Spectrophotometric titration of bimetallic metal cation binding in polyamido(amine) dendrimer templates

Katherine A. Marvin, Justin A. Johnson, Stacia E. Rodenbusch, Lucy Gong, David A. Vanden Bout, Keith J. Stevenson

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11 Citations (Scopus)


Spectrophotometric titration and a binding isotherm were used to accurately assess the loading capacity of generation four polyamido(amine) (PAMAM) dendrimer templates with terminal alcohol groups (G4-OH). Preparation of bimetallic G4-OH dendrimer-encapsulated metal nanoclusters (DENs) necessitates knowledge of the precise metal-ion binding capacity. The binding of metal ions such as Pt2+ and Pd2+ has proven difficult to assess via UV-vis spectroscopy because the absorbance shifts associated with metal-ion binding within the dendrimer template are masked by the absorbance of the PAMAM dendrimer itself. In contrast, the binding of Cu2+ to G4-OH PAMAM dendrimer results in a strong, distinct absorption band at 300 nm, making UV-vis spectrophotometric titration with copper straightforward. Here we use copper binding as a means to assess the number of binding sites remaining within the PAMAM G4-OH dendrimer after the complexation of a specified molar excess of Pd2+ or Pt2+. In addition, we use a binding isotherm to mathematically estimate the loading capacity of the dendrimer in each case. The loading capacities for M2+ in the G4-OH dendrimer were found to be ∼16 for copper alone, ∼21 for copper combined with palladium, and ∼25 for copper combined with platinum.

Original languageEnglish
Pages (from-to)5154-5158
Number of pages5
JournalAnalytical Chemistry
Issue number11
Publication statusPublished - 5 Jun 2012
Externally publishedYes


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