Organometallic complex for organic electroluminescent device

1. An organometallic complex having formula (I)

wherein

M is a transition metal;

each A 1 and A 2 is independently a monodentate ligand, or A 1 and A 2 are covalently joined together to form a bidentate ligand;

R 1 is H, C 1-18 alkyl, C 1-18 alkoxy, C 3-18 heteroalkyl, C 3-20 aryl, C 3-20 heteroaryl, or C 3-20 cycloalkyl;

R 2 is the same or different and is C 1-18 alkyl, C 1-18 alkoxy, C 3-18 heteroalkyl, C 3-20 aryl, C 3-20 heteroaryl, or C 3-20 cycloalkyl;

R 3 is the same or different and is H, CN, tricyanovinyl, halogen, CX 3 , C 1-18 alkyl, C 1-18 alkoxy, C 3-18 heteroalkyl, C 3-20 aryl, C 3-20 heteroaryl, or C 3-20 cycloalkyl, wherein X is halogen;

m is the charge of M;

n is 1, 2, or 3.

2. The organometallic complex as claimed in claim 1 , wherein M is Ir, Pt, Os, Re, Ru, or Rh.

3. The organometallic complex as claimed in claim 1 , wherein A 1 and A 2 are covalently joined together to form a bidentate ligand.

4. The organometallic complex as claimed in claim 1 , wherein R 1 is an electron-donating group.

5. The organometallic complex as claimed in claim 1 , wherein R 1 is C 1-18 alkyl, C 1-18 alkoxy, C 3-18 heteroalkyl, C 3-20 aryl, or C 3-20 heteroaryl.

6. The organometallic complex as claimed in claim 1 , wherein R 3 is an electron-withdrawing group.

7. The organometallic complex as claimed in claim 1 , wherein R 3 is halogen, CN, tricyanovinyl or CX 3 , wherein X is halogen.

8. The organometallic complex as claimed in claim 7 , wherein R 3 is halogen.

9. The organometallic complex as claimed in claim 1 , which emits light.

10. The organometallic complex as claimed in claim 9 , which emits phosphorescence.

11. The organometallic complex as claimed in claim 10 , which emits blue phosphorescence.

12. The organometallic complex as claimed in claim 1 , which has a hole transport property.

13. An organic electroluminescent device, comprising a pair of electrodes and a layer of organic light emitting medium disposed between the pair of electrodes, wherein the layer of organic light emitting medium includes an organometallic complex having formula (I)

wherein

M is a transition metal;

each A 1 and A 2 is independently a monodentate ligand, or A 1 and A 2 are covalently joined together to form a bidentate ligand;

R 1 is H, C 1-18 alkyl, C 1-18 alkoxy, C 3-20 heteroalkyl, C 3-20 aryl, C 3-20 heteroaryl, or C 3-20 cycloalkyl;

R 2 is the same or different and is C 1-18 alkyl, C 1-18 alkoxy, C 3-20 heteroalkyl, C 3-20 aryl, C 3-20 heteroaryl, or C 3-20 cycloalkyl;

R 3 is the same or different and is H, CN, tricyanovinyl, halogen, CX 3 , C 1-18 alkyl, C 1-18 alkoxy, C 3-18 heteroalkyl, C 3-20 aryl, C 3-20 heteroaryl, or C 3-20 cycloalkyl, wherein X is halogen;

m is the charge of M;

n is 1, 2, or 3.

14. The organic electroluminescent device as claimed in claim 13 , wherein the layer of organic light emitting medium includes a light emitting layer, and the light emitting layer includes an organometallic complex of formula (I).

15. The organic electroluminescent device as claimed in claim 13 , wherein the layer of organic light emitting medium includes a light emitting layer and a hole transport layer, and the hole transport layer includes an organometallic complex of formula (I).

16. An organometallic complex, which is selected from the following formulae

17. An organic electroluminescent device, comprising a pair of electrodes and a layer of organic light emitting medium disposed between the pair of electrodes, wherein the layer of organic light emitting medium includes an organometallic complex, which is selected from the following formulae