Use for dyeing keratin fibres of a compound of azomethine type bearing two pyrazolopyridine units

A compound chosen from dyes of azomethine type comprising two pyrazolopyridine units, chosen from compounds of formulae (I) or (II) and leuco forms thereof, optical or geometrical isomers thereof, tautomers thereof, addition salts thereof with an acid or a base, and solvates or hydrates thereof:

• wherein in formulae (I) and (II):
• Z1 represents an oxygen atom or a group —N(R6)—;
• Z′1 represents an oxygen atom or a group —N(R′6)—;
• with the proviso that when Z1 represents —N(R6)— and/or Z′1 represents —N(R′6)—, then R1 and R6 and/or R′1 and R′6, respectively, may form, together with the nitrogen atom to which they are attached, an optionally substituted, 5- to 8-membered, optionally cationic, saturated, unsaturated or aromatic heterocycle;
• R1, R′1, R6, and R′6 each independently represent:
• a hydrogen atom,
• a C1-C10 alkyl radical optionally interrupted with one or more non-adjacent heteroatoms and/or optionally substituted, optionally with one or more groups chosen from i) hydroxyl, ii) optionally substituted, 5- to 8-membered, cationic or non-cationic, saturated, unsaturated or aromatic (hetero)cycle, iii) —N(R′)R″, and iv) —N+R′R″R′″, with R′, R′ and R′″ each independently representing a C1-C6 alkyl group;
• or
• an optionally substituted, 5- to 8-membered, cationic or non-cationic, saturated, unsaturated or aromatic (hetero)cyclic radical;
• R2, R3, R4, R5, R′2, R′3, R′4 and R′5 each independently represent:
• a hydrogen atom,
• an optionally substituted C1-C4 alkyl radical, or
• a group chosen from —NH2, —N(H)R10, —N(R11)R12, OH or —OR9, with R9 and R10 representing an optionally substituted, linear or branched C1-C6 alkyl, R11 and R12, which may be identical or different, representing an optionally substituted, linear or branched C1-C6 alkyl, or R11 and R12 forming, together with the nitrogen atom to which they are attached, a saturated, unsaturated or aromatic 5- to 8-membered heterocycle optionally containing one or more other heteroatoms or groups chosen from N, O, S, S(O)2 and C(O), the heterocycle being optionally substituted;
• or
• R2, R3, R4, R5, R′2, R′3, R′4 and R′5 may form, in pairs with adjacent radicals, an optionally substituted, saturated or unsaturated (hetero)cycle;
• it being understood that when the compound of formula (I) or (II) is positively charged, then it comprises as many anionic counterions as cationic charges to achieve the electrical neutrality of the molecule.