The molecule is an organosulfonate oxoanion obtained by deprotonation of the sulfo groups of Congo corinth (acid form). It is a conjugate base of a Congo corinth (acid form).
4-amino-3-[[4-[4-[(1-hydroxy-4-sulfonatonaphthalen-2-yl)diazenyl]phenyl]phenyl]diazenyl]naphthalene-1-sulfonate