bipyridyls

Bipyridyls, also known as bipyridines or by their IUPAC name bipyridines, are a group of organic compounds with the chemical formula (C5H4N)2. They consist of two pyridine rings joined by a single bond. The relative positions of the nitrogen atoms in the two rings define the different isomers. The most common and widely studied isomer is 2,2'-bipyridyl, where the nitrogen atoms are adjacent. Other isomers include 2,3'-bipyridyl, 2,4'-bipyridyl, 3,3'-bipyridyl, and 4,4'-bipyridyl.

These compounds are colorless solids that are soluble in organic solvents and often in water. Bipyridyls are well-known for their ability to act as chelating ligands in coordination chemistry. The nitrogen atoms in the pyridine rings can donate electron pairs to metal ions, forming stable complexes. This chelating ability is particularly pronounced in 2,2'-bipyridyl, where the two nitrogen atoms can bind to a single metal center, forming a five-membered ring. This property makes bipyridyls valuable in a variety of applications.

Bipyridyl ligands are extensively used in catalysis, particularly in transition metal-catalyzed reactions. They are also employed in the development of luminescent materials, sensors, and as redox-active components in electrochemical devices. Some bipyridyl derivatives have found applications as herbicides, such as paraquat and diquat, although their use is subject to strict regulation due to toxicity concerns. The synthesis of bipyridyls typically involves coupling reactions of pyridine derivatives.