| abstract |
According to one embodiment, a compound comprising a ligand L A of Formula I n nis described. In the structure of Formula I, A 1 through A 8 are independently carbon or nitrogen, with at least one being nitrogen; X 1 is selected from the group consisting of O, S, and Se; X 2 and X 3 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 X 2 —C bond and bonded to M through a metal-carbene bond; any adjacent substitutions in R 1 and R 2 are optionally linked together to form a ring; the ligand L A is coordinated to a metal M; and the ligand L A 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 L A of formula I are also described. |