Synthesis of a Tetrabenzotetraaza[8]circulene by a “Fold‐In” Oxidative Fusion Reaction

Tetrabenzotetraaza[8]circulene ( 1 ) has been synthesized in good yield by a “fold‐in” oxidative fusion reaction of a 1,2‐phenylene‐bridged cyclic tetrapyrrole. X‐ray diffraction analysis of 1 has revealed a planar square structure with a central cyclooctatetraene (COT) core that shows little alternation of the bond lengths. Despite these structural features, 1 shows aromatic‐like character, such as sharp absorption bands, high fluorescence quantum yields ( Φ F =0.55 in THF), and a single exponential fluorescence decay with τ F =3.8 ns. These observations indicate a dominant contribution of an [8]radialene‐like π conjugation and hence aromatic character of the local aromatic segments in 1 .