Dissymmetrical Diazo Compounds Containing Having at Least One 2-imidazolium Unit and a Cationic or Non-cationic Linker, Compositions Comprising Them, Method of Coloring, and Device

A dyeing composition comprising, in a medium appropriate for dyeing keratin fibers, a direct dye chosen from at least one compound chosen from those of formulae (I), (II), (III) and (IV), acid addition salts thereof, and solvates thereof, wherein in the compounds of formulae (I), (II), (III) and (IV), the formula members attached to each side of the linker L are either compositionally different or positionally different such that the compounds as a whole are dissymmetrical:

• wherein:
• the radicals R1, which are identical or different, independently of one another are chosen from:
• optionally substituted C1-C4 alkyl radicals;
• optionally substituted phenyl radicals;
• optionally substituted benzyl radicals;
• the radicals R2, which are identical or different, independently of one another are chosen from:
• optionally substituted C1-C16 alkyl radicals optionally interrupted by at least one heteroatom and/or at least one group containing at least one heteroatom, said alkyl radical being further optionally substituted by at least one group chosen from thio (—SH), C1-C4 thioalkyl;
• C1-C4 alkylsulphinyl and C1-C4 alkylsulphonyl groups;
• hydroxyl groups;
• C1-C4 alkoxy groups;
• C2-C4 (poly)hydroxyalkoxy groups;
• alkoxycarbonyl groups (RO—CO—) wherein R is a C1-C4 alkyl radical;
• alkylcarbonyloxy groups (RCO—O—) wherein R is a C1-C4 alkyl radical;
• alkylcarbonyl groups (R—CO—) wherein R is a C1-C4 alkyl radical;
• amino groups;
• amino groups substituted by one or two identical or different C1-C4 alkyl radicals optionally carrying at least one hydroxyl group, wherein the two alkyl radicals may optionally form, with the nitrogen atom to which they are attached, a heterocycle containing 1 to 3 heteroatoms chosen from N, O and S, and containing 5 to 7 ring members, wherein said heterocycle is saturated or unsaturated, aromatic or non-aromatic and is optionally substituted;
• alkylcarbonylamino groups (RCO—NR′—) wherein R is a C1-C4 alkyl radical and R′ is chosen from hydrogen and a C1-C4 alkyl radical;
• aminocarbonyl groups ((R)2N—CO—) wherein radicals R independently of one another are chosen from a hydrogen atom and a C1-C4 alkyl radical;
• ureido groups (N(R)2—CO—NR′—) wherein radicals R and R′ independently of one another are chosen from a hydrogen atom and a C1-C4 alkyl radical;
• aminosulphonyl groups ((R)2N—SO2—) wherein radicals R independently of one another are chosen from a hydrogen atom and a C1-C4 alkyl radical;
• alkylsulphonylamino groups (RSO2—NR′—) wherein R is a C1-C4 alkyl radical and R′ is chosen from a hydrogen atom and a C1-C4 alkyl radical;
• optionally substituted aryl radicals;
• optionally substituted (C1-C4)alkylaryl radicals;
• alkylsulphinyl groups (R—SO—) wherein R is a C1-C4 alkyl radical;
• alkylsulphonyl groups (R—SO2—) wherein R is a C1-C4 alkyl radical;
• nitro groups;
• cyano groups;
• halogen atoms;
• thio groups (HS—);
• alkylthio groups (RS—) wherein R is an optionally substituted C1-C4 alkyl radical;
• when e is 2, for each of the formulae (I), (II), (III) and (IV), two radicals R2 may optionally form, with the carbon atoms to which they are attached, a secondary ring, aromatic or non-aromatic, containing 5 or 6 ring members, which is optionally substituted by at least one identical or different group chosen from hydroxyl, C1-C4 alkyl, C1-C4 alkoxy, C2-C4 (poly)hydroxyalkoxy, amino, and amino substituted by one or two identical or different C1-C4 alkyl radicals which optionally carry at least one hydroxyl group;
• e is an integer ranging from 0 to 4;
• when e is less than 4, the unsubstituted carbon atom(s) of the heterocycle of the formulae (I), (II), (III) and (IV) carry a hydrogen atom, the radicals R3, from formulae (I), (II), (III) and (IV), which are identical or different, independently of one another are chosen from:
• optionally substituted C1-C16 alkyl radicals optionally interrupted by at least one heteroatom or by at least one group containing at least one heteroatom;
• hydroxyl groups;
• C1-C4 alkoxy groups;
• C2-C4 (poly)hydroxyalkoxy groups;
• alkoxycarbonyl groups (RO—CO—) wherein R is a C1-C4 alkyl radical;
• alkylcarbonyloxy groups (RCO—O—) wherein R is a C1-C4 alkyl radical;
• alkylcarbonyl groups (R—CO—) wherein R is a C1-C4 alkyl radical;
• amino groups;
• amino groups substituted by one or two identical or different C1-C4 alkyl radicals optionally carrying at least one hydroxyl group;
• wherein the two alkyl radicals may optionally form, with the nitrogen atom to which they are attached, a heterocycle containing 1 to 3 heteroatoms chosen from N, O and S, containing 5 to 7 ring members, and which is saturated or unsaturated, aromatic or non-aromatic and is optionally substituted;
• alkylcarbonylamino groups (RCO—NR′—) wherein the radical R is a C1-C4 alkyl radical and the radical R′ is chosen from a hydrogen atom and a C1-C4 alkyl radical;
• aminocarbonyl groups ((R)2N—CO—) wherein radicals R independently of one another are chosen from a hydrogen atom and a C1-C4 alkyl radical;
• ureido groups (N(R)2—CO—NR′—) wherein radicals R and R′ independently of one another are chosen from a hydrogen atom and a C1-C4 alkyl radical;
• aminosulphonyl groups ((R)2N—SO2—) wherein radicals R independently of one another are chosen from a hydrogen atom and a C1-C4 alkyl radical;
• alkylsulphonylamino groups (RSO2—NR′—) wherein radicals R and R′ independently of one another are chosen from a hydrogen atom and a C1-C4 alkyl radical;
• thio groups (HS—);
• alkylthio groups (RS—) wherein R is a C1-C4 alkyl radical;
• alkylsulphinyl groups (R—SO—) wherein R is a C1-C4 alkyl radical;
• alkylsulphonyl groups (R—SO2—) wherein R is a C1-C4 alkyl radical;
• nitro groups;
• cyano groups;
• halogen atoms;
• when m′ is greater than or equal to 2, two adjacent radicals R3 may form, with the carbon atoms to which they are attached, a secondary ring, aromatic or non-aromatic containing 6 ring members, which is optionally substituted by at least one identical or different group chosen from:
• hydroxyl, C1-C4 alkyl, C1-C4 alkoxy, C2-C4 (poly)hydroxyalkoxy, C1-C4 alkylcarbonylamino, amino, and amino substituted by one or two identical or different C1-C4 alkyl radicals which optionally carry at least one hydroxyl group;
• m′ is an integer from 0 to 4;
• when m′ is less than 4, then the unsubstituted carbon atom(s) of the aromatic ring of the formulae (I), (II), (III) and (IV) carry a hydrogen atom;
• the W1 groups of the formulae (I), (II), (III) and (IV), which are identical or different, independently of one another, are chosen from:
• hydrogen atoms;
• halogen atoms chosen from bromine, chlorine and fluorine;
• a group chosen from —NR5R6, OR7, —NR4-Ph-NR5R6, —NR4-Ph-OR7, —O-Ph-OR7 and —O-Ph-NR5R6 groups, wherein:
• R4 and R7, which are identical or different, are chosen from hydrogen atoms, optionally substituted C1-C20 alkyl radicals, optionally substituted C1-C3 aralkyl radicals and optionally substituted phenyl radicals;
• R5 and R6, which are identical or different, are chosen from hydrogen atoms optionally substituted C1-C20 alkyl radicals, optionally substituted phenyl radicals, optionally substituted C1-C3 aralkyl radicals and alkylcarbonyl radicals (R—CO—) wherein R is a C1-C4 alkyl radical;
• R5 and R6 may optionally form, with the nitrogen atom to which they are attached, a heterocycle containing 1 to 3 heteroatoms, chosen from N, O and S, and containing 5 to 7 ring members, which is saturated or unsaturated, aromatic or non-aromatic and is optionally substituted;
• R5 and R6 may optionally form, with the carbon atom of the aromatic ring adjacent to that to which —NR5R6 is attached, a 5- or 6-membered saturated heterocycle;
• Ph is an optionally substituted phenyl radical;
• L is chosen from a cationic linker and a non-cationic linker;
• An is chosen from at least one identical or different cosmetically acceptable anions which ensure the electroneutrality of the compounds of formula (I), (II), (III) and (IV).

A method of coloring keratin fibers comprising contacting said fibers, dry or wet, with a dyeing composition for a time sufficient to give a desired color, wherein the dyeing composition comprises, in a medium appropriate for dyeing keratin fibers, at least one direct dye chosen from those of formulae (I), (II), (III) and (IV), acid addition salts thereof, and solvates thereof, wherein in the compounds of formulae (I), (II), (III) and (IV), the formula members attached to each side of the linker L are either compositionally different or positionally different such that the compounds as a whole are dissymmetrical:

• wherein:
• the radicals R1, which are identical or different, independently of one another are chosen from:
• optionally substituted C1-C4 alkyl radicals;
• optionally substituted phenyl radicals;
• optionally substituted benzyl radicals;
• the radicals R2, which are identical or different, independently of one another are chosen from:
• optionally substituted C1-C16 alkyl radicals optionally interrupted by at least one heteroatom and/or at least one group containing at least one heteroatom, said alkyl radical being further optionally substituted by at least one group chosen from thio (—SH), C1-C4 thioalkyl;
• C1-C4 alkylsulphinyl and C1-C4 alkylsulphonyl groups;
• hydroxyl groups;
• C1-C4 alkoxy groups;
• C2-C4 (poly)hydroxyalkoxy groups;
• alkoxycarbonyl groups (RO—CO—) wherein R is a C1-C4 alkyl radical;
• alkylcarbonyloxy groups (RCO—O—) wherein R is a C1-C4 alkyl radical;
• alkylcarbonyl groups (R—CO—) wherein R is a C1-C4 alkyl radical;
• amino groups;
• amino groups substituted by one or two identical or different C1-C4 alkyl radicals optionally carrying at least one hydroxyl group, wherein the two alkyl radicals may optionally form, with the nitrogen atom to which they are attached, a heterocycle containing 1 to 3 heteroatoms chosen from N, O and S, and containing 5 to 7 ring members, wherein said heterocycle is saturated or unsaturated, aromatic or non-aromatic and is optionally substituted;
• alkylcarbonylamino groups (RCO—NR′—) wherein R is a C1-C4 alkyl radical and R′ is chosen from hydrogen and a C1-C4 alkyl radical;
• aminocarbonyl groups ((R)2N—CO—) wherein radicals R independently of one another are chosen from a hydrogen atom and a C1-C4 alkyl radical;
• ureido groups (N(R)2—CO—NR′—) wherein radicals R and R′ independently of one another are chosen from a hydrogen atom and a C1-C4 alkyl radical;
• aminosulphonyl groups ((R)2N—SO2—) wherein radicals R independently of one another are chosen from a hydrogen atom and a C1-C4 alkyl radical;
• alkylsulphonylamino groups (RSO2—NR′—) wherein R is a C1-C4 alkyl radical and R′ is chosen from a hydrogen atom and a C1-C4 alkyl radical;
• optionally substituted aryl radicals;
• optionally substituted (C1-C4)alkylaryl radicals;
• alkylsulphinyl groups (R—SO—) wherein R is a C1-C4 alkyl radical;
• alkylsulphonyl groups (R—SO2—) wherein R is a C1-C4 alkyl radical;
• nitro groups;
• cyano groups;
• halogen atoms;
• thio groups (HS—);
• alkylthio groups (RS—) wherein R is an optionally substituted C1-C4 alkyl radical;
• when e is 2, for each of the formulae (I), (II), (III) and (IV), two radicals R2 may optionally form, with the carbon atoms to which they are attached, a secondary ring, aromatic or non-aromatic, containing 5 or 6 ring members, which is optionally substituted by at least one identical or different group chosen from hydroxyl, C1-C4 alkyl, C1-C4 alkoxy, C2-C4 (poly)hydroxyalkoxy, amino, and amino substituted by one or two identical or different C1-C4 alkyl radicals which optionally carry at least one hydroxyl group;
• e is an integer ranging from 0 to 4;
• when e is less than 4, the unsubstituted carbon atom(s) of the heterocycle of the formulae (I), (II), (III) and (IV) carry a hydrogen atom,
• the radicals R3, from formulae (I), (II), (III) and (IV), which are identical or different, independently of one another are chosen from:
• optionally substituted C1-C16 alkyl radicals optionally interrupted by at least one heteroatom or by at least one group containing at least one heteroatom;
• hydroxyl groups;
• C1-C4 alkoxy groups;
• C2-C4 (poly)hydroxyalkoxy groups;
• alkoxycarbonyl groups (RO—CO—) wherein R is a C1-C4 alkyl radical;
• alkylcarbonyloxy groups (RCO—O—) wherein R is a C1-C4 alkyl radical;
• alkylcarbonyl groups (R—CO—) wherein R is a C1-C4 alkyl radical;
• amino groups;
• amino groups substituted by one or two identical or different C1-C4 alkyl radicals optionally carrying at least one hydroxyl group;
• wherein the two alkyl radicals may optionally form, with the nitrogen atom to which they are attached, a heterocycle containing 1 to 3 heteroatoms chosen from N, O and S, containing 5 to 7 ring members, and which is saturated or unsaturated, aromatic or non-aromatic and is optionally substituted;
• alkylcarbonylamino groups (RCO—NR′—) wherein the radical R is a C1-C4 alkyl radical and the radical R′ is chosen from a hydrogen atom and a C1-C4 alkyl radical;
• aminocarbonyl groups ((R)2N—CO—) wherein radicals R independently of one another are chosen from a hydrogen atom and a C1-C4 alkyl radical;
• ureido groups (N(R)2—CO—NR′—) wherein radicals R and R′ independently of one another are chosen from a hydrogen atom and a C1-C4 alkyl radical;
• aminosulphonyl groups ((R)2N—SO2—) wherein radicals R independently of one another are chosen from a hydrogen atom and a C1-C4 alkyl radical;
• alkylsulphonylamino groups (RSO2—NR′—) wherein radicals R and R′ independently of one another are chosen from a hydrogen atom and a C1-C4 alkyl radical;
• thio groups (HS—);
• alkylthio groups (RS—) wherein R is a C1-C4 alkyl radical;
• alkylsulphinyl groups (R—SO—) wherein R is a C1-C4 alkyl radical;
• alkylsulphonyl groups (R—SO2—) wherein R is a C1-C4 alkyl radical;
• nitro groups;
• cyano groups;
• halogen atoms;
• when m′ is greater than or equal to 2, two adjacent radicals R3 may form, with the carbon atoms to which they are attached, a secondary ring, aromatic or non-aromatic containing 6 ring members, which is optionally substituted by at least one identical or different group chosen from:
• hydroxyl, C1-C4 alkyl, C1-C4 alkoxy, C2-C4 (poly)hydroxyalkoxy, C1-C4 alkylcarbonylamino, amino, and amino substituted by one or two identical or different C1-C4 alkyl radicals which optionally carry at least one hydroxyl group;
• m′ is an integer from 0 to 4;
• when m′ is less than 4, then the unsubstituted carbon atom(s) of the aromatic ring of the formulae (I), (II), (III) and (IV) carry a hydrogen atom;
• the W1 groups of the formulae (I), (II), (III) and (IV), which are identical or different, independently of one another, are chosen from:
• hydrogen atoms;
• halogen atoms chosen from bromine, chlorine and fluorine;
• a group chosen from —NR5R6, OR7, —NR4-Ph-NR5R6, —NR4-Ph-OR7, —O-Ph-OR7 and —O-Ph-NR5R6 groups, wherein:
• R4 and R7, which are identical or different, are chosen from hydrogen atoms, optionally substituted C1-C20 alkyl radicals, optionally substituted C1-C3 aralkyl radicals and optionally substituted phenyl radicals;
• R5 and R6, which are identical or different, are chosen from hydrogen atoms, optionally substituted C1-C20 alkyl radicals, optionally substituted phenyl radicals, optionally substituted C1-C3 aralkyl radicals and alkylcarbonyl radicals (R—CO—) wherein R is a C1-C4 alkyl radical;
• R5 and R6 may optionally form, with the nitrogen atom to which they are attached, a heterocycle containing 1 to 3 heteroatoms, chosen from N, O and S, and containing 5 to 7 ring members, which is saturated or unsaturated, aromatic or non-aromatic and is optionally substituted;
• R5 and R6 may optionally form, with the carbon atom of the aromatic ring adjacent to that to which —NR5R6 is attached, a 5- or 6-membered saturated heterocycle;
• Ph is an optionally substituted phenyl radical;
• L is chosen from a cationic linker and a non-cationic linker;
• An is chosen from at least one identical or different cosmetically acceptable anions which ensure the electroneutrality of the compounds of formula (I), (II), (III) and (IV).

A multi-compartment device, wherein a first compartment comprises a dyeing composition and a second compartment comprises an oxidizing composition, said dyeing composition comprising, in a medium appropriate for dyeing keratin fibers, at least one direct dye chosen from those of formulae (I), (II), (III) and (IV), acid addition salts thereof, and solvates thereof, wherein in the compounds of formulae (I), (II), (III) and (IV), the formula members attached to each side of the linker L are either compositionally different or positionally different such that the compounds as a whole are dissymmetrical:

• wherein:
• the radicals R1, which are identical or different, independently of one another are chosen from:
• optionally substituted C1-C4 alkyl radicals;
• optionally substituted phenyl radicals;
• optionally substituted benzyl radicals;
• the radicals R2, which are identical or different, independently of one another are chosen from:
• optionally substituted C1-C16 alkyl radicals optionally interrupted by at least one heteroatom and/or at least one group containing at least one heteroatom, said alkyl radical being further optionally substituted by at least one group chosen from thio (—SH), C1-C4 thioalkyl;
• C1-C4 alkylsulphinyl and C1-C4 alkylsulphonyl groups;
• hydroxyl groups;
• C1-C4 alkoxy groups;
• C2-C4 (poly)hydroxyalkoxy groups;
• alkoxycarbonyl groups (RO—CO—) wherein R is a C1-C4 alkyl radical;
• alkylcarbonyloxy groups (RCO—O—) wherein R is a C1-C4 alkyl radical;
• alkylcarbonyl groups (R—CO—) wherein R is a C1-C4 alkyl radical;
• amino groups;
• amino groups substituted by one or two identical or different C1-C4 alkyl radicals optionally carrying at least one hydroxyl group, wherein the two alkyl radicals may optionally form, with the nitrogen atom to which they are attached, a heterocycle containing 1 to 3 heteroatoms chosen from N, O and S, and containing 5 to 7 ring members, wherein said heterocycle is saturated or unsaturated, aromatic or non-aromatic and is optionally substituted;
• alkylcarbonylamino groups (RCO—NR′—) wherein R is a C1-C4 alkyl radical and R′ is chosen from hydrogen and a C1-C4 alkyl radical;
• aminocarbonyl groups ((R)2N—CO—) wherein radicals R independently of one another are chosen from a hydrogen atom and a C1-C4 alkyl radical;
• ureido groups (N(R)2—CO—NR′—) wherein radicals R and R′ independently of one another are chosen from a hydrogen atom and a C1-C4 alkyl radical;
• aminosulphonyl groups ((R)2N—SO2—) wherein radicals R independently of one another are chosen from a hydrogen atom and a C1-C4 alkyl radical;
• alkylsulphonylamino groups (RSO2—NR′—) wherein R is a C1-C4 alkyl radical and R′ is chosen from a hydrogen atom and a C1-C4 alkyl radical;
• optionally substituted aryl radicals;
• optionally substituted (C1-C4)alkylaryl radicals;
• alkylsulphinyl groups (R—SO—) wherein R is a C1-C4 alkyl radical;
• alkylsulphonyl groups (R—SO2—) wherein R is a C1-C4 alkyl radical;
• nitro groups;
• cyano groups;
• halogen atoms;
• thio groups (HS—);
• alkylthio groups (RS—) wherein R is an optionally substituted C1-C4 alkyl radical;
• when e is 2, for each of the formulae (I), (II), (III) and (IV), two radicals R2 may optionally form, with the carbon atoms to which they are attached, a secondary ring, aromatic or non-aromatic, containing 5 or 6 ring members, which is optionally substituted by at least one identical or different group chosen from hydroxyl, C1-C4 alkyl, C1-C4 alkoxy, C2-C4 (poly)hydroxyalkoxy, amino, and amino substituted by one or two identical or different C1-C4 alkyl radicals which optionally carry at least one hydroxyl group;
• e is an integer ranging from 0 to 4;
• when e is less than 4, the unsubstituted carbon atom(s) of the heterocycle of the formulae (I), (II), (III) and (IV) carry a hydrogen atom,
• the radicals R3, from formulae (I), (II), (III) and (IV), which are identical or different, independently of one another are chosen from:
• optionally substituted C1-C16 alkyl radicals optionally interrupted by at least one heteroatom or by at least one group containing at least one heteroatom;
• hydroxyl groups;
• C1-C4 alkoxy groups;
• C2-C4 (poly)hydroxyalkoxy groups;
• alkoxycarbonyl groups (RO—CO—) wherein R is a C1-C4 alkyl radical;
• alkylcarbonyloxy groups (RCO—O—) wherein R is a C1-C4 alkyl radical;
• alkylcarbonyl groups (R—CO—) wherein R is a C1-C4 alkyl radical;
• amino groups;
• amino groups substituted by one or two identical or different C1-C4 alkyl radicals optionally carrying at least one hydroxyl group;
• wherein the two alkyl radicals may optionally form, with the nitrogen atom to which they are attached, a heterocycle containing 1 to 3 heteroatoms chosen from N, O and S, containing 5 to 7 ring members, and which is saturated or unsaturated, aromatic or non-aromatic and is optionally substituted;
• alkylcarbonylamino groups (RCO—NR′—) wherein the radical R is a C1-C4 alkyl radical and the radical R′ is chosen from a hydrogen atom and a C1-C4 alkyl radical;
• aminocarbonyl groups ((R)2N—CO—) wherein radicals R independently of one another are chosen from a hydrogen atom and a C1-C4 alkyl radical;
• ureido groups (N(R)2—CO—NR′—) wherein radicals R and R′ independently of one another are chosen from a hydrogen atom and a C1-C4 alkyl radical;
• aminosulphonyl groups ((R)2N—SO2—) wherein radicals R independently of one another are chosen from a hydrogen atom and a C1-C4 alkyl radical;
• alkylsulphonylamino groups (RSO2—NR′—) wherein radicals R and R′ independently of one another are chosen from a hydrogen atom and a C1-C4 alkyl radical;
• thio groups (HS—);
• alkylthio groups (RS—) wherein R is a C1-C4 alkyl radical;
• alkylsulphinyl groups (R—SO—) wherein R is a C1-C4 alkyl radical;
• alkylsulphonyl groups (R—SO2—) wherein R is a C1-C4 alkyl radical;
• nitro groups;
• cyano groups;
• halogen atoms;
• when m′ is greater than or equal to 2, two adjacent radicals R3 may form, with the carbon atoms to which they are attached, a secondary ring, aromatic or non-aromatic containing 6 ring members, which is optionally substituted by at least one identical or different group chosen from:
• hydroxyl, C1-C4 alkyl, C1-C4 alkoxy, C2-C4 (poly)hydroxyalkoxy, C1-C4 alkylcarbonylamino, amino, and amino substituted by one or two identical or different C1-C4 alkyl radicals which optionally carry at least one hydroxyl group;
• m′ is an integer from 0 to 4;
• when m′ is less than 4, then the unsubstituted carbon atom(s) of the aromatic ring of the formulae (I), (II), (III) and (IV) carry a hydrogen atom;
• the W1 groups of the formulae (I), (II), (III) and (IV), which are identical or different, independently of one another, are chosen from:
• hydrogen atoms;
• halogen atoms chosen from bromine, chlorine and fluorine;
• a group chosen from —NR5R6, OR7, —NR4-Ph-NR5R6, —NR4-Ph-OR7, —O-Ph-OR7 and —O-Ph-NR5R6 groups, wherein:
• R4 and R7, which are identical or different, are chosen from hydrogen atoms, optionally substituted C1-C20 alkyl radicals, optionally substituted C1-C3 aralkyl radicals and optionally substituted phenyl radicals;
• R5 and R6, which are identical or different, are chosen from hydrogen atoms, optionally substituted C1-C20 alkyl radicals, optionally substituted phenyl radicals, optionally substituted C1-C3 aralkyl radicals and alkylcarbonyl radicals (R—CO—) wherein R is a C1-C4 alkyl radical;
• R5 and R6 may optionally form, with the nitrogen atom to which they are attached, a heterocycle containing 1 to 3 heteroatoms, chosen from N, O and S, and containing 5 to 7 ring members, which is saturated or unsaturated, aromatic or non-aromatic and is optionally substituted;
• R5 and R6 may optionally form, with the carbon atom of the aromatic ring adjacent to that to which —NR R6 is attached, a 5- or 6-membered saturated heterocycle;
• Ph is an optionally substituted phenyl radical;
• L is chosen from a cationic linker and a non-cationic linker;
• An is chosen from at least one identical or different cosmetically acceptable anions which ensure the electroneutrality of the compounds of formula (I), (II), (III) and (IV).