Design, Synthesis and Hydrogen Bonding of B3N6-[4]Triangulene

Replacement of the allylic C=C-C unit with a N-B-N unit at each of the three zigzag edges of [4]triangulene gives rise to B3N6-[4]triangulene, which is envisioned to represent a key structural unit of a new hypothetical boron carbon nitride (BC4N). A tert-butylated B3N6-[4]triangulene has been successfully synthesized by three-fold nitrogen-directed borylation, and the X-ray crystallographic analysis indicates that its slightly bent triangular polycyclic framework can be viewed as a 1,3,5-triphenylbenzene connected by three 4 pi-electron N-B-N units. The HN-B-NH moiety provides a dual hydrogen-bond donor, which forms H-bonds with halide or carboxylate anions in solution, and form DD-AA hydrogen-bond arrays with 2,7-di(tert-butyl)-pyrene-4,5,9,10-tetraone in the co-crystal. Moreover, the blue fluorescence of B3N6-[4]triangulene in solution is responsive to binding p-nitrobenzoate anion through hydrogen bonds.

Automated summary

The B3N6-[4]triangulene, a key structural unit of BC4N, was successfully synthesized through nitrogen-directed borylation, showing hydrogen-bonding properties. Its slightly bent triangular polycyclic framework consists of 4 pi-electron N-B-N units and forms hydrogen bonds with other molecules like halide or carboxylate anions.