Self-Assembly Pathways of Carbazole-derived Macrocycles Into Nanotubular Architectures

Abstract

Cooperative self-assembly based on multiple non-covalent interactions is ubiquitous in nature, yet the rational design of artificial cooperative systems remains challenging. Here we synthesize two carbazole derivatives, CbzE (with an ester group) and CbzA (with amide groups), to investigate how hydrogen bonding (HB) and halogen bonding (XB) jointly guide self-assembly into nanotubular supramolecular polymers. Using 1,4-diiodotetrafluorobenzene (DITFB) as XB donor or diplatinum(II) as linker, two types of [4 + 4] macrocycles are constructed and characterized by high-resolution mass spectrometry, ultraviolet-visible, infrared, and atomic force microscopy. CbzA, benefiting from strong HB, cooperatively assembles with DITFB into nanofibers and nanotubes, whereas CbzE, lacking amide groups, forms only disordered aggregates. Pt(II) coordination disrupts HB networks and redirects CbzA toward lateral aggregation, underscoring the sensitivity of assembly pathways to the balance of interactions. Remarkably, nanotubular CbzA + DITFB structures disassemble rapidly under trifluoroacetic acid vapor but are restored by triethylamine, demonstrating a reversible gel–sol–gel transition. This orthogonal acid/base responsiveness highlights the tunable and dynamic features of cooperative HB/XB systems. Overall, these results reveal the critical role of HB and XB cooperativity in directing ordered architectures and provide new design principles for intelligent supramolecular polymers with stimuli-responsive functions.