Synthetic strategies towards preparation and functionalization of ullazines, a promising class of light-harvesting materials

Abstract

Polycyclic aromatic hydrocarbons (PAHs) have gained significant attention from the scientific community due to their remarkable optoelectronic properties, which make them ideal candidates for applications in organic electronic materials, such as organic photovoltaics (OPVs) and dye-sensitized solar cells (DSSCs). These compounds, characterized by extended π-conjugation, enable electron delocalization, enhancing their electronic and optical behaviors. The incorporation of heteroatoms in PAHs has been shown to further modify their electronic properties without disrupting the aromaticity, providing additional opportunities for the design of advanced organic semiconductors. A notable example is ullazine, a nitrogen-containing polycyclic system with a 16 π-electron structure. It has emerged as a promising material for organic electronics due to its unique electron-donating and electron-accepting capabilities. Recent advances in synthetic methodologies, including metal-catalyzed cyclization and hydride shift reactions, have enabled the development of ullazine derivatives with tunable electronic properties. Furthermore, the inclusion of heteroatoms such as boron and sulfur and the expansion of the ullazine framework through mono- and bis-annulation strategies have enhanced the charge transport properties and light-harvesting capabilities of these compounds, making them highly attractive for photovoltaic applications. This review comprehensively discusses the latest synthetic strategies for ullazine derivatives, their electronic and optical properties, and their potential applications in next-generation organic electronic devices.