Copper(II) Complexes with 4‑Carbomethoxypyrrolidone Functionalized PAMAM-Dendrimers: An EPR Study

The internal flexibility and interacting ability of PAMAM-dendrimers having 4-carbomethoxypyrrolidone-groups as surface groups (termed Gn-Pyr), which may be useful for biomedical purposes, and ion traps were investigated by analyzing the EPR spectra of their copper­(II) complexes. Increasing amounts (with respect to the Pyr groups) of copper­(II) gave rise to different signals constituting the EPR spectra at room and low temperature corresponding to different coordinations of Cu²⁺ inside and outside the dendrimers. At low Cu²⁺ concentrations, CuN₄ coordination involving the DAB core is preferential for G3- and G5-Pyr, while G4-Pyr shows a CuN₃O coordination. CuN₂O₂ coordination into the external dendrimer layer was also contributing to G3- and G4-Pyr spectra. The structures of the proposed copper–dendrimer complexes were also shown. G4-Pyr displays unusual binding ability toward Cu­(II) ions. Mainly the remarkably low toxicity shown by G4-Pyr and its peculiar binding ability leads to a potential use in biomedical fields