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Nadiia I Gumerova, Tania Caldera Fraile, Alexander Roller, Gerald Giester, Magda Pascual-Borràs, C André Ohlin, Annette Rompel
Since the first successful triol-functionalization of the Anderson polyoxometalates, the six protons of their central octahedron X(OH)6 (X-heteroatom, p- or d-element) have been considered as a prerequisite for their functionalization with tripodal alcohols, and therefore, the functionalization of Anderson structures from the unprotonated sides have never been reported. Here, we describe the triol-functionalization of [Cr(OH)3 W6 O21 ]6- leading to the single-side grafted anions [Cr(OCH2 )3 CRW6 O21 ]6- (CrW6 -tris-R, R = -C2 H5 , -NH2 , -CH2 OH) and the unprecedented double-side functionalized anion [Cr((OCH2 )3 CC2 H5 )2 W6 O18 ]3- (CrW6 -(tris-C2 H5 )2 ), despite the lack of protons in the parent anion in the solid state...
December 13, 2018: Inorganic Chemistry
Xin-Bao Han, Xing-Yan Tang, Yue Lin, Eduardo Gracia-Espino, Sang-Gui Liu, Hai-Wei Liang, Guang-Zhi Hu, Xin-Jing Zhao, Hong-Gang Liao, Yuan-Zhi Tan, Thomas Wagberg, Su-Yuan Xie, Lan-Sun Zheng
The oxygen evolution reaction is a crucial step in water electrolysis to develop clean and renewable energy. Although noble metal-based catalysts have demonstrated high activity for oxygen evolution reaction, their application have been limited by their high costs and low availability. Here we report the use of a molecule-to-cluster strategy to prepare ultra-small trimetallic clusters by using polyoxometalate molecule as precursors. The ultrafine (0.8 nm) transition metal clusters with controllable chemical composition are obtained...
December 12, 2018: Journal of the American Chemical Society
Junping Zhang, Zhiliang Miao, Jing Yan, Xue Zhang, Xuezhuang Li, Qiuyu Zhang, Yi Yan
A negative-charged, metal-containing cyclomatrix polyphosphazene microsphere (MCPM) is synthesized using the strategy of precipitation polymerization of di-functionalized polyoxometalates (POMs) and hexachlorocyclotriphosphazene. The chemical structure of these MCPMs is well characterized by 13 C MAS NMR and 31 P MAS NMR, as well as FT-IR, electron microscopy, and X-ray photoelectron spectroscopy. The covalent grafting of the rigid POMs clusters into the framework of these microspheres prevents the collapsing of the pores, making these MCPMs porous materials...
December 7, 2018: Macromolecular Rapid Communications
Shikai Liu, Wenting Li, Shili Gai, Guixin Yang, Chongna Zhong, Yunlu Dai, Fei He, Piaoping Yang, Yung Doug Suh
Near-infrared (NIR) light-induced imaging-guided cancer therapy has been studied extensively in recent years. Herein, we report a novel theranostic nanoplatform by modifying polyoxometalate (POM) nanoclusters onto mesoporous silica-coated upconversion nanoparticles (UCNPs), followed by loading doxorubicin (DOX) in the mesopores and coating a folate-chitosan shell onto the surface. In this nanoplatform, the core-shell structured UCNPs (NaYF4:Yb,Er@NaYF4:Yb,Nd) showed special upconverting luminescence (UCL) when irradiated with high-penetration 808 nm NIR light, and the doped Yb and Nd ions endowed the sample with CT imaging properties, thus achieving a dual-mode imaging function...
December 10, 2018: Biomaterials Science
Xiya Yang, Peipei Zhu, Jing Ren, Yuhao Chen, Xiao Li, Jingquan Sha, Jianzhuang Jiang
The first polyoxometalate (POM)-containing nanocage based metal-organic framework (Zn-POMCF) was synthesized by a surfactant-assisted method. In contrast to the Zn-based metal-organic framework (Zn-MOF), the cooperative assembly of POM and a Zn/trz macrocycle gave rise to high stability and good electrochemical ability of the Zn-POMCF in lithium-ion batteries (LIBs).
December 10, 2018: Chemical Communications: Chem Comm
Antonios M Douvas, Dimitris Tsikritzis, Charalampos Tselios, Ali Haider, Ali S Mougharbel, Ulrich Kortz, Anastasia Hiskia, Athanassios G Coutsolelos, Leonidas C Palilis, Maria Vasilopoulou, Stella Kennou, Panagiotis Argitis
The investigation of conditions allowing multi-electron reduction and reoxidation of polyoxometalate (POM) films onto solid substrates is considered an issue of critical importance for their successful incorporation in electronic devices, different types of sensors and catalytic systems. In the present paper, the rich multi-electron redox chemistry of films of Wells-Dawson ammonium salts, namely (NH4)6P2Mo18O62 and (NH4)6P2W18O62, on top of metallic (Al), semiconducting (ITO) and dielectric (SiO2) substrates under ambient conditions is investigated...
December 10, 2018: Physical Chemistry Chemical Physics: PCCP
Laura S Van Rompuy, Tatjana N Parac-Vogt
Polyoxometalates have long been studied in a variety of biological applications. Interactions between the highly charged POM molecules and biological molecules frequently occur through hydrogen-bonding and electrostatic interactions. Tellurium-centred Anderson-Evans POMs show exceptional promise as crystallization agents, while acidic and metal-substituted POMs may provide interesting alternatives to enzymes in proteomics applications. While POMs also show interesting results in a number of medicinal applications, for example as anti-amyloid agents for the treatment of Alzheimer's disease and as anti-tumoral agents, their use is often impeded by their toxicity...
December 6, 2018: Current Opinion in Biotechnology
Jian Zhang, Mingyu Zhan, Lulu Zheng, Chen Zhang, Guodong Liu, Jingquan Sha, Shaojie Liu, Shuo Tian
To enhance the Fenton catalytic performance in a neutral solution under indoor sunlight, a novel FeOCl/polyoxometalate (POM) (FeOCl/POM-W and FeOCl/POM-Mo) composite was successfully synthesized for the first time, which shows significantly improved Fenton catalytic activity and stability for phenol degradation compared with FeOCl. Furthermore, the degradation constants ( k) of FeOCl/POM-Mo (0.08 min-1 ) and FeOCl/POM-W (0.06 min-1 ) are a factor of 4 and 3 times greater than that of FeOCl (0.02 min-1 ), respectively...
December 11, 2018: Inorganic Chemistry
Agata Wawrzynczak, Izabela Nowak, Agnieszka Feliczak-Guzik
Classification of polyoxometalates (POMs) is based on their chemical composition, basically represented by two general formulae: a) [Mm Oy ]p- b) [Xx Mm Oy ]q- , where M is the main transition metal, O is the oxygen atom and X can be a non-metal atom such as Si. Additionally, in the most cases, the structure of the polyoxometalates is derived from a combination of octahedral units MO6 with a central metal atom M and the oxygen atoms placed at their corners. In such octahedra, oxygen atoms allow the condensation between two octahedral units, while one oxygen atom (or max...
2018: Frontiers in Chemistry
Swati Parbhakar, Reetam Kaushik, Firasat Hussain
A series of 12 inorganic-organic hybrid 4f-substituted arsenotungstates decorated with 3d-based complexes along with acetate bridging, viz. {[Cu2 (H2 O)(1,10-phen)2 (μ-CH3 COO)2 ]4 [Ln2 (H2 O)2 (μ-CH3 COO)2 (α-AsW11 O39 )2 ]}2- (LnIII = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu), have been synthesized. These compounds were isolated using a one-pot synthetic strategy with copper, lanthanoid, trilacunary arsenotungstate and 1,10-phenanthroline as precursors. They were characterized using various analytical techniques, such as single-crystal X-ray diffraction (SC-XRD), powder XRD (PXRD), Fourier transform IR (FT-IR) spectroscopy, UV-Vis spectroscopy and thermogravimetric analysis (TGA)...
December 1, 2018: Acta Crystallographica. Section C, Structural Chemistry
Nuttaporn Samart, Zeyad Arhouma, Santosh Kumar, Heide A Murakami, Dean C Crick, Debbie C Crans
51 V NMR spectroscopy is used to document, using speciation analysis, that one oxometalate is a more potent growth inhibitor of two Mycobacterial strains than other oxovanadates, thus demonstrating selectivity in its interaction with cells. Historically, oxometalates have had many applications in biological and medical studies, including study of the phase-problem in X-ray crystallography of the ribosome. The effect of different vanadate salts on the growth of Mycobacterium smegmatis ( M. smeg ) and Mycobacterium tuberculosis ( M...
2018: Frontiers in Chemistry
Beñat Artetxe, Amaia Iturrospe, Pablo Vitoria, Estibaliz Ruiz-Bilbao, José S Garitaonandia, Juan M Gutiérrez-Zorrilla
A new hybrid inorganic-organometallic salt has been obtained from the reaction of the Keggin-type silicotungstate anion with ferrocene in a water/methanol mixture as a result of the partial oxidation of ferrocene molecules to ferrocenium cations. Single-crystal X-ray diffraction analysis reveals the presence of four ferrocenium (FeIII ) cations and one ferrocene (FeII ) molecule per plenary Keggin anion in the crystal structure of [FeIII (Cp)₂]₄[SiW12 O40 ]·[FeII (Cp)₂]·2CH₃OH ( 1 ). Compound 1 thus constitutes the first example in the literature in which ferrocenium and ferrocene species coexist in the structure of a polyoxometalate-based salt...
November 30, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Yeongkyu Choi, Dasom Jeon, Yuri Choi, Dongseok Kim, Nayeong Kim, Minsu Gu, Sanghyun Bae, Taemin Lee, Hyun-Wook Lee, Byeong-Su Kim, Jungki Ryu
An efficient water oxidation photoanode based on hematite has been designed and fabricated by tailored assembly of graphene oxide (GO) nanosheets and cobalt polyoxometalates (Co-POM) water oxidation catalysts into a nacre-like multilayer architecture on a hematite photoanode. The deposition of catalytic multilayers provides a high photocatalytic efficiency and photoelectrochemical stability to underlying hematite photoanodes. Compared to the bare counterpart, the catalytic multilayer electrode exhibits a significantly higher photocurrent density and large cathodic shift in onset potential (~ 369 mV) even at neutral pH conditions due to the improved charge transport and catalytic efficiency from the rational and precise assembly of GO and Co-POM...
December 4, 2018: ACS Nano
Marcella Bonchio, Zois Syrgiannis, Max Burian, Nadia Marino, Erica Pizzolato, Konstantin Dirian, Francesco Rigodanza, Giulia Alice Volpato, Giuseppina La Ganga, Nicola Demitri, Serena Berardi, Heinz Amenitsch, Dirk M Guldi, Stefano Caramori, Carlo Alberto Bignozzi, Andrea Sartorel, Maurizio Prato
The oxygen in Earth's atmosphere is there primarily because of water oxidation performed by photosynthetic organisms using solar light and one specialized protein complex, photosystem II (PSII). High-resolution imaging of the PSII 'core' complex shows the ideal co-localization of multi-chromophore light-harvesting antennas with the functional reaction centre. Man-made systems are still far from replicating the complexity of PSII, as the majority of PSII mimetics have been limited to photocatalytic dyads based on a 1:1 ratio of a light absorber, generally a Ru-polypyridine complex, with a water oxidation catalyst...
December 3, 2018: Nature Chemistry
Xiaolin Xing, Rongji Liu, Kecheng Cao, Ute Kaiser, Guangjin Zhang, Carsten Streb
The oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are key catalytic processes for sustainable energy technologies such as water electrolysis or fuel cells. Here, a novel metal oxide - nanostructured carbon composite is reported which acts as OER and ORR electrocatalyst under technologically relevant conditions. A facile synthetic process allows the deposition of a molecular manganese vanadium oxide precursor, [Mn4V4O17(OAc)3]3-, on reduced graphene oxide. Simultaneously, the precursor is converted into insoluble nanostructured solid-state Mn-V-oxide catalysts...
December 3, 2018: ACS Applied Materials & Interfaces
Hong-Kai Liu, Li-Jun Ren, Han Wu, Yong-Li Ma, Sven Richter, Michael Godehardt, Christian Kübel, Wei Wang
Cubosomes are bicontinuous cubic-phase particles generated by amphiphile self-assembly with bicontinuous cubic phases, which creates an intricate network of interconnected nanochannels endows these materials with special functions for advanced applications. On the other hand, clusters are an attractive class of molecules that exhibit intriguing functions and properties that differ from those of atoms and nanoparticles. Inspired by lipid self-assembly and attracted to the new functionalities of clusters, we prepared special hetero-cluster Janus dumbbells (HCJDs) composed of dissimilar nanoclusters namely, a polyoxometalate and polyhedral oligomeric silsesquioxane...
December 2, 2018: Journal of the American Chemical Society
Shuntaro Tsubaki, Shogo Hayakawa, Tadaharu Ueda, Satoshi Fujii, Ei-Ichi Suzuki, Jie Zhang, Alan Bond, Yuji Wada
Application of radio frequency (RF) electromagnetic waves enhances the electrocatalytic water oxidation by protonated tetraruthenium polyoxometalate ([Ru4(μ-O)4(μ-OH)2(H2O)4(γ-SiW10O36)2]10-). In particular, an enhancement factor of 3.6 is achieved when the level of proton substitution of protonated tetraruthenium polyoxometalate is changed from zero to 9 under application of RF at 200 MHz.
November 30, 2018: Chemical Communications: Chem Comm
Weimin Xuan, Robert Pow, Nancy Watfa, Qi Zheng, Andrew J Surman, De-Liang Long, Leroy Cronin
The synthesis of chiral polyoxometalates (POMs) is a challenge because of the difficulty to induce the formation of intrin-sically chiral metal-oxo frameworks. Herein we report the stereoselective synthesis of a series of gigantic chiral Mo Blue (MB) POM clusters 1-5 that form by exploiting the synergy between coordinating lanthanides ions as symmetry breakers to produce MBs with chiral frameworks decorated with amino acids ligands; these promote the selective formation of en-antiopure MBs. All the compounds share the same framework archetype, based on {Mo124Ce4}, which forms an intrinsical-ly chiral or  configurations controlled by the configurations of functionalized chiral amino acids...
November 29, 2018: Journal of the American Chemical Society
Nan Shi, Dong Liu, Falu Dang, Qingtai Chen, Min Li, Fushan Wen
Acid-redox bifunctional Dawson-type polyoxometalates K6 P2 W18 O62 (P2 W18 ) and K10 P2 W17 O61 (P2 W17 ) were introduced as the new-type catalysts in oxidative decomposition of lignocellulose. The lignin and hemicellulose ingredients of lignocellulose could be decomposed by P2 W17 to produce diisobutyl phthalate with the selectivity of 75.67% and other aromatic and aliphatic compounds under mild conditions, evidently differed from other POMs-catalyzed lignocellulose depolymerization in which aromatic ketones and phenols were the main compounds...
November 13, 2018: Bioresource Technology
Biswarup Chakraborty, Gal Gan-Or, Manoj Raula, Eyal Gadot, Ira A Weinstock
While molecular water-oxidation catalysts are remarkably rapid, oxidative and hydrolytic processes in water can convert their active transition metals to colloidal metal oxides or hydroxides that, while quite reactive, are insoluble or susceptible to precipitation. In response, we propose using oxidatively-inert ligands to harness the metal oxides themselves. This approach is demonstrated by covalently attaching entirely inorganic oxo-donor ligands (polyoxometalates) to 3-nm hematite cores, giving soluble anionic structures, highly resistant to aggregation, yet thermodynamically stable to oxidation and hydrolysis...
November 20, 2018: Nature Communications
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