Light emitting device containing phosphorescent complex

1. An OLED device comprising a cathode, an anode, and having therebetween a light emitting layer comprising a phosphorescent emitter represented by Formula (V):

wherein;

M is Ir or Pt;

each L independently represents a cyclometallated ligand;

each X independently represents the atoms necessary to form a substituted or unsubstituted ring;

each R independently represents hydrogen or a substituent, provided that two adjacent R groups are able to form a ring;

Y and Z are each independently an oxygen atom and a carbonyl group such that when one is a carbonyl group the other is an oxygen atom;

p is an integer from 2 to 4;

m is a integer from 0 to 2; and

q is a integer from 1 to 3.

2. An OLED device of claim 1 wherein, M is Ir.

3. An OLED device of claim 1 wherein, the phosphorescent emitter is represented by Formula (VI):

wherein;

each L independently represents a cyclometallated ligand;

each R independently represents hydrogen or a substituent, provided that two adjacent R groups are able to form a ring;

Y and Z are each independently an oxygen atom and a carbonyl group such that when one is a carbonyl group the other is an oxygen atom;

m is a integer from 0 to 2;

q is a integer from 1 to 3; and

the sum of m+q is 3.

4. An OLED device of claim 1 wherein, the phosphorescent emitter is represented by Formula (VII):

wherein;

each L independently represents a cyclometallated ligand;

Y and Z are each independently an oxygen atom and a carbonyl group such that when one is a carbonyl group the other is an oxygen atom;

m is a integer from 0 to 2;

q is a integer from 1 to 3; and

the sum of m+q is 3.

5. An OLED device of claim 2 wherein the phosphorescent emitter is chosen from the following: