The present invention includes novel compounds containing heterocycles or azaheterocycles and fused phenylene or aza and cyano substituted variants thereof. These compounds may be useful as host materials for phosphorescent electroluminescent devices. In some embodiments, the invention includes compounds of Formula I: ##STR00001##

The present invention includes novel compounds containing heterocycles or azaheterocycles and fused phenylene or aza and cyano substituted variants thereof. These compounds may be useful as host materials for phosphorescent electroluminescent devices. In some embodiments, the invention includes compounds of Formula I: ##STR00001##

The present invention includes novel compounds containing heterocycles or azaheterocycles and fused phenylene or aza and cyano substituted variants thereof. These compounds may be useful as host materials for phosphorescent electroluminescent devices.