Terrylene and quaterrylene derivatives

A process for preparing a rylenetetracarboxylic dianhydride, or a salt thereof having formula Ib

• wherein
• R is phenoxy, phenylthio, pyridyloxy, pyrimidyloxy, pyridylthio or pyrimidyl-thio, each of which may optionally be mono- or polysubstituted by C1-C12-alkyl, C1-C12-alkoxy and/or aryl;
• m is 1 or 2;
• n is 4 when m=1;
• 4 or 6 when m=2,
• the process comprising
• a) subjecting a rylenetetracarboximide of general formula II
• wherein R, m and n are as defined above and R′ is hydrogen or a C1-C30-alkyl whose carbon chain may, optionally, be interrupted by one or more —O— and/or —CO— moieties and which may, optionally, be mono- or polysubstituted by:
• C1-C6-alkoxy, cyano and/or aryl which may, optionally, be mono- or polysubstituted by C1-C18-alkyl or C1-C6-alkoxy;
• or phenyl, or naphthyl, or pyridyl, or pyrimidyl, each of which may be, optionally, mono or polysubstituted by:
• C1-C18-alkyl, C1-C6-alkoxy, halogen, cyano, nitro, —CONR2R3, —SO2NR2R3, or phenyl or naphthylazo, each of which may be, optionally, mono- or polysubstituted by C1-C10-alkyl, C1-C6-alkoxy and/or cyano;
• or C5-C8-cycloalkyl which, optionally, may be mono- or polysubstituted by C1-C6-alkyl, where R2 and R3 are each independently hydrogen;
• C1-C18-alkyl whose carbon chain may be interrupted by one or more —O—, —S—, —CO—, —SO— and/or —SO2— moieties and which may be mono- or polysubstituted by C1-C12-alkoxy, C1-C6-alkylthio, hydroxyl, mercapto, halogen, cyano, nitro and/or —COOR1;
• aryl or hetaryl to each of which may be fused further saturated or unsaturated 5- to 7-membered rings whose carbon skeleton may be interrupted by one or more —O—, —S—, —CO— and/or —SO2— moieties, where the entire ring system may be mono- or polysubstituted by C1-C12-alkyl and/or the above radicals specified as substituents for alkyl;
• and R1 is hydrogen or C1-C18-alkyl, where the R1 radicals may be the same or different when they occur more than once;
• to a hydrolysis under alkaline conditions in the presence of a polar organic solvent and removing the rylenetetracarboxylic dianhydride Ib from any rylenetetracarboxylic monoimide monoanhydride of formula Ia which is formed
• where R′, R, n and m have the same meanings as above,
• to form the rylenetetracarboxylic dianhydride, or the salt thereof having formula Ib or
• b) hydrolyzing the rylenetetracarboximide of general formula II under conditions that form the compound of formula Ib and substantially no rylenetetracarboxylic monoimide monoanhydride of the formula Ia.