Agents for coloring keratin fibers

An agent for the nonoxidative coloring of keratin fibers, comprising at least one zwitterionic azo dye of the general formula (I);

• wherein
• R1 is an alkyl sulfonate radical of the formula (II);
• R2 is hydrogen or a hydroxyl group;
• m is 0 to (n−1);
• p is 0 to (n−1) where m+p=(n−1);
• n is an integer from 1 to 6;
• X is oxygen, sulfur, N—R3 or C—R4;
• Y is C—R5, nitrogen, N—R6, sulfur or oxygen;
• Z is C—R7 or nitrogen;
• and
• wherein the heterocycle of the formula (I) comprises at least two and at most three heteroatoms, where the heterocycle has at most one sulfur atom or oxygen atom;
• R3 and R6 may be identical or different and, independently of one another, are a saturated or unsaturated (C1-C12)-alkyl group, a (C1-C12)-alkyl group substituted by a halogen atom, a hydroxy-(C2-C12)-alkyl group, an amino-(C1-C12)-alkyl group, a substituted or unsubstituted phenyl group or a substituted or unsubstituted benzyl group;
• R4, R5 and R7 may be identical or different and, independently of one another, are hydrogen, a halogen atom, a saturated or unsaturated (C1-C12)-alkyl group, a (C1-C12)-alkyl group substituted by a halogen atom (F, Cl, Br, I), a hydroxyl group, a hydroxy-(C1-C12)-alkyl group, a (C1-C12)-alkoxy group, a cyano group, a nitro group, an amino group, a (C1-C12)-alkylamino group, a (C1-C12)-dialkylamino group, a carboxylic acid group, a C(O)O—(C1-C12)-alkyl group, a substituted or unsubstituted C(O)O-phenyl group, a substituted or unsubstituted phenyl group or a naphthyl group, or a substituted or unsubstituted heteroaryl group;
• or if Y and Z are C—R5 and C—R7, the radical groups R5 and R7, together with the remaining molecule, can form a heterocyclic or carbocyclic, saturated or unsaturated, substituted or unsubstituted ring system;
• or if X and Y are C—R4 and C—R5, the radical groups R4 and R5, together with the remaining molecule, can form a heterocyclic or carbocyclic, saturated or unsaturated, substituted or unsubstituted ring system;
• K is a radical group of the aniline or phenol series or a monocyclic or polycyclic heterocyclic radical group.