Polyoxometalate

About: Polyoxometalate is a research topic. Over the lifetime, 3493 publications have been published within this topic receiving 94123 citations. The topic is also known as: POM.

A stable hybrid bisphosphonate polyoxometalate single-molecule magnet.

Abstract: The long history of polyoxometalate (POM) chemistry initially featured the characterization of diamagnetic species. However, the last few decades have seen the development of several families of paramagnetic POM molecules that display a diverse range of structures and properties. These entities can be of nanosize scale, as exemplified by the discovery of the spin-frustrated Keplerate clusters of general formula {(Mo)Mo5}12M30 (M=Fe , Cr, V). Although of smaller size than these molybdenum compounds, high-nuclearity polyoxovanadate mixed-valent species have also been characterized. The unexpectedly strong magnetic couplings observed in a number of these systems have been studied in detail both experimentally and theoretically. The third— and most extended—magnetic POM family is that of polyoxotungstates. Large clusters in which vacant polyoxotungstate ligands encapsulate 3d or 4f metals have been obtained, and most of these systems are purely inorganic. In particular, very few hybrid polynuclear 3d magnetic polyoxotungstates synthesized under mild conditions have been characterized to date. Moreover, to the best of our knowledge, no general method for the preparation of hybrid, soluble, and stable polyoxotungstates encapsulating magnetic clusters has been proposed. This contrasts with the case of the diamagnetic polyoxotungstates, for which numerous triol-functionalized, organosilyl and organostannic derivatives have been reported. Hybrid molybdenum-based POM chemistry has also been widely developed, but mainly {Mo6} Lindqvist and Anderson-type systems encapsulating a maximum of one 3d cation have been used as a platform for connecting various organic substrates. The establishment of a method allowing the rational synthesis of stable hybrid POMs incorporating several divalent or trivalent 3d metal centers thus remains a challenge. Such materials would be of interest in various fields as they would permit the covalent grafting of POMs containing 3d clusters to a range of organic substrates or surfaces, and thus the elaboration of new functional materials. For example, the covalent connection of photoactive organic groups to multi-electrochromic 3d-substituted inorganic entities may afford optical materials with new properties. Alternatively, Co-substituted polyoxotungstates have been shown to be efficient photocatalysts, which may in itself motivate the search for related hybrid materials. Clearly, hybrid 3d magnetic polyoxotungstates are also interesting in the molecular magnetism field. Since 2008, it is known that 3dor 4f-substituted polyoxotungstates can behave as single molecule magnets (SMMs). Moreover, deposition of POM SMMs on single-wall carbon nanotubes (SWCNTs) has provided evidence that individual POM molecules present a slow relaxation of the magnetization, a crucial point with respect to the potential use of such nanocomposites as information storage devices. However, in such a system, no control of the SWCNT/POM interface is possible. This is due to the purely inorganic nature of the deposited POM—a characteristic of all the 3d POM SMMs species reported to date. Indeed, the reinforcement of the interactions between the two components via covalent grafting or p–p stacking together with the control of the POM/substrate distance obviously implies the elaboration of hybrid POM SMM systems. Herein, we report the characterization of the polyanion [{(B-a-PW9O34)Co3(OH) ACHTUNGTRENNUNG(H2O)2ACHTUNGTRENNUNG(O3PC(O) ACHTUNGTRENNUNG(C3H6NH3)PO3)}2Co] 14 (1), which is built of a heptanuclear Co core sandwiched by two {PW9} units and connected to two bisphosphonato ligands, each possessing a functionalizable alkyl ammonium arm. The stability of this hybrid unit has been unambiguously assessed by using P and H NMR spectroscopy and electrochemical techniques. Single-crystal studies performed on an array of micro-SQUIDs have revealed that the ferromagnetic species 1 exhibits SMM behavior. [a] Dr. H. El Moll, Dr. A. Dolbecq, Dr. J. Marrot, G. Rousseau, Dr. M. Haouas, Dr. F. Taulelle, Prof. P. Mialane Institut Lavoisier de Versailles UMR 8180, Universit de Versailles Saint-Quentin 45 Avenue des Etats-Unis, 78035 Versailles Cedex (France) Fax: (+33)1-39-25-43-81 E-mail : mialane@chimie.uvsq.fr [b] Dr. G. Rogez Institut de Physique et de Chimie des Mat riaux de Strasbourg (IPCMS) UMR 7504, CNRS Universit de Strasbourg 23 rue du Lœss, BP 43, 67034 Strasbourg Cedex 2 (France) [c] Dr. W. Wernsdorfer Institut N el, CNRS et Universit Joseph Fourier BP 166, F-38042 Grenoble Cedex 9 (France) [d] Dr. B. Keita Laboratoire de Chimie Physique Groupe d’Electrochimie et de Photo lectrochimie, UMR 8000, CNRS Universit Paris-Sud, B timent 350, 91405 Orsay cedex (France) E-mail : bineta.keita@lcp.u-psud.fr Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201200140.

{W48} Ring Opening: Fe16‐Containing, Ln4‐Stabilized 49‐Tungsto‐8‐Phosphate Open Wheel [Fe16O2(OH)23(H2O)9(P8W49O189)Ln4(H2O)20]11−

Abstract: Wheely: For the first time and very unexpectedly, a rupture of the very stable {P(8)W(48)} wheel was observed in aqueous solution at pH 4 and 80 °C in the presence of Fe(III), Eu(III)/Gd(III), and H(2)O(2). This inorganic ring opening is unprecedented in polyoxometalate chemistry.

Influence of Transition Metal Coordination Nature on the Assembly of Multinuclear Subunits in Polyoxometalates-Based Compounds

Abstract: Four inorganic−organic hybrids based on Keggin-type polyoxometalate (POM), [Ag3(bmte)2(PMo12O40)] (1), [CuI3(bmte)3(PMo12O40)] (2), [CuII(bmte)3(HPMo12O40)] (3), and [Ni(bmte)3(HPMo12O40)] (4) (bmte = 1,2-bis(1-methyl-5-mercapto-1,2,3,4-tetrazole)ethane), have been synthesized under hydrothermal conditions by tuning the coordination nature of transition metal (TM) ions. The transformation of coordination modes of TM ions has a crucial influence on the multinuclear structures of this series. In compound 1, binuclear subunits [Ag(1)2(bmte)2]2+ occur, which is connected by PMo12O403− (PMo12) anions to construct a one-dimensional (1D) chain. Furthermore, these chains are linked by Ag(2) ions acting as fuses to construct a two-dimensional (2D) gridlike sheet. Compound 2 shows trinuclear clusters, [CuI3(bmte)3]3+, which are also connected by PMo12 anions to construct a 1D chain. These two neighboring chains arrange like a “zipper”. Compounds 3 and 4 are isostructural. In compound 3, the metal−organic subunit is...