diaryls

Diaryls are chemical compounds that contain two aryl groups (Ar) linked within a single molecule. They cover a broad range of structural motifs, from two aromatic rings connected directly to one another to pairs of rings joined through a heteroatom such as oxygen or nitrogen. The common thread is the diaryl motif, in which two aryl rings form the core of the molecule. Diaryls appear in natural products, dyes and pigments, and various functional materials.

Common diaryl motifs include biphenyls (two phenyl rings connected by a C–C bond), benzophenones (two phenyl rings attached to a carbonyl carbon), diphenyl ethers (two phenyl rings joined by an oxygen), and diarylamines (two phenyl rings attached to nitrogen). Other diaryl species include diaryl sulfides (Ar–S–Ar) and diaryl sulfones (Ar–SO2–Ar). These motifs serve as versatile scaffolds in chemistry and materials science.

Synthesis of diaryls employs several strategies. Carbon–carbon diaryl bonds are typically formed by metal-catalyzed cross-coupling reactions such as Suzuki–Miyaura, Kumada, or Negishi couplings. Diaryl ethers can be prepared by Ullmann-type couplings or copper- and nickel-catalyzed etherifications of phenols. Diarylamines arise from amination or arylation of amines, often via Buchwald–Hartwig-type couplings. In many cases, diaryl motifs are built by coupling partners that each supply one aryl unit.

Applications and properties of diaryls include their influence on planarity, electronic structure, and optical behavior. Substituents can induce atropisomerism in hindered biphenyls, affecting chiral materials and devices. Diaryl motifs are common in dyes, pigments, liquid-crystal materials, pharmaceuticals, and polymers, where tuning substituents modulates UV absorption, fluorescence, and redox characteristics.