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Addition of small amphiphiles such as 1,4-dioxane is found to affect radical recombination and escape rates in micelles such as sodium dodecyl sulphate (SDS). This has been demonstrated with the hydrogen-abstracted product of triplet benzophenone as the probe molecule. This result has been interpreted on the basis of the ability of dioxane to form “mixed” micelles, which thereby affect the size, viscosity and reflectivity of the boundary of SDS. Studies in presence of magnetic fields up to 15 kG show that the magnetic field effect remains unaffected by the addition of dioxane. This his been explained as due to the combined effect of size, viscosity and reflectivity of the boundary of the micelle.

The magnetic field sensitivity of the pyrene-dimethylaniline (Py-DMA) system, linked by a polystrene (PS) spacer, was examined. It was found that isodielectric mixtures of tetrahydrofuran (THF) and dimethylformamide (DMF) and benzene and dimethylsulphoxide (DMSO) behave differently, the latter quenching the magnetic field effect more than the former; this is opposite to that found for the unlinked Py-DMA system. These studies demonstrate the importance of the solvent-dependent polymer backbone conformation. It was found that, in both of the above solvent mixture, the normal luminescence (φ) and the magnetic-field-modulated luminescence (Δφ) exhibit a shift in wavelength, indicating conformers with different magnetic sensitivities. The spectra taken at different times after excitation also support this conclusion.

The excited state complexation reaction between 1,4-diphenyl-1,3-butadiene and N,N-dimethylaniline was studied. In a sufficiently polar medium, 1: 2 complexes (or exterplexes) were formed. This exterplex system is magnetic field (MF) sensitive. The various parameters which characterize the MF effect in radical ion pair systems, namely wavelength dependence of the MF, field dependence, dielectric constant dependence and time dependence, were studied. The anomaly between the theoretically estimated and experimentally determined B 1 2 values was explained on the basis of the hopping mechanism.

Excited benzil, encaged in sodium dodecylsulphate (SDS) surfactant in aqueous solution, generates a radical pair (benzil ketyl radical and SDS radical) on hydrogen abstraction from the micelle. The lifetime of this triplet-born radical pair is dependent on the magnetic field, reaching saturation at fields greater than 1 kG. An intermediate radical pair, as demonstrated by the occurrence of a magnetic field effect, is also observed on ππ* excitation of this fairly labile molecule. In addition, Cu2+ ions quench the effect of the magnetic field on the decay of the radical pair. From the temporal response and the magnetic field effect, it is concluded that radicals initially generated by nπ* and ππ* excitation are different.

The excited state proton transfer reaction was studied for carbazole (CAZL) in non-ionic (Triton X-100), cationic (cetyltrimethylammonium bromide (CTAB)) and anionic (sodium dodecylsulphate (SDS) micelles. The micelles strongly affect the equilibrium quotient of the process. Taking the excited state proton transfer reaction as a probe, the critical micelle concentrations (CMCs) for the three micellar solutions were estimated. Furthermore, a phase transition was observed at high ionic strengths for Triton X-100.