Abstract: The invention relates to copper(I) complexes of the formula A wherein X=Cl, Br or I (independently of one another); N*?E=a bidentate ligand, wherein E=a phosphinyl group including a phosphorus atom or an arsenyl group including an arsenic atom, wherein the phosphinyl group or the arsenyl group is combined with R in the form of R2E (where R=alkyl, aryl, alkoxy, or phenoxy; N*=imine function which is part of an aromatic group selected from pyridyl, pyrimidyl, pyridazinyl, triazinyl, oxazolyl, thiazolyl and imidazolyl, the aromatic group optionally having at least one substituent to increase the solubility of the copper(I) complex in an organic solvent; and ?=at least one carbon atom which is likewise part of the aromatic group. The carbon atom is located directly adjacent both to the imine nitrogen atom, coordinating to Cu in the case of a bridging ligand and to the phosphorus or arsenic atom.