Decoding Supramolecular Order in Naphthalene Diimides through Locally Disordered Entities

Materials design for wider organic electronics greatly benefits from supramolecular chemistry approaches, whereby elucidating structure-driven noncovalent interactions across length scales represents a characterization challenge. Methods probing long-range order often struggle to identify the heterogeneous nature of van der Waals interactions, leaving locally disordered regions and their impact on bulk properties unexamined. This study demonstrates that structural polymorphism in regioisomeric pyridine-substituted naphthalene diimide (PyNDI) assemblies imparts varying degrees of order and disorder. A synergistic combination of X-ray diffraction (XRD) and solid-state nuclear magnetic resonance (ssNMR) spectroscopy, supported by computational modeling, reveals that supramolecular order in ortho (o)- and para (p)-PyNDIs arises from cooperative π-stacking, lone-pair-π interactions, and lamellar interdigitation. In contrast, the meta (m)-isomer exhibits local disorder with different packing motifs that can be iteratively modeled using the structural knowledge obtained from their o- and p-PyNDIs crystalline analogues. The approach uniquely resolves locally disordered motifs by leveraging information obtained from structurally similar, but well-ordered, isomers of π-conjugated assemblies relevant to the optoelectronic paradigm.