title: Anion and ion-pair binding by a G-2 poly(ethylene imine) dendrimer.
abstract: The second-generation poly(ethylene imine) dendrimer (L), based on ammonia as the initiating core molecule, forms anion and ion-pair complexes in aqueous solution. Speciation of the complex species formed and determination of the relevant stability constants were performed by means of potentiometric titration in a 0.10 M NMe4Cl solution at 298.1 K. Protonated forms of L interact with NO3(-), SO4(2-), SeO4(2-), HPO4(2-) and H2PO4(-) forming stable 1 : 1 anion complexes. The dendritic structure endows the molecule with a greater anion binding ability relative to analogous linear polyamines. It was previously reported that L forms stable metal complexes. We show here that protonated forms of the mononuclear complexes with Cu(2+), Zn(2+) and Cd(2+) bind these anions, and Pb(2+) complexes bind NO3(-). The resulting ion-pair complexes show considerable stability thanks to the cooperative effect of the oppositely charged partners. Molecular modelling calculations show that both anion-ligand and anion-metal ion interactions can participate in stabilizing such ion-pair complexes.
authors.affiliation: Department of Chemistry Ugo Schiff, University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy.
authors.forename: Carla
authors.initials: C
authors.lastname: Bazzicalupi
authors.forename: Antonio
authors.initials: A
authors.lastname: Bianchi
authors.forename: Claudia
authors.initials: C
authors.lastname: Giorgi
authors.forename: Paola
authors.initials: P
authors.lastname: Gratteri
authors.forename: Palma
authors.initials: P
authors.lastname: Mariani
authors.forename: Barbara
authors.initials: B
authors.lastname: Valtancoli
mesh_terms: D000641:Ammonia / Q000737:chemistry; D000838:Anions / Q000737:chemistry; D050091:Dendrimers / Q000737:chemistry*; D007097:Imines / Q000737:chemistry*; D008024:Ligands; D011095:Polyethylenes / Q000737:chemistry*
chemical_list: D000838:Anions; D050091:Dendrimers; D007097:Imines; D008024:Ligands; D011095:Polyethylenes; C505405:poly(ethylene imine); D000641:Ammonia