Synthesis, Structure, and Optical Properties of Di‑m‑benzihexaphyrins (1.1.0.0.0.0) and Di‑m‑benziheptaphyrins (1.0.1.0.0.0.0): Blackening of m‑Phenylene-Linked Dicarbaporphyrinoids by Simple π‑Expansion

Acid-catalyzed condensation of a newly prepared di-m-benzipentapyrrane with appropriate mono- and diheterocyclic dialcohols selectively produced stable di-m-benzihexaphyrins and di-m-benziheptaphyrins with only two meso-carbon bridges. Single-crystal X-ray diffraction analyses reveal planar conformation with slight distortion of bridged phenylene rings. Despite the presence of m-phenylene units interrupting the global delocalization, the presence of bithiophene units in di-m-benziheptaphyrins 3a–b exhibits altered optical features covering the entire visible region (ca. 250–720 nm), exhibiting a black dye property as a “metal-free” porphyrinoid.