Metal-assisted delayed fluorescent emitters containing tridentate ligands

A compound represented by Formula A-1:

• wherein:
• M is Pt, Pd, or Au,
• L1 is a five-membered heterocyclyl, five-membered heteroaryl, five-membered carbene, or five-membered N-heterocyclic carbene,
• L2 is phenyl,
• L3 is pyridyl,
• RL4 is an inorganic anion or organic anion,
• each of LP1, LP2, and LP3 is independently present or absent, wherein at least one of LP1, LP2, or LP3 is present and is independently an aromatic hydrocarbon, an aromatic hydrocarbon derivative, a polyphenyl hydrocarbon, a hydrocarbon with condensed aromatic nuclei, naphthalene, anthracene, phenanthrene, chrysene, pyrene, triphenylene, perylene, acenaphthene, tetracene, pentacene, tetraphene, coronene, fluorene, biphenyl, p-terphenyl, o-diphenylbenzene, m-diphenylbenzene, p-quaterphenyl, benzo[a]tetracene, benzo[k]tetraphene, indeno[1,2,3-cd]fluoranthene, tetrabenzo[de,hi,op,st]pentacene, arylethylene, arylacetylene, an arylacetylene derivative, a diarylethylene, a diarylpolyene, a diaryl-substituted vinylbenzene, a distyrylbenzene, a trivinylbenzene, an arylacetylene, a functional substitution product of stilbene, a five-, six- or seven-membered heterocyclic compound derivative, a furan derivative, a thiophene derivative, a pyrrole derivative, an aryl-substituted oxazole, a 1,3,4-oxadiazole, a 1,3,4-thiadiazole, an aryl-substituted 2-pyrazoline, an aryl-substituted pyrazole, a benzazole, 2H-benzotriazole, a substitution product of 2H-benzotriazole, a heterocycle with one, two or three nitrogen atoms, an oxygen-containing heterocycle, a coumarin, a coumarin derivative, a dye, an acridine dye, a xanthene dye, an oxazine, a thiazine, or a derivative thereof,
• A is O,
• V1 is N, C, P, B, or Si,
• V2 is C,
• V3 is N,
• each of Y1, Y2, Y3, and Y4 is independently C, N, O, S, S═O, SO2, Se, Se═O, SeO2, PR3, R3P═O, AsR3, R3As═O, or BR3,
• each of Ra, Rb, and Rc is independently present or absent, and if present each of Ra, Rb and Rc is independently a mono-, di-, tri-, or tetra-substitution, valency permitting, and each Ra, Rb, and Rc is independently deuterium, halogen, hydroxyl, thiol, nitro, cyano, nitrile, isonitrile, sulfinyl, mercapto, sulfo, carboxyl, hydrazino;
• substituted or unsubstituted:
• aryl, cycloalkyl, cycloalkenyl, heterocyclyl, heteroaryl, alkyl, alkenyl, alkynyl, amino, monoalkylamino, dialkylamino, monoarylamino, diarylamino, alkoxy, aryloxy, haloalkyl, aralkyl, ester, alkoxycarbonyl, acylamino, alkoxycarbonylamino, aryloxycarbonylamino, sulfonylamino, sulfamoyl, carbamoyl, alkylthio, ureido, phosphoramide, silyl, polymeric;
• or any conjugate or combination thereof, and
• each of R3 is independently hydrogen, aryl, cycloalkyl, cycloalkenyl, heterocyclyl, heteroaryl, alkyl, alkenyl, alkynyl, deuterium, halogen, hydroxyl, thiol, nitro, cyano, amino, monoalkylamino, dialkylamino, monoarylamino, diarylamino, alkoxy, aryloxy, haloalkyl, aralkyl, ester, nitrile, isonitrile, heteroaryl, alkoxycarbonyl, acylamino, alkoxycarbonylamino, aryloxycarbonylamino, sulfonylamino, sulfamoyl, carbamoyl, alkylthio, sulfinyl, ureido, phosphoramide, mercapto, sulfo, carboxyl, hydrazino, substituted silyl, or polymeric;
• or any conjugate or combination thereof.