Complexes with tridentate ligands

An organic light emitting device, comprising:

• an anode;
• a cathode;
• and
• a phosphorescent emissive region disposed between the anode and the cathode,
• wherein the emissive region comprises an emissive material having the formula I:
• wherein:
• at least one of X2, Y2 and Z2 is a carbene carbon, forming a carbene-metal bond with M;
• M is a second or third row transition metal;
• the dotted lines represent optional double bonds;
• L is an ancillary ligand;
• X1 is selected from C and N;
• X2 is selected from C, N, O, S and P;
• X3 is selected from C and N;
• each Q is independently selected from a chemical bond and —C(R′)2—;
• Y1 is C or N;
• Y2 is C, N, O, S or P, wherein when Y1 is N, Y2 is C or N;
• R1 is selected from H, alkyl, alkenyl, alkynyl, aralkyl, C(O)R′, C(O)OR′, C(O)NR′2, aryl and heteroaryl;
• a is 1 or 2;
• R3 is selected from H, alkyl, alkenyl, alkynyl, aralkyl, C(O)R′, C(O)OR′, C(O)NR′2, aryl and heteroaryl;
• c is 1 or 2;
• alternatively, R1 and R3, taken together with Y1 and Y2, form a 5- or 6-membered cyclic group or a 8- to 10-membered fused bicyclic group, which may be optionally substituted with one or more substituents independently selected from alkyl, alkenyl, alkynyl, aralkyl, O—R′, N(R′)2, SR′, C(O)R′, C(O)OR′, C(O)NR′2, CN, CF3, NO2, SO2, SOR′, or SO3R′ halo, aryl and heteroaryl;
• Z1 is C or N;
• Z2 is C, N, O, S or P, wherein when Y1 is N, Y2 is C or N;
• R2 is selected from H, alkyl, alkenyl, alkynyl, aralkyl, C(O)R′, C(O)OR′, C(O)NR′2, aryl and heteroaryl;
• b is 1 or 2;
• R4 is selected from H, alkyl, alkenyl, alkynyl, aralkyl, C(O)R′, C(O)OR′, C(O)NR′2, aryl and heteroaryl;
• d is 1 or 2;
• alternatively, R2 and R4, taken together with Z1 and Z2, form a 5- or 6-membered cyclic group or a 8- to 10-membered fused bicyclic group, which may be optionally substituted with one or more substituents independently selected from alkyl, alkenyl, alkynyl, aralkyl, O—R′, N(R′)2, SR′, C(O)R′, C(O)OR′, C(O)NR′2, CN, CF3, NO2, SO2, SOR′, or SO3R′ halo, aryl and heteroaryl;
• R5 and R6 are independently selected from H, alkyl, alkenyl, alkynyl, aralkyl, C(O)R′, C(O)OR′, C(O)NR′2, aryl and heteroaryl;
• or alternatively, R5 and R6, taken together with X1, X2 and X3 form a 5- or 6-membered cyclic group or a 8- to 10-membered fused bicyclic group, which may be optionally substituted with one or more substituents independently selected from alkyl, alkenyl, alkynyl, aralkyl, O—R′, N(R′)2, SR′, C(O)R′, C(O)OR′, C(O)NR′2, CN, CF3, NO2, SO2, SOR′, or SO3R′ halo, aryl and heteroaryl;
• additionally or alternatively R1 and R5 taken together with X1, Q and Y1 form a 5- or 6-membered cyclic group or a 8- to 10-membered fused bicyclic group, which may be optionally substituted with one or more substituents independently selected from alkyl, alkenyl, alkynyl, aralkyl, O—R′, N(R′)2, SR′, C(O)R′, C(O)OR′, C(O)NR′2, CN, CF3, NO2, SO2, SOR′, or SO3R′ halo, aryl and heteroaryl;
• additionally or alternatively R2 and R6 taken together with X3, Q and Z′ form a 5- or 6-membered cyclic group or a 8- to 10-membered fused bicyclic group, which may be optionally substituted with one or more substituents independently selected from alkyl, alkenyl, alkynyl, aralkyl, O—R′, N(R′)2, SR′, C(O)R′, C(O)OR′, C(O)NR′2, CN, CF3, NO2, SO2, SOR′, or SO3R′ halo, aryl and heteroaryl;
• each R′ is independently selected from H, alkyl, alkenyl, alkynyl, aralkyl, aryl and heteroaryl;
• n is 1 or 2;
• and
• m is 0 to 3, wherein when n is 1, m is 1 to 3, and when n is 2, m is 0.