A compound of formula wherein R1, R2, independently of each other, represent hydrogen, substituted or unsubstituted C1-C4 alkyl, substituted or unsubstituted C1-C4 alkoxyl, substituted or unsubstituted phenyl, amino, sulfonic, carboxyl, hydroxyl, or halogen groups, wherein the substituents are amino, hydroxyl, sulfonic or carboxylic groups, and R1 and/or R2 are sulfonic groups; C, D, independently of each other, represent R3 and R5, independently of each other, represent hydrogen, substituted or unsubstituted C1-C4 alkyl, substituted or unsubstituted C1-C4 alkoxyl, substituted or unsubstituted phenyl, amino, nitro, sulfonic, carboxyl, hydroxyl, or halogen groups; R8 is as defined below; R4, R6, independently of each other, represent hydrogen, substituted or unsubstituted C1-C4 alkyl, substituted or unsubstituted C1-C4 alkoxyl, substituted or unsubstituted phenyl, amino, sulfonic, carboxyl, hydroxyl, or halogen groups; m, n, r, s, independently of each other, are 1, A, B independently of each other, represent or tautomeric forms; R8 to R11 represent, independently of each other, hydrogen, substituted or unsubstituted C1-C4 alkyl, substituted or unsubstituted C1-C4 alkoxy, substituted or unsubstituted phenyl, sulfonic, carboxyl, amino, nitro, hydroxyl, or halogen groups, wherein the substituents are amino, hydroxyl, sulfonic or carboxylic groups; and X represents O, S, NH, SO 2, CH=CH, NHCO, or NH-CO-NH. R1, R2, independently of each other, represent hydrogen, substituted or unsubstituted C1-C4 alkyl, substituted or unsubstituted C1-C4 alkoxyl, substituted or unsubstituted phenyl, amino, sulfonic, carboxyl, hydroxyl, or halogen groups, wherein the substituents are amino, hydroxyl, sulfonic or carboxylic groups, and R1 and/or R2 are sulfonic groups; C, D, independently of each other, represent R3 and R5, independently of each other, represent hydrogen, substituted or unsubstituted C1-C4 alkyl, substituted or unsubstituted C1-C4 alkoxyl, substituted or unsubstituted phenyl, amino, nitro, sulfonic, carboxyl, hydroxyl, or halogen groups; R8 is as defined below; R4, R6, independently of each other, represent hydrogen, substituted or unsubstituted C1-C4 alkyl, substituted or unsubstituted C1-C4 alkoxyl, substituted or unsubstituted phenyl, amino, sulfonic, carboxyl, hydroxyl, or halogen groups; m, n, r, s, independently of each other, are 1, A, B independently of each other, represent or tautomeric forms; R8 to R11 represent, independently of each other, hydrogen, substituted or unsubstituted C1-C4 alkyl, substituted or unsubstituted C1-C4 alkoxy, substituted or unsubstituted phenyl, sulfonic, carboxyl, amino, nitro, hydroxyl, or halogen groups, wherein the substituents are amino, hydroxyl, sulfonic or carboxylic groups; and X represents O, S, NH, SO 2, CH=CH, NHCO, or NH-CO-NH. R8 to R11 represent, independently of each other, hydrogen, substituted or unsubstituted C1-C4 alkyl, substituted or unsubstituted C1-C4 alkoxy, substituted or unsubstituted phenyl, sulfonic, carboxyl, amino, nitro, hydroxyl, or halogen groups, wherein the substituents are amino, hydroxyl, sulfonic or carboxylic groups; and X represents O, S, NH, SO 2, CH=CH, NHCO, or NH-CO-NH.