Dichromophore carbonyl or heterocyclic dye, dye composition comprising this dye, process for dyeing keratin materials using this dye

A dye of formula (I):

• A-(L)p-Csat—S—Y-(L′)p′-Y—S—Csat-(L)p-A (I)
• the organic or mineral acid salts, optical isomers and geometric isomers thereof, and the solvates such as hydrates:
• in which formula (I):
• A represents a radical containing at least one chromophore which is optionally cationic, colored, or colored and fluorescent;
• L and L′, which may be identical or different, represent:
• a saturated or unsaturated, linear or branched C1-C20 hydrocarbon-based chain which is optionally substituted, optionally interrupted and/or optionally terminated at one or both of its ends with one or more divalent groups or combinations thereof chosen from —N(R)—, —O—, —S—, —C(O)— and —SO2—, with R, R′, which may be identical or different, being chosen from a hydrogen, and a C1-C4 alkyl, hydroxyalkyl and aminoalkyl radical;
• it being understood that said combination cannot form a disulfide bond —S—S—;
• an arylene group,
• a heteroarylene group,
• a cycloalkylene group, or
• a heterocycloalkylene group;
• Y represents a carbonyl group —C(O)— or a heteroaryl group, which is cationic or noncationic, which comprises 5-13 members, which is optionally substituted, and which comprises from 1 to 5 heteroatoms chosen from oxygen, sulfur or nitrogen atoms;
• p and p′, which may be identical or different, represent an integer equal to 0 or 1;
• Csat represents an optionally substituted, linear or branched C1-C18 alkylene chain.