Abstract: According to one embodiment, a compound comprising a ligand LA of Formula I is described. In the structure of Formula I, A1 through A8 are independently carbon or nitrogen, with at least one being nitrogen; X1 is selected from the group consisting of O, S, and Se; X2 and X3 are independently selected from the group consisting of C, N, O, P, and S; ring A is a 5- or 6-membered heterocyclic ring bonded to ring B through a X2—C bond and bonded to M through a metal-carbene bond; any adjacent substitutions in R1 and R2 are optionally linked together to form a ring; the ligand LA is coordinated to a metal M; and the ligand LA is optionally linked with other ligands to comprise up to a hexadentate ligand. Formulations and devices, such as an OLEDs, that include the compound comprising ligand LA of formula I are also described.

Abstract: According to one embodiment, a compound comprising a ligand LA of Formula I is described. In the structure of Formula I, A1 through A8 are independently carbon or nitrogen, with at least one being nitrogen; X1 is selected from the group consisting of O, S, and Se; X2 and X3 are independently selected from the group consisting of C, N, O, P, and S; ring A is a 5- or 6-membered heterocyclic ring bonded to ring B through a X2—C bond and bonded to M through a metal-carbene bond; any adjacent substitutions in R1 and R2 are optionally linked together to form a ring; the ligand LA is coordinated to a metal M; and the ligand LA is optionally linked with other ligands to comprise up to a hexadentate ligand. Formulations and devices, such as an OLEDs, that include the compound comprising ligand LA of formula I are also described.