Indolium is a

cation An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

with molecular formula C₈H₈N⁺, and forms

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

s in combination with anions. It is an

onium ion In chemistry, an onium ion is a cation formally obtained by the protonation of mononuclear parent hydride of a pnictogen (group 15 of the periodic table), chalcogen (group 16), or halogen (group 17). The oldest-known onium ion, and the namesake ...

derived from its

parent compound In chemistry, a parent structure is the structure of an unadorned ion or molecule from which derivatives can be visualized. Parent structures underpin systematic nomenclature and facilitate classification. Fundamental parent structures have one o ...

indole Indole is an aromatic heterocyclic organic compound with the formula C8 H7 N. It has a bicyclic structure, consisting of a six-membered benzene ring fused to a five-membered pyrrole ring. Indole is widely distributed in the natural environmen ...

, by the addition of a proton.

References

Indoles {{heterocyclic-stub