Topology and peripheral functionality govern intramolecular π-π stacking, solid-state self-assembly and chiroptical...

Precise control over interlayer organization in nanographenes is a central challenge in carbon materials science because stacking geometry governs their electronic, supramolecular and chiroptical behaviors. Here we report a topological design strategy for rigid bilayer nanographenes with extensive intramolecular π-π overlap and tunable chiroptical properties. Two covalently locked extended helicenes, 1 and 2, were synthesized through a concise Sonogashira/Diels-Alder sequence followed by a kinetically controlled Scholl oxidation forming thirteen C-C bonds. Structural analysis revealed highly ordered bilayer architectures, while peripheral triflyloxy substitution in 2 markedly altered solid-state self-assembly and increased CPL brightness. Comparison with the topological isomer EP9H establishes a clear topology-property relationship across ground- and excited-state behaviour: although the more open topology of EP9H favours stronger intrinsic chiral induction, functionalization of 2 enhances molar absorptivity and overall chiroptical output.