Generating extended foldamer dye stacks and unravelling their evolving exciton dynamics

Additional Data to report: https://doi.org/10.1038/s41557-026-02082-0 In biomacromolecules, many amino acids or nucleotides are needed to obtain defined secondary structures and concomitant advanced functionalities. However, when researchers generate synthetic model analogues composed of dyes to predict the (photo-)functional properties of the respective solid-state aggregates they often use dimer models. Here we introduce a foldamer series of closely π-stacked dyes from dimer to 14-mer, obtained by an iterative block-based coupling protocol, that enable the study of oligomer-length effects on their photophysical properties. Spectroscopic techniques identify a distinct change of fluorescence properties at around four to six dye units—affording narrowed fluorescence bands and an increase of the total quantum yield from 47% for the dimer up to 75% for the 14-mer—that is accompanied by the development of a multiexciton state. These results highlight the limitation of the dimer model and motivate future research on well-defined π-stacked foldamers, both as models for solid-state materials and as supramolecular wires for future electronic and photonic applications.