Patent ID: 7723553

Claim:
A compound of formula (V): wherein R 3 and R 4 are fused to each other to form a substituted or unsubstituted fused aromatic ring, and wherein R 1 , R 2 , R 5 and R 6 , which may be the same or different, are independently selected from aryl and heteroaryl, each of which is optionally substituted by aryl, heteroaryl, diarylamine, alkyl, cycloalkyl, a fused ring system, halo, haloalkyl, cyano and alkyloxy groups, provided that R 1 and R 2 are not fused to each other to form a ring system, and provided that R 5 and R 6 are not fused to each other to form a ring system, and provided that R 1 , R 2 , R 5 and R 6 are not all phenyl.