Organic electroluminescent materials and devices

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 structure of a formula selected from the group consisting of
• wherein,
• M is selected from the group consisting of Os, Pd, Pt, Ir, Cu, and Au;
• at least one of RA1, RA2, RA4, RA5, or RA6 is a structure of
• Y1A to Y4A are each independently C or N;
• no more than two of Y1A to Y4A are N;
• Z1 to Z25 are each independently C or N;
• three consecutive Z1 to Z21 in the same ring cannot be N;
• RA3, RA6, RM, RN, RO, RX, RY, and RZ each independently represent mono to the maximum allowable substitutions, or no substitution;
• each RA1, RA2, RA3, RA4, RA5, RA6, RM, RN, RO, RX, RY, and RZ is independently a hydrogen or a substituent selected from the group consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, boryl, and combinations thereof;
• M is coordinated to at least one monoanionic bidentate ligand;
• any two substituents can be joined or fused to form a ring;
• provided that when one of RA1, RA2, RA4, RA5, or RA6 is a structure of Formula VIII, then at least one of RX, RY, and RZ is selected from the group consisting of deuterium, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, aryl, heteroaryl, and combinations thereof;
• and
• provided that when one of RA1, RA2, RA4, or RA5 is Formula VII, then at least one of RM, RN, and RO is selected from the group consisting of deuterium, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, aryl, heteroaryl, and combinations thereof.