Polarizability and isotope effects on dispersion interactions in water

True understanding of dispersion interaction in solution remains elusive because of difficulty in the precise evaluation of its interaction energy. Here, the effect of substituents with different polarizability on dispersion interactions in water is discussed based on the thermodynamic parameters determined by isothermal titration calorimetry for the formation of discrete aggregates from gear-shaped amphiphiles (GSAs). The substituents with higher polarizability enthalpically more stabilize the nanocube, which is due to stronger dispersion interactions and to the hydrophobic effect. The differences in the thermodynamic parameters for the nanocubes from the GSAs with CH3 and CD3 groups are also discussed to lead to the conclusion that the H/D isotope effect on dispersion interactions is negligibly small, which is due to almost perfect entropy-enthalpy compensation between the two isotopomers.

Importance of Molecular Meshing for the Stabilization of Solvophobic Assemblies

The effect of the methyl groups in neutral gear-shaped amphiphiles (GSAs) on the stability of nanocubes was investigated using a novel C_{2 v}-symmetric GSA, which was synthesized using selective alternate trilithiation of a pentabrominated hexaphenylbenzene derivative. The lack of only one methyl group in the GSA decreased the association constant for the assembly of the nanocube by 3 orders of magnitude. A surface analysis recently developed by the authors (SAVPR: surface analysis with varying probe radii) was carried out for characteristic isomers of the nanocube consisting of C_{2 v}-symmetric GSAs. It was found that the methyl groups near the equator of the nanocube play a significant role in the stabilization of the nanocubes.

Anion-enhanced solvophobic effects in organic solvent

Molecular balanced measured a two-fold anion-induced enhancement of the solvophobic effect in organic solvents.