bipyridine

Bipyridine is a class of dihydro heteroaromatic compounds consisting of two pyridine rings connected by a single carbon–carbon bond. The three common isomers are 2,2'-bipyridine (ortho), 3,3'-bipyridine (meta), and 4,4'-bipyridine (para), all sharing the formula C10H8N2. The nitrogen atoms in each ring can act as coordination sites for metals.

In coordination chemistry, bipyridine acts as a bidentate N,N' ligand, binding through both pyridine nitrogens to form five-membered chelate rings. The resulting metal complexes are often robust and well-characterized, with the exact geometry and reactivity influenced by the isomer used and the metal center. The 4,4'- isomer is particularly common as a bridging ligand in supramolecular assemblies and in the construction of metal–organic frameworks.

A notable example is tris(bipyridine) complexes, such as Ru(bpy)3^2+ (where bpy denotes 2,2'-bipyridine), a classic photoredox sensitizer used in dye-sensitized solar cells and various photocatalysis applications. Derivatives of bipyridine are widely prepared to tune electronic properties, sterics, and redox potentials for targeted catalysis and material science uses.

Physically, bipyridine is a colorless to off-white solid and is generally poorly soluble in water but dissolves in many organic solvents. It is typically synthesized from pyridine derivatives by coupling reactions or related synthetic routes.

Applications extend across inorganic and organometallic chemistry, including stabilization of transition metal centers, formation of coordination polymers, and studies of electron transfer processes. As with many laboratory chemicals, bipyridine should be handled with standard safety practices.