Organic electroluminescent materials and devices

A compound having a first ligand LA comprising a structure of Formula I,

• wherein:
• moiety A is a monocyclic ring or a polycyclic fused ring system, wherein the monocyclic ring or each ring of the polycyclic fused ring system is independently a 5-membered to 10-membered carbocyclic or heterocyclic ring;
• each of Z1 and Z2 is independently C or N;
• each of Y1, Y2, and Y3 is independently selected from the group consisting of O, S, Se, BR, NR, PR, PRR′, AsRR′, CR, CRR′, SiRR′, and GeRR′, except that the one of Y1 and Y2 bonded to L or metal M is selected from the group consisting of B, N, P, As, C, Si, and Ge;
• each of A1 and A2 is independently C, N, P, or As;
• K is selected from the group consisting of a direct bond, O, S, N(Rα), P(Rα), B(Rα), C(Rα)(Rβ), and Si(Rα)(Rβ);
• C1 is a carbon or a carbene carbon;
• L is selected from the group consisting of a direct bond, BR, BRR′, NR, PR, P(O)R, O, S, Se, C═O, C═S, C═Se, C═NR′, C═CRR′, S═O, SO2, CR, CRR′, SiRR′, and GeRR′;
• each independently represents a single bond or a double bond;
• RA represents mono to the maximum allowable substitution, or not substitution;
• each R, R′, Rα, Rβ, R1, R2, and RA is hydrogen or a substituent selected from the group consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, germyl, boryl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, selenyl, and combinations thereof;
• any two substituents may be joined or fused to form a ring;
• first ligand LA is coordinated to a metal M through the two open dashed lines;
• metal M is selected from the group consisting of Ir, Rh, Re, Ru, Os, Pt, Pd, Ag, Au, and Cu;
• metal M may be coordinated to other ligands;
• and
• LA may join with other ligands to comprise a tridentate, tetradentate, pentadentate or hexadentate ligand;
• with the following being true:
• (1) if M is Ir, Y3 is NR, and R1 and R2 are joined to form a 6-membered ring, then R of Y3 does not join with R2 to form a fused 5-membered ring;
• (2) if M is Ir and R1 and R2 are joined to form a 5 or 6-membered ring, then the following are true:
• (i) the compound is not homoleptic Ir(LA)3;
• (ii) the compound does not contain a bidentate ligand selected from
• and
• (iii) if R1 and R2 are joined to form a 5-membered ring B, then ring B does not contain S.
• (3) if M is Ir and R1 and R2 are not joined to form a ring, then Y2 and Y3 are independently selected from O, S, or Se, and Y2 and Y3 are not both Se;
• (4) if Y1 is NR, Y2 is NR, and C1 forms a carbene bond with metal M, then R and R′ are not Me, CD3, or phenyl (Ph), and R of Y2 does not join with Y3 to form a ring;
• and
• (5) the compound is not