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Full Paper
Hexa- and Dodecanuclear Polyoxomolybdate Cyclic Compounds: Application toward the Facile Synthesis of Nanoparticles and Film Electrodeposition
Article first published online: 28 NOV 2008
DOI: 10.1002/chem.200800719
Copyright © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Additional Information
How to Cite
Dolbecq, A., Compain, J.-D., Mialane, P., Marrot, J., Sécheresse, F., Keita, B., Holzle, L., Miserque, F. and Nadjo, L. (2009), Hexa- and Dodecanuclear Polyoxomolybdate Cyclic Compounds: Application toward the Facile Synthesis of Nanoparticles and Film Electrodeposition. Chem. Eur. J., 15: 733–741. doi: 10.1002/chem.200800719
Publication History
- Issue published online: 29 DEC 2008
- Article first published online: 28 NOV 2008
- Manuscript Revised: 13 OCT 2008
- Manuscript Received: 15 APR 2008
Keywords:
- electrochemistry;
- molybdenum;
- nanoparticles;
- NMR spectroscopy;
- polyoxometalates
Abstract
Two new compounds based on O3PCH2PO34− ligands and {MoV2O4} dimeric units have been synthesized and structurally characterized. The dodecanuclear MoV polyoxomolybdate species in (NH4)18[(MoV2O4)6(OH)6(O3PCH2PO3)6]⋅33 H2O (1) is a cyclohexane-like ring in a chair conformation with pseudo S6 symmetry. In the solid state, the wheels align side by side, thus delimiting large rectangular voids. The hexanuclear anion in Na8[(MoV2O4)3(O3PCH2PO3)3(CH3AsO3)]⋅ 19 H2O (2) has a triangular framework and encapsulates a methylarsenato ligand. 31P NMR spectroscopic analysis revealed the stability of 2 in various aqueous media, whereas the stability of 1 depends on the nature of the cations present in solution. It has been evidenced that the transformation of 1 into 2 occurs in the presence of CH3AsO32− ions. This behavior shows that 1 can be used as a new precursor for the synthesis of MoV/diphosphonate systems. The two complexes were very efficient both as reductants of Pt and Pd metallic salts and as capping agents for the resulting Pt0 and Pd0 nanoparticles. The size of the obtained nanoparticles depends both on the nature of the polyoxometalate (POM; i.e., 1 or 2) and on the [metallic salt]/[POM] ratio. In all cases, X-ray photoelectron spectroscopy (XPS) measurements have revealed the presence of MoVI species that stabilize the nanoparticles and the absence of MoV moieties. Diffuse-reflectance FTIR spectra of the Pt nanoparticles show that the capping MoVI POMs are identical for both systems and contain the diphosphonato ligand. The colloidal solutions do not show any precipitate and the nanoparticles remain well-dispersed for several months. The electrochemical reduction of MoV species was studied for 2. Cyclic voltammetry alone and electrochemical quartz crystal microbalance coupled with cyclic voltammetry show the deposition of a film on the electrode surface during this reduction.