Restricted rotation and tunable fluorescence in atropisomeric naphthyl pyridine chromophores.

Enhanced fluorescence quantum yields are enabled by simple reactions at the heterocyclic nitrogen in naphthyl-pyridine chromophores in which the electronic properties can be tuned through protonation, oxidation, and alkylation at the nitrogen center. Fluorescence quantum yield is increased by reacting the pyridine lone pair with either a proton or an alkyl group. Restricted intramolecular rotation (RIR) was observed upon alkylation, as evidenced by the presence of atropisomers.

Phosphonium Polyelectrolyte Complexes for the Encapsulation and Slow Release of Ionic Cargo.

Polyelectrolyte complexation, the combination of anionically and cationically charged polymers through ionic interactions, can be used to form hydrogel networks. These networks can be used to encapsulate and release cargo, but the release of cargo is typically rapid, occurring over a period of hours to a few days and they often exhibit weak, fluid-like mechanical properties. Here we report the preparation and study of polyelectrolyte complexes (PECs) from sodium hyaluronate (HA) and poly[tris(hydroxypropyl)(4-vinylbenzyl)phosphonium chloride], poly[triphenyl(4-vinylbenzyl)phosphonium chloride], poly[tri(-butyl)(4-vinylbenzyl)phosphonium chloride], or poly[triethyl(4-vinylbenzyl)phosphonium chloride].