A compound represented by Formula I: wherein M is a metal; L is a charge-neutral ligand, which coordinates to the metal M; n is an integer selected from 1 to 4, which corresponds to the oxidation number of M; m is an integer selected from 0 to 2; R 1, R 2 and R 3 are independently selected from H, D, substituted or unsubstituted C 1 to C 12 alkyl, substituted or unsubstituted C 1 to C 12 alkoxy, substituted or unsubstituted C 6 to C 24 aryl, and substituted or unsubstituted C 2 to C 24 heteroaryl group selected from the group comprising pyridyl, pyrimidinyl, pyrazinyl, or triazinyl group, and wherein the at least one substituent is selected from halogen, F, Cl, CN, substituted or unsubstituted C 1 to C 6 alkyl, partially or fully fluorinated C 1 to C 6 alkyl, substituted or unsubstituted C 1 to C 6 alkoxy, partially or fully fluorinated C 1 to C 6 alkoxy, substituted or unsubstituted C 6 to C 18 aryl, and substituted or unsubstituted C 2 to C 18 heteroaryl, wherein the substituents are selected from halogen, F, Cl, CN, C 1 to C 6 alkyl, CF 3, OCH 3 and OCF 3; wherein at least one R 1, R 2 and/or R 3 is selected from a substituted C 2 to C 24 heteroaryl group selected from the group comprising pyridyl, pyrimidinyl, pyrazinyl, or triazinyl group, and wherein at least one substituent is selected from halogen, F, Cl, CN, partially or fully fluorinated C 1 to C 6 alkyl, partially or fully fluorinated C 1 to C 6 alkoxy; wherein a compound of formula 1a is excluded: wherein R 1 and R 3 are selected the same from methyl, trifluoromethyl, pentafluoroethyl, heptafluoro-n-propyl, heptafluoro-isopropyl, tert-butyl, nonafluoro-n-butyl, pentafluorophenyl, 4-pyrimidyl and 2-pyrimidyl; R 2 is selected from tetrafluoro-2-pyridyl, tetrafluoro-3-pyridyl or tetrafluoro-4-pyridyl. M is a metal; L is a charge-neutral ligand, which coordinates to the metal M; n is an integer selected from 1 to 4, which corresponds to the oxidation number of M; m is an integer selected from 0 to 2; R 1, R 2 and R 3 are independently selected from H, D, substituted or unsubstituted C 1 to C 12 alkyl, substituted or unsubstituted C 1 to C 12 alkoxy, substituted or unsubstituted C 6 to C 24 aryl, and substituted or unsubstituted C 2 to C 24 heteroaryl group selected from the group comprising pyridyl, pyrimidinyl, pyrazinyl, or triazinyl group, and wherein the at least one substituent is selected from halogen, F, Cl, CN, substituted or unsubstituted C 1 to C 6 alkyl, partially or fully fluorinated C 1 to C 6 alkyl, substituted or unsubstituted C 1 to C 6 alkoxy, partially or fully fluorinated C 1 to C 6 alkoxy, substituted or unsubstituted C 6 to C 18 aryl, and substituted or unsubstituted C 2 to C 18 heteroaryl, wherein the substituents are selected from halogen, F, Cl, CN, C 1 to C 6 alkyl, CF 3, OCH 3 and OCF 3; wherein at least one R 1, R 2 and/or R 3 is selected from a substituted C 2 to C 24 heteroaryl group selected from the group comprising pyridyl, pyrimidinyl, pyrazinyl, or triazinyl group, and wherein at least one substituent is selected from halogen, F, Cl, CN, partially or fully fluorinated C 1 to C 6 alkyl, partially or fully fluorinated C 1 to C 6 alkoxy; wherein a compound of formula 1a is excluded: wherein R 1 and R 3 are selected the same from methyl, trifluoromethyl, pentafluoroethyl, heptafluoro-n-propyl, heptafluoro-isopropyl, tert-butyl, nonafluoro-n-butyl, pentafluorophenyl, 4-pyrimidyl and 2-pyrimidyl; R 2 is selected from tetrafluoro-2-pyridyl, tetrafluoro-3-pyridyl or tetrafluoro-4-pyridyl. at least one R 1, R 2 and/or R 3 is selected from a substituted C 2 to C 24 heteroaryl group selected from the group comprising pyridyl, pyrimidinyl, pyrazinyl, or triazinyl group, and wherein at least one substituent is selected from halogen, F, Cl, CN, partially or fully fluorinated C 1 to C 6 alkyl, partially or fully fluorinated C 1 to C 6 alkoxy; wherein a compound of formula 1a is excluded: wherein R 1 and R 3 are selected the same from methyl, trifluoromethyl, pentafluoroethyl, heptafluoro-n-propyl, heptafluoro-isopropyl, tert-butyl, nonafluoro-n-butyl, pentafluorophenyl, 4-pyrimidyl and 2-pyrimidyl; R 2 is selected from tetrafluoro-2-pyridyl, tetrafluoro-3-pyridyl or tetrafluoro-4-pyridyl. R 1 and R 3 are selected the same from methyl, trifluoromethyl, pentafluoroethyl, heptafluoro-n-propyl, heptafluoro-isopropyl, tert-butyl, nonafluoro-n-butyl, pentafluorophenyl, 4-pyrimidyl and 2-pyrimidyl; R 2 is selected from tetrafluoro-2-pyridyl, tetrafluoro-3-pyridyl or tetrafluoro-4-pyridyl.