dye structures were eluciated by chemical analyses and spectral methods. The solvatochromic behaviour of these monoazo dyes in various solvents was evaluated.

Novel azo dyes derived from 8-methyl-4-hydroxyl-2-quinolone: Synthesis, UV–vis studies and biological activity

In this study, N,N′-di-(2-methylphenyl)malonamide was synthesized and reacted with polyphosphoric acid to afford 8-methyl-4-hydroxyl-2-quinolone. Eight novel azo disperse dyes were then synthesized by linking diazotized p-substituted aniline derivatives with 8-methyl-4-hydroxyl-2-quinolone. The solvatochromism of these azo dyes in various solvents was evaluated. All the compounds were then evaluated for their antibacterial activity against four bacteria, namely, Bacillus subtilis, Micrococcus luteus, Salmonella enterica, and Pseudomonas aeruginosa. The results showed that some of these compounds have high levels of antibacterial activity.

A tetraphenylethene-decorated BODIPY monomer/dimer with intense fluorescence in various matrices

Three novel boron dipyrromethene (BODIPY) derivatives containing tetraphenylethene (TPE) with emissions ranging from orange to red were synthesized and characterized. Spectroscopic properties of the dyes in various solvents and in the solid state have been investigated. They all exhibit high fluorescence intensity in solution and moderate fluorescence in the solid state, due to inhibiting intermolecular π–π stacking resulting from tetraphenylethene substituents. Cyclic voltammetry and time-dependent density functional theory (TD-DFT) calculations were carried out to explore the electronic coupling between the tetraphenylethene group and the BODIPY unit, giving consistent results with photophysical measurements.

Synthesis and absorption spectra of some novel hetaryltetrakisazocalix[4]arene derivatives

Abstract In this study, a convenient method for the synthesis of thirteen novel tetrakisazo dyes containing 25,27-bis-(4-nitrobenzyloxy)-26,28-dihydroxycalix[4]arene have been described. 5,11,17,23-Tetra-tert-butyl-25,26,27,28-tetrahydroxycalix[4]arene, 25,26,27,28-tetrahydroxycalix[4]arene and 25,27-bis-(4-nitrobenzyloxy)-26,28-dihydroxycalix[4]arene were synthesized. 2-arylhydrazone-3-ketiminobutyronitriles 1(a–m) were synthesized and reacted with hydrazine hydrate to afford the corresponding 5-amino-4-arylazo-3-methyl-1-H-pyrazoles 2(a–m). Thirteen novel hetaryltetrakisazocalix[4]arene derivatives 6(a–m) were achieved by diazotisation of 5-amino-4-arylazo-3-methyl-1-H-pyrazoles using nitrosylsulphuric acid, coupling with 25,27-bis-(4-nitrobenzyloxy)-26,28-dihydroxycalix[4]arene. The obtained hetaryltetrakisazocalix[4]arene dyes 6(a–m) were characterized based on FT-IR, 1H NMR and Mass spectroscopic techniques as well as Elemental Analysis. The solvatochromic behaviour of these dyes in various solvents was examined. Acid-base effect on the visible absorption maxima of the dyes were also reported.

Synthesis and tautomeric structures of some novel thiophene-based bis-heterocyclic monoazo dyes

In this study, ethyl 2-amino-5-methyl-4-(phenylcarbamoyl)thiophene-3-carboxylate (1) was prepared using Gewald’s methodology. This 2-aminothiophene derivative was diazotised and coupled with, 3-methyl-1H-pyrazolin-5-one, 3-methyl-1-phenylpyrazolin-5-one, 3-amino-5-hydroxy-1H-pyrazole, 3-amino-5-hydroxy-1-phenylpyrazole, 3-cyano-6-hydroxy-4-methyl-2-pyridone, barbituric acid and 4-hydroxycoumarin, respectively (2–8). The newly synthesized bis-heterocyclic monoazo dyes based on thiophene ring were characterised by elemental analysis and spectral methods. The solvatochromic behaviour and tautomeric structures of these bis-heterocyclic monoazo dyes in various solvents was evaluated. Acid and base effects on the visible absorption maxima of the dyes are also reported.

Tuning the Solid‐State Luminescence of BODIPY Derivatives with Bulky Arylsilyl Groups: Synthesis and Spectroscopic Properties

Boron dipyrromethenes (BODIPYs) with bulky triphenylsilylphenyl(ethynyl) and triphenylsilylphenyl substituents on pyrrole sites were prepared via Hagihara-Sonogashira and Suzuki-Miyaura cross-coupling with ethynyl-terminated tetraphenylsilane and boronic acid-terminated tetraphenylsilane. The chromophores are designed to prevent intermolecular π-π stacking interaction and enhance fluorescence in the solid state. Single crystals of 1 a and 2 b for X-ray structural analysis were obtained, and weak π-π stacking interactions of the neighboring BODIPY molecules were observed. Spectroscopic properties of all of the dyes in various solvents and in films were investigated. Triphenylsilylphenyl-substituted BODIPYs generally show more pronounced increases in solid-state emission than triphenylsilylphenyl(ethynyl)-substituted BODIPYs. Although the simple BODIPYs do not exhibit any fluorescence in the solid state (Φ=0), arylsilyl-substituted BODIPYs exhibit weak to moderate solid-state fluorescence with quantum yields of 0.03, 0.07, 0.10, and 0.25. The structure-property relationships were analyzed on the basis of X-ray crystallography, optical spectroscopy, cyclic voltammetry, and theoretical calculations.

Simultaneous measurements of absorption spectrum and refractive index in a microfluidic system

The characterization of dyes in various solvents requires determination of the absorption spectrum of the dye as well as the refractive index of the solvent. Typically, the refractive index of the solvent and the absorption spectrum of the solute are measured using separate experimental setups where significant liquid volumes are required. In this work the first optical measurement system that is able to do simultaneous measurements of the refractive index of the solvent and the spectral properties of the solute in a microscopic volume is presented. The laser dye Rhodamine 6G in glycerol is investigated, and the refractive index of the solution is monitored using the interference pattern of the light scattered off the channel, while its spectral properties is found by monitoring reflected light from the channel.

Synthesis and spectroscopic properties of bodipy dimers with effective solid-state emission

Boron-dipyrromethenes (BODIPYs) dimers with phenyl and bulky triphenylsilylphenyl substituents were synthesized through oxidative self-coupling of the 2-position with FeCl3. Spectroscopic properties of all the dyes in various solvents and on films have been investigated. In comparison with the corresponding monomers, the dimers exhibit higher molar absorption coefficients, relative moderate fluorescent quantum yields and redshifted wavelengths. The luminescence yields of the dimers are solvent polarity dependent and decrease dramatically in acetonitrile. More intensive solid-state emission of triphenylsilylphenyl substituted BODIPY dimer is observed with a quantum yield of 9.7% relative to the phenyl substituted dimer, which could be attributed to the introduction of the bulky group that inhibits aggregation.

Semi-empirical method for analysis of electronic absorption spectra of 3,6-tetramethyldiaminophthalimide solutions

A new semi-empirical method (mωT or modified ω-technique adapted to thermosolvatochromic effect analysis) based on the first approximation by a self-consistent field procedure (ω-technique) is proposed to calculate solvatochromic effects of dyes in various solvents. The method relies on the direct dependence of the relative change of charge at a dye molecule atom influenced by an external solvent molecule on the atom/molecule interaction energy. The method was validated using the calculation of solvatochromic and thermosolvatochromic effects for 3,6-tetramethyldiaminophthalimide [4,7-tetramethyldiamino-1H-isoindole-1,3(2H)-dione] in inert solvents as an example.

Synthesis and absorption spectra of some novel hetaryldisazocalix[4]arene derivatives

In this study, a convenient method for the synthesis of thirteen novel disazo dyes containing 25,26,27-tribenzoyloxy-28-hydroxycalix[4]arene have been described. 5,11,17,23-Tetra-tert-butyl-25,26,27,28-tetrahydroxycalix[4]arene, 25,26,27,28-tetrahydroxycalix[4]arene and 25,26,27-tribenzoyloxy-28-hydroxycalix[4]arene were synthesised based on previously published literature. 2-Arylhdrazone-3-ketiminobutyronitriles were synthesised and reacted with hydrazine hydrate to afford the corresponding 5-amino-4-arylazo-3-methyl-1H-pyrazoles. Thirteen novel hetaryldisazocalix[4]arene derivatives were achieved by diazotisation of 5-amino-4-arylazo-3-methyl-1H-pyrazoles using nitrosylsulphuric acid, coupled with 25,26,27-tribenzoyloxy-28-hydroxycalix[4]arene. The obtained hetaryldisazocalix[4]arene dyes were characterised based on Fourier Transform–infrared, proton nuclear magnetic resonance and mass spectroscopic techniques, as well as elemental analysis. The solvatochromic behaviour of these dyes in various solvents was examined. Acid-base effects on the visible absorption maxima of the dyes were also reported.

Merocyanine dyes containing an isoxazolone nucleus: Synthesis, X-ray crystal structures, spectroscopic properties and DFT studies

Two merocyanine dyes, each with an isoxazolone nucleus, were synthesized and characterized by NMR, IR, UV–Vis spectroscopy, elemental analyses and single X-ray diffraction. Crystallographic data revealed that one dye crystallized in an orthorhombic system, Cmca space group, while the other dye crystallized in a monoclinic system, P2 1/n space group. In the case of both dyes, the molecules adopted the most stable ketonic tautomeric form, and the crystal packing was stabilized by hydrogen bonds and π–π stacking interactions. The absorption spectra of the dyes in various solvents of different polarities were studied at room temperature. The equilibrium geometries, vibrational data and electronic spectra of the compounds were also investigated by the B3LYP method. Importantly, the predicted results fit to the experimental data, showing that this quantum chemical technology is an efficient approach to predict the properties of merocyanine dyes.

Changes induced by solvent polarity in electronic absorption spectra of some azo disperse dyes

The electronic absorption spectra of some azo disperse dyes in various solvents of different polarities have been studied at room temperature. The solvent effects on the wavenumbers of the absorption band maxima ( ṽ max) were discussed using the following solvent parameters, refractive index, n, dielectric constant, ε and empirical Kamlet–Taft solvent parameters, π* (dipolarity/polarizability), α (hydrogen bond donating capacity) and β (hydrogen bond accepting ability). The solute–solvent interactions were determined on the basis of multilinear solvation energy relationships concept. The fitting coefficients obtained from this analysis allowed us to estimate the contribution of each type of interactions to the total spectral shifts in solution. The established dependences between ṽ max and the solvent parameters emphasize that the visible band of the studied molecules is affected by both non-specific and specific solute–solvent interactions.

The synthesis, spectroscopic properties and theoretical calculation of some novel disperse disazo dyes derived from 3-amino-5-hydroxy-1-phenylpyrazole

In this study 5-amino-4-arylazo-3-methyl-1H-pyrazoles ( 1a– 1m) were diazotised and coupled with 3-amino-5-hydroxy-1-phenylpyrazole to give disperse disazo dyes ( 2a– 2m). The newly synthesized 13 disperse disazo dyes were characterized by elemental analysis and spectral methods. The solvatochromic behaviour of these disperse disazo dyes in various solvents was evaluated. Substituent, acid and base effects on the visible absorption spectra of the disperse disazo dyes substituted with electron-withdrawing and electron-donating groups at their o-, m-, p-position were also reported in detail. Additionally, theoretical calculations are performed for the disazo dyes. The molecular geometry and chemical shift are calculated by using ab initio calculations based on the density functional theory (DFT) in the ground state. The results obtained are in agreement with the experimental results.

Steady-state and time-resolved emission studies of Thioflavin-T

Steady-state absorption and emission properties of 3,6-dimethyl-2(4-dimethylaminophenyl)-benzothiazolium cation (ThT +) were studied at room temperature in variety of solvents. The multifluorescence of this dye was observed in different environmental conditions. The predominant emission bands observed are around 400 nm (I band), 450 nm (II band) and 485 nm (III band). The fluorescence emission bands I and II observed in acidic, basic and aqueous solutions are for 350 nm excitation and band III for 390 nm excitation at low concentration (1 × 10 −5 mol dm −3). However, the emission band at 520 nm was observed in all solvents at high concentration (1 × 10 −2 mol dm −3). The emission band around 400 nm shifts from 400 nm to 470 nm (shift 70 nm) when the excitation wavelength is varied from 350 nm to 380 nm and the emission at 485 nm shifts from 485 nm to 520 nm (shift 35 nm) for excitation wavelength 390–420 nm. Fluorescence decays of this dye in various solvents monitored over each emissions showed a tri-exponential behavior and the analysis yielded three decay components, respectively, in the range 0.13–0.76 ns, 1.08–2.00 ns and 2.50–12 ns. Based on the steady-state and time-resolved emission measurements band I (400 nm) is assigned due to protonation, band II (450 nm) locally excited state (LE) and the band III (485 nm) due to dimerization via H-bonding. Time-resolved fluorescence anisotropy measurements as a function of viscosity were carried out over emissions 450 nm and 550 nm and were fitted to single exponential. The shorter reorientation times (56–332 ps) at emission maximum 450 nm were compared with the theoretical values estimated using the hydrodynamic model (SED model) and are attributed to free rotations of the molecule. However, longer reorientation times (188–726 ps) at emission maximum 550 nm were assigned to dimerization/higher aggregates of the solute molecule. The deviations of experimentally measured τ r values at emission maxima 450 nm with those of theoretically estimated values were discussed.

The synthesis and characterization of novel coumarin dyes derived from 1,4-diethyl-1,2,3,4-tetrahydro-7-hydroxyquinoxalin-6-carboxaldehyde

1,4-Diethyl-1,2,3,4-tetrahydro-7-hydroxyquinoxalin-6-carboxaldehyde was synthesized and condensed with substituted active methylene compounds to obtain a series of novel coumarin compounds. Solutions of the dyes in various solvents exhibited an orange hue and brilliant fluorescence and displayed high thermal stability, as determined using thermogravimetric analysis. The dye having a heterocyclic benzimidazole ring as an electron withdrawing system was selected as a representative compound for comparison of its spectral characteristics with known analogues.

Solvatochromic behavior on the absorption and fluorescence spectra of Rose Bengal dye in various solvents

The absorption and fluorescence spectra of Rose Bengal dye were studied in various solvents. It was found that solvent effects on the absorption wavelength are consistent with the solvatochromic model of Kamlet, Abboud and Taft. The solvent polarizability value π* was found to have a linear relationship with the absorption wavelength of the dye in various solvents. Additionally, the normalized transition energy value ( E T N ) showed some scattering when plotted versus Δ ν af. Density functional calculations were used to assign the absorption in the region 540–570 nm to a π– π* transition between the HOMO and LUMO of the anion. Experimental ground state and excited state dipole moments were calculated by using the solvatochromatic shifts of absorption and fluorescence spectra as a function of the dielectric constant ( ɛ) and refractive index ( n). The dipole moment for Rose Bengal was found to be 1.72 Debye in the ground state, whereas this value was 2.33 Debye in the excited state.

Ab initio studies of the λmax of naphthoquinones dyes

Using a state-of-the-art time-dependent density functional (TD-DFT) approach that includes the explicit consideration of bulk medium effects on both the ground-state geometry and the electronic spectrum, we have determined the λ max of 86 naphthoquinones (NQ) dyes in various solvents for a total of 151 cases. In most cases, TD-DFT provides the correct ordering of transitions for substituted NQ dyes. Comparisons with experimental values lead to a mean signed error of −7.2 nm (0.039 eV) and a mean absolute error of 20.1 nm (0.113 eV). It turns out that the average errors are smaller for the hydroxy and methoxy derivatives, than for amino substituted dyes. It is also demonstrated that the statistical treatment of the data does not significantly improve the agreement between the experimental and the theoretical values. We also discuss average basis set effects and solvatochromism.

Synthesis and absorption spectra of some novel heterocyclic disazo dyes derived from pyridone and pyrazolone derivatives

Heterocyclic amines were diazotized and coupled with 3-aminocrotononitrile to give the 2-hetarylhydrazone-3-ketiminobutyronitrile ( 1a– 1e) which can react with hydrazine hydrate and phenylhydrazine to afford the corresponding 5-amino-3-methyl-4-hetarylazo-1H-pyrazoles and 5-amino-3-methyl-4-hetarylazo-1-phenylpyrazoles ( 2a– 2j), respectively. Then, some novel disazo dyes 3a– 3j and 4a– 4j were synthesized by diazotisation of 5-amino-3-methyl-4-hetarylazo-1H-pyrazoles and 5-amino-3-methyl-4-hetarylazo-1-phenylpyrazoles using nitrosyl sulphuric acid, coupling with 3-cyano-6-hydroxy-4-methyl-2-pyridone and 3-methyl-1H-pyrazole-5-one. The dyes were characterized by elemental analysis and spectral methods and the solvatochromic behaviour of the dyes in various solvents was evaluated. Substituent, acid and base effects on the visible absorption maxima of the dyes were also reported.

Synthesis of some novel pyrazolo[5,1- c][1,2,4]triazine derivatives and investigation of their absorption spectra

In this study, 5-amino-4-hetarylazo-3-methyl-1 H-pyrazoles were diazotised and coupled with malononitrile and ethyl cyanoacetate to give pyrazolylazo malononitriles and ethyl pyrazolylazo cyanoacetate, respectively. Ten novel pyrazolo[5,1- c][1,2,4]triazine dyes were synthesized by heating of pyrazolylazo malononitriles and ethyl pyrazolylazo cyanoacetate in glacial acetic acid. The dyes were characterized by elemental analysis and spectral methods. The solvatochromic behaviour of these diazo dyes in various solvents was evaluated. Substituent, acid and base effects on the visible absorption maxima of the dyes are also reported.

Synthesis, structure and photophysical properties of three new hemicyanine dyes

Three new hemicyanine dyes that feature a fixed pyridine cation as electron acceptor, trans, trans-4-{4-[4-( N, N-diphenylamino)styryl]styryl}- N-methylpyridinium iodide ( 1), trans, trans-4-{4-[4-( N-carbazolyl)styryl]styryl}- N-methylpyridinium iodide ( 2) and trans, trans-4-{4-[2-(benzothiazole-2-yl)ethenyl]styryl}- N-methylpyridinium iodide ( 3), have been synthesized. The crystal structure of dye 1 was determined. X-ray diffraction analyses reveal that 1 crystal belongs to monoclinic, P2 1/ c space group. Composite materials with these organic dyes doped into polymer-impregnated composite glass were prepared. Photophysical properties of these dyes in various solvents and composite glass were investigated in detail. Generally, photophysical properties of the dyes greatly increase in glass matrices compared with that in solution and there is no obvious fluorescence quenching in high doped concentration. The relationships between molecular structure and photophysical properties of this series of dyes were discussed.