A compound having a structure of Formula I: is described. In the structure of Formula I, RA, RB, and RC are each independently 5 or 6 membered aryl or heteroaryl rings; R1, R2, R3, and A are selected from a variety of substituents, including being joined or fused to form a ring; A is optionally bonded to at least one benzo or azabenzo ring to form fused rings; X1 is B, C, N, O, S or Se; and X2-X7 are independently B, C or N. Formulations and devices, such as an OLEDs, that include the compound containing a structure of Formula I are also described.