SYMMETRICAL DIAZO COMPOUNDS CONTAINING 3-PYRIDINIUM GROUPS AND A NON-CATIONIC LINKER, COMPOSITIONS COMRISISNG THEM, METHOD OF COLOURING, AND DEVICE

摘要

The present invention relates to symmetrical cationic diazo compounds of formula (I) below, their resonance forms, and also their acid addition salts and their solvates: in which W₁ radicals, which are identical, represent a hydrogen atom, a halogen atom, or an -NR₄-Ph-NR₅R₆, -NR₄-Ph-OR₇, -O-Ph-OR₇ or -O-Ph-NR₅R₆ group; -NR₅R₆, -OR₇ under certain conditions; L, a non-cationic linker connecting the two identical azo chromophores, represents a covalent bond; an optionally substituted C₁-C₄₀ alkyl radical which is optionally interrupted by a (hetero)cycle, it being possible for the said alkyl radical to be optionally interrupted by one or more heteroatoms or groups containing at least one heteroatom; or an optionally substituted phenyl radical. The invention further relates to dyeing compositions comprising such compounds as a direct dye in a medium appropriate for the dyeing of keratin fibres, and also to a method of colouring keratin fibres that employs this composition, and a device having a plurality of compartments.