Synthesis of a Bis‐Boron/Sulfur Doped Ullazine and Direct Comparison with Its Boron/Nitrogen and Boron/Oxygen Analogues

Ullazine, a typical polycyclic aromatic hydrocarbon with a 14 π‐electron nitrogen‐containing core, has garnered significant attention due to its excellent performance in optoelectronics applications. Integration of heteroatoms into the frameworks of polycyclic aromatic hydrocarbons is a well‐established strategy for modifying molecular characteristics and functionalities. In this study, heteroatom‐doped ullazine congener Bis‐BS‐U containing two boron‐sulfur bonds was synthesized. The structures and properties of Bis‐BS‐U were systematically compared to those of the previously reported bis‐boron/nitrogen doped ullazine (Bis‐BN‐U) and bis‐boron/oxygen doped ullazine (Bis‐BO‐U). Notably, the absorption and fluorescence spectra of Bis‐BS‐U exhibited a pronounced red shift relative to those of Bis‐BN‐U and Bis‐BO‐U. Theoretical calculations suggest that the boron/sulfur six‐member ring in Bis‐BS‐U exhibits very weak antiaromaticity. Moreover, the fluorescence intensity of Bis‐BS‐U showed an initial increase upon addition of Hg²⁺, followed by gradual decrease over time. This study expands the family of ullazine and provides valuable insights for the future development of heteroatom‐doped ullazines.