The photophysical properties and molecular structures of triangulenes can be modified by substituting carbon atoms in the polybenzoid framework with alternate atoms. However, only a limited set of central and bridging heteroatoms is accommodated by conventional linear approaches to triangulene skeleton construction such as Friedel–Crafts or S_NAr nucleophilic aromatic substitution reactions.

To address this issue, Takuji Hatakeyama, Kwansei Gakuin University, Sanda, Japan, and colleagues have developed a divergent synthesis approach. The team incorporated a boron, phosphorus, or silicon heteroatom into a nitrogen-containing macrocyclic precursor by electrophilic carbon–lithium and carbon–hydrogen bond substitutions. Boron-, phosphorus-, and silicon-centered 4,8,12-triazatriangulenes (pictured) with unusual properties were produced using this method.

The boron adduct displayed ambipolar charge-carrier transport properties suited to organic light-emitting diodes, whereas the phosphorus and silicon adducts assumed bowl-shaped structures with different depths. Substituted triangulenes could meet the demands of functional materials requiring versatile photophysical and supramolecular properties.

• Divergent Synthesis of Heteroatom-Centered 4,8,12-Triazatriangulenes,
  Soichiro Nakatsuka, Hajime Gotoh, Keisuke Kinoshita, Nobuhiro Yasuda, Takuji Hatakeyama,
  Angew. Chem. Int. Ed. 2017.
  DOI: 10.1002/anie.201701246