Novel heterogeneous PET fluorescent sensors selective for transition metal ions or protons: polymers regularly labelled with naphthalimide

4-(N,N-Dimethylaminoethylene)amino-N-allyl-1,8-naphthalimide has been synthesized as a new polymerizable dye in monomeric form, and can increase its fluorescence intensity in the presence of protons or metal cations. Two intensely yellow green fluorescent co-polymers of the dye with methyl methacrylate (MMA) and styrene (ST) have been obtained. These polymeric fluorophores, which could be used as heterogeneous photoinduced electron transfer ( PET) fluorescent sensors, show different fluorescence behaviour in the presence of protons and Cu2+ ions, depending on the structures of their main polymer chains. The fluorescence of poly( MMA-co-dye) is not sensitive towards H+ ions, but it is to Cu2+ ions. That of poly(ST-co-dye) is sensitive to the presence of both H+ and Cu2+ ions, the signal increasing and decreasing, respectively.