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

Abstract

Replacement of the allylic C=CÀC unit with a NÀBÀ N unit at each of the three zigzag edges of [4]triangulene gives rise to B 3 N 6 -[4]triangulene, which is envisioned to represent a key structural unit of a new hypothetical boron carbon nitride (BC 4 N). A tert-butylated B 3 N 6 -[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 4p-electron N À B À N units. The HN À B À NH moiety provides a dual hydrogenbond 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 B 3 N 6 -[4]triangulene in solution is responsive to binding p-nitrobenzoate anion through hydrogen bonds.

Topological Design and Synthesis of High-Spin Aza-triangulenes without Jahn–Teller Distortions

“…There are several examples of smaller doped triangulenes in the literature, with heteroatoms either incorporated within their structure ,,, or at their zigzag edges . Among these, the largest examples are [4]­triangulenes with boron/oxygen (BO)- or boron/nitrogen (BN)-doped edges. − Doping triangulenes with heteroatoms alters the number of unpaired electrons originating from the sublattice imbalance. In the case of aza-triangulenes, it is expected that replacing a central carbon (which can be viewed as having a single unpaired electron in its p-orbital) with a nitrogen (with its accompanying lone pair) will deprive one sublattice of an unpaired electron, thereby modifying the total spin of the molecule.…”