Nucleotide-Induced Supramolecular Assembly of Phosphonium-Containing Conjugated Polyelectrolytes

Designing ordered nanoscale molecular assemblies has been inspired by natural occurring supramolecular structures in which dynamic noncovalent interactions play a key role in the nanotemplating process. Herein, we describe the self-assembly and quenching properties of a series of phosphonium-substituted poly(phenylene ethynylene) (PPE)-based conjugated polyelectrolytes (CPEs) in the presence of nucleotide phosphates. The study includes a detailed analysis of the changes in the absorption and fluorescence induced by the addition of nucleotides (AMP, ADP, ATP, GTP, and UTP). Notably, the polymer chains of PPh-4-3C were observed to undergo self-assembly upon interacting with ATP, resulting in a chiral, optically active supramolecular assembly with the spectroscopic signature of a J-aggregate. The supramolecular assembly derives from the intermolecular interactions between PPh-4-3C and ATP as confirmed by steady-state absorption, fluorescence, and circular dichroism spectroscopy in methanol solutions. The observations confirm that PPh-4-3C as a novel phosphonium-bearing cationic conjugated polymer forms optically active J-type aggregates in the presence of ATP. Interestingly, microscopy analysis techniques confirm the self-assembly of the PPh-4-3C/ATP system into capsule-like nanostructures.