Pathway Complexity in Naphthalene Diimide Supramolecular Polymers: Interruption by an Aromatic Solvent

Solvents critically influence supramolecular assembly pathways, providing a straightforward strategy to steer structural outcomes without complex synthetic modifications. Here, by regulating solvent composition and employing synchrotron-based x-ray absorption spectroscopy, we elucidate how toluene (Tol) disrupts the continuous assembly of a naphthalene diimide (NDI) derivative. In methylcyclohexane, the system follows a sequential pathway from metastable nanoparticles to nanofibers. Introducing Tol interrupts this progression, stabilizing the nanoparticles as the sole product. Oxygen K-edge X-ray absorption spectroscopy analysis indicates that Tol selectively suppresses intermolecular hydrogen bonding via π-π interactions while leaving intramolecular hydrogen bonds (HBs) intact. These insights, framed through solute-solvent π-interactions, advance the concept of "solvent engineering" for rationally programming assembly pathways and functional architectures.