For potential applications of organic materials as active components In electronics, the energetic position of their valence and conduction levels are important parameters. For a given parent molecule, e.g. an aromatic hydrocarbon, the positions of these levels can be shifted substantially by attaching donor- or acceptor-type side group units. This will be demonstrated for the perylene skeleton in perylene-3,4,9,10-tetra-carboxylic-dianhydride. N,N′-diphenyl-perylene-3,4,9,10-tetracarboxylic-diimide, and diindeno[1,2,3.-c,d:1′,2′,3′-Imlperylene. Energy level manipulation by introducing donor: acceptor ground state interactions is another possible concept which has been checked withsingle crystalsof the stoichiometric donor: acceptor complexes tetrathiafulvalene: p-chloranil, phenothiazine: tetracyanoquinodimethane. phenothazine: pyromellitic-dianhydride, perylene: pyromellitic-dianhydride and perylene: tetracyanoquinodimethane. where a certain dark conductivity or light-induced photoconductivity served to eliminate charging problems.