Rare-earth-metal-containing polymers. 5. Synthesis,characterization, and fluorescence properties of Eu3+-polymer complexes containing carboxylbenzoyl and carboxylnaphthoyl ligands

Partially 2-carboxylbenzoyl (1) and 3-carboxyl-2-naphthoyl (2) substituted polystyrene were prepared by the Friedel-Crafts reaction of polystyrene with corresponding dicarboxylic anhydrides. Europium (III) salts of (1) and (2) and the copolymer of 4-vinylbenzoyl 2′-carboxylbenzoate-di(2-benzoyl benzoate) and styrene (5) were prepared. Polymer (5) was prepared by the copolymerization of the Eu³⁺ salt of 4-vinylbenzoyl 2′-benzoate and 2-benzoylbenzoate (ratio 1:2) with styrene. The fluorescence emission intensity was measured on fine powder samples. The intensity of (5) increased linearly as the Eu content increased. However, for the 1 and 2 systems the intensity reached a maximum at a Eu content as small as 0.5 wt% and remained constant when further increases were made. This phenomenon was accounted for by steric hindrance and a decrease in the freedom of bond rotation, which prevent the formation of multiple coordination linkages between Eu³⁺ and the benzoate groups.