Synthesis of Tetracoordinate Boron-Fused Benzoaceanthrylene Analogs via Tandem Electrophilic C-H Borylation.

Benzoaceanthrylene analogs with tetracoordinate boron at the ring junction were synthesized through tandem electrophilic C-H borylation of 2,6-dinaphthylpyridine followed by nucleophilic substitution. Notably, the [5,6]-annulation occurred selectively over [6,6]-annulation with the assistance of nitrogen coordination of the pyridine ring. The X-ray crystallographic analysis revealed the polycyclic skeleton with a distorted tetracoordinate boron atom and a unique packing structure with intermolecular π-π interaction. The photophysical and electrochemical properties of these benzoaceanthrylene analogs were evaluated by UV-vis spectroscopy and differential pulse voltammetry. The electron affinity of the fluorine-substituted derivative is estimated to be 3.49 eV from the ionization potential and optical band gap. Thus, this derivative is expected to be a promising n-type semiconducting material.