Transition metal complexes comprising carbene ligands serving as emitters for organic light-emitting diodes (OLED's)

#The present invention relates to the use of transition metal complexes comprising at least one carbene ligand in organic light-emitting diodes (OLEDs), a light-emitting layer, blocking layer for electrons or excitons or blocking layer for holes comprising these transition metal complexes, OLEDs comprising these transition metal complexes, devices comprising an OLED according to the present invention and also specific transition metal complexes comprising at least two carbene ligands.

#In organic light-emitting diodes (OLEDs), use is made of the ability of materials to emit light when they are excited by an electric current. OLEDs are of particular interest as alternatives to cathode ray tubes and liquid crystal displays for producing flat VDUs. Owing to their very compact construction and the intrinsically low power consumption, devices comprising OLEDs are particularly useful for mobile applications, for example for use in mobile telephones, laptops, etc.

#Numerous materials which emit light on excitation by an electric current have been proposed.

#FIG. 1 shows an organic light-emitting diode made up of a plurality of layers.

#FIG. 2 shows the crystal structure of the fac isomer of the Ir complex (7).

#We have found that these objects are achieved by the use of uncharged transition metal complexes of the formula I comprising at least one carbene ligand in organic light-emitting diodes (OLEDs)

#where the symbols have the following meanings: M1 is a metal atom selected from the group consisting of Co, Rh, Ir, Nb, Pd, Pt, Fe, Ru, Os, Cr, Mo, W, Mn, Tc, Re, Cu, Ag and Au in any oxidation state possible for the respective metal atom; carbene is a carbene ligand which may be uncharged or monoanionic and monodentate, bidentate or tridentate, with the carbene ligand also being able to be a biscarbene or triscarbene ligand; L is a monoanionic or dianionic ligand, preferably a monoanionic ligand, which may be monodentate or bidentate; K is an uncharged monodentate or bidentate ligand selected from the group consisting of phosphines, preferably trialkylphosphines, triarylphosphines or alkylarylphosphines, particularly preferably PAr3, where Ar is a substituted or unsubstituted aryl radical and the three aryl radicals in PAr3 may be identical or different, particularly preferably PPh3, PEt3, PnBu3, PEt2Ph, PMe2Ph, PnBu2Ph; phosphonates and derivatives thereof, arsenates and derivatives thereof, phosphites, CO; pyridines which may be substituted by alkyl or aryl groups; nitriles and dienes which form a π complex with M1, preferably η4-diphenyl-1,3-butadiene, η4-1,3-pentadiene, η4-1-phenyl-1,3-pentadiene, η4-1,4-dibenzyl-1,3-butadiene, η4-2,4-hexadiene, η4-3-methyl-1,3-pentadiene, η4-1,4-ditolyl-1,3-butadiene, η4-1,4-bis(trimethylsilyl)-1,3-butadiene and η2- or η4-cyclooctadiene (each 1,3 and 1,5), particularly preferably 1,4-diphenyl-1,3-butadiene, 1-phenyl-1,3-pentadiene, 2,4-hexa-diene, butadiene, η2-cyclooctene, η4-1,3-cyclooctadiene and η4-1,5-cyclo-octadiene; n is the number of carbene ligands, where n is at least 1 and when n>1 the carbene ligands in the complex of the formula I can be identical or different; m is the number of ligands L, where m can be 0 or ≥1 and when m>1 the ligands L can be identical or different; o is the number of ligands K, where o can be 0 or ≥1 and when o>1 the ligands K can be identical or different; where the sum n+m+o is dependent on the oxidation state and coordination number of the metal atom and on the denticity of the ligands carbene, L and K and also on the charge on the ligands carbene and L, with the proviso that n is at least 1.

#The transition metal complexes of the formula I can be used in any layer of an OLED, with the ligand skeleton or central metal being able to be varied to match it to desired properties of the metal complexes. For example, the transition metal complexes of the formula I can be used in a blocking layer for electrons, a blocking layer for excitons, a blocking layer for holes or the light-emitting layer of the OLED. The compounds of the formula I are preferably used as emitter molecules in OLEDs.