Group 22 herbicides

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.

Diquat is the ISO common name for an organic dication that, as a salt with counterions such as bromide or chloride is used as a contact herbicide that produces desiccation and defoliation. Diquat is no longer approved for use in the European Union, although its registration in many other countries including the USA is still valid.

MPP+ (1-methyl-4-phenylpyridinium) or cyperquat is a positively charged organic molecule with the chemical formula C12H12N+. It is a monoaminergic neurotoxin that acts by interfering with oxidative phosphorylation in mitochondria by inhibiting complex I, leading to the depletion of ATP and eventual cell death.