Electron micellar solutions

Utilizing FT-EPR teclmiques, van Willigen and co-workers have studied the photoinduced electron transfer from zinc tetrakis(4-sulfonatophenyl)porphyrin (ZnTPPS) to duroquinone (DQ) to fonn ZnTPPS and DQ in different micellar solutions [34, 63]. Spin-correlated radical pairs [ZnTPPS. . . DQ ] are fomied initially, and the SCRP lifetime depends upon the solution enviromnent. The ZnTPPS is not observed due to its short T2 relaxation time, but the spectra of DQ allow for the detemiination of the location and stability of reactant and product species in the various micellar solutions. While DQ is always located within the micelle, tire... 

Mechanisms of micellar reactions have been studied by a kinetic study of the state of the proton at the surface of dodecyl sulfate micelles [191]. Surface diffusion constants of Ni(II) on a sodium dodecyl sulfate micelle were studied by electron spin resonance (ESR). The lateral diffusion constant of Ni(II) was found to be three orders of magnitude less than that in ordinary aqueous solutions [192]. Migration and self-diffusion coefficients of divalent counterions in micellar solutions containing monovalent counterions were studied for solutions of Be2+ in lithium dodecyl sulfate and for solutions of Ca2+ in sodium dodecyl sulfate [193]. The structural disposition of the porphyrin complex and the conformation of the surfactant molecules inside the micellar cavity was studied by NMR on aqueous sodium dodecyl sulfate micelles [194]. 

Transmission electron micrography has, remarkably, been successfully used to image micelles formed by block copolymers in dilute solutions. Price and coworkers used two preparation methods. In the first method (Price and Woods 1973), f reeze etching, a drop of solution was rapidly frozen by quenching in liquid nitrogen. Solvent was then allowed to evaporate from a freshly microtomed surface of the droplet. Finally, a replica was made of collapsed micelles raised proud from the frozen surface. In the second method (Booth et al. 1978), a drop of micellar solution was allowed to spread and evaporate on a carbon substrate, and 0s04 was used to selectively stain one of the blocks. 

The term photoredox axial ligand addition is used in instances when a stable molecule (e.g. 02, NO) is coordinated to an electronically excited complex. As one of the rare examples of this kind of reactions, the visible-light-induced reversible formation of dioxygen adducts of Co(TPP) and its derivatives occurring in aqueous micellar solutions at room temperature, can be shown (the encapsulation of the complexes into Triton X micelles is a key factor of the reactions)... 

Quinones-Torrelo et al. (1999 2001) have demonstrated a correlation of pharmacokinetic properties with results from micellar liquid chromatography. In this method micellar solutions of nonionic surfactants are used as the mobile phase in reverse-phase liquid chromatography. Interactions between the mobile and stationary phases are purported to correspond to the membrane/water interface of biological barriers as hydrophobic, steric, and electronic interactions are important for both. For a series of 18 antihistamines Quinones-Torrelo et al. (2001) showed that both volume of distribution and half-life values were better correlated with retention on these columns than with the classical log K, w descriptor. 

Electrochemistry in micellar solutions can take several forms. A key question is whether aggregates form on the electrode surface, as shown in Fig. 2 below if they do, then electron transfer kinetics to species in solution will depend on whether the species can displace the surfactant or only approach the electrode to within the... 

Polarographic studies show, in addition to oxidation waves for [Os(bipy)3]2+, several reduction waves 130,158 this is also the case for [Os(4,4 -Me2bipy)3]2+, [Os(5,5 -Me2bipy)3]2+121 and [Os-(phen)3]2+. Recent cyclic voltammetry and coulombetry studies on [Os(bipy)3]2+ and [Os(phen)3]2+ in liquid S02 show successive one-electron oxidations to [Os(LL)3]3+ and [Os(LL)3]4+.lls There is a small but real difference in the Os111/u redox potential for [Os(phen)3]2+ in aqueous and in non-aqueous sodium lauryl sulfate micellar solutions.138 Correlations have been made between the oxidation potentials and charge-transfer transition frequencies in complexes [M(LL)3]2+ (Me = Fe, Ru, Os LL = bipy, 4,4 -Me2bipy, 5,5 -Me2bipy).159... 

Interfacial Electron Transfer Processes In Micellar Solutions... 

Spin correlated radical pairs, SCRPs, have been observed in micellar solutions and their origin was elucidated by Eorbes et al. These SCRP have been widely studied under pho tor eduction of benzophenone and other electron/hydrogen acceptors mostly... 

Acenaphthylene forms [2 + 2]-cycloaddition products with electron-deficient alkenes such as acrylonitrile and methyl acrylate (Nakamura et al., 1978). Cycloaddition is favoured by carrying out the reaction in a micellar solution owing to the inefficiency of the dimerisation in such an organised system. 

It has been observed that the SWNTs suspended in a micellar solution exhibit a well-defined optical spectrum and show a bright photoluminescence in the near infrared region (Figme 22). The individual SWNT suspended in air at room temperature also shows a bright photoluminescence. The emission spectrum of the semiconducting SWNTs correlates well with the absorption spectrum in a micellar solution. The intensity of emission decreases dramatically when the isolated nanotubes start aggregating in a destabilized micellar solution. The decrease in the emission is attributed to the quenching of electrons by the metallic nanotubes when... 

Chromatographic and related electrophoretic methods for the separation of transition metal complexes or their ligands were reviewed . Micellar electrokinetic chromatography (MEKC) presents a new development in the field of capillary zone electrophoresis (CZE). The use of micellar solutions expands the application of CZE to electronically neutral solutes, as well as charged ones. Thus, electrically neutral / -diketonates Cr(dik)3, Co(dik)3, Rd(dik)3, Pt(dik)2 and Pd(dik)2 were separated by CZE in micellar solutions of sds. A linear log-log relationship was found between the distribution coefficient and the partition coefficient of the complex between dodecane and water, which was used for prediction of both the distribution coefficients and the migration times of different metal complexes . 

CT complexes are formed and electron transfer occurs from excited molecules of anthracene derivatives to methylviologen in aqueous micellar media. Methylene blue quenches pyrene fluorescence by electron transfer in SDS micelles . E.lectron transfer between anthraquinone sulphonate radicals and duroquinone in SDS micellar solution occurs in the aqueous phase there is no evidence of intramicellar transfer. Photoionisation of... 

When a bicontinuous cubic lipid-water phase is mechanically fragmented in the presence of a liposomal dispersion or of certain micellar solutions e.g. bile salt solution), a dispersion can be formed with high kinetic stability. In the polarising microscope it is sometimes possible to see an outer birefringent layer with radial symmetry (showing an extinction cross like that exhibited by a liposome). However, the core of these structures is isotropic. Such dispersions are formed in ternary systems, in a region where the cubic phase coexists in equilibrium with water and the L(x phase. The dispersion is due to a localisation of the La phase outside cubic particles. The structure has been confirmed by electron microscopy by Landh and Buchheim [15], and is shown in Fig. 5.4. It is natural to term these novel structures "cubosomes". They are an example of supra self-assembly. 

M. J. Colaneri, L. Kevan, and R. Schmehl, An electron spin resonance study of charge separation in frozen sodium dodecyl sulfate micellar solutions containing tris(2,2 -bipyridine)ruthenium (II) complexes and alkylmethylviologens, J. Phys. Chem. 93, 397-401 (1989). 

The chemical shifts (5s) of substrate protons are different in reversed micellar media compared to aqueous solution. The chemical shift is a complex function of the environment around a proton, Influenced by the solvent type, external electrostatic forces and the internal electronic structure of the molecule. A change in the chemical shift for substrate protons between an aqueous and reversed micellar solution is an indication of a change in the local electronic environment. 

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