Compounds of the formula (I), wherein R1, R2, R3, R4, R5, R6, R7 and R8 for example independently of each other are hydrogen, C1-C20alkyl, (II), COR16 or NO2, provided that at least one pair of R1 and R2, R2 and R3, R3 and R4, R5 and R6, R6 and R7, or R7 and R8 is (III); R9, R10, R11 and R12 for example independently of each other are hydrogen, C1-C20alkyl which optionally substituted; or R9, R10, R11, and R12 independently of each other are unsubstituted or substituted phenyl; X is CO or a direct bond; R13 is for example C1-C20alkyl which optionally is substituted, C2-C12alkenyl, C4-C8cycloalkenyl, C2-C12alkinyl, C3-C10-cycloalkyl, phenyl or naphthyl both of which are optionally substituted; R14 is for example hydrogen, C3-C8cycloalkyl, C2-C5alkenyl, C1-C20alkoxy, C1-C20alkyl, phenyl or naphthyl; R15 is for example C6-C20aryl or C5-C20heteroaryl; R16 is for example C6-C20aryl which is unsubstituted or substituted by one or more C1-C20alkoxy or C1-C20alkyl; are in particular suitable as photoinitiators for color filter applications.