meso-ionic compound

meso-ionic compound

[¦mez·ō·ī¦än·ik ′käm‚pau̇nd]
(organic chemistry)
Any of a class of five-membered ring heterocycles and their benzo derivatives which possess a sextet of pi electrons in association with the atoms composing the ring but which cannot be represented satisfactorily by any one covalent or polar structure.