| A. The presence of counterions in the headgroup region of ionic micelles is crucial for their existence. Although experiments can provide valuable insight into the nature of ion binding to micelles, they are not devoid of limitations and model assumptions. Also, theoretical study of ionic micelles has received relatively little attention compared to other polyelectrolytes. In this work we address this issue with a combination of molecular modeling tools using a well-known example, dodecyl sulfate. First, the Poisson-Boltzmann and Monte Carlo methods are employed to analyze the distribution of monovalent counterions in the vicinity of a static atomic model of dodecyl sulfate micelle in a dielectric continuum. The latter approach is also applied to the practically important case of micellar catalysis and provides a simpler and more consistent kinetic description than other methods. The next level of sophistication are molecular dynamics simulations of micelle solutions where the solvent is modeled explicitly. It is found that simple monovalent ions favor direct coordination to headgroup(s) and this tendency is much more pronounced compared to a methyl sulfate solution. Structural information on ion-headgroup contact pairs obtained from classical molecular dynamics simulations is found to correlate with the results of quantum mechanical calculations on small clusters.; B. Fluorine hyperfine coupling constants (hfccs) in aromatic radicals are of significance in the elucidation of their electronic structure. However, experimental ESR data on fluorinated anion and polyacene radicals in general are lacking in the literature and to date there has not been a systematic study of fluorine hfccs in molecules of this size using modern methods of electronic structure calculation. This work reports ESR spectra and hfccs of anion radicals of 1,2,3,4-tetrafluoronaphthalene, 1,2,3,4-tetrafluoroanthracene, and 9,10-perfluoroanthraquinone. For these and other fluorinated aromatic ion-radicals density functional (B3LYP) calculations of F-hfccs with the EPR-III basis set give the best agreement with experiment (15%). It is also possible to correlate the experimental fluorine hfccs with the calculated π-electron spin populations in the C-F fragment, thus supporting the generally accepted view of the separation of σ- and π-electrons in aromatic molecules. |
