Organic electroluminescent materials and devices

A compound having a structure of Formula I

• wherein:
• G1, G2, and G3 are each independently B or N;
• X1-X12 are each independently C, N or CR;
• A1, A2, and A3 are each independently a monocyclic ring comprising one 5-membered or 6-membered carbocyclic or heterocyclic ring or a multicyclic ring system comprising at least two fused 5-membered or 6-membered carbocyclic or heterocyclic rings;
• RA, RB, and RC each independently represents zero, mono to the maximum allowable substitution;
• each R, RA, RB, and RC 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;
• at least one of X1, X4, X3, X8, X9, and X12 is CR of which R is joined with at least one of adjacent RA, RB, or RC to form a fused ring;
• and
• any two adjacent R, RA, RB, and RC can be joined or fused together to form a ring.