A compound having a formula M(L A) x (L B) y (L C) z: wherein the ligand L A is selected from the group consisting of wherein the ligand L B is wherein the ligand L C is wherein M is a metal having an atomic weight greater than 40; wherein x is 1, 2, or 3; wherein y is 0, 1, or 2; wherein z is 0, 1, or 2; wherein x+y+z is the oxidation state of the metal M; wherein Z 1 to Z 5 are each independently a carbon or nitrogen; wherein ring A is a 5- or 6-membered aromatic ring fused to the ring having Z 1; wherein rings C, and D are each independently a 5 or 6-membered carbocyclic or heterocyclic ring; wherein R 3, R 4, R C, and R D each independently represents no substitution to a maximum possible number of substitutions; wherein one of R 1 and R 2 is an electron donating group selected from the group consisting of the other one of R 1 and R 2 is selected from the group consisting of 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, partially or fully deuterated variants thereof, and combinations thereof; wherein each of R 3, R 4, R C, R D, R X, R Y, and R Z are 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; and wherein any plurality of R 1, R 2, R 3, R 4, R C, R D, R X, R Y, and R Z are optionally joined or fused into a ring, provided that when ring A is a 6-membered aromatic ring, at least one of Z 1, Z 2, and the ring atoms in ring A is nitrogen. wherein the ligand L A is selected from the group consisting of wherein the ligand L B is wherein the ligand L C is wherein M is a metal having an atomic weight greater than 40; wherein x is 1, 2, or 3; wherein y is 0, 1, or 2; wherein z is 0, 1, or 2; wherein x+y+z is the oxidation state of the metal M; wherein Z 1 to Z 5 are each independently a carbon or nitrogen; wherein ring A is a 5- or 6-membered aromatic ring fused to the ring having Z 1; wherein rings C, and D are each independently a 5 or 6-membered carbocyclic or heterocyclic ring; wherein R 3, R 4, R C, and R D each independently represents no substitution to a maximum possible number of substitutions; wherein one of R 1 and R 2 is an electron donating group selected from the group consisting of the other one of R 1 and R 2 is selected from the group consisting of 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, partially or fully deuterated variants thereof, and combinations thereof; wherein each of R 3, R 4, R C, R D, R X, R Y, and R Z are 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; and wherein any plurality of R 1, R 2, R 3, R 4, R C, R D, R X, R Y, and R Z are optionally joined or fused into a ring, provided that when ring A is a 6-membered aromatic ring, at least one of Z 1, Z 2, and the ring atoms in ring A is nitrogen.