Structure and Electronic Properties of Large Oligomeric Heterometallic 3d/Ce Polyoxometalates.

Merging the rich chemistry of Ce(IV) polyoxometalates (POMs) with that of 3d polyanions remains a challenge due to the strong competition between these highly oxophilic lanthanide cations and 3d metallic ions for coordination to lacunary molecular metal oxides. We report herein the characterization of an unprecedented water stable hexameric Ce/Co POM () made of two {(SiW)Ce} units connected to a {(SiW)Co(PO)} core. In addition, the pentameric Ce/Ni compound , where two {PWNiW} and a {PWNi} fragments are grafted on a {(PW)Ce} moiety, has been obtained.

Tailoring the Solid-State Fluorescence of BODIPY by Supramolecular Assembly with Polyoxometalates.

A cationic boron dipyrromethene (BODIPY) derivative () has been successfully combined with two polyoxometalates (POMs), the Lindqvist-type [WO] and the β-[MoO] units, into three new supramolecular fluorescent materials , , and . The resulting hybrid compounds have been fully characterized by a combination of single-crystal X-ray diffraction, IR and UV-vis spectroscopies, and photoluminescence analyses. This self-assembly approach prevents any π-π stacking interactions not only between the BODIPY units, responsible for aggregation-caused quenching (ACQ) effects, but also between the BODIPY and the POMs, avoiding intermolecular charge-transfer effects.

Photoactive Polyoxometalate/DASA Covalent Hybrids for Photopolymerization in the Visible Range.

The synthesis of TBA-DASA-POM-DASA, the first photoactive covalent hybrid polyoxometalate (POM) incorporating a donor-acceptor Stenhouse adduct (DASA) reverse photochrome, is presented. It has been evidenced that in solution the equilibrium between the colorless cyclopentenone and the highly colored triene conformers is strongly dependent not only on the nature of the solvent but also the countercations, allowing to tune its optical properties. This complex has been further associated to photochromic spironaphtoxazine cations, resulting in a material which can be activated by two distinct optical stimuli.

An unprecedented {NiSiW} hybrid polyoxometalate with high photocatalytic hydrogen evolution activity.

A unique polyoxometalate complex made up of a tetradecanuclear nickel bisphosphonate cluster capping a {SiW9} unit has been characterized. This stable compound exhibits a high hydrogen evolution reaction photocatalytic activity under visible light irradiation via a reductive quenching mechanism.

Anderson-Type Polyoxometalates Functionalized by Tetrathiafulvalene Groups: Synthesis, Electrochemical Studies, and NLO Properties.

Three polyoxometalates (POMs) functionalized by tetrathiafulvalene (TTF) molecules have been synthesized by a coupling reaction between the Anderson-type POMs [MnMoO{(OCH)CNH}] or [AlMoO(OH){(OCH)CNH}] and the TTF carboxylic acid derivative (MeS)TTF(S-CH-COH). The monofunctionalized TTF-AlMo POM contains one TTF group covalently grafted on an Al Anderson platform. The symmetrical TTF-MnMo-TTF POM possesses two TTF groups grafted on each side of a Mn Anderson derivative while the asymmetrical TTF-MnMo-SP POM contains a TTF and a spiropyran groups.

Anticancer Activity of Polyoxometalate-Bisphosphonate Complexes: Synthesis, Characterization, In Vitro and In Vivo Results.

We synthesized a series of polyoxometalate-bisphosphonate complexes containing MoO octahedra, zoledronate, or an N-alkyl (n-C or n-C) zoledronate analogue, and in two cases, Mn as a heterometal. MoL (L = Zol, ZolC, ZolC) and MoLMn (L = Zol, ZolC) were characterized by using single-crystal X-ray crystallography and/or IR spectroscopy, elemental and energy dispersive X-ray analysis and P NMR. We found promising activity against human nonsmall cell lung cancer (NCI-H460) cells with IC values for growth inhibition of ∼5 μM per bisphosphonate ligand.

Photochromism and Dual-Color Fluorescence in a Polyoxometalate-Benzospiropyran Molecular Switch.

The photophysical properties of a Keggin-type polyoxometalate (POM) covalently bounded to a benzospiropyran (BSPR) unit have been investigated. These studies reveal that both closed and open forms are emissive with distinct spectral features (λ (closed form)=530 nm, λ (open form)=670 nm) and that the fluorescence of the BSPR unit of the hybrid is considerably enhanced compared to BSPR parent compounds. While the fluorescence excitation energy of the BSPR reference compounds (370 nm) is close to the intense absorption responsible of the photochromic character (350 nm), the fluorescence excitation of the hybrid is shifted to lower energy (400 nm), improving the population of the emissive state.

Light- and Solvent-Controlled Self-Assembly Behavior of Spiropyran-Polyoxometalate-Alkyl Hybrid Molecules.

A molecular photochromic spiropyran-polyoxometalate-alkyl organic-inorganic hybrid has been synthesized and fully characterized. The reversible switching of the hydrophobic spiropyran fragment to the hydrophilic merocyanine one can be easily achieved under light irradiation at different wavelengths. This switch changes the amphiphilic feature of the hybrid, leading to a light-controlled self-assembly behavior in solution.

Heteroanionic Materials Based on Copper Clusters, Bisphosphonates, and Polyoxometalates: Magnetic Properties and Comparative Electrocatalytic NO(x) Reduction Studies.

Three compounds associating for the first time polyoxotungstates, bisphosphonates, and copper ions were structurally characterized. They consist in heteropolyanionic monodimensional materials where [Cu6(Ale)4(H2O)4](4-) (Ale = alendronate = [O3PC(O)(C3H6NH3)PO3](4-)) complexes alternate with polyoxometalate (POM) units. In Na12[{SiW9O34Cu3(Ale)(H2O)}{Cu6(Ale)4(H2O)4}]·50H2O (SiW9CuAle), the polyoxometalate core consists in a {SiW9Cu3} monomer capped by a pentacoordinated Ale ligand, while sandwich-type Keggin {(SbW9O33)2Cu3(H2O)(2.

A high fatigue resistant, photoswitchable fluorescent spiropyran-polyoxometalate-BODIPY single-molecule.

The tuning of the fluorescence through the activation of the photochromic part in an unprecedented covalent spiropyran-polyoxometalate-BODIPY tricomponent points out the high photofatigue resistance of such molecular switches.

Sequential Synthesis of 3 d-3 d, 3 d-4 d, and 3 d-5 d Hybrid Polyoxometalates and Application to the Electrocatalytic Oxygen Reduction Reactions.

The Co7 (AlePy)2 polyoxometalate, which encloses a {(PW9 )2 Co(II) 7 } core covalently bound to two free aminopyridine groups through bisphosphonate ligands (AlePy), has been isolated. It can be used as a precursor, allowing the synthesis of heterometallic hybrid compounds, as illustrated by the characterization of cobalt/zinc (Co7 (AlePyZn)2 ), cobalt/palladium (Co7 (AlePyPd)2 ), and cobalt/platinum (Co7 (AlePyPt)2 ) species. A composite based on the water-insoluble precious metal-free Co7 (AlePyZn)2 compound and the low-cost carbon material Vulcan XC-72 has been selected as a cathode material (Co7 Zn/C) for oxygen reduction reaction studies.

Photochromic properties of polyoxotungstates with grafted spiropyran molecules.

The first systems associating in a single molecule polyoxotungstates (POTs) and photochromic organic groups have been elaborated. Using the (TBA)4[PW11O39{Sn(C6H4I)}] precursor, two hybrid organic-inorganic species where a spiropyran derivative (SP) has been covalently grafted onto a {PW11Sn} fragment via a Sonogashira coupling have been successfully obtained. Alternatively, a complex containing a silicotungstate {PW11Si2} unit connected to two spiropyran entities has been characterized.

Properties of a tunable multinuclear nickel polyoxotungstate platform.

A series of hybrid nickel bisphosphonate (BP) polyoxometalates (POMs) has been isolated. The complexes NaK-Ni7-Ale2 (Ale = [H2O3PC(C3H6NH2)(OH)PO3H2]) and NaNH4-Ni7-Ale2 are both made of two {PW9O34} fragments enclosing a heptanuclear Ni(II) core connected to two alendronate ligands. By pre-functionalising the alendronate moiety through the amino group, the naphthalene (napht) derivative Ni7-(AleNapht)2 and the compounds Ni7-(AlePy2 Ni)2 (py = pyridyl) and Ni7-(AleAc2Ni)2 (Ac = acyl) have been obtained.

Sulfonium polyoxometalates: a new class of solid-state photochromic hybrid organic-inorganic materials.

For the very first time, sulfonium polyoxometalate (POM) assemblies are shown to develop efficient solid-state photochromism in ambient conditions. The optical properties of the already known Rb(0.75)(NH(4))(5.

Photo- and electrochromic properties of covalently connected symmetrical and unsymmetrical spiropyran-polyoxometalate dyads.

Polyoxometalates covalently linked to one or two spiropyran entities have been isolated. These organic-inorganic hybrids exhibit multi-electrochromic and photochromic properties.

Diversity in structures and properties of 3d-incorporating polyoxotungstates.

This critical review surveys the 3d substituted magnetic polyoxotungstate (POT) molecular compounds reported these last ten years, illustrating the huge variety of topologies that these systems can adopt. Both purely inorganic and organic/inorganic species have been considered, and the cited compounds have been classified according to their nuclearity, i.e.

Route for the elaboration of functionalized hybrid 3d-substituted trivacant Keggin anions.

On the basis of four examples involving various transition-metal cations and various carboxylic acid derivatives, we have shown that hybrid 3d metal-containing polyoxometalate systems can be easily built under mild conditions.

Functionalized polyoxometalates with intrinsic photochromic properties and their association with spiropyran cations.

The presence of alkylammonium groups covalently grafted on bisphosphonato ligands induces photochromic properties to ligand-coordinated polyoxomolybdate systems. Such intrinsically photoactive polyanions can be used for the preparation of materials combining photochromic polyoxometalates and functional countercations.

Verdazyl-lanthanide(III) one dimensional compounds: synthesis, structure and magnetic properties.

The first one-dimensional compounds where [Ln(hfac)(3)] (Ln = Gd, Tb, Dy) building blocks are bridged by a verdazyl-based radical, namely 3-imidazolyl-1,5-dimethyl-6-oxoverdazyl, were prepared and their structures elucidated; the magnetic properties were measured for all compounds and quantitatively fitted for Ln = Gd(III) using an alternate chain model leading to J(1) = -1.58 cm(-1) and to J(2) = -0.42 cm(-1).

Synthesis of planar five-connected nodal ligands.

Synthetic routes to a penta(4-pyridyl)cyclopentadienyl ligand are explored. The most successful route uses a palladium-catalysed pentapyridation of di(tert-butyl)phosphinoferrocene by using a procedure developed by Hartwig. The same method allows the synthesis of cyclopentadiene ligands substituted with 4-benzaldehydes or 4-phenylthiols.

Redox-active pH-responsive molecules: ferrocenylphosphonic acid, ferrocenylmethylphosphonic acid and 1,1'-ferrocenylbisphosphonic acid. Structural determination of FcPO3Na2.5H2O.

The acidity constants of the reduced and oxidized species of ferrocenylphosphonic acids FcPO3H2, FcCH2PO3H2 and fc(PO3H2)2 (Fc = (eta5-C5H5)Fe(eta5-C5H4), fc = (eta5-C5H4)Fe(eta5-C5H4)) in water have been evaluated by potentiometric, 31P NMR, and electrochemical methods. The oxidized forms are more acidic than the reduced ones. The interaction between the redox centre and the charged oxygen atoms of the phosphonate group is shown to be electrostatic.

Mixed 1D-2D inorganic polymeric zinc ferrocenylphosphonate: crystal structure and electrochemical study.

Needs for ferrocene immobilization on robust host structures are considerable since derivative materials may find applications in medical areas, optical devices, or catalysis. Synthesis of phosphonate functionalized ferrocene allowed its subsequent inorganic polymerization with a zinc salt. The crystallographic structure of the compound obtained, Zn(HO(3)PFc)(2).