ORGANIC ELECTROLUMINESCENT MATERIALS AND DEVICES

1 . A compound comprising a first ligand L A having Formula I:

wherein ring B is a 5 or 6-membered carbocyclic or heterocyclic ring;

wherein R B represents mono to the possible maximum number of substitution, or no substitution;

wherein Z 1 and Z 2 are each independently selected from the group consisting of carbon or nitrogen;

wherein A 1 , A 2 , A 3 , At, A 5 , A 6 , A 7 , and A 8 are each independently CR or N;

wherein each R in CR can be the same or different;

wherein n=1 and ring C is a 6-membered aromatic ring;

wherein at least two adjacent A 1 , A 2 , A 3 , A 4 , A 5 , A 6 , A 7 , and A 8 are CR and the Rs are joined together to form a six-membered ring D fused to ring A or ring C, wherein ring D is benzene, pyridine, pyridazine, pyrimidine, or pyrazine, and ring D may be further substituted;

wherein at least one of the following is true: at least one of A 1 to A 4 is N, or ring D is pyridine, pyridazine, pyrimidine, or pyrazine;

wherein X is O, S, or Se;

wherein R, R′ and R B are each independently selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof;

wherein any adjacent substituents are optionally joined or fused into a ring;

wherein the ligand L A is coordinated to a metal M;

wherein the metal M is bonded to ring A through a M-C bond;

wherein the metal M can be coordinated to other ligands; and

wherein the ligand L A is optionally linked with other ligands to comprise a tridentate, tetradentate, pentadentate or hexadentate ligand.

2 . The compound of claim 1 , wherein ring D is pyridazine, pyrimidine, or pyrazine.

3 . The compound of claim 1 , wherein ring D is pyridazine, pyrimidine, or pyrazine and each of A 1 to A 8 is CR.

4 . The compound of claim 1 , wherein at least one of A 1 to A 4 is N.

5 . The compound of claim 1 , wherein ring D is pyridine, pyridazine, pyrimidine, or pyrazine.

6 . The compound of claim 1 , wherein Ring D is fused to ring A and ring D is pyridine, pyridazine, pyrimidine, or pyrazine.

7 . The compound of claim 1 , wherein Ring D is fused to ring C and ring D is pyridine, pyridazine, pyrimidine, or pyrazine.

8 . The compound of claim 1 , wherein at least one of A 1 to A 8 is N, and ring D is pyridine, pyridazine, pyrimidine, or pyrazine.

9 . The compound of claim 1 , wherein at least one of A 5 to A 8 is N, and ring D is pyridine, pyridazine, pyrimidine, or pyrazine.

10 . The compound of claim 1 , wherein at least one of A 1 to A 4 is N, and ring D is pyridine, pyridazine, pyrimidine, or pyrazine.

11 . The compound of claim 1 , wherein ring B is pyridine, and Z 1 is N.

12 . The compound of claim 1 , wherein ring B is imidazole, and Z 1 is N.

13 . The compound of claim 1 , wherein M is selected from the group consisting of Ir, Rh, Re, Ru, Os, Pt, Au, and Cu.

14 . The compound of claim 1 , wherein X is O.

15 . The compound of claim 1 , wherein the ligand L A is selected from the group consisting of:

wherein Y is selected from the group consisting of O, S, Se, and NR″; and

wherein R A and R C have the same definition as R B .

16 . The compound of claim 1 , wherein the compound has the formula of M(L A ) x (L B ) y (L C ) z ;

wherein L B is a second ligand, and L C is a third ligand, and L B and L C can be the same or different;

wherein x is 1, 2, or 3;

wherein y is 0, 1, or 2:

wherein z is 0, 1, or 2;

wherein x+y+z is the oxidation state of the metal M;

wherein the second ligand L B and the third ligand L C are each independently selected from the group consisting of:

wherein X 1 to X 13 are each independently selected from the group consisting of carbon and nitrogen;

wherein X is selected from the group consisting of BR′, NR′, PR′, O, S, Se, C═O, S═O, SO 2 , CR′R″, SiR′R″, and GeR′R″;

wherein R′ and R″ are optionally fused or joined to form a ring;

wherein each R a , R b , R c , and R d may represent from mono substitution to the possible maximum number of substitution, or no substitution;

wherein R′, R″, R a , R b , R c , and R d are each independently selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; and

wherein any two adjacent substituents of R a , R b , R c , and R d are optionally fused or joined to form a ring or form a multidentate ligand.

17 . The compound of claim 1 , wherein the ligand L A is selected from the group consisting of:

18 . The compound of claim 16 , wherein the compound has the formula of Ir(L A ) n (L B ) 3-n or Ir(L A )(L B ) (L C ); wherein n is 1, 2, or 3.

19 . An organic light-emitting device (OLED) comprising:

an anode;

a cathode; and

an organic layer, disposed between the anode and the cathode, comprising a compound comprising a first ligand L A having Formula I:

wherein ring B is a 5 or 6-membered carbocyclic or heterocyclic ring;

wherein R B represents mono to the possible maximum number of substitution, or no substitution;

wherein Z 1 and Z 2 are each independently selected from the group consisting of carbon or nitrogen;

wherein A 1 , A 2 , A 3 , A 4 , A 5 , A 6 , A 7 , and A 8 are each independently CR or N;

wherein each R in CR can be the same or different;

wherein n=1 and ring C is a 6-membered aromatic ring;

wherein at least two adjacent A 1 , A 2 , A 3 , A 4 , A 5 , A 6 , A 7 , and A 8 are CR and the Rs are joined together to form a six-membered ring D fused to ring A or ring C, wherein ring D is benzene, pyridine, pyridazine, pyrimidine, or pyrazine, and ring D may be further substituted;

wherein at least one of the following is true: at least one of A 1 to A 4 is N, or ring D is pyridine, pyridazine, pyrimidine, or pyrazine;

wherein X is O, S, or Se;

wherein R, R′ and R B are each independently selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof;

wherein any adjacent substituents are optionally joined or fused into a ring;

wherein the ligand L A is coordinated to a metal M;

wherein the metal M is bonded to ring A through a M-C bond;

wherein the metal M can be coordinated to other ligands; and

wherein the ligand L A is optionally linked with other ligands to comprise a tridentate, tetradentate, pentadentate or hexadentate ligand.

20 . A consumer product comprising an organic light-emitting device (OLED) comprising:

an anode;

a cathode; and

an organic layer, disposed between the anode and the cathode, comprising a compound having a ligand of Formula I:

wherein ring B is a 5 or 6-membered carbocyclic or heterocyclic ring;

wherein R B represents mono to the possible maximum number of substitution, or no substitution;

wherein Z 1 and Z 2 are each independently selected from the group consisting of carbon or nitrogen;

wherein A 1 , A 2 , A 3 , A 4 , A 5 , A 6 , A 7 , and A 8 are each independently CR or N;

wherein each R in CR can be the same or different;

wherein n=1 and ring C is a 6-membered aromatic ring;

wherein at least two adjacent A 1 , A 2 , A 3 , At, A 5 , A 6 , A 7 , and A 8 are CR and the Rs are joined together to form a six-membered ring D fused to ring A or ring C, wherein ring D is benzene, pyridine, pyridazine, pyrimidine, or pyrazine, and ring D may be further substituted;

wherein at least one of the following is true: at least one of A 1 to A 4 is N, or ring D is pyridine, pyridazine, pyrimidine, or pyrazine;

wherein X is O, S, or Se;

wherein R, R′ and R B are each independently selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof;

wherein any adjacent substituents are optionally joined or fused into a ring;

wherein the ligand L A is coordinated to a metal M;

wherein the metal M is bonded to ring A through a M-C bond;

wherein the metal M can be coordinated to other ligands; and

wherein the ligand L A is optionally linked with other ligands to comprise a tridentate, tetradentate, pentadentate or hexadentate ligand.