Use of Dibenzanthrone and Isodibenzanthrone Derivatives as Marking Substances for Liquids

A marker for liquid comprising dibenzanthrone derivatives of the general formula Ia

• or isodibenzanthrone derivatives of the general formula Ib
• wherein the variables are:
• X1, X2 are each independently —O—, —S—, —NH—, —NY—, —CO—,—O—CO—, —CO—O—, —S—CO—, —CO—S—, —NH—CO—, —CO—NH—, —NY—CO—, —CO—NY—, —CH2—NH—, —CH2—NY—, —CH2—NH—CO— or —CH2—NY—CO—, where the latter four groups mentioned are each bonded via the CH2 group to the basic dibenzanthrone or isodibenzanthrone structure,
• R1, R2, Y are each independently
• C1-C20-alkyl which is optionally interrupted by from 1 to 4 oxygen atoms in ether function;
• C5-C7-cycloalkyl which is optionally substituted by one or more C1-C20-alkyl groups which are optionally interrupted by from 1 to 4 oxygen atoms in ether function;
• saturated heterocyclic five- or six-membered radical which is optionally substituted by one or more C1-C20-alkyl groups which are optionally interrupted by from 1 to 4 oxygen atoms in ether function;
• C6-C10-aryl which is optionally substituted by one or more halogen, cyano, nitro, hydroxyl, amino, C1-C20-alkyl which is optionally interrupted by from 1 to 4 oxygen atoms in ether function, C1-C20-alkoxy, C1-C20-alkylamino or di(C1-C20-alkyl)amino;
• heteroaryl which has from 3 to 12 carbon atoms and may optionally be substituted by one or more C1-C20-alkyl which is optionally interrupted by from 1 to 4 oxygen atoms in ether function, C1-C20-alkoxy, C1-C20-alkylamino or di(C1-C20-alkyl)amino;
• C6-C10-aryl-C1-C4-alkyl which is optionally substituted in the aryl radical by one or more halogen, cyano, nitro, hydroxyl, amino, C1-C20-alkyl which is optionally interrupted by from 1 to 4 oxygen atoms in ether function, C1-C20-alkoxy, C1-C20-alkylamino or di(C1-C20-alkyl)-amino;
• or
• heteroaryl-C1-C4-alkyl having from 3 to 12 carbon atoms in the heteroaryl radical, the latter optionally being substituted by one or more C1-C20-alkyl which is optionally interrupted by from 1 to 4 oxygen atoms in ether function, C1-C20-alkoxy, C1-C20-alkylamino or di(C1-C20-alkyl)amino,
• and
• n, m are integers from 1 to 16, where, when n>1 or m>1, the n (X1—R1) moieties or the m (X2—R2) moieties may be the same or different.