Organic electroluminescent materials and devices

A compound, or a neutral molecular form thereof, or a monovalent or polyvalent form thereof, or a monomeric or polymeric form thereof, or a macromolecular or supramolecular form thereof;

• wherein the compound has a first bidentate 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 and each ring of the polycyclic fused ring system is independently a 5-membered to 10-membered carbocyclic or heterocyclic ring;
• moiety C is an aryl or heteroaryl, a saturated cycloalkyl or heterocycloalkyl group;
• each of Z1 to Z5 is independently C or N;
• K is selected from the group consisting of a direct bond, O, S, N(Rα), P(Rα), B(Rα), C(Rα)(Rβ), or Si(Rα)(Rβ);
• RA, RB, and RC each independently represent mono to the maximum allowable substitution, or no substitution;
• each Rα, Rβ, RA, RB, and RC is independently 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 of Rα, Rβ, RA, RB, and RC may be joined or fused to form a ring;
• LA is coordinated to a metal M;
• metal M is selected from the group consisting of Ir, Rh, Re, Ru, Os, Pt, Pd, Ag, Au, and Cu;
• and
• metal M may be coordinated to other ligands.