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Giant Crown-Shaped Polytungstate Formed by Self-Assembly of CeIII-Stabilized Dilacunary Keggin Fragments†

Polyoxometalates (POMs) are anionic metal–oxygen clusters with a remarkable variety of structures and potential applications (catalysis, medicine, materials science, and nanotechnology). The combination of their bifunctional activity as H/e reservoirs with the unique features of 4f ions (luminescence, magnetism, Lewis acid catalysis) is of particular interest and could afford species with enhanced properties owing to synergistic effects. Because of their oxophilicity and high coordination numbers, 4f ions display a powerful ability to link lacunary polytungstates (POTs) to build unprecedented architectures. The larger size of 4f ions compared to 3d metals prevents their full incorporation in lacunary frameworks as addendum atoms, and therefore additional sites are available for further derivatization. For monolacunary POTs, this mainly results in Peacock–Weakley sandwich POTs or in dimers and extended arrangements of 1:1 monomers. The use of diand trilacunary building blocks has led to a dramatic increase in the number and size of 4f-containing POTs in recent years. In addition to several medium to large assemblies, this approach has also resulted in a few giant species with more than 100 W atoms, which are amongst the largest POTs known. These are [As12Ce16W148O524(H2O)36] 76 , which has remained the largest POT since 1997; [Gd8As12W124O432(H2O)36] 60 , recently reported as the longest and second-largest POT; and [Ce20Ge10W100O376(OH)4(H2O)30] 56 , which contains the largest number of 4f ions besides being the fourth-largest POT. However, these assemblies are still small compared to Moblue POMs, for which a cluster as large as Mo368 is known. [5] Therefore, the search for giant POTs comparable to Mo blues is an attractive challenge, and supramolecular chemistry of 4f ions and lacunary fragments appears to be a suitable strategy that could allow rational design of tailored assemblies. Here we report [K K7Ce24Ge12W120O456(OH)12(H2O)64] (1) as the largest tungstogermanate and third-largest POT to date. Besides containing the largest number of 4f ions in a POM, 1 can be considered as the first giant POTwith a crown shape, that is, with a ring structure displaying a central cavity available for ion encapsulation in an inorganic analogue of the crown ethers, and thus a new type of topology is added to this still limited family of POMs. Recently, we reported the first 3d–4f heterometallic POM derived from the Weakley-type structure. With the aim of systematically incorporating 4f ions into this sandwich structure, we replaced half of the 3d precursor by a source of 4f ions in the direct synthesis of Weakley tungstogermanates. Instead of the expected 3d–4f POT, 1 was obtained as Na40K6[Ni(H2O)6]3[1]·nH2O (Ni-1, n 178) in moderate yield from this simple one-pot procedure. Polyanion 1 (Figure 1 a) can be viewed as the product of the K-directed self-assembly of twelve [Ce2GeW10O38] 6 subunits ({Ce2GeW10}) formed in situ, each of which is composed of a dilacunary Keggin fragment stabilized by coordination of two Ce ions on the vacant sites through four Ce O bonds (Figure 1b). As many as three distinct types of {GeW10} skeletons are observed: the enantiomeric forms b(1,8) and b(1,5) and the g(3,4) fragment, and all of them are of the anti-Lipscomb type. The vacant sites in the b forms are located at the W3O15 group and the central belt, whereas the Cs-symmetric g(3,4) form is obtained by removal of one WO6 octahedron from each rotated W3O13 triad (Figure S1, Supporting Information). Among the reported {bXW10}-containing POTs, [4c,10] only one b form displays vacancies at the belt and a W3O15 group to the best of our knowledge, namely, b(1,9). On the other hand, a single gdilacunary species was known to date: the C2v-symmetric g(1,2) form with vacancies at the two edge-sharing octahedra of the rotated triads. Therefore, all three {GeW10} fragments in 1 are completely unprecedented and they represent additional, interesting building blocks in POM chemistry. The fact that {Ce20W100}, composed of {b(4,11)-Ce2GeW10} subunits, is obtained from the [A-a-GeW9O34] 10 precursor at a similar pH suggests that a diversity of {GeW10} isomers may be formed under moderately acidic conditions regardless of the tungstogermanate source. Most likely, they are rapidly interexchangeable, highly reactive intermediates in the formation of the predominant {GeW11} species. In both cases, they could be stabilized by Ce coordination, which allowed [*] Dr. S. Reinoso, M. Gim nez-Marqu s Instituto de Ciencia Molecular (ICMol) Universidad de Valencia Catedr tico J. Beltr n 2, 46980 Paterna, Valencia (Spain) E-mail: santiago.reinoso@uv.es

Synthesis, chemical characterization, X-ray crystal structure and magnetic properties of oxalato-bridged copper(II) binuclear complexes with 2,2′-bipyridine and diethylenetriamine as peripheral ligands

Abstract Two new μ-oxalato binuclear copper(II) complexes, [{Cu(NO3)(H2O)(bipy)}2(ox)] (1) and [{Cu(dien)}2(ox)](NO3)2 (2), with ox=oxalate, dien=diethylenetriamine and bipy=2,2′-bipyridine, have been synthesized and their crystal and molecular structures have been determined by single-crystal X-ray diffraction methods. The crystal structure of 1 consists of centrosymmetric neutral dimers where the copper atoms lie in a strongly elongated octahedral environment, surrounded by two nitrogen atoms of a bipy molecule and two oxygen atoms of the bridging oxalato group in the equatorial plane and oxygen atoms of water molecules and nitrate ions in the axial positions. Crystal structure of 2 is made up of non-coordinated nitrate anions and asymmetric binuclear cations in which copper atoms are in a distorted square–pyramidal coordination with three atoms of a diethylenetriamine ligand and an oxygen atom of the asymmetrically coordinated oxalato bridge building the basal plane and the other oxygen atom of the oxalato ligand filling the apical position. Both compounds have been also characterized by Fourier transform infrared (FT-IR) and electron spin resonance (ESR) spectroscopies, thermal analysis and variable temperature magnetic susceptibility measurements. The two compounds exhibit antiferromagnetic exchange with a singlet–triplet separation of −382 and −6.5 cm−1 for 1 and 2, respectively. Magnetic and ESR results are discussed with respect to the crystal structure of the compounds.

Synthesis, vibrational study, crystal structure and density functional calculations of [Ni(dien)2]2+ complexes. Configurational and conformational study of [M(dien)2]n+ complexes

Abstract Two new complexes containing the complex cation [Ni(dien)2]2+ (dien=diethylenetriamine) have been synthesised [Ni(dien)2]CA·2H2O (CA=chloranilate) (1) and [Ni(dien)2][Ni(CN)4]·2H2O (2). The structures of compounds have been determined by single crystal X-ray diffraction methods. In the cationic unit of compound 1, the ligand geometry around nickel(II) is nearly octahedral. Two chelating tridentate diethylenetriamine molecules with terminal amino groups in cis and secondary amino groups in trans position define the s-fac geometry. The conformations of the two independent chelate rings are enantiomeric with each other. The nickel atom of [Ni(dien)2]2+ unit in compound 2 also shows a distorted octahedral environment, but the two tridentate dien molecules are coordinated meridionally. Crystallographic observations of fused five-membered ring of bis(dien) complexes, retrieved from Cambridge Structural Database, have been mapped and classified using principal component analysis. Several density functional calculations of the geometry of the s-fac and mer isomers of the complex cation [Ni(dien)2]2+ have been carried out, and the results have been compared to the crystallographic data.

Binuclear Ni(II) complexes based on bridging oxalate and tetracyanometallates.: Synthesis, crystal structure and magnetic properties

The trimeric complexes, [{Ni(dien)}2(m-ox){(m-Pd(CN)4)}] (2) and [{Ni(dien)}2(m-ox){(m-Pt(CN)4)}] (3) were synthesised by the reaction of [{Ni(dien)(H2O)}2(m-ox)](PF6)2/2H2O (dien � /dietylenetriamine and ox� /oxalate) with K2Pd(CN)4 and K2Pt(CN)4, respectively. In this reaction, water substitution and molecular reconstruction reactions take place to afford trimer complexes. These compounds are isostructural with the molecular compound [{Ni(dien)}2(m-ox){(m-Ni(CN)4)}] (1). In each complex, the two octahedrally coordinated Ni atoms are oxalate bridged and the sphere of coordination of each Ni is completed by three nitrogen atoms from a diethylenetriamine ligand in fac arrangement and one nitrogen atom from a bridging cyanide ligand, which belongs to the corresponding square-planar complex [M(CN)4] 2� . The three compounds present antiferromagnetic behaviour. The magnetic coupling between the two nickel atoms might occur through both bridges, but the length of the exchange pathway through the bidentate tetracyanometallate ligands is large enough to predict that the magnetic interaction may take place mainly through the

tert-Butylammonium silicododecamolybdate. Synthesus, vibrational study, crystal structure, thermal behaviour and electrochemical properties

Abstract The compound [(CH3)3CNH3]4[SiMo12O40]·2H2O has been synthesized and characterized chemically by means of FT-IR and Raman spectroscopy, microanalyses and thermal analyses. The X-ray diffraction crystal analysis reveals the presence of the Keggin cluster, t-butylammonium cations and water molecules joined by means of electrostatic interactions and hydrogen contacts. On the other hand, an electrochemical study using cyclic voltammetry was carried out, showing reversible cathodic redox processes.

Organic–inorganic hybrids based on four-electron reduced Keggin β-isomer phosphododecamolybdates and diazines

Six salts of diazonium cations (C4H5N2+) with the four-electron reduced β-Keggin phosphododecamolybdate, (1,2-C4H5N2)3[H4PMo12O40]·9H2O (1), (1,3-C4H5N2)2[H5PMo12O40]·(1,3-C4H4N2)·10H2O (2), (1,4-C4H5N2)3[H4PMo12O40]·5H2O (3), (1,2-C4H5N2)3[H4PMo12O40]·2H2O (4), (1,3-C4H5N2)3[H4PMo12O40]·2H2O (5), and (1,4-C4H5N2)2[H5PMo12O40]·½(1,4-C4H4N2)·5H2O (6), have been synthesised in aqueous solution. Compounds 1–3 were obtained photochemically using methanol as electron donor, and compounds 4–6 were prepared using thiophosphate as reducing agent. These compounds contain the four-electron reduced β-Keggin polyanion with a variable degree of protonation. The crystal packing in compound 1 consists of chains formed by pairs of polyanions hydrogen bonded along the [010] direction. The diazonium cations are connected, via NX1–HX1⋯Ow hydrogen bonds, to a ten-membered ring of hydrogen bonded water molecules. The crystal packing in compound 6 is formed by antiparallel chains of polyanions connected through the hydrogen bond OHpoly⋯Opoly along the [010] direction. These polyanion chains are embedded in a 3D-channel structure formed by a helicoidal arrangement of the diazine species hydrogen bonded via the water molecules. The dimensions of these tunnels are approximately 14 × 13.5 A. Ab initio RHF calculations have been performed on idealised α- and β-Keggin isomers in order to get information about stability and protonation sites and interactions between the organic rings and the surface of the Keggin anions.

Aqua-(dicyanamido-κN)(nitrato-κO,O')(2,3,5,6-tetra-2-pyridylpyrazine-κN,N,N)manganese(II).

In the title compound, [Mn(C2N3)(NO3)(C24H16N6)(H2O)], the central manganese(II) ion is heptacoordinated to a tridentate 2,3,5,6-tetra-2-pyridylpyrazine ligand (tppz), a bidentate nitrate ligand, a terminal monodentate dicyanamide ligand (dca) and a water molecule. The structure contains isolated neutral complexes, which are linked by O(water)—H⋯N hydrogen bonds generating chains along [010].

Tetra-kis(μ(2)-ferrocene-carboxyl-ato-κO:O')bis-[(methanol-κO)copper(II)] methanol disolvate.

The complex molecule of the title compound, [Cu2Fe4(C5H5)4(C6H4O2)4(CH3OH)2]·2CH3OH, lies about an inversion centre and contains two centrosymetrically related CuII atoms bridged by four O:O′-bidentante ferrocenecarboxylate anions, leading to a dimeric tetrabridged unit with a paddle-wheel geometry. The CuII atom has a distorted square-pyramidal coordination environment with four O atoms from four ferrocenecarboxylate ligands in basal positions and an O atom from a methanol molecule in an apical position. One of the two crystallographically independent ferrocenyl groups has a staggered conformation, while the other is eclipsed. The molecules are connected into a chain along the b axis by O—H⋯O hydrogen bonds involving coordinated and uncoordinated methanol molecules and the O atom from a ferrocenecarboxylate unit.

(μ-Oxalato-O1,O2:O1′,O2′)bis[aqua(diethyl­enetri­amine)nickel(II)] bis(hexafluorophosphate) dihydrate

The title compound, [Ni(2)(C(2)O(4))(C(4)H(13)N(3))(2)(H(2)O)(2)](PF(6))(2).2H(2)O, contains a dinuclear oxalato-bridged nickel(II) complex cation. The structure determination reveals the presence of a centrosymmetric binuclear complex where the oxalate ligand is coordinated in a bis-bidentate mode to the Ni atoms. The distorted octahedral environment of each Ni atom is completed by the three N atoms of the diethylenetriamine ligand in a fac arrangement and by one O atom from a water molecule. PF(6)(-) acts as counter-anion. A two-dimensional network of hydrogen bonds links the cations and anions and stabilizes the structure.

Structure of the β-cyclodextrin: acetamiprid insecticide inclusion complex in solution and solid state

The molecular microencapsulation process, through the formation of the inclusion complex with β-cyclodextrin (β-CD), shows numerous environmental and industrial cost advantages, such as, stability improvement of the active substance, synthesis of water-based products, option of commercializing the final product either in solid state or in solution and avoidance of the undesired side-effects derived from the use of insecticides. Furthermore, the inclusion complexes have other advantages that involve controlled and specific release of active component in the medium. In this work the synthesis of the inclusion complex formed by β-CD and the acetamiprid (ACET) nicotinoid insecticide ((E)-N1-[(6-chloro-3-pyridyl)methyl]-N2-cyano-N1-methyl-acetamidine) was done and their molecular structure was studied in solid state and in solution, by means of experimental techniques. The 2:2 stoichiometry found in solid state, a structure based on dimmers classified as a channel type, is similar to that found in solution (1:1 stoichiometry). In both cases, the nitrile and chloropyridine groups of the insecticide molecules are oriented toward primary rim and secondary rim of the β-CD molecule, respectively.