Very facile polarity Umpolung and noncovalent functionalization of inorganic nanoparticles : a tool kit for supramolecular materials chemistry

The facile assembly of shell-by-shell (SbS)-coated nanoparticles [TiO2-PAC16]@shell1-7 (PAC16=hexadecylphosphonic acid), which are soluble in water and can be isolated as stable solids, is reported. In these functional architectures, an umpolung of dispersibility (organic apolar versus water) was accomplished by the noncovalent binding of ligands 1-7 to titania nanoparticles [TiO2-PAC16] containing a first covalent coating with PAC16. Ligands 1-7 are amphiphilic and form the outer second shell of [TiO2-PAC16]@shell1-7. The tailor-designed dendritic building blocks 3-5 contain negative and positive charges in the same molecule, and ligands 6 and 7 contain a perylenetetracarboxylic acid dimide (PDI) core (6/7) as a photoactive reporter component. In the redox and photoactive system [TiO2-PAC16]@shell7, electronic communication between the inorganic core to the PDI ligands was observed. Nanochameleons with switchable dispersion behavior: In these new shell-by-shell architectures, ionic and redox-active amphiphiles make the difference because they form an outer ligand shell that provides polarity umpolung, water solubility, and facile nanoparticle functionalization (see figure). © 2015 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim