Heterocyclic Nanographenes Doped with Boron and Phosphorus: Post-Phosphorization Synthesis, Excited-State Dynamics...

Incorporating more than one kind of heteroatom into polycyclic aromatic hydrocarbons is a powerful method for achieving diversiform heterocyclic structures and desirable physical properties. Herein, we disclose precise post-phosphorization of conjugated organoboranes, which enables the successful synthesis of unprecedented boron-/phosphorus-codoped nanographenes. Two as-obtained heterocyclic molecules, featuring boron atoms and phosphine oxide groups at the zigzag edges, show the curved C₄₂B₂P and C₄₂B₂P₂ frameworks, respectively, attributed to the structural distortion effects of the phosphorus-containing hexagonal rings. They display intriguing properties, such as disturbed aromaticity, enhanced electron affinity, and enlarged energy gaps. Notably, the blue-shifted stimulated emission and amplified spontaneous emission characteristics are observed, demonstrating not only the important effects of the boron atoms and phosphorus units but also their potential optical-gain and lasing utility. Furthermore, the sulfuration reaction of the phosphorus center produced another heterocyclic derivative containing the phosphine sulfide units. Coordination of its boron atoms and phosphine sulfide groups with the fluoride and silver ions, respectively, is realized, indicating its uncommon dual ion-responsive properties. This post-phosphorization strategy, along with these findings, will inspire research of boron/phosphorus-containing heterocycle chemistry and materials.