<unk>  (trivial name; ), or N,N′-dimethyl-4,4′-bipyridinium dichloride (systematic name), also known as methyl viologen, is an organic compound with the chemical formula (C6H7N)2Cl2. It is classified as a viologen, a family of redox-active heterocycles of similar structure. This salt is one of the most widely used herbicides. It is quick-acting and non-selective, killing green plant tissue on contact. It is also toxic (lethal) to human beings and animals due to its redox activity, which produces superoxide anions. It has been linked to the development of Parkinson's disease and is banned in several countries.<unk>  may be in the form of salt with chloride or other anions; quantities of the substance are sometimes expressed by cation mass alone<unk>  cation,<unk>  ion). The name is derived from the para positions of the quaternary nitrogens.
Paraquat
Coal tar
Methanol
Triphenylchloroethylene
Keldur
Tanapox
Soylent 
Diiodohydroxyquinoline