Eu- and Tb-Based Coordination Complexes of Poly(-Isopropyl,-methylacrylamide---dimethylacrylamide) Copolymer: Synthesis, Characterization and Property.

This contribution reports the syntheses, structural analyses and properties of europium (Eu)- and terbium (Tb)-based coordination complexes of poly(-isopropyl,-methylacrylamide---dimethylacrylamide) (poly(iPMAm--DMAm)) copolymer, named as poly-Eu(III) and poly-Tb(III), respectively. In greater detail, poly(iPMAm--DMAm) is first prepared by random copolymerization of -isopropyl,-methylacrylamide (iPMAm) and -dimethylacrylamide (DMAm) via group transfer polymerization (GTP). Next, poly(iPMAm--DMAm) is used as the polymer matrix for chelating with Eu and Tb cations at its side amide groups, to produce poly-Eu(III) and poly-Tb(III). Their structural characterizations by FT-IR spectroscopy and XPS confirm the formation of polymeric complexes. The study on their fluorescence emission characteristics and luminescence lifetime demonstrates that Poly-Eu(III) shows four strong emission peaks at 578, 593, 622, and 651 nm, which are responsible for the electron transitions from the excited state to the multiplet (J = 0, 1, 2, 3) states, respectively, and poly-Tb(III) also displays four emission peaks at 489, 545, 588, and 654 nm, mainly due to the electron transitions of → (i = 6, 5, 4, 3). The luminescence lifetimes of poly-Eu(III) (τ) and poly-Tb(III) (τ) are determined to be 4.57 and 7.50 ms, respectively. In addition, in aqueous solutions, poly-Eu(III) and poly-Tb(III) are found to exhibit thermoresponsivity, with their cloud temperatures (s) locating around 36.4 and 36.8 °C, respectively. Finally, the cytotoxicity study on the human colon carcinoma cells LoVo and DLD1 suggests that the luminescent Eu and Tb in the chelated state with poly(iPMAm--DMAm) show much better biocompatibility and lower toxicity than their inorganic salts.