Heteroleptic transition metal-carbene complexes and their use in organic light-emitting diodes

Abstract

The present invention relates to heteroleptic carbene complexes comprising at least two different carbene ligands, to a process for preparing the heteroleptic carbene complexes, to the use of the heteroleptic carbene complexes in organic light-emitting diodes, to organic light-emitting diodes comprising at least one inventive heteroleptic carbene complex, to a light-emitting layer comprising at least one inventive heteroleptic carbene complex, to organic light-emitting diodes comprising at least one inventive light-emitting layer, and to devices which comprise at least one inventive organic light-emitting diode.

Claims

1. A heteroleptic carbene complex of the general formula (I)
M.sup.1[carbene].sub.n  (I) comprising at least two different carbene ligands, wherein the symbols are each defined as follows: M.sup.1 is Ir(III) n is 3 wherein the first of the at least two different carbene ligands has the general formula: ##STR00051## and the second of the at least two different carbene ligands has the general formula: ##STR00052## wherein Q is CF.sub.3 or CN; Y.sup.3 is an alkyl group having 1, 2, or 3 carbon atoms; and Ar.sup.1 is a phenyl group.

2. The heteroleptic carbene complex of claim 1, wherein the first of the at least two different carbene ligands has one of the following structures: ##STR00053##

3. An organic light-emitting diode comprising at least one heteroleptic carbene complex according to according to claim 1.

4. A device selected from the group consisting of stationary visual display units, and mobile visual display units comprising at least the organic light emitting diode according to claim 3.

5. A light-emitting layer comprising at least one heteroleptic carbene complex according to according to claim 1.

6. An organic light emitting diode comprising at least one light-emitting layer according to claim 5.

Description

EXAMPLES

a) Synthesis of Complex K I

(1) ##STR00040##

(2) In a 1 l three-neck flask, 16.11 g (45 mmol) of benzimidazolium salt S I were suspended in 250 ml of toluene and cooled to −8° C. 90 ml of bis(trimethylsilyl)potassium amide (KHMDS, 0.5M in toluene, 45 mmol) are then added within 30 min. The mixture is stirred at room temperature for 1 hour and then added dropwise at −78° C. to a solution of 15.12 g (22.5 mmol) of [(μ-Cl)Ir(η.sup.4-1,5-COD)].sub.2 in 400 ml of toluene within 30 min. The reaction mixture is stirred at room temperature for 1.5 h and then heated at reflux for 18 h. After cooling, the precipitate is filtered off and washed with toluene. The combined toluene phases are concentrated to dryness and purified by column chromatography. 13.4 g (49%) of yellow powder are obtained.

(3) .sup.1H NMR (CD.sub.2Cl.sub.2, 500 MHz): δ=7.96 (m, 4H), 7.51 (m, 6H), 7.25 (m, 2H), 7.18 (m, 2H) (je CH.sub.Ph), 4.31 (m, 2H, CH.sub.cod), 2.43 (m, 2H, CH.sub.cod), 1.61 (m, 2H), 1.34 (m, 4H), 1.17 (m, 2H) (je CH.sub.2,cod).

(4) .sup.13C NMR (CD.sub.2Cl.sub.2, 125 MHz): δ=191.5 (NCN), 137.0, 135.0 (Cq), 128.1, 127.8, 127.1, 122.5, 110.0 (CH.sub.Ph), 84.5, 51.4 (je CH.sub.cod), 32.1, 28.1 (je CH.sub.2,cod).

b) Synthesis of Complex K II

(5) ##STR00041##

(6) 13.74 g (44.16 mmol) of imidazolium iodide S II are suspended in 200 ml of THF and admixed at −8° C. with 88.32 ml of bis(trimethylsilyl)potassium amide (0.5M in toluene, 44.16 mmol) within 30 min. The suspension is stirred at room temperature for 1 hour and then added dropwise at −78° C. to a solution of 4.94 g (7.36 mmol) of [(μ-Cl)Ir(η.sup.4-1,5-COD)].sub.2 in 360 ml of THF within 30 min. The mixture is stirred at room temperature for 1.5 h and under reflux for 17 h. After cooling, the precipitate is filtered off, washed with THF, H.sub.2O and methanol, and dried. 4.02 g (34%) of orange powder are obtained.

(7) .sup.1H NMR (DMSO, 500 MHz): δ=8.09 (d, .sup.3J.sub.H,H=7.8 Hz, 4H, CH.sub.ph), 7.53 (d, .sup.3J.sub.H,H=7.8 Hz, 4H, CH.sub.ph), 7.46 (s, 2H, NCHCHN), 7.34 (s, 2H, NCHCHN), 4.64 (m, 2H, CH.sub.cod), 3.58 (m, 2H, CH.sub.cod), 3.06 (s, 6H, NCH.sub.3), 2.33-2.01 (m, 4H, CH.sub.2,cod), 1.76-1.1.59 (m, 4H, CH.sub.2,cod).

c) Synthesis of Complex K III (Route 1)

(8) ##STR00042##

(9) 6.9 ml of bis(trimethylsilyl)potassium amide (KHMDS, 0.5M in toluene, 3.45 mmol) are then added within 10 min. The mixture is stirred at room temperature for a half hour and then added dropwise to a mixture of 1.37 g (1.73 mmol) of K II and 0.34 g (1.73 mmol) of silver tetrafluoroborate in 90 ml of dioxane within 20 min. The reaction mixture is stirred at room temperature for 1 hour and then heated at reflux for 21 h. After cooling, the precipitate is filtered off and washed with dioxane. The filtrate is freed from the solvent and with extracted methylene chloride. 0.38 g (27%) of yellow powder is obtained from the extract after column chromatography purification.

d) Synthesis of Complex K III (Route 2)

(10) ##STR00043##

(11) 2.31 g (7.38 mmol) of imidazolium salt S II are suspended in 135 ml of dioxane. 14.8 ml of bis(trimethylsilyl)potassium amide (KHMDS, 0.5M in toluene, 7.40 mmol) are then added within 10 min. The mixture is stirred at room temperature for 1 hour and then added dropwise to a mixture of 1.5 g (2.46 mmol) of K I and 0.48 g (2.46 mmol) of silver tetrafluoroborate in 90 ml of dioxane within 20 min. The reaction mixture is stirred at room temperature for 1 hour and then heated at reflux for 21 h. After cooling, the precipitate is filtered off and washed with dioxane. The filtrate is freed from the solvent and with extracted methylene chloride. 0.70 g (34%) of slightly yellowish powder is obtained from the extract after column chromatography purification.

(12) .sup.1H NMR (CD.sub.2Cl.sub.2, 500 MHz): δ=2.44 (s, 3H), 3.21 (s, 3H), 6.21-6.23 (m, 1H), 6.26 (d, J=2.1 Hz, 1H), 6.51 (dd, J=7.3 Hz, J=1.5 Hz, 1H), 6.59-6.60 (m, 1H), 6.72 (dt, J=7.3 Hz, J=1.1 Hz, 1H), 6.77 (d, J=2.3 Hz, 1H), 6.81-6.82 (m, 1H), 6.85-6.87 (m, 1H), 7.06-7-19 (m, 4H), 7.21-7.26 (m, 3H), 7.28-7.33 (m, 2H), 7.35-7.39 (m, 2H), 7.43-7.49 (m, 2H), 7.98 (d, J=7.9 Hz, 1H), 8.25 (d, J=8.2 Hz, 1H).

(13) .sup.13C NMR (CD.sub.2Cl.sub.2, 126 MHz): δ=36.5 (CH.sub.3), 37.5 (CH.sub.3), 108.02 (C.sub.q, CN), 108.04 (C.sub.q, CN), 110.5 (CH), 110.9 (CH), 111.2 (CH), 111.7 (CH), 113.0 (CH), 114.6 (CH), 115.1 (CH), 121.0 (C.sub.q), 121.1 (C.sub.q), 121.66 (CH), 121.73 (CH), 121.8 (CH), 122.7 (CH), 123.8 (CH), 125.3 (CH), 126.3 (CH), 126.5 (CH), 126.7 (CH), 128.6 (CH), 128.8 (CH), 129.1 (CH), 130.0 (CH), 132.7 (C.sub.q), 137.4 (CH), 138.2 (C.sub.q), 138.4 (C.sub.q), 140.2 (CH), 141.3 (CH), 147.2 (C.sub.q), 149.1 (C.sub.q), 149.7 (C.sub.q), 150.7 (C.sub.q), 151.17 (C.sub.q), 151.23 (C.sub.q), 176.6 (C.sub.q, NCN), 177.5 (C.sub.q, NCN), 187.1 (C.sub.q, NCN).

e) Optical Spectroscopy

(14) Photoluminescence (polymethyl methacrylate (PMMA) films doped with 2% by weight of the particular carbene complex)

(15) TABLE-US-00002 Emission wavelength Quantum yield 390 nm 15% 460 nm 78% 450 nm 78% * for preparation, see Ir complex (7) in the application WO 05/019373 ** for preparation, see German application 102004057072.8, filed on: 11.25.2004, title: ″Verwendung von Übergangsmetall-Carbenkomplexen in organischen Licht-emittierenden Dioden (OLEDs)″ [Use of transition metal-carbene complexes in organic light-emitting diodes (OLEDs)]

f) Production of an OLED

(16) The ITO substrate used as the anode is first cleaned with commercial detergents for LCD production (Deconex® 20NS and neutralizer 25ORGAN-ACID®) and then in an acetone/isopropanol mixture in an ultrasound bath. To remove possible organic residues, the substrate is exposed to a continuous ozone flow in an ozone oven for a further 25 minutes. This treatment also improves the hole injection properties of the ITO.

(17) Thereafter, the organic materials specified below are applied to the cleaned substrate by vapor deposition at a rate of approx. 2-3 nm/min at about 10.sup.−7 mbar. The hole conductor and exciton blocker applied to the substrate is Ir(dpbic).sub.3 with a thickness of 20 nm.

(18) ##STR00047##

(19) (for preparation, see Ir complex (7) in the application WO 05/019373).

(20) Subsequently, a mixture of 30% by weight of the compound

(21) ##STR00048##

(22) and 70% by weight of the compound

(23) ##STR00049##

(24) (for preparation, see German application 102005014284.2, filed on: Mar. 24, 2005, title: “Verwendung von Verbindungen, welche aromatische oder heteroaromatische über Carbonyl-Gruppen enthaltende Gruppen verbundene Ringe enthalten, als Matrixmaterialien in organischen Leuchtdioden” [Use of compounds which comprise aromatic or heteroaromatic rings bonded via groups comprising carbonyl groups as matrix materials in organic light-emitting diodes]) is applied by vapor deposition in a thickness of 20 nm, the former compound functioning as an emitter, the latter as a matrix material.

(25) Subsequently, the material

(26) ##STR00050##

(27) (for preparation, see German application 102004057073.6, filed on: Nov. 25, 2004, title: “Verwendung von Phenothiazin-S-oxiden und-S,S-dioxiden als Matrixmaterialien fir organische Leuchtdioden” [Use of phenothiazine S-oxides and S,S-dioxides as matrix materials for organic light-emitting diodes]) is applied by vapor deposition with a thickness of 9 nm as an exciton and hole blocker.

(28) Next, an electron transporter TPBI (1,3,5-tris(N-phenylbenzylimidazol-2-yl)benzene) is applied by vapor deposition in a thickness of 40 nm, as are a 0.75 nm-thick lithium fluoride layer and finally a 110 nm-thick Al electrode.

(29) To characterize the OLED, electroluminescence spectra are recorded at different currents and voltages. In addition, the current-voltage characteristic is measured in combination with the emitted light output. The light output can be converted to photometric parameters by calibration with a photometer.

(30) For the OLED described, the following electrooptical data are obtained:

(31) TABLE-US-00003 Emission maximum 456 nm CIE(x, y) 0.155; 0.12 Photometric efficiency at 4 V 9.6 cd/A Power efficiency at 4 V 7.5 Im/W External quantum yield at 4 V 9.7% Luminance at 7 V 1500 cd/m.sup.2