Unique Supramolecular Assembly of Wheel‐Shaped Nanoscale Polyanions with a Hydrophobic Core

Abstract

AbstractThe unique self‐assembly behavior of the amphiphilicwheel‐shaped polyanion [{K(H2O)}3{Ru(p‐cymene)(H2O)}4P8W49O186(H2O)2]27– (1) in binary mixed solvents of water and various organic solvents is reported. Polyanion 1 does not undergo supramolecular assembly formation in water/acetone solutions with acetone contents below 55 vol.‐%. However, in solutions with acetone contents of 55–80 vol.‐%, vesicle‐like structures were observed by light scattering and further confirmed by transmission electron microscopy. The average size of the vesicles decreases with increasing acetone contents. Similar results were found in water/THF and water/acetonitrile binary solvents. This relation between assembly size and solvent composition contradicts the self‐assembly of all other polyanions reported to date, which all follow the charge–regulation mechanism. However, for various binary solvents containing 75 vol.‐% organic solvents (acetonitrile, ethanol, 2‐propanol, THF, dioxane), the assembly sizes of 1 decrease with increasing dielectric constants of the solvents, which is again consistent with the charge–regulation mechanism. This unique solution behavior of 1 could be partially due to possible involvement of the hydrophobic organic p‐cymene ligands in the self‐assembly process.