Organic electroluminescent materials and devices

1. A compound selected from formula I or formula II

wherein X 1 to X 8 are independently selected from N or C;

Y 1 to Y 4 are independently selected from the group consisting of O, S, Se, CRR′, and NR;

a, b, c, d, e, f, and g is an integer independently selected from 0 or 1; wherein two of a, b, and c are 1; and

one of d, e, f, and g is 1, or three of d, e, f, and g are 1;

wherein R 1 to R 7 represent monosubstitution, to the maximum allowable substitution, or no substitution;

wherein R, R′, and each of R 1 to R 7 are independently selected from the group consisting of hydrogen, deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, cyclic amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof;

two groups R 1 , two groups R 2 , two groups R 3 , two groups R 4 , two groups R 5 , two groups R 6 , and two groups R 7 can optionally join to form a ring;

wherein at least one of R 1 to R 7 comprises a group selected from the group consisting of

and combinations thereof;

wherein X 9 to X 24 are independently selected from N or CR; and

Z is selected from the group consisting of CRR′, NR, N, O, S, and Se.

2. The compound of claim 1 , wherein R, R′, and R 1 to R 7 is each independently selected from the group consisting of hydrogen, deuterium, fluorine, alkyl, cycloalkyl, heteroalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, aryl, heteroaryl, nitrile, isonitrile, sulfanyl, and combinations thereof.

3. The compound of claim 1 , wherein R, R′, and R 1 to R 7 is each independently selected from the group consisting of hydrogen, deuterium, fluorine, alkyl, cycloalkyl, alkoxy, aryloxy, amino, silyl, aryl, heteroaryl, sulfanyl, and combinations thereof.

4. The compound of claim 1 , wherein X 1 to X 8 are each C.

5. The compound of claim 4 , wherein, if present, each of Y 1 to Y 4 is selected from NR, O, or S.

6. The compound of claim 1 , wherein the compound is selected from the group consisting of:

7. The compound of claim 1 , wherein, if present, Y 1 , Y 2 , Y 3 , and Y 4 are the same.

8. The compound of claim 1 , wherein at least one of the adjacent R 1 , R 2 , and R 3 joins to form a ring.

9. The compound of claim 1 , wherein, if present, Y 1 , Y 2 , Y 3 , and Y 4 are S.

10. The compound of claim 1 , wherein, if present, Y 1 , Y 2 , Y 3 , and Y 4 are O.

11. The compound of claim 1 , wherein, if present, Y 1 , Y 2 , Y 3 , and Y 4 are NR.

12. The compound of claim 1 , wherein at least one of R 1 to R 7 is selected from the group consisting of:

and any combination thereof,

wherein Y, Y′, and Y″ is independently selected from the group consisting of O, S, Se, C(CH 3 ) 2 and N-Ph; and

wherein Z 1 to Z 12 are independently selected from CH or N.

13. A formulation comprising a compound according to claim 1 .

14. An organic light emitting device (OLED) comprising:

an anode; a cathode; and an organic layer disposed between the anode and the cathode, the organic layer comprising a compound selected from Formula I or Formula II

wherein X 1 to X 8 are independently selected from N or C;

Y 1 to Y 4 are independently selected from the group consisting of O, S, Se, CRR′, and NR;

a, b, c, d, e, f, and g is an integer independently selected from 0 or 1; wherein at least two of a, b, and c are 1; and

one of d, e, f, and g is 1; three of d, e, f, and g are 1, or four of d, e, f, and g are 1;

wherein R 1 to R 7 represent monosubstitution, to the maximum allowable substitution, or no substitution;

wherein R, R′, and each of R 1 to R 7 are independently selected from the group consisting of hydrogen, deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, cyclic amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof;

two groups R 1 , two groups R 2 , two groups R 3 , two groups R 4 , two groups R 5 , two groups R 6 , and two groups R 7 can optionally join to form a ring;

wherein at least one of R 1 to R 7 comprises a group selected from the group consisting of

 and combinations thereof;

wherein X 9 to X 24 are independently selected from N or CR; and

Z is selected from the group consisting of CRR′, NR, N, O, S, and Se;

with the proviso that at least one of conditions (i), (ii), and (iii) is true:

(i) the compound is represented by Formula II and each of Y 1 to Y 4 is NR;

(ii) one of a, b, and c is 0; and

(iii) one of d, e, f, and g is 0.

15. The OLED of claim 14 , wherein the organic layer further comprises a phosphorescent emissive dopant;

wherein the emissive dopant is a transition metal complex having at least one ligand or part of the ligand if the ligand is more than bidentate selected from the group consisting of:

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

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

wherein R e and R f are optionally fused or joined to form a ring;

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

wherein each R a , R b , R c , R d , R e , and R f is 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.

16. A consumer product comprising the organic light-emitting device (OLED) of claim 14 .

17. The consumer product of claim 16 , wherein the consumer product is selected from the group consisting of a flat panel display, a curved display, a computer monitor, a medical monitor, a television, a billboard, a light for interior or exterior illumination and/or signaling, a heads-up display, a fully or partially transparent display, a flexible display, a rollable display, a foldable display, a stretchable display, a laser printer, a telephone, a cell phone, tablet, a phablet, a personal digital assistant (PDA), a wearable device, a laptop computer, a digital camera, a camcorder, a viewfinder, a micro-display that is less than 2 inches diagonal, a 3-D display, a virtual reality or augmented reality display, a vehicle, a video walls comprising multiple displays tiled together, a theater or stadium screen, and a sign.

18. A compound selected from the group consisting of:

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

an anode; a cathode; and an organic layer disposed between the anode and the cathode, the organic layer comprising a compound according to claim 18 .