Tuning the formal potentials of new VIV-substituted Dawson-type polyoxometalates for facile synthesis of metal nanoparticles

Dawson-type V-substituted POMs were synthesized and characterized both in their oxidized V-V and reduced V-IV states. They were stable in the presence of dioxygen. The apparent formal potentials of the V-centers within these molecules can be manipulated to span an appreciable potential range through variation of the overall atomic composition of the POMs and/or localization of the substituent V-atom in the framework. For each molecule, this formal potential is pH-independent for pH values larger than 2.5. The stability of both forms of these molecules over a large pH domain was exploited for the synthesis of metal nanoparticles, because this class of POMs presents several interesting features not available usually with other chemical reductants. The preparation of Pd-0 nanoparticles from [PdCl4](2-) was selected as an illustrative example. UV-Vis spectroscopy and TEM micrograph were used to confirm this successful synthesis. (C) 2004 Elsevier B.V. All rights reserved.