4,9,13,18‐Tetraazateropyrenes: Synthesis, Cross‐Locked Saddle Packing and Unique Geometry Reorganization

ABSTRACT Shape control in fully fused nanographenes remains challenging because rigid π‐skeletons resist reorganization. Teropyrenes provide an attractive platform, but programmable shape control within this framework remains underdeveloped. Here, we report a fourfold Bischler–Napieralski annulation that affords 4,9,13,18‐tetraazateropyrenes in up to 56% yield. Substituent engineering dictates both molecular shape and packing: nearly planar TATP‐M forms a one‐dimensional slipped π‐stack, whereas saddle‐shaped TATP‐T adopts a distinctive cross‐locked saddle dimer motif. Despite similar ground‐state electronic structures and absorption profiles, the two compounds exhibit markedly different emission behaviors: TATP‐M emits at 577 and 623 nm with a fluorescence quantum yield of 46.4%, whereas TATP‐T shows intense red fluorescence at 625 nm with a higher quantum yield of 67.2%. Remarkably, TATP‐T retains conformational adaptability after full π‐extension. C 60 co‐crystallization promotes a saddle‐to‐twist transformation, generating conformationally chiral P and M conformers and demonstrating C 60 ‐regulated reshaping of an otherwise rigid fused backbone. Variable‐temperature NMR spectroscopy and activation‐barrier analysis further reveal a thermally activated, reversible exchange between conformational states. These findings establish a design principle for adaptive aza‐nanographenes, in which steric, supramolecular, and thermal inputs couple molecular curvature, conformational dynamics, packing, and excited‐state behavior across multiple structural and energetic dimensions.