Bipyridines

Paraquat (trivial name; ), or '''N,N′-dimethyl-4,4′-bipyridinium dichloride (systematic name), also known as methyl viologen''', is a toxic organic compound with the chemical formula [(C6H7N)2]Cl2. It is classified as a viologen, a family of redox-active heterocycles of similar structure. It is one of the most widely used herbicides worldwide. It is quick-acting and non-selective, killing green plant tissue on contact.

2,2′-Bipyridine (bipy or bpy, pronounced ) is an organic compound with the formula . This colorless solid is an important isomer of the bipyridine family. It is a bidentate chelating ligand, forming complexes with many transition metals. Ruthenium and platinum complexes of bipy exhibit intense luminescence. ==Preparation, structure, and general properties== 2,2'-Bipyridine was first prepared by decarboxylation of divalent metal derivatives of pyridine-2-carboxylate:

Orellanine or orellanin is a mycotoxin found in a group of mushrooms known as the Orellani within the family Cortinariaceae. Structurally, it is a bipyridine N-oxide compound somewhat related to the herbicide diquat.

4,4′-Bipyridine (abbreviated to 4,4′-bipy or 4,4′-bpy) is an organic compound with the formula . It is one of several isomers of bipyridine. It is a colorless solid that is soluble in organic solvents. is mainly used as a precursor to N,N′-dimethyl-4,4′-bipyridinium [(C5H4NCH3)2]2+, known as paraquat.

Bipyridines are a family of organic compounds with the formula (C5H4N)2, consisting of two pyridyl (C5H4N) rings. Pyridine is an aromatic nitrogen-containing heterocycle. The bipyridines are all colourless solids, which are soluble in organic solvents and slightly soluble in water. Bipyridines, especially the 4,4' isomer, are mainly of significance in pesticides.

thumb|220px|class=skin-invert-image|Paraquat is a prominent viologen. Viologens are a family of organic compounds with the formula (C5H4NR)2n+(X-)2. They are N-alkyl derivatives of bipyridines. In some viologens, the pyridyl groups are further modified.

Phanquinone is an organic compound with the formula . It is derived by oxidation of 4,7-phenanthroline.