The molecule is an organosulfonate oxoanion obtained by deprotonation of the sulfonic acid groups of Sirius red 4B (acid form). It is a conjugate base of a Sirius red 4B (acid form).
7-benzamido-4-hydroxy-3-[[4-[(4-sulfonatophenyl)diazenyl]phenyl]diazenyl]naphthalene-2-sulfonate