Metal-assisted delayed fluorescent emitters employing benzo-imidazo-phenanthridine and analogues

A complex represented by General Formula VIII or General Formula XII:

• wherein:
• M is Pt (II) or Pd (II),
• N is nitrogen,
• each of V1a-V1e, V2a-V2c, V3a, V4a-V4c, and V5a-V5d, if present, is independently N or C,
• X1 is absent,
• X represents CR7R8, SiR7R8, NR7, O, or S,
• each of L1 and L2 is independently present or absent, and each L1 and L2 present independently represents a substituted or unsubstituted aryl or heteroaryl,
• each of R1, R2, R3, R4, R5, R7, and R8 is independently absent or present as a single substituent or multiple substituents, valency permitting, and each R1, R2, R3, R4, R5, R7, and R8 present independently represents deuterium, halogen, hydroxyl, thiol, nitro, cyanide, isocyanide, 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.