Donor-Acceptor co-assembly of twisted 1,8-difunctionalized carbazole and naphthalenediimide

Functionalized carbazoles are versatile organic building blocks that play pivotal roles in diverse applications, particularly in charge-transfer complexes, hole-transport materials, and interfacial modifiers. In this study, we synthesized 1,8-functionalized carbazole derivatives ( C1 - C5 ) with various aryl substituents that provided extended conjugation via Mizoroki-Heck coupling reaction using our previously developed phosphine ligand-based Pd catalysis. Among them, the di(1-vinylpyrene) derivative ( C4 ) exhibited a unique molecular conformation in which one pyrene unit is nearly coplanar with the carbazole. At the same time, the other is twisted by about 49°, resulting in a bidirectional π-stacking arrangement, as revealed by its single crystal structure. Photophysical, electrochemical, and computational studies collectively supported the influence of aryl substitution on the electronic nature of carbazole by tuning the HOMO-LUMO energy gap. AFM analysis showed that C4 self-assembled into spherical aggregates. In contrast, in the presence of naphthalenediimide ( NDI8 ), it formed a donor-acceptor charge-transfer complex (1:2 ratio) that further self-assembled into a highly ordered, micrometer-long fibrillar structure. This long-range structural uniformity offers promising architectures for emerging applications of organic functional materials.