arylaryl

Arylaryl is a structural motif in organic chemistry describing a bond between two aryl groups, i.e., two aryl rings connected directly by a carbon–carbon single bond. The simplest and most common example is biphenyl, two phenyl rings joined by a single C–C bond. More complex examples include terphenyls, binaphthyls, and other diaryl systems derived from phenyl, naphthyl, or heteroaryl rings.

Biaryl systems often exhibit restricted rotation about the aryl–aryl bond, particularly when bulky ortho substituents are present. This can give rise to atropisomerism, yielding isolatable enantiomeric conformers in some compounds. Physical properties—such as melting point, solubility, and optical activity—depend on the degree of steric hindrance and substituents.

Synthesis of aryl–aryl bonds is a central area of cross-coupling and direct aryl–aryl coupling methods. Common routes include Pd- or Ni-catalyzed cross-couplings (for example, Suzuki–Miyaura, Stille, Negishi, and Kumada couplings) between aryl halides and aryl nucleophiles or organometallic partners. Direct biaryl coupling methods, such as the Ullmann reaction, also exist. Applications of arylaryl motifs span pharmaceuticals, organic electronics (OLEDs, organic photovoltaics), and liquid-crystal materials, where rigid biaryl cores influence performance and stability.

Terminology: in some contexts aryl–aryl compounds are referred to as biaryls or diaryls; the descriptor arylaryl appears in systematic nomenclature to indicate an aryl substituent linked to another aryl ring. The term is used primarily in chemistry and materials science and does not designate a single specific molecule.