Abstract: The present invention relates to fluorescent diketopyrrolopyrrole analogues of the general formula (I), wherein A1 and A2 are C1-C18alkyl, C2-C18alkenyl, C2-C18alkynyl, C5-C8cycloalkyl, C5-C8cycloalkenyl, aryl or heteroaryl, A3 and A4 are independently of each other C1-C18alkyl, Ar3, —CR30R31—(CH2)m—Ar3, or Y-R32, wherein R30 and R31 independently of each other stand for hydrogen or C1-C4alkyl, or phenyl which can be substituted up to three times with C1-C3alkyl, Ar3 stands for aryl, in particular phenyl or 1- or 2-naphthyl, C5-C8cycloalkyl, in particular cyclohexyl, or heteroaryl, which can be substituted one to three times with C1-C8alkyl, C1-C8alkoxy, halogen or phenyl, which can be substituted with C1-C8alkyl or C1-C8alkoxy one to three times, and m stands for 0, 1, 2, 3 or 4, Y is C(O)— or SO2— and R32 is C1-C18alkyl, Ar3, or aralkyl and A3 can additionally be hydrogen, C1-C8alkyloxycarbonyl, such as tertbutoxycarbonyl, or aralkyloxycarbonyl, such as benzyloxycarbonyl, a pro