Tetraazacoronenes and Their Dimers, Trimers and Tetramers.

Tetraazacoronenes were synthesized from bay-functionalized tetraazaperylenes via Zr-mediated cyclization and four-fold Suzuki-Miyaura cross coupling. In the Zr-mediated approach, an η4-cyclobutadiene-zirconium(IV) complex was isolated as intermediate to cyclobutene-annulated derivatives. Using bis(pinacolatoboryl)vinyl)trimethylsilane as an C2 building block gave the tetraazacoronene target compound along with the condensed azacoronene dimer as well as higher oligomers. The series of extended azacoronenes show highly resolved UV/Vis absorption bands with increasing extinction coefficients for the extended aromatic cores and fluorescence quantum yields of up to 80% at 659 nm.