Electrostatic self-assembly of composite materials containing Keggin structure polyoxoanions and functionalized Anderson structure polyoxometallic cations

• Three new POM-based nanocomposite materials are prepared.
• Each contains a Keggin type anion and a common organo-functionalized polyoxocation.
• E.g., [NaVIV6O6{(OCH2CH2)2N(CH2CH2OH)}6]3(PW12O40)·12H2O (G1).
• Aqueous phase synthesis produces a gel-like intermediate.
• Intercluster Coulombic interactions are the driving force of composite formation.

We have synthesized and characterized three new nanocomposite materials—[NaVIV6O6{(OCH2CH2)2N(CH2CH2OH)}6]3(PW12O40)·12H2O G1, [NaVIV6O6{(OCH2CH2)2N(CH2CH2OH)}6]4(SiW12O40)·20H2O G2, and [NaVIV6O6{(OCH2CH2)2N(CH2CH2OH)}6]3(HSiMo12O40)·13H2O G3, containing the well-defined organo-functionalized polyoxocationic species, [NaVIV6O6{(OCH2CH2)2N(CH2CH2OH)}6]+, and Keggin polyoxoanions [(PW12O40)3−, (SiW12O40)4− or (SiMo12O40)4−] as molecular constituents. The new materials, prepared by combining their constituents in an aqueous medium, are obtained following partial dehydration of a gel-like intermediate phase and have a transparent, glass-like appearance. Powder XRD patterns indicate that the new materials are nanocrystalline. FTIR vibrational spectroscopic studies indicate that the materials are composite in nature, containing intact oxometallic cores of their respective polyoxoanion and polyoxocation building block units. Intercluster Coulombic interactions are the driving force of composite formation. UV–Vis–NIR spectral analysis indicates that the oxidation state of the constituent polyoxoanions and polyoxocations remains unchanged upon composite formation. Reactant ratio studies, along with elemental and vibrational (FTIR) analysis, are consistent with polyoxocation–polyoxoanion Coulombic interaction as the preponderant intermolecular force driving composite formation. To the best of our knowledge, these are the first materials derived from Coulombic interactions of polyoxoanions with covalently organo-functionalized polyoxocations.

We have synthesized and characterized three new nanocomposite materials—[NaVIV6O6{(OCH2CH2)2N(CH2CH2OH)}6]3(PW12O40)·12H2O (G1), [NaVIV6O6{(OCH2CH2)2N(CH2CH2OH)}6]4(SiW12O40)·20H2O (G2), and [NaVIV6O6{(OCH2CH2)2N(CH2CH2OH)}6]3(HSiMo12O40)·13H2O (G3), containing the well-defined organo-functionalized polyoxocationic species, [NaVIV6O6{(OCH2CH2)2N(CH2CH2OH)}6]+, and Keggin polyoxoanions [(PW12O40)3−, (SiW12O40)4− or (SiMo12O40)4−] as molecular constituents.Figure optionsDownload as PowerPoint slide