A compound having a first ligand LA having the Formula: Formula I is disclosed, wherein rings A is a 5- or 6-membered carbocyclic or heterocyclic ring; wherein RA and RB each independently represent mono to the possible maximum number of substitution, or no substitution; wherein Z1 is carbon or nitrogen; wherein each RA and RB is independently selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; wherein any two substituents are optionally joined or fused into a ring; wherein X1 to X4 each independently represent a carbon or nitrogen; wherein at least one of X1 to X4 is nitrogen; wherein the ligand LA is coordinated to a metal M; wherein the metal M can be coordinated to other ligands; and wherein the ligand LA is optionally linked with other ligands to comprise a tridentate, tetradentate, pentadentate or hexadentate ligand.