Metal-assisted delayed fluorescent emitters containing tridentate ligands

A compound represented by Formula A-2:

• wherein:
• M is Pt or Pd
• L1 is pyridine,
• L2 is phenyl,
• L3 is pyridine,
• RL4 is an inorganic anion or organic anion,
• each of LP1, LP2, and LP3 is independently a fluorescent luminophore, each of LP1, LP2, and LP3 is independently present or absent, and at least one of LP1, LP2, or LP3 is present,
• LP1 is covalently bonded to L1 directly,
• LP2 is covalently bonded to L2 directly,
• LP3 is covalently bonded to L3 directly,
• A is O,
• each of V1 and V3 is N,
• V2 is C,
• each of Y1, Y2, Y3, and Y4 is C,
• 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.