TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation (Claimed): Preparation of (I) comprises chlorinating (I) (in which R11-R14, R21-R24 = H, Cl or CN, where at least one residue of R11-R14, R22-R24 is H, 0-7 residues of R11-R14, R22-R24 is Cl and 0-2 residue of R11-R14, R22-R24 is CN) to obtain (I) (in which R11-R14, R22-R24 is Cl, and R11-R14, R22-R24 is H), and optionally completely or partially replacing the chlorine group in (I) by fluorine. Preferred Process: The chlorinating process takes place by the reaction with chlorine in chlorosulfonic acid and in the presence of a catalytic quantity of iodine. The replacing process takes place using an alkali fluoride preferably under water-free conditions. SPECIFIC COMPOUNDS - 52 Compounds (I) are disclosed e.g. octafluoro-N,N'-(2,6-diisopropylphenyl)-perylen-3,4:9,10-tetracarboxylic acid diimide of formula (Ia), 4,5,6,7,11,12,13,14-octafluoro-2,9-bis-pentafluorophenyl-anthra(2,1,9-def;6,5,10-d'e'f')diisoquinoline-1,3,8,10-tetraone, 4,5,6,7,11,12,13,14-octafluoro-2,9-diphenyl-anthra(2,1,9-def;6,5,10-d'e'f')diisoquinoline-1,3,8,10-tetraone, 4,5,6,7,11,12,13,14-octafluoro-anthra(2,1,9-def;6,5,10-d'e'f')diisoquinoline-1,3,8,10-tetraone and 4,5,6,7,11,12,13,14-octafluoro-2,9-dimethyl-anthra(2,1,9-def;6,5,10-d'e'f')diisoquinoline-1,3,8,10-tetraone.    EXAMPLE - A mixture of octachloroperylen-3,4:9,10-tetracarboxylic acid dianhydride (1 g) and 2,6-diisopropylaniline (6 mmol) in propionic acid (16 ml) was stirred at 100 degrees C for 5 hours. The obtained mixture was cooled and transferred with water. The solid material was precipitated, filtered and vacuum dried to obtain octachloro-N,N'-bis(2,6-diisopropylphenyl)-perylen-3,4:9,10-tetracarboxylic acid diimide. To a mixture of o-xylene (35 ml), N,N'-dimethylimidazolidino-tetramethylguanidinium chloride (0.25 g) and potassium fluoride (4.5 g), octachloro-N,N'-bis(2,6-diisopropylphenyl)-perylen-3,4:9,10-tetracarboxylic acid diimide (1 g) were added. The reaction mixture was heated for one hour, subsequently cooled to obtain octafluoro-N,N'-(2,6-diisopropylphenyl)-perylen-3,4:9,10-tetracarboxylic acid diimide.