Polymer Science Faculty Research

Title

Crown-Shaped Tungstogermanates as Solvent-Controlled Dual Systems in the Formation of Vesicle-Like Assemblies

Document Type

Article

Publication Date

Spring 5-18-2015

Abstract

Reaction of early lanthanides, GeO2, and Na2WO4 in a NaOAc buffer results in large crown-shaped polyoxometalates based on [Ln2GeW10O38]6− subunits. By using Ni2+ as a crystallizing agent, [Na⊂Ln12Ge6W60O228(H2O)24]35− (Na⊂Ln12) hexamers formed by alternating β(1,5)/β(1,8) subunits were obtained for Ln=Pr, Nd. The addition of K+ led to a similar anion for Ln=Sm, namely, [K⊂Sm12Ge6W60O228(H2O)22]35− (K⊂Sm12) and [K⊂K7Ln24Ge12W120O444(OH)12(H2O)64]52− (K⊂Ln24) dodecamers that consist of a central core identical to K⊂Sm12 decorated with six external γ(3,4) subunits for Ln=Pr, Nd. These anions dissociate in water into hexameric cores and monomeric entities, as shown by ESI mass spectrometry. The former self-assemble into spherical, hollow, and single-layered blackberry-type structures with radii of approximately 75 nm, as monitored by laser light scattering (LLS) and TEM techniques. Analogous studies performed for K⊂Nd24 in water/acetone mixtures show that the dodecamers remain stable and form in turn their own type of blackberries with sizes that increase from approximately 20 to 50 nm with increasing acetone content. This control over both the composition and size of the vesicle-like assemblies is achieved for the first time by modifying the architecture of the species that undergoes supramolecular association through the solvent polarity.

Publication Title

Chemistry - A European Journal

Volume

21

Issue

21

First Page

7736

Last Page

7745