Structure And Properties Of Supramolecules Based On Electrostatic Self-assembly

A serious of anionic amphiphilic molecules with amide or urea group have been synthesized and characterized in detail. They can self-assemble to form micelles driven by a combined effect of hydrophobic interactions and hydrogen bonds. When these molecules are mixed with a cationic platinum(Ⅱ) complex, metallosupramolecular amphiphiles form in aqueous solution. The resulting supra-amphiphiles self-assemble into sheet nanostructures. Their critical micelle concentrations are much lower than their corresponding molecular precursors. When a-cyclodextrin was added, a host-guest interaction occurs between a-cyclodextrin and alkyl chain and thus the aggregates of the supra-amphiphiles dissociated. In these aggregates, the platinum(Ⅱ) complexes are brought closely, leading to the presence of Pt-Pt and π-π stacking interactions. Therefore, both the metal-metal-to-ligand charge-transfer absorption (MMLCT,550nm) and3MMLCT luminescence (628nm) bands are remarkably enhanced in their intensities. By disassembling the aggregates through host-guest recognition with a-cyclodextrin, both the MMLCT absorption and luminescence decrease back to the original intensities of the platinum(Ⅱ) complex as a result of the absence of Pt···Pt and π-π stacking interactions. The fluorescence reversibility has been realized by the reversible aggregate process.The electrostatic combination of cationic polyelectrolytes with polyoxometalates (POMs) in aqueous solution yielded POM-based free-suspended sheets with a plan-view size of sub-millimeter ranges and a nanoscale thickness. Furthermore, the sheets formed by the polyelectrolyte and phthalocyanine tetrasulfonate acid had a plan-view size of almost1mm. These findings were attributed to the anisotropic electrostatic interactions induced by the molecular shapes/conformations of ionic building blocks.