Basic hydrolysis of crystal violet in beta-cyclodextrin/surfactant mixed systems

The basic hydrolysis of crystal violet (CV) in mixed systems consisting of beta-cyclodextrin (beta-CD) and a micelle-forming surfactant, cetyltrimethylammonium chloride (CTACl), has been studied. beta-CD was found to catalyze the basic hydrolysis of CV through the interaction of its hydroxyl group, in its deprotonated form, with the carbocation in the complexed substrate. The addition of small amounts of CTACl, with [CTACl] below the critical micelle concentration, to beta-CD solutions does not have an effect upon the observed rate constant for the basic hydrolysis of CV. This behavior is different from that observed for the alkaline hydrolysis of N-methyl-N-nitroso-p-toluenesulfonamide and nitrophenyl acetates in mixed beta-CD/cationic surfactant systems. The proposed mechanism allows us to explain the experimental results on the basis of the high percentage of uncomplexed beta-CD in equilibrium with the micellar system, the low CV concentration, and the high value for the binding constant of CV by beta-CD.     

Aggregation behavior of fluorocarbon and hydrocarbon cationic surfactant mixtures: a study of 1H NMR and 19F NMR

The aggregation behavior and the interaction of four mixed systems for a cationic fluorocarbon surfactant, diethanolheptadecafluoro-2-undecanolmethylammonium chloride (DEFUMACl), mixing with cationic hydrocarbon surfactants, alkyltrimethylammonium chloride, CnTACl (n=12, 14, 16, and 18; where n=12 is DTACl, n=14 is TTACl, n=16 is CTACl, and n=18 is OTACl), were studied by 1H and 19F NMR in more detail. The results of 19F NMR measurements strongly indicate that in the three mixed systems of DEFUMACl/DTACl, DEFUMACl/TTACl, and DEFUMACl/CTACl at different molar fractions of fluorocarbon surfactant (alphaF=(cDEFUMACl/cDEFUMACl+cCnTACl)), with an increase of the total concentration of fluorocarbon and hydrocarbon surfactants (cT=cF+cH), the mixed micelles at the first break point and the individual DEFUMACl micelles at the second break point form. However, three different types of micelles were determined in DEFUMACl/OTACl mixtures by 19F NMR measurements, OTACl-rich and DEFUMACl-rich mixed micelles and individual DEFUMACl micelles, respectively. The chemical shifts of proton Deltadelta (1H) for -CH3 in the mixed systems of DEFUMACl/CnTACl (n=12, 14, 16, and 18) have different variation trends from the 19F NMR measurements. For the two systems of DEFUACl/DTACl and DEFUMACl/TTACl, the mixed micelles form at the first break point. At the second break point, for lower alpha F values the DTACl-rich and TTACl-rich mixed micelles form with a strong downfield shift and for higher alpha F values DEFUMACl-rich mixed micelles form with a strong upfield. For the other two systems of DEFUMACl/CTACl and DEFUMAC/OTACl, the chemical shifts of proton Deltadelta (1H) of -CH3 increase with an increase of the total concentration of DEFUMACl/CTACl or OTACl, and mixed CH- and CF-surfactant micelles form. At higher total concentration, the greater effect of fluorinated chains of DEFUMACl on CH-chains was obvious, resulting in the strong upfield chemical shifts. In cationic fluorocarbon and hydrocarbon surfactant mixtures, the different kinds of micelles observed by 19F and 1H NMR measurements could be caused by the increase in alkyl chain length of hydrocarbon surfactants with different critical micelle concentrations. Combining two theoretical models for mixing, for the four different chain-length hydrocarbon surfactants studied, one can conclude that the two components of mixtures interact with each other and form mixed micelles in two completely different ways according to their molecular properties and cmc values in a certain range of total concentrations. One is close to an ideal mixing case with the formation of one type of mixed micelles, such as the DEFUMACl/DTACl and DEFUMACl/TTACl systems. The other is a demixing case with the formation of two types of micelles, i.e., fluorocarbon-rich and hydrocarbon-rich mixed micelles, such as DEFUMACl/CTACl and DEFUMACl/OTACl systems. However, as the total concentrations of the mixed systems are high enough, the four systems tend to demix and to form individual micelles of corresponding components due to the initial respective interaction between fluorocarbon and hydrocarbon chains. That is to say, at high total concentration, the individual DEFUMACl micelles in all four systems could form. These results may be primarily directed toward acquiring an understanding of the mechanism of CF-CH mixtures in aqueous solution and secondarily directed toward providing more detailed information on nonideal mixing.     

N-Alkylamines-Based Micelles Aggregation Number Determination by Fluorescence Techniques

Aggregation numbers of micelles based on N-alkylamines and mixed systems CTACl/N-alkylamines have been determined using fluorescence techniques. The values of aggregation number are compared as a function of hydrocarbon chain length and as a function of the molar fraction in the mixed systems.     

A simple and sensitive analytical method for the determination of antimony in environmental and biological samples.

The results of a study and application of leucocrystal violet for the determination of antimony in parts per million levels is described here. The proposed method is based on the reaction of antimony(III) with acidified potassium iodate to liberate iodine. The liberated iodine selectively oxidizes leucocrystal violet to crystal violet dye. The formed dye shows maximum absorbance at 590 nm. The color system obeys Beer's law in the concentration range from 0.4 - 3.6 microg antimony per 25 ml of final solution. The molar absorptivity and Sandell's sensitivity were found to be 7.32 x 10(5) l mol(-1) cm(-1) and 0.0016 microg cm(-2), respectively. All variables were studied in order to optimize the reaction. The proposed method is satisfactorily applicable for the analysis of antimony in various environmental and biological samples. The method is simple, highly sensitive, accurate and reliable.     

Investigation on the basic hydrolysis of crystal violet in mixed reverse micelles formed with AOT and nonionic surfactants

 The kinetics and thermodynamics of the basic hydrolysis of crystal violet (CV) in mixed reverse micelles formed with anionic surfactant AOT and nonionic surfactants have been investigated. It was found that the mixed reverse micelles had inhibitory effects on CV hydrolysis compared with the normal aqueous solution, and the equilibrium constant K of the reaction in mixed reverse micellar systems is smaller than that in pure water. The influence of water content and surfactant composition in reverse micelles on the second-order rate constant k ₁ of the positive reaction, on the first-order rate constant k _-1 of the reverse reaction, as well as on the equilibrium constant K of the reaction has been studied, and the results obtained were interpreted in terms of the nature of surfactants and the properties of microenvironment where the reaction took place. Received: 24 October 1997 Accepted: 18 March 1998     

New insights in cyclodextrin: surfactant mixed systems from the use of neutral and anionic cyclodextrin derivatives

The kinetics of the hydrolysis of 4-methoxybenzenesulfonyl chloride (MBSC) have been studied in mixed systems made up of surfactant, sodium dodecyl sulfate (SDS) or tetradecyltrimethylammonium bromide (TTABr), and cyclodextrin, beta-CD or SBE-beta-CD(Captisol). The use of SBE-beta-CD instead of beta-CD allowed us to indicate certain characteristics of the mixed cyclodextrin-surfactant system: (a) The percentage of uncomplexed cyclodextrin is higher for SBE-beta-CD than for beta-CD when we use SDS, but the opposite effect was observed when we use TTABr. This behavior can be explained by taking into account the increase in salinity when we add SBE-beta-CD, and the electrostatic forces between the SBE-beta-CD and the surfactant that have influence on the complexation. (b) The presence or even the charge of cyclodextrin has no effect on the properties of surfactant micelles once they have been formed; in particular, it does not alter K(s)(m) or k(m), parameters very sensitive to the micellar system structure. Therefore, we can conclude that for surfactants concentrations lower than the micellization point, the charge of cyclodextrin modifies the cyclodextrin-surfactant interactions but once the micelles have been formed there is no interaction between them and the cyclodextrins.     

Origin of the sphere-to-rod transition in cationic micelles with aromatic counterions: specific ion hydration in the interfacial region matters

Sphere-to-rod transitions of cetyltrimethylammonium (CTA+) micelles with dichlorobenzoate counterions are remarkably substituent dependent. Simultaneous estimates of the interfacial molarities of H2O, MeOH, and Cl- and 2,6- and 3,5-dichlorobenzoate (2,6OBz and 3,5OBz) counterions were obtained by the chemical trapping method in mixed micelles of CTACl/CTA3,5OBz and CTACl/CTA2,6OBz without added salt. Increasing the CTA3,5OBz mole fraction produces a marked concurrent increase in interfacial 3,5OBz- and a decrease in interfacial H2O concentrations through the sphere-to-rod transition. No abrupt concentration changes are observed with increasing CTA2,6OBz mole fraction. Counterion-specific changes in the interfacial water concentration may be a major contributor to the delicate balance of forces governing micellar morphology.     

Spectral characteristics and nonlinear studies of crystal violet dye

Solid-state dye-doped polymer is an attractive alternative to the conventional liquid dye solution. In this paper, the spectral characteristics and the nonlinear optical properties of the dye crystal violet are studied. The spectral characteristics of crystal violet dye doped poly(methylmethacrylate) modified with additive n-butyl acetate (nBA) are studied by recording its absorption and fluorescence spectra and the results are compared with the corresponding liquid mixture. The nonlinear refractive index of the dye in nBA and dye doped polymer film were measured using z-scan technique, by exciting with He-Ne laser. The results obtained are intercompared. Both the samples of dye crystal violet show a negative nonlinear refractive index. The origin of optical nonlinearity in the dye may be attributed due to laser-heating induced nonlinear effect.     

PHOTOREDUCTION OF CRYSTAL VIOLET IN SOLUTION AND IN POLY(VINYL ALCOHOL) FILMS

Abstract— The photolysis of crystal violet oxalate has been studied in aqueous and non-aqueous solutions and in films of poly(viny1 alcohol) at room temperature. Evidence has been obtained from electron-spin-resonance, absorption and fluorescence spectroscopy for the formation of the semireduced dye radical, tri-( p -dimethylaminophenyl)methyl, both in solution and in the solid state. Electron spin resonance and luminescence spectra of the radical produced by electrolytic reduction of the dye are also reported.     

Zero kinetic energy photoelectron study of SO2+(X2A1) using coherent extreme ultraviolet radiation

Using our newly built extreme ultraviolet (XUV) photoelectron and photoion spectrometer, we have obtained the pulsed field ionization zero kinetic energy (ZEKE) photoelectron spectra of SO2+(X2A1)<--SO2(X1A1) by coherent XUV radiation in the energy range of 12.29-12.82 eV. The adiabatic ionization potential (IP) of SO2 is 12.3458+/-0.0002 (eV), which was determined by comparing the partially resolved rotational branch contour with the simulated one. Besides the bending vibrational mode (upsilon2) which was found to be exclusive in the photoelectron spectra (PE) reported previously, we also observed the other two modes: the symmetric stretching (upsilon1) and the antisymmetric stretching (upsilon3) vibrations. The fundamental of the symmetric stretching (upsilon(1)) is 1057 cm(-1) and the overtone of the antisymmetric stretching (2upsilon(3)) is 2494 cm(-1). The new vibrational progressions (upsilon(1)00)+, (1upsilon(2)0)+, (2upsilon(2)0)+, and (0upsilon(2)2)+ have also been observed, and these new observations suggested that the irregular structure of (0upsilon(2)0)+ assigned to the previous PE spectra should be reconsidered. The comparison of the intensities of these vibrational bands with the calculated Franck-Condon factors with harmonic approximation was also made.     

Molecular interaction of Congo Red with conventional and cationic gemini surfactants

Interaction of tetradecyltrimethylammonium bromide (TTAB), octylophenylpolyoxyethylene ether (TX-100), sodium dodecylsulfate (SDS), N,N′-ditetradecyl-N,N,N′,N′-tetramethyl-N,N′-butanediyl-diammonium dibromide (14,4,14) and N,N′-didodecyl-N,N,N′,N′-tetramethyl-N,N′-butanediyl-diammonium dibromide (12,4,12) with an anionic diazo dye, Congo Red, was investigated using conductometry, spectroscopy, tensiometry, and pulsed field gradient NMR (PFG-NMR). The formation of dye-surfactant ion pairs, their small mixed aggregates (below the critical micelle concentration (CMC) of these surfactants) and surfactant micelles were detected successfully. Above the CMC, the dye reverted to its monomeric state and solubilized in the micelles. Job's method was used to determine the stoichiometric ratio of dye and surfactant in ion pairs and revealed the formation of more hydrophile ion pairs for geminis compared to their conventional analogs. Quantitative results obtained from tensiometry indicated the existence of considerable synergism for cationic surfactants and antagonism for anionic SDS. In addition, the synergism observed for TX-100 revealed the effect of π-π stacking and hydrophobic forces on ion pair and mixed micelle formation. The increase of dye-surfactant interactions by increasing the electrical charge and chain length of cationic surfactants confirmed the importance of both electrostatic and hydrophobic forces in binary dye/surfactant systems. The hydrodynamic radii of the micelles were determined by self-diffusion coefficient measurements. The average size of the cationic and nonionic micelles increased in the presence of CR molecules.     

Study on the photodissociation spectra of CS2+ via B2Sigma u+ and C2Sigma g+ electronic states

The photodissociation spectra of CS(2)(+) ions via B(2)Sigma(u)(+) and C(2)Sigma(g)(+) electronic states have been studied by using two-photon excitation, where the parent CS(2)(+) ions were prepared by [3 + 1] REMPI (resonance-enhanced multiphoton ionization) at 483.2 nm from the jet-cooled CS(2) molecules. The [1 + 1] photodissociation spectrum of CS(2)(+) via the B(2)Sigma(u)(+)(upsilon(1)upsilon(2)0) <-- X(2)Pi(g,3/2)(000) transition was obtained by scanning the dissociation laser in the wavelength range of 270-285 nm and detecting the signal of both S(+) and CS(+). The [1 + 1'] photodissociation spectra of CS(2)(+) were obtained by fixing the first dissociation laser at 281.94 or 277.15 nm to excite the B(2)Sigma(u)(+) (000 or 100) <-- X(2)Pi(g,3/2)(000) transitions and scanning the second dissociation laser in the range of 606-763 nm to excite C(2)Sigma(g)(+)(upsilon(1)upsilon(2)0) <-- B(2)Sigma(u)(+)(000,100) transitions. New spectroscopic constants of nu(1) = 666.2 +/- 2.5 cm(-1), nu(2) = 363.2 +/- 1.9 cm(-1), chi(11) = -5.5 +/- 0.1 cm(-1), chi(22) = 1.6 +/- 0.1 cm(-1), chi(12) = -8.6 +/- 0.2 cm(-1), and k(122) = 44.9 +/- 2.5 cm(-1) (Fermi resonance constant) for the C(2)Sigma(g)(+) state are deduced from the [1 + 1'] photodissociation spectra. On the basis of the [1 + 1] and [1 + 1'] photodissociation spectra, the wavelength and level dependence of the product branching ratios CS(+)/S(+) has been found and the dissociation dynamics of CS(2)(+) ions via B(2)Sigma(u)(+) and C(2)Sigma(g)(+) electronic states are discussed.     

Effects of surfactants on the adsorptive removal of basic dyes from water using an organomineral sorbent-iron humate

The sorption of basic dyes (methylene blue, malachite green, rhodamine B, crystal violet) onto a nonconventional organomineral sorbent-iron humate-was examined in the presence of various kinds of surfactants. It was found that nonionic (Triton X-100) and cationic (cetyltrimethylammonium bromide) surfactants exhibited a relatively small effect on the dye sorption. Anionic surfactants (sodium dodecyl sulfate), on the other hand, affected (in most cases) dramatically the sorption of basic (cationic) dyes. Typically, the dye sorption was enhanced in the presence of low concentrations of anionic surfactants. At high surfactant concentrations, a steep decrease in the dye sorption was observed in some systems, probably due to the formation of micelles that solubilize the dye molecules and prevent their sorption. A model describing these experimental dependencies was proposed. The sorption of basic dyes onto iron humate may be described by the pseudo-second-order kinetic equation. Diffusion processes were identified as the main mechanisms controlling the rate of the dye sorption.     

Spectroscopic Investigations on the Interaction of Crystal Violet with Nonionic Micelles of Brij and Igepal Surfactants in Aqueous Media

The behavior of the triphenylmethane dye crystal violet in aqueous solutions containing polyoxyethylene nonionic surfactants was investigated using absorption and fluorescence spectroscopic techniques. The interactions of the dye were examined in micellar media in order to prevent dye aggregation and to ensure maximum dye and surfactant interaction. The relative fluorescence enhancements and the binding constants of the dye to the surfactant micelles were determined. The micropolarities of the micellar environment sensed by the pyrene probe were estimated from the I ₁/I ₃ intensity ratios of the fluorescence spectra of pyrene. The fluorescence quenching of pyrene by hexadecylpyridinium chloride was investigated in aqueous surfactant mixtures at a fixed concentration of surfactant in order to determine the aggregation numbers. Attempts were made to correlate the binding constants obtained in this investigation to various micellar parameters.     

Investigating the interaction of crystal violet probe molecules on sodium dodecyl sulfate micelles with hyper-Rayleigh scattering

We report the use of the nonlinear optical technique of hyper-Rayleigh scattering to investigate the interaction of the cationic probe molecule crystal violet with micelles of sodium dodecyl sulfate. An absolute value of (847 +/- 80) x 10(-30) esu is measured at the fundamental wavelength of 870 nm for the molecular hyperpolarizability of crystal violet free in pure aqueous solutions. In aqueous solutions of sodium dodecyl sulfate, above and below the critical micelle concentration, the measured hyperpolarizability of crystal violet is weaker than in the solution free of sodium dodecyl sulfate. From the comparison with linear optical photoabsorption spectroscopy data, this difference is attributed to electrostatic interactions between the cationic crystal violet molecules and the negatively charged sodium dodecyl sulfate surfactant molecules present in excess. Polarization resolved hyper-Rayleigh scattering measurements are then performed to show that, below and above the critical micelle concentration, crystal violet molecules also undergo symmetry changes upon interaction with sodium dodecyl sulfate. Above the critical micelle concentration, the minimum fraction of micelles interacting with at least one CV molecule is estimated. For instance, for a crystal violet aqueous concentration of 150 microM, this fraction is larger than 7%.     

Influence of negatively charged interfaces on the ground and excited state properties of methylene blue

Properties of the ground and excited states of methylene blue (MB) were studied in negatively charged vesicles, normal and reverse micelles and sodium chloride solutions. All these systems induce dimer formation as attested by the appearance of the dimer band in the absorption spectra (lamdaD approximately 600 nm). In reverse micelles the dimerization constant (KD) corrected for the aqueous pseudophase volume fraction is two-three orders of magnitude smaller than KD of MB in water, and it does not change when W0 is increased from 0.5 to 10. Differences in the fluorescence intensity as a function of dimer-monomer ratio as well as in the resonance light scattering spectra indicate that distinct types of dimers are induced in sodium dodecyl sulfate (SDS) micelles and aerosol-OT (sodium dioctyl sulfoxinate, AOT) reversed micelles. The properties of the photoinduced transient species of MB in these systems were studied by time-resolved near infrared (NIR) emission (efficiency of singlet oxygen generation), by laser flash photolysis (transient spectra, yield and decay rate of triplets) and by thermal lensing (amount of heat deposited in the medium). The competition between electron transfer (dye*-dye) and energy transfer (dye*-O2) reactions was accessed as a function of the dimer-monomer ratio. The lower yield of electron transfer observed for dimers in AOT reverse micelles and intact vesicles compared with SDS micelles and frozen vesicles at similar dimer-monomer ratios is related with the different types of aggregates induced by each interface.     

Analysis of FT-IR spectra of dicyclopentadienyl (bis-substituted cyclopentadienyl) dithiocyano of titanium, zirconium and hafnium

The FT-IR spectra of 18 (R-Cp)2M(NCS)2 were measured. The M-Cp, M-NCS (M=Ti, Zr, Hf) and other vibration modes were reasonably assigned. All complexes of (R-Cp)2M(NCS)2 determined in this paper are bonded by N-M, and the absorption of upsilon(s)(M-Cp)(A1) (M=Ti, Zr and Hf) vibration all appear in 365 cm(-1) or so, while upsilon(as)(M-Cp)(B) appear successively around 420, 350 and 320 cm(-1) in order of Ti, Zr and Hf. The influence of the center metal atoms and the substituents on cyclopentadienyl upon the spectra was discussed. It is mainly in far infrared region that center metal atoms influence upon the infrared spectra. The influence of the substituents to cyclopentadienyling upon its vibration is not significant. Only between 1500 and 1480 cm(-1) did a new absorbing peak appear due to the introduction of substituents to activate upsilon(CC) vibration.     

Effects of pharmaceutical excipients on cloud points of amphiphilic drugs

The clouding behavior, i.e., formation of phase separation at elevated temperature (the temperature being known as cloud point (CP)), of three amphiphilic drugs, amitriptyline (AMT), clomipramine (CLP) and imipramine (IMP) hydrochlorides in the presence of various additives, like cationic surfactants (conventional and gemini), nonionic surfactants, bile salts, anionic hydrotropes, sodium salts of fatty acids and cyclodextrin has been investigated. These additives are generally used as drug delivery systems. The drugs used are tricyclic antidepressants. All the surfactants increase the CP of mixed micelles formed by cationic (conventional and gemini) and nonionic surfactants. Hydrotropes, bile salts and fatty acid salts, when added in low concentrations, increase the CP, whereas at high concentrations, they decrease it. β-Cyclodextrin behaves as simple sugar and decreases the CP of the drug solutions.     

Solvent and concentration effects on the visible spectra of tri-para-dialkylamino-substituted triarylmethane dyes in liquid solutions

We have characterized the spectroscopy properties of crystal violet (CV+) and ethyl violet (EV+) in liquid solutions as a function of the solvent type and dye concentration. The analysis of how solvent properties and dye concentration affects the electronic spectra of these tri-para-dialkylamino substituted tryarylmethane (TAM+) dyes was performed on the basis of two spectroscopic parameters, namely the difference in wavenumber (deltanu) between the maximum and the shoulder that appears in the short-wavelength side of the respective maximum visible band (deltanu = 1/lambda(shoulder)-1/lambda(max) cm(-1)), and the wavelength of the maximum absorption (lambda(max)). The solvent and the concentration effects on lambda(max) and deltanu have indicated that both solute/solute (ion-pairing and dye aggregation) and solute/solvent (H-bonding type) interactions modulate the shape of the visible electronic spectra of these dyes in solution. In solvent with small dieletric constant (epsilon < approximately 10), the formation of ion-pairs represents a major contribution to the shaping of these spectra. Upon increasing dye concentration the formation of ion-pairs was characterized by an increase in deltanu observed concomitantly with a red shift in lambda(max) In chloroform and chlorobenzene the ion-pair association constant of CV+ and EV+ with Cl- ions were found to be in the order of 10(6) and 10(5) M(-1), respectively. In trichloroethylene the association constant for the CV+Cl- pair was 10(8) M(-1). In water, dye aggregation instead of ion-pairing represents a major contribution to the shaping of the visible spectra of CV+ and EV+. Dye aggregation was indicated by an increase in deltanu observed concomitantly with a blue shift in lambda(max) upon increasing dye concentration. The distinct behavior of deltanu for dye aggregation and ion-pairing as a function of dye concentration can therefore assist in the characterization of these two distinct phenomena. The solute/solvent interactions were studied in a series of polar solvents in which solute/solute interactions do not occur in any detectable extent. The dependence found for deltanu as a function of the Kamlet-Tafts solvatochromic parameters (alpha, beta and pi*) is in keeping with previous inferences indicating that the splitting in the overlapped absorption band of CV+ and EV+ in hydroxilated solvents arises from a perturbation in the molecular symmetry induced by hydrogen bonding (donor-acceptor) type interactions with solvent molecules. A distinction between the effects of solute/solute and solute/solvent interactions on the visible spectra of these dyes is provided.     

Spectrophotometric determination of <Emphasis Type="Italic">L</Emphasis>-ascorbic acid in pharmaceuticals

A simple and sensitive spectrophotometric method for the determination of L-ascorbic acid with leuco crystal violet is proposed. The determination is based on the oxidation of analyte by potassium iodate. The colourless oxidation products were formed in the quantity equivalent to iodide ions. The iodide ions react with the excess of iodate ions in acidic medium, to form free iodine which oxidized leuco crystal violet (LCV) to the liberated crystal violet (CV ⁺) dye, showing maximum absorption at 588 nm. The absorbance was measured at pH of 4.1–4.2 in 1 cm cuvettes. Beer’s law was obeyed in the concentration range 0.5–4.0 μg/mL. The molar absorptivity of the coloured compound is 4.14 × 10⁴ L/mol cm for L-ascorbic acid. The analytical parameters were optimized and the method was successfully applied to the determination of L-ascorbic acid in pharmaceuticals. The results were compared with those obtained by methods proposed in Polish Standard.