[Na+].[Na+].OS(=O)(=O)C1=CC=C(C=C1)N=C1C=CC(C=C1)=C(C1=CC=C(NC2=CC=C(C=C2)S([O-])(=O)=O)C=C1)C1=CC=C(NC2=CC=C(C=C2)S([O-])(=O)=O)C=C1