The use of cyclic compounds of the formula (I) where n is a number in the range from 1 to 7, X—Y—Z, in each case independently of one another, is O—C═N, N═C—O, NR5—C═N, N═C—NR5, N+R52—C═N, N═C—N+R52, O—C═N+R5, N+R5═C—O, S—C═N+R5, N+R5═C—S, S—C═N, N═C—S, R1, R2 and R3 each independently are, for example, H or a substituent or corresponding heterocyclic compounds in which at least one group —CR1═, —CR2═, CR3═ is replaced by —N, R5 in each case independently are, for example, H or a substituent R7 in each case independently of one another, are H, C1-12-alkyl or C6-12-aryl, or metal complexes of the cyclic compounds or complexes of the cyclic compounds with mineral acids, chloride, sulfate, bisulfate, phosphate, hydrogen phosphate, nitrate, BF4− or methanesulfonate being present as opposite ions X− in the case of cationic cyclic structures, as light absorbers, materials for hole injection layers in OLEDs, light-emitting compounds in OLED, phase-transfer catalysts or synergistic agents for the dispersing of pigments or for optical data storage, is described.