The invention relates to neutral mononuclear
copper (I) complexes for emitting light and with a structure according to formula (A) in which: M represents: Cu(I); L∩L represents: a single, negatively charged, bidentate ligand; N∩N represents: a
diimine ligand (substituted with R and FG), in particular a substituted 2,2′-
bipyridine derivative (bpy) or a substituted 1,10-
phenanthroline derivative (phen); R represents: at least one sterically demanding
substituent for preventing the planarisation of the complex in the
excited state; FG=functional group, and represents: at least one second
substituent for increasing
solubility in organic solvents. The
substituent can also be used for
electron transport or alternatively for hole transport, said functional group being bound to the
diimine ligands either directly or by means of suitable bridges; and the
copper (I) complex: having a ΔE(S1−T1) value of less than 2500 cm−1 between the lowest
excited singlet state (S1) and the
triplet state (T1) which lies below; having an emission lifespan of at most 20 μs; having an emission
quantum yield of greater than 40%, and a
solubility of at least 1 g / L in organic solvents, in particular polar organic hydrocarbons such as
acetone, methyl ethyl
ketone,
benzene,
toluene,
chlorobenzene,
dichlorobenzene,
dichloromethane,
chloroform,
dichloroethane,
tetrachloroethylene, alcohols,
acetonitrile or water.