Dye labeled imidazoquinoline compounds

A compound of the formula (I):

• wherein:
• R1 is a spacer group selected from the group consisting of
• R2 is hydrogen, alkyl, hydroxyalkyl, haloalkyl, aminoalkyl, alkylaminoalkyl, dialkylaminoalkyl, amidoalkyl, alkylamidoalkyl, dialkylamidoalkyl, alkanoylalkyl, azidoalkyl, carbamoylalkyl, alkyl optionally interrupted by a heteroatom;
• alkenyl, alkenyloxyalkyl;
• cycloalkylalkyl, heterocycloalkyl;
• aryl, aralkyl, aralkenyl, heteroarylalkyl, in which aryl is optionally substituted by alkyl of 1 to 4 carbon atoms, alkoxy of 1 to 4 carbon atoms, halo, amino, alkylamino or dialkylamino;
• aroylalkyl, or heteroaroylalkyl;
• R3 and R4 are each independently hydrogen, alkyl, alkoxy of 1 to 4 carbon atoms, halo, amino, alkylamino, or dialkylamino, or when taken together, R3 and R4 form a fused aryl group that is optionally substituted by one or more substituents selected from alkyl of 1 to 4 carbon atoms, alkoxy of 1 to 4 carbon atoms, halo, amino, alkylamino, dialkylamino, hydroxy and alkoxymethyl;
• and
• DYE is a dye moiety selected from the group consisting of dipyrrometheneboron difluoride dyes, fluorescein dyes, rhodamine dyes and Texas Red, or a pharmaceutically acceptable acid addition salt thereof.