Absorption spectra of nitroanilines in micellar solution--II

The absorption spectra of nitroanilines (o-, m- and p-) in aqueous and nonaqueous solution of neutral surfactant-Triton X-100 (TX-100) reveal many interesting phenomena. Nitroanilines and TX-100 behave as electron acceptor and donor, respectively, in both media during charge-transfer (CT) complex formation though water plays an important role in aqueous media. The thermodynamic and spectrophotometric parameters of nitroanilines-TX-100 interactions in two media have been determined and the electron accepting capability among the nitroanilines have been also established. In addition to this, role of surface in CT interaction, the site of CT interaction, intensity and stability of CT interaction between nitroanilines and TX-100 have been pointed out.     

Absorption spectra of dysprosium compounds in nonaqueous solutions. Spectral intensity analysis

Absorption spectra of dysprosium compounds were measured in amides and D₂O within the 5500–35000 cm^?1 region and in alcohols within the 7000–34300 cm^?1 region. The oscillator strengths of f-f absorptions bands below 35000 cm^?1 were determined. The intensities of the Dy³⁺ ground state absorption were analyzed according to the Judd-Ofelt theory of forced electric dipole transitions.A good fit to the measurements was obtained with the intensity parameter given in Tables 4–6. The polarizability effect on the intensity of the f-f transition with high value matrix elements U⁽⁴⁾ and U⁽⁶⁾ were considered.     

UV Absorption spectra of solutions of dipropargyl ethers

Conclusions The dipropargyl ethers of 4,4-dihydroxydiphenylpropane, methylphosphinic acid, diphenoxysilane, hexafluoro-2,2-bis-(hydroxyphenyl)propane, terephthalic, isophthalic acids, orcinol, resorcinol, 1,4-dihydroxyanthraquinone, maleic and succinic acids, dipropargylbenzal, dipropargylacetal, and dipropargylformal were identified by means of their UV spectra.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1349–1352, July, 1964     

Absorption and fluorescence spectra of 7-aminocoumarin derivatives

The absorption and fluorescence spectra of twelve 7-aminocoumarin derivatives have been studied with methanol and chloroform as solvents. Electronic transitions to nπ^* states have been traced. The effect of different substituents on the nitrogen was easily observed in the fluorescence spectra. Fluorescence quantum yields and oscillator strengths were evaluated. The role of hydrogen bonding on emission maxima, quantum yields and photolytic dissociation were discussed.     

Kinetic micellar effects in tetradecyltrimethylammonium bromide-pentanol micellar solutions

The reactions 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane + OH(-) and 2-(p-nitrophenyl)ethyl bromide + OH(-) were studied in tetradecyltrimethylamonium bromide, TTAB, and TTAB-pentanol micellar solutions. The influence of changes in the surfactant concentration as well as changes in the hydroxide ion concentration on the observed rate constant was investigated. If changes in the cmc and ionization degree provoked by the presence of the different amounts of n-pentanol in the micellar solutions are taken into account, the experimental kinetic data can be rationalized quantitatively by using the PIE model. Assuming that the ion-exchange equilibrium constant, K(OH(-)/Br(-)), for the competition between the bromide and the hydroxide ions in all TTAB and in TTAB-pentanol micellar solutions studied is the same, a good agreement between the theoretical and the experimental kinetic data was found in all the micellar media for the two processes studied. This assumption was checked by experimentally determining the ion-exchange equilibrium constant K(OH(-)/Br(-)) in TTAB and TTAB-pentanol micellar solutions through a spectroscopic method, results showing that the presence of n-pentanol does not affect substantially the value of K(OH(-)/Br(-)). The second-order rate constants obtained from the fittings decrease slightly when the amount of pentanol increases, being greater than that in aqueous solution. This acceleration can be explained considering that micelles accelerate the reactions in which the charge is delocalized in the transition state.     

Oxygen effects in aqueous solutions of laccases: Absorption spectra and reactivity

The optical absorption spectra of laccases in aqueous solutions were found to undergo reversible changes in the presence of O₂. It was suggested that dioxygen is coordinated in the active center of the completely oxidized native enzyme. Abnormal behavior of superoxide radical anions upon variation of the laccase concentration was found by pulse radiolysis. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1471–1474, August, 2000.     

Pyrene-N,N-dimethylaniline heteroexcimer systems in aqueous micellar solutions

Strong quenching of fluoroscence of pyrene by N,N-dimethylaniline as well as N,N-dimethylaniline sulfonate has been observed in aqueous micellar solutions. Photoinduced electron transfer from the anilines to excited pyrene near the micelle-water interface has been demonstrated by means of laser photolysis studies.     

13C NMR spectra of 7-substituted 8-mercaptoquinolines

The¹³C NMR spectra of 7-substituted [7-CH₃, 2,7-(CH₃)₂, 7-Cl, 7-Br, and 7-SCH₃] 8-mercaptoquinolines and 8-methylmercaptoquinolines were examined. It is shown that the changes in the¹³C chemical shifts of the quinoline ring in the spectra of 7-substituted 8-mercaptoquinolines are in good agreement with the additive contribution of the increments of the substituents, i.e., their conjugation with the ring is not disrupted. The conjugation of the SCH₃ group with the quinoline ring in 7-substituted 8-methylmercaptoquinolines is disrupted as a consequence of steric hindrance, and this leads to a decrease in the increments of this group. The data obtained are compared with the results of a calculation within the CNDO/2 approximation. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 801–805, June, 1980.     

Slow water diffusion in micellar solutions

Slowly diffusing water molecules were found by quasi-elastic neutron scattering (QENS) in a sodium dodecyl sulfate (SDS) micellar solution, and both their diffusion coefficient (4.33 x 10(-6) cm2 x s(-1)) and mole fraction (0.057) were determined. After successfully checking the mean slowing down of solvent molecules by the gradient compensated stimulated spin-echo (GCSTE) pulse sequence NMR method, a similar effect was observed with this technique in the solvent phase of dodecyl trimethylammonium bromide (DTAB) and differing chain length (X = 12, 20, 30, and 40) ethoxylated nonyl phenol (9NX) micellar systems. Following the literature, the experimental results are qualitatively explained by assuming that, apart from ionic hydration, H-bonds may form between the solvent molecules and the O or N atoms present in the hydrophilic (head)groups of the micelle-forming monomers.     

Two-photon absorption in aqueous micellar solutions

Addition of the surfactant sodium dodecyl sulfate at concentrations above the critical micelle concentration increases the fluorescence quantum yield and the two-photon absorption cross-section of charged [2.2]paracyclophane chromophores containing pairs of D-pi-D chromophores. The resulting spectra in the micellar solutions are very similar to those obtained for neutral isostructural analogues in toluene. The measured etadelta values are 1300 GM for 1C and 1920 GM for 2C, which are comparable or larger to those in toluene. These results highlight possible misleading interpretation of two-photon-induced emission for evaluating the concentration of labeled substrates used in two-photon microscopy and provide guidelines for designing molecular structures with optimized two-photon action cross-sections in water.     

(CTAB+BY)体系水溶液的光谱研究

用UV-Vis和共振Raman光谱,研究了阳离表面活性剂溴化二六烷基三甲胺(CTAB)和对阴离子染料亮黄(BY)混合体系在水溶液中的胶束化过程,结果表明,难溶盐的形成诱导了该体系胶束的提前形成,形成的胶束使BY由酸式结构转变为碱式结构,进一步研究水溶液和胶束溶液中BY的酸碱平衡过程,发现胶束表面使BY的表观解离常数增加了两个数量级,而在胶束水溶液中,随着电解质浓度的增加,BY的表观解离常数下降,由此说明BY处于胶束的扩散层中,并导致BY结构发生变化.     

Alternant molecular orbitals (amo's) for some organic semiconductors: Ion radical salts from 7, 7, 8, 8-tetracyanoquinodimethane (TCNQ) and chloranil/ para-phenylenediamine (PDC) charge transfer complex

We report an attempt of ab initio computation for the ground-state wave-function of a few organic semiconductors (namely TCNQ salts and the PDC charge transfer complex) for which we show that electrical conduction appears to look strongly like that of a band-gap semiconductor.     

Size distribution of aggregates in micellar solutions

A general expression for the equilibrium size distribution of polydisperse ionic aggregates in micellar solutions is proposed. This expression accounts for the interactions between the micelles. The interaction is modeled via screened electrostatic potential. Asymptotic formulae for nearly monodisperse case and for high polydispersity of the micelles are presented. The results show that the interactions lead to the stabilization of the monodispersity in the first case. In the second case the interactions cause an increase in the polydispersity of the micellar solution.     

Dynamics of molecular oxygen in micellar solutions

Fluorescence quenching by molecular oxygen has been employed to estimate dynamic parameters and solubility characteristics of molecular oxygen in micelle forming detergent solutions. A kinetic model which assumes that oxygen quenching occurs only in the micellar phase is employed to analyze the data.     

The solubilization of alcohols in micellar solutions

The specific conductivities of dodecyldimethylbenzylammonium bromide (C12BBr) have been determined in aqueous butanol and aqueous benzyl alcohol solutions in the temperature range of 5-40°C. From these data the temperature dependent critical micelle concentration (cmc) was determined. The molar fraction of alcohol in the micelle was estimated using the theory suggested by Motomura et al. for surfactant binary mixtures. The thermal properties such as standard Gibbs free energy, enthalpy and entropy of solubilization of alcohols in the micelles were estimated for the phase separation model. The change in heat capacity upon solubilization of alcohol in the micelle has been estimated form the above properties. This revised version was published online in July 2006 with corrections to the Cover Date.     

Absorption spectra,emission spectra,and magnetic susceptibility of chromium in sodium-β-alumina

Absorption spectra, emission spectra, and magnetic susceptibility from 4.2 to 300°K have been measured for β-alumina doped with $\text{2w}\text{o}$ chromium. Chromium-doped β-alumina sintered in air was found to contain only Cr(IV) even though Cr(III) was the oxidation state initially present. Heating air-sintered samples at 1200°C in $\text{10\% H}{}_2\text{90\% N}{}_2$ for 5 hr reduced the Cr(IV) to Cr(III). The absorption spectra for Cr(IV) and Cr(III) have been fitted to the Tanabe-Sugano diagram and Dq and B were calculated. Results are consistent with the assignment of both Cr(III) and Cr(IV) to octahedral coordination sites in β-alumina. A parallel study of chromium doped α-alumina also showed the existence of Cr(IV) and Cr(III) in that host lattice depending on the firing atmosphere.     

Fast dynamics of wormlike micellar solutions

We present the first measurements of the fast dynamics of cationic wormlike micelles (WLM) using neutron spin echo (NSE). The comparison with theory [Zilman, A.; Granek, R. Phys. Rev. Lett. 1996, 77, 4788. Granek, R. J. Phys. II 1997, 7, 1761]1,2 enables coarse grained parameters to be identified. We propose and validate a calibration procedure to extract the bending constant kappa from NSE measurements.     

Thermal analysis of aqueous micellar solutions

A micro differential temperature scanning calorimeter was used to characterize the structural changes between different types of micelles in aqueous solutions of ionic surfactants: anionic — sodium dodecylsulfate (SDS) — and cationic — hexadecyltrimethyl ammonium bromide (CTAB). Moreover, this technique allowed to confirm the existence of peculiar types of complexes between surfactants and selected solutes. In SDS solutions containing polyethylene glycols (PEG), the presence of complexes formed by small micelles adsorbed along the chains of the polymers was evidenced in the case of long enough polymer chains. In CTAB-phenol solutions, due to strong interactions between the polar heads of surfactant and phenol, molecular complexes of a composition of 1:1 molar ratio have been characterized. Depending on the ratio [phenol]/[CTAB], the rheological behaviour was found to change from fluid to viscoelastic and gel-like solutions, owing to the growth of elongated rod-like micelles. With entangled worm-like micelles, the important role of kinetics to reach the thermodynamic equilibria was shown.