Dye-ascorbic acid derivatives

Compounds of the formula I

• where X stands for a single bond or a substituent of the formula IIa or IIb
• where *1 is oriented towards the N═N,
• where precisely one of the substituents R1 to R14 stands for a substituent of the formula IIIa, IIIb or IIIc
• where R15 in each case stands, independently of one another, for an ascorbic acid radical of the formula IVa or IVb or a dehydroascorbic acid radical of the formula IVc or IVd, in each case as the L or D enantiomer,
• where the remaining substituents R1 to R14 each stand, independently of one another,
• for H, OH, NH2, NO2, F, Cl, Br, I, CF3, OCF3, O(C═O)—CH2—NH2, Alk1, OAlk1, NHAlk1, NAlk12, Cyc, (NAlk13)+nAnx−, (SO2)NH2, (SO2)NHAlk1, O(SO2)OAlk1, O(SO2)OArl, (C═O)OAlk1, (C═O)OArl or Arl,
• where Alk1 in each case stands, independently of one another,
• for a straight-chain or branched C1- to C20-alkyl group or for a straight-chain or branched C2- to C20-alkenyl group, which may have a plurality of double bonds, where at least one C atom or a plurality of non-adjacent C atoms of the C1- to C20-alkyl or C2- to C20-alkenyl group may be replaced by 0, where the C1- to C20-alkyl or C2- to C20-alkenyl group may have at least one OH, F, Cl, Br or I bonded to a primary or secondary C atom,
• where Arl in each case stands, independently of one another,
• for an unsubstituted, mono- or polysubstituted C6- to C20-aryl group,
• where Cyc stands for a C3- to C8-cycloalkyl group, which may have at least one double bond and/or in which at least one CH2 may be replaced by O or NH,
• where Anx− in each case stands, independently of one another, for an anion having the charge 1≦x≦3 and/or tautomers, stereoisomers thereof, including mixtures thereof in all ratios.