Patent ID: 6849348

Claim:
An organic compound comprising a complex fluorene structure represented by one of the following formulas: wherein: X 1 , X 2 , X 3 , and X 4 for formulas I and II include carbon atoms and at least one nitrogen atom; R 1 , R 2 , R 3 , and R 4 are substituents each being individually hydrogen, or alkyl, or alkenyl, or alkynyl, or alkoxy of from 1 to 40 carbon atoms; aryl or substituted aryl of from 6 to 60 carbon atoms; or heteroaryl or substituted heteroaryl of from 4 to 60 carbons; or F, Cl, or Br; or a cyano group; or a nitro group; or R 3 , or R 4 or both are groups that form fused aromatic or heteroaromatic rings.