Revised Ion Exchange Method for Estimation of Conditional Stability Constants of Metal−Dendrimer Complexes

Abstract

This study reports a revised method for determination of the conditional stability constant (K c ) and the equilibrium metal-to-ligand molar ratio (n) for various metal-dendrimer complexes. The method employs a system containing an ion-exchange resin, a dendrimer, and a metal (Cu 2+ or Pb 2+ ) solution. It considers the multi-dentate nature of dendrimers and employs a nonlinear (Langmuir) isotherm model to interpret the ion exchange isotherm. For its minimal dendrimer uptake, a weak acid cation-exchange resin, IRC-50, was found most suitable for the study. For complexes of Cu 2+ with a homologue of dendrimers with NH 2 terminal groups K c increased from 10 16.2 to 10 36.6 , and n increased from 1 to 13 as the generation number rose from 0.0 to 4.0. K c for complexes of Pb 2+ with a generation-1 dendrimer with NH 2 terminal groups was 10 17.2 at pH 5, compared to 10 20.9 for complexes of Pb 2+ with a generation-1.5 dendrimer with carboxylate terminal groups.

Cyclic voltammetry studies of Cd2+ and Zn2+ complexation with hydroxyl-terminated polyamidoamine generation 2 dendrimer at a mercury microelectrode

“…PAMAM dendrimers were first synthesized two decades ago by Tomalia et al [1,2] and have since become well-characterized and widely studied systems. The highly branched dendritic structure has advantages over other macromolecular systems and can be potentially used for drug delivery [3], catalysis [4,5], and, extraction of aqueous waste [6][7][8][9] under optimal conditions. Recent studies have shown that PAMAM dendrimers can interact with metal ions through their interior or exterior complexing groups, and can serve as precursors in the preparation of metal nanoparticles.…”

Dendrimer-Tetrachloroplatinate Precursor Interactions. 2. Noncovalent Binding in PAMAM Outer Pockets

“…Metal precursor binding can also be affected not only by pH 16 but also by competing species present in solution, 17 like counterions K + and Cl -. By studying these interactions and how they relate to each other, we expect to obtain a better understanding of the complexation process itself.…”

Effect of PAMAM Dendrimers on *Ru(bpy)32+ Emission Quenching by Ferrocyanide and on ANS Fluorescence: Quantitative Binding Parameters as a Function of Dendrimer Size, pH, and Buffer Composition

“…Dendrimers are a novel class of hyperbranched macromolecules that consist of a polyfunctional core with shells of monomer units extending off of branching points. , The resulting macromolecules have well-defined molecular weights, sizes, and end-group functionalities. An explosion of unique applications has recently appeared in the dendrimer literature in such areas as macromolecular catalysis, − drug delivery, − MRI contrast agents, − surface modifications, − and metal ion binding. − The appeal of dendrimeric macromolecules is the ability to tailor the structure, shape, and surface functional groups for the application desired.…”

“…An explosion of unique applications has recently appeared in the dendrimer literature in such areas as macromolecular catalysis, [3][4][5][6] drug delivery, [7][8][9][10][11] MRI contrast agents, [12][13][14][15] surface modifications, [16][17][18][19][20] and metal ion binding. [21][22][23][24][25] The appeal of dendrimeric macromolecules is the ability to tailor the structure, shape, and surface functional groups for the application desired.…”