A compound having a Pt tetradentate structure of Formula 1,




is provided. In the structure of Formula 1, rings C and D each independently represent 5- or 6-membered carbocyclic or heterocyclic ring; L1, L2, and L3 are each independently a direct bond, BR, NR, PR, O, S, Se, C═O, S═O, SO2, SiRR′, GeRR′, alkyl, cycloalkyl, or a combination thereof; the sum of n1 and n2 is 1 or 2; X is selected from NRE, O, S, and Se; X3 and X4 each independently carbon or nitrogen; and one of Q1, Q3, and Q4 is oxygen, and the remaining two of Q1, Q3, and Q4 each represents a direct bond. Formulations and devices, such as an OLEDs, that include the compound of Formula 1 are also described.