Applications

Publications of other groups based on our nanoobjects
(see also Molecular Magnetism)

Preparation of a molybdenum-oxide based catalyst exhibiting the pentagonal unit of the Keplerate Mo₁₃₂ used as starting material.

Publication:

"Synthesis of Orthorhombic Mo-V-Sb Oxide Species by Assembly of Pentagonal Mo₆O₂₁ Polyoxometalate Building Blocks"

Mix and match

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₂₁

^n-

"Selective conversion of {Mo₁₃₂} Keplerate ion into 4-electron reduced crown-capped Keggin derivative [Te₅Mo₁₅O₅₇]^8-. A key intermediate to single-phase M1 multielement MoVTeO light-alkanes oxidation catalyst"

"Aiding the Self-Assembly of Supramolecular Polyoxometalates under Hydrothermal Conditions To Give Precursors of Complex Functional Oxides"

"Assembly of a Pentagonal Polyoxomolybdate Building Block, [Mo₆O₂₁]^6-, into Crystalline MoV Oxides"

Influencing Progress in Polyoxometalate Chemistry Based on the Keplerate-Type Pentagonal Units - one example

Publication:

"Structural Link between Giant Molybdenum Oxide Based Ions (e.g. our Keplerates) and Derived Keggin Structure: Modular Assemblies Based on the [BW₁₁O₃₉]^9- Ion and Pentagonal {M'M₅} Units (M' = W; M = Mo, W)"

Part of the text:
"Actually, until the beginning of the 1990s, this wide class of compounds was dominated by a few structural archetypes, namely, the Lindqvist, Keggin, and Dawson anions. From 1994, Müller has advanced the knowledge of polyoxometalate chemistry with numerous reports on unprecedented nanosized arrangements based on molybdenum oxide clusters. These topological structures are characterized by a striking pentagonal building unit {Mo(Mo₅)}, which condenses with metal cations to form either spheroidal capsules (keplerate) or wheel-shaped clusters."

Graphical Abstract:

Linked to the Pentagon: The addition of molybdate to [HBW₁₁O₁₉]^8- ions leads to the formation of mixed pentagonal units {W(Mo₅)} and {W(WMo₄)} trapped as linkers in the resulting modular assemblies, thus establishing the first link between the conventional Keggin ions derivatives and the giant molybdenum oxide and keplerate ions.

Reactions and Catalysis Can be Performed in the Cavity of the Mo₁₃₂ Keplerate

Publications:

"A regioselective Huisgen reaction inside a Keplerate polyoxomolybdate nanoreactor"

"Catalysis in a Porous Molecular Capsule: Activation by Regulated Access to Sixty Metal Centers Spanning a Truncated Icosahedron"

Molybdenum Oxide-Based Keplerates and Unique Solid-State Reactions

Publication:

"Crystallization of a Keplerate-type polyoxometalate into a superposed kagome-lattice with hugh channels"

Cover picture of the corresponding themed issue "Polyoxometalates" of Dalton Transactions showing the Keplerate based structure

"Cross-linking nanostructured spherical capsules as building units by crystal engineering: related chemistry"

Materials obtained by encapsulation of our metal-oxide species in cationic surfactants; this refers to the construction of nanostructures at interfaces (I), of liquid crystals (II) as well as of LB films and monolayers (III).

Related Publications:

(I) "Self-Patterning of Hydrophobic and Highly Ordered Honeycomb Nanostructures at the Air/Water Interface"
D. Fan, X. Jia, P. Tang, J. Hao, T. Liu (Angew. Chem. Int. Ed. 2007, 46, 3342).

SEM images of highly ordered honeycomb architectures of {Mo₇₂Fe₃₀}-DODMA complexes.

(II) a) "Colloidal Organization and Clusters: Self-Assembly of Polyoxometalate-Surfactant Complexes towards Three Dimensional Organized Structures"
S. Polarz, B. Smarsly, M. Antonietti (ChemPhysChem 2001, 2, 457).

b) "Evidence of ionic liquid crystal properties for a DODA⁺ salt of the keplerate [Mo₁₃₂ O₃₇₂(CH₃COO)₃₀(H₂O)₇₂]^42-"
S. Floquet, E. Terazzi, A. Hijazi, L. Guénée, C. Piguet, E. Cadot (New J. Chem. 2012, 36, 865).

Liquid crystalline organization of clusters DODA-Mo₁₃₂. (a) View parallel to the layers illustrating the long range layered organization. (b) View perpendicular to the layers highlighting the local hexagonal packing.

(III) "Langmuir-Blodgett Films of a Mo-Blue Nanoring [Mo₁₄₂O₄₂₉H₁₀(H₂O)₄₉(CH₃ CO₂)₅(CH₃CH₂CO₂)]^30- (Mo₁₄₂) by the Semiamphiphilic Method"
M. Clemente-León, T. Ito, H. Yashiro, T. Yamase, E. Coronado (Langmuir 2007, 23, 4042).

See also:
"Nanoscale Assemblies of Gigantic Molecular {Mo₁₅₄}-Rings: (Dimethyldioctadecylammonium)₂₀[Mo₁₅₄O₄₆₂ H₈(H₂O)₇₀]"
T. Akutagawa, R. Jin, R. Tunashima, S.-i. Noro, L. Cronin, T. Nakamura (Langmuir 2008, 24, 231).

"Metallo-supramolecular modules as a paradigm for materials science"
D. G. Kurth (Sci. Technol. Adv. Mater. 2008, 9, 014103).

Construction of hybrid materials obtained by sol-gel processes, while the clusters' integrities as well as reactivities are maintained.

Publication:

"The Interplay of Colloidal Organization and Oxo-Cluster Chemistry: Polyoxometalate-Silica Hybrids - Materials with a Nanochemical Function"

Study of cation transport through inorganic membranes/vesicles formed from {Mo₇₂Fe₃₀} Keplerates.

Publication:

"Membranes Based on "Keplerate"-Type Polyoxometalates: Slow, Passive Cation Transportation and Creation of Water Microenvironment"

Important in the context: A theoretical study of the formation/stabilization mechanisms of the mentioned new type of vesicles.

Publication:

"Charge Regulation as a Stabilization Mechanism for Shell-Like Assemblies of Polyoxometalates"

Abstract: "We show that the equilibrium size of single-layer shells composed of polyoxometalate macroions is inversely proportional to the dielectric constant of the medium in which they are dispersed. [...] This observation points to a new class of thermodynamically stable shell-like objects. We point out the possible relevance our findings have for certain surfactant systems."

"Lag Periods During the Self-Assembly of {Mo₇₂Fe₃₀} Macroions: Connection to the Virus Capsid Formation Process"

Fig. 1 Polyoxometalates Mo₇₂Fe₃₀ (top, left) and Mo₁₃₂ (bottom, left) and a cartoon of their shell-like superstructure where the size range refers to the situation in aqueous solutions.

Fig. 2 Shell radius as determined by dynamic light scattering as a function of the inverse relative dielectric constant of the solvent (water, methanol, ethanol, propanol, acetone, acetone-water mixtures) for two different polyoxometalates: Mo₇₂Fe₃₀ and Mo₁₃₂.

Preparation of unprecedented supramolecular compounds.

Publications:

(I) "Directed 1D Assembly of a Ring-Shaped Inorganic Nanocluster Templated by an Organic Rigid-Rod Molecule: An Inorganic/Organic Polypseudorotaxane"

(II)"A Molybdenum Crown Cluster Forms Discrete Inorganic-Organic Nanocomposites with Metalloporphyrins"

Separation of {Mo₇₂Fe₃₀}-embedded nanocapsules which could be aligned in a magnetic field.

Publication:

"Magnetic {Mo₇₂Fe₃₀}-embedded hybrid nanocapsules"

Scheme 1: Illustration of the LbL assembly of PAH, PSS and POM ({Mo₇₂Fe₃₀}) on PSA particles and hollow microcapsules. The first stage (a-b) involves stepwise deposition of PE on PSA colloidal particles. (b-e) Alternative assembly PAH and {Mo₇₂Fe₃₀} nanoparticles. (e-f) Decomposition of PSA cores and formation of hollow [(PAH/PSS)₂(PAH/{Mo₇₂Fe₃₀})₆PAH] microcapsules.

Fig. 6 TEM image of {Mo₇₂Fe₃₀}-embedded nanocapsules aligned in an external magnetic field.

Modeling of water ligand exchange rates on mineral surfaces with relevance for geochemical aspects.

Publication:

"Minerals as Molecules - Use of Aqueous Oxide and Hydroxide Clusters to Understand Geochemical Reactions"

Figure 11 of the paper with the legend: Balogh et al. examined the rates of water exchange on a Keplerate molecule that had thirty >Fe^III - OH₂ accessible to the bulk aqueous solution. The molecule was intenden to shed light on the rates of ligand substitution in ferric hydroxide soil minerals, like the geothite structure shown, which also have isolated >Fe^III - OH₂.

See also: "Rates of Ligand Exchange between >Fe^III - OH₂ Functional Groups on a Nanometer-Sized Aqueous Cluster and Bulk Solution"
E. Balogh, A. M. Todea, A. Müller, W. H. Casey (Inorg. Chem. 2007, 46, 7087).

The Mo₁₅₄ and Mo₁₇₆ type "big-wheels" have unique surface properties. Some of these are reported in the following.

Publication:

"Adsorption and Catalytic Properties of the Inner Nanospace of a Gigantic Ring-Shaped Polyoxometalate Cluster"

The Graphical Abstract shows:

Functional inner space: A gigantic ring-shaped {Mo₁₅₄} polyoxometalate cluster anion can be stabilized by encapsulation in dimethyldioctadecylammonium (DODA) cations. Its inner nanospace enables adsorption of gases and vapors, and it acts as a water-tolerant solid acid catalyst .

In context with our interest for the high formation tendency of spherical structures we wrote in the abstract of a related paper:

"Generation of cluster capsules (I_h) from decomposition products of a smaller cluster (Keggin-T_d) while surviving ones get encapsulated: species with core-shell topology formed by a fundamental symmetry-driven reaction" (Chem. Commun. 2001, 657) the following:

"A novel and fundamental reaction system of matter following a type of 'supramolecular Darwinism' leads to the formation of giant spherical nano-sized cluster capsules as kinetically controlled destination having the highest possible symmetry (I_h) and formed directly from the decomposition products of the well known but less symmetrical Keggin anions (T_d) in aqueous medium in the presence of Fe^III - acting as a type of environmental influence - under conditions where Keggin anions are known to be extremely stable; remarkably the remaining non-decomposed Keggin anions finally get (non-covalently) encapsulated protected by the formed spherical capsules of a new type (of supramolecular compound...)"

This is highlighted in the following.

Publication:

"From supramolecular chemistry towards constitutional dynamic chemistry and adaptive chemistry"

We read there: "Such a self-optimisation (the formation of guanine quartet-based hydrogels) behaviour may be of broader significance, namely for prebiotic chemical evolution, whereby selection is driven by phase cohesion, the entity selected being that giving the most stable organised supramolecular assembly in a sort of prebiotic Darwinism driven by self-organisation. The supramolecular organisation drives the selection of the components giving the " fittest" constituent."⁶⁰ (Ref. 60: For systems presenting a type of supramolecular Darwinism, see: A. Müller, S. K. Das, H. Bögge, M. Schmidtmann, A. Botar, A. Patrut, Chem. Commun. 2001, 657).

In the following figure the process published in the mentioned Chem. Commun. paper is shown.

Regarding catalytic properties of Keplerates.

Publications:

(I) "Catalytic properties of the macromolecular polyoxomolybdate cluster in selective oxidation of sulfides"

(II) "CVD growth of carbon nanotubes using molecular nanoclusters as catalyst"

Regarding electronic structures of giant Keplerates.

Publications:

(I) "On the electronic structure of giant polyoxometalates: Mo₁₃₂ vs. W₇₂Mo₆₀"

(II) "Electronic structure and soft-X-ray-induced photoreduction studies of iron-based magnetic polyoxometalates of type {(M)M₅}₁₂Fe^III₃₀ (M = Mo^VI, W^VI)"

General Literature (Reviews): A. Proust, R. Thouvenot, P. Gouzerh, "Functionalization of polyoxometalates: towards advanced applications in catalysis and materials science", Chem. Commun. 2008, 1837 (see sections "Introduction" and "Nanosized polyoxomolybdates with multifunctionality"); A. Müller, S. Roy , "Multifunctional metal oxide based nanoobjects: spherical porous capsules/artificial cells and wheel-shaped species with unprecedented materials properties", J. Mater. Chem. 2005, 15, 4673; A. Müller, S. Roy, "Linking Giant Molybdenum Oxide Based Nano-Objects Based on Well-Defined Surfaces in Different Phases", Eur. J. Inorg. Chem. 2005, 3561; D.-L. Long, L. Cronin, "Towards Polyoxometalate-Integrated Nanosystems", Chem. Eur. J. 2006, 12, 3698; P. Gouzerh, M. Che, "From Scheele and Berzelius to Müller: Polyoxometalates (POMs) revisited and the "missing link" between the bottom up and top down approaches", L'Actualité Chimique 2006, June Issue, p. 9; A. Müller, S. Roy, in "The Chemistry of Nanomaterials: Synthesis, Properties and Applications" (Eds.: C. N. R. Rao, A. Müller, A. K. Cheetham), Wiley-VCH, Weinheim 2004, p. 452.

Publications of other groups based on our nanoobjects (see also Molecular Magnetism)

Publications of other groups based on our nanoobjects
(see also Molecular Magnetism)