Large-Scale Supramolecular Structure in Solutions of Low Molar Mass Compounds and Mixtures of Liquids. III. Correlation with Molecular Properties and Interactions

The presence of a large-scale supramolecular structure is evidenced in a large variety of electrolyte solutions, nonelectrolyte solutions, and mixtures of liquids. This structure comprises submicron-sized domains with different solute concentration from that in the rest of solution. While the first paper of this series [J. Phys. Chem. B 2006, 110 (9), 4329-4338] dealt with a detailed characterization of the supramolecular structure and the second paper [J. Phys. Chem. B 2006, 110 (9), 4339-4345] dealt with the kinetics of the formation of this structure and its long-time stability, the present work contains a detailed classification of systems with respect to the capability of formation of the supramolecular organization. Around 100 different solute-solvent pairs were investigated in total, covering most common inorganic and organic electrolytes, nonionic solid compounds, and a large variety of liquids. The main experimental techniques used were static and dynamic light scattering, which are very effective techniques in observing and characterizing association. Light scattering data were complemented by osmotic pressure data obtained by vapor pressure osmometry, which reflects association on a different principle. The presence and intensity of the supramolecular domain organization was correlated with properties and interactions between constituent molecules and ions. The most plausible explanation of the observed effect of the large-scale supramolecular structure at this stage of our knowledge is that domains form due to directional attractive interactions between solute molecules via hydrogen bond bridges formed by one or several solvent molecules, which are themselves hydrogen bonded.