Organic electroluminescent materials and devices

1. A compound comprising a ligand L selected from the group A consisting of:

wherein each X 1 to X 11 are independently selected from the group consisting of carbon nitrogen;

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

wherein each R a , R b , and R c are 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, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; wherein when R a , R b , and R c represent at least di substitution, each of the two adjacent R a , two adjacent R b , and two adjacent R c are optionally fused or joined to form a ring;

wherein the ligand L is coordinated to a metal M;

wherein the ligand L is optionally linked with other ligands to form a tridentate, tetradentate, pentadentate or hexadentate ligand;

wherein the compound comprises at least one intramolecular hydrogen bonding interaction as shown in the scheme:

Z 1 —H—Z 2 ,  scheme 1;

wherein Z 1 is a carbon of an alkyl group directly bonded to one of X 1 to X 11 ;

wherein Z 2 is nitrogen and is one of X 1 to X 11 ; and

wherein in scheme 1, the proton NMR chemical shift of H is shifted downfield by at least 1.3 ppm compared to the compound when Z 2 is carbon.

2. The compound of claim 1 , wherein in scheme 1, the proton NMR chemical shift of H is shifted downfield by at least 1.4 ppm compared to the compound when Z 2 is carbon.

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

4. The compound of claim 1 , wherein M is Ir or Pt.

5. The compound of claim 1 , wherein the compound has a formula of Ir(L) n (L′) 3-n ;

wherein L′ is a bidentate ligand; and

wherein n is 1, 2, or 3.

6. The compound of claim 5 , wherein n is 3.

7. The compound of claim 5 , wherein L′ is different from L.

8. The compound of claim 1 , wherein the compound has a formula of Pt(L) m (L′) 2-m ;

wherein L′ is a bidentate ligand; and

wherein m is 1, or 2.

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

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

11. A first device comprising a first organic light emitting device, the first organic light emitting device comprising:

an anode;

a cathode; and

an organic layer, disposed between the anode and the cathode, comprising a compound comprising a ligand L selected from the group A consisting of

wherein each X 1 to X 11 are independently selected from the group consisting of carbon nitrogen;

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

wherein each R a , R b , and R c are 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, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; wherein when R a , R b , and R c represent at least di substitution, each of the two adjacent R a , two adjacent R b , and two adjacent R c are optionally fused or joined to form a ring;

wherein the ligand L is coordinated to a metal M;

wherein the ligand L is optionally linked with other ligands to form a tridentate, tetradentate, pentadentate or hexadentate ligand;

wherein the compound comprises at least one intramolecular hydrogen bonding interaction as shown in the scheme:

Z 1 —H—Z 2 ,  scheme 1;

wherein Z 1 is a carbon of an alkyl group directly bonded to one of X 1 to X 11 ;

wherein Z 2 is nitrogen and is one of X 1 to X 11 ; and

wherein in scheme 1, the proton NMR chemical shift of H is shifted downfield by at least 1.3 ppm compared to the compound when Z 2 is carbon.

12. The first device of claim 11 , wherein the first device is selected from the group consisting of a consumer product, an electronic component module, an organic light-emitting device, and a lighting panel.

13. The first device of claim 11 , wherein the organic layer is an emissive layer and the compound is an emissive dopant or a non-emissive dopant.

14. The first device of claim 11 , wherein the organic layer further comprises a host; wherein the host comprises a triphenylene containing benzo-fused thiophene or benzo-fused furan;

wherein any substituent in the host is an unfused substituent independently selected from the group consisting of CH n H 2n+1 , OC n H 2n+1 , OAr 1 , N(C n H 2n+1 ) 2 , N(Ar 1 )(Ar 2 ), CH═CH—C n H 2n+1 , C≡CC n H 2n+1 , Ar 1 , Ar 1 —Ar 2 , C n H 2n —Ar 1 , or no substitution;

wherein n is from 1 to 10; and

wherein Ar 1 and Ar 2 are independently selected from the group consisting of benzene, biphenyl, naphthalene, triphenylene, carbazole, and heteroaromatic analogs thereof.

15. The first device of claim 11 , wherein the organic layer further comprises a host, wherein the host comprises at least one chemical group selected from the group consisting of triphenylene, carbazole, dibenzothiophene, dibenzofuran, dibenzoselenophene, azatriphenylene, azacarbazole, aza-dibenzothiophene, aza-dibenzofuran, and aza-dibenzoselenophene.

16. The first device of claim 11 , wherein the organic layer further comprises a host and the host is selected from the group consisting of:

and combinations thereof.

17. A formulation comprising the compound of claim 1 .