Bipyridines also known as bipyridyls, dipyridyls, and dipyridines, are a family of chemical compounds with the formula (C₅H₄N)₂, which are formed by the coupling of two pyridine rings. They are aromatic nitrogen heterocycles that form complexes with most transition metals. They interact with metals via both σ-donating nitrogen atoms and π-accepting molecular orbitals. Bipyridines figure prominently in studies of electron and energy transfer, supramolecular and materials chemistry, and catalysis.