The Ce-Ni-Si System Revisited: More Homologue Compounds?

The nickel-rich region of the system Ce-Ni-Si has been reinvestigated utilizing X-ray single-crystal, powder, and electron diffraction as well as electron microprobe and thermal analyses. Two novel hexagonal compounds, τ-Ce20+xNi36+ySi30-z and τ'-Ce30+xNi50+ySi42-z, were identified. The crystal structure of τ-Ce20+xNi36+ySi30-z was derived from single-crystal X-ray diffraction and found to be isotypic with the Sm10Ni20.8P15-type structure (S.G. P63/m, x = 1.8, y = 3.0, z = 1.8, a = 2.07156(2) nm, c = 0.39990(1) nm, RF = 0.048). Rietveld refinement of τ'-Ce30+xNi50+ySi42-z revealed isotypism with Tb15Ni28P21 (S.G. P63/m, a = 2.46926(13) nm, c = 0.40019(3) nm, RF = 0.058). The compound Ce3Ni4Si2 from X-ray single-crystal analysis was found to crystallize in a novel structure type with monoclinic unit cells (S.G. C2/c, a = 1.54708(3) nm, b = 0.58677(1) nm, c = 0.74331(1) nm, ß = 102.985(1)°, RF = 0.017). This compound belongs to a new homologue series in the RE-Ni-Si system (RE = La and Ce) with general formula of RE(3×2n)Ni(3×2n + 1)Si(2n+1); n = 0,1, ..., ∞. The crystal structure of this series is characterized by alternating numbers (2n) of corner-sharing Si-polyhedral blocks sandwiched between zigzag nickel chains. Higher-order members of this series are produced by the formation of more corner-sharing Si-polyhedral blocks due to removal of nickel chains.

Electronic and Structural Properties of MPtxB6-2x (M = Y, Yb): Structural Disorder in an Octahedral Boron Framework.

Two new ternary platinum borides, YPtxB6-2x and YbPtxB6-2x, were obtained by argon-arc melting of the elements followed by annealing at 780 °C (750 °C). The structures of these compounds combine the fragments of CaB6- and AuCu3-type structures [space group Pm3̅m; x = 1.15, a = 4.0550(4) Å and x = 1.34, a = 4.0449(2) Å for YPtxB6-2x and YbPtxB6-2x, respectively; single-crystal X-ray diffraction]. Two possible variants of B/Pt ordering (space group P4/mmm) were created via a group-subgroup approach targeting the derived stoichiometry. The architecture of the type-I YPtxB6-2x structure model (a' = a, b' = b, c' = c) combines the 4.82 boron nets alternating with the layers of Y and Pt; the type-II YPtxB6-2x structure model (a' = 2a, b' = 2b, c' = c) exhibits columns of linked [B24] truncated cubes filled with Y running along the c axis. The striking features of both structural models are [B4Pt2] octahedra. The structural similarities with hitherto reported structures (YB2C2, M2Ni21B20, MNi21B20, and ErNiB4) were drawn supporting the verity of these models. A chemical bonding analysis for type-I and type-II YPtxB6-2x based on electron localization function distribution revealed a two-center interaction forming the 4.82 boron nets for type-I YPtxB6-2x and a covalent bonding within [B4Pt2] octahedra as well as a two-center interaction for B-B intraoctahedral bonds for type-II YPtxB6-2x. Analysis of Bader charges revealed the cationic character of the yttrium atoms. The interactions for nondistorted areas of the structures agree well with the bonding picture calculated for constituent building structures, YB6 and YPt3. Electronic structure calculations predict YPtxB6-2x to be a metal with the density of states of around N(EF) = 1 states eV-1 f.u.-1. The exploration of the Y-Pt-B system in the relevant concentration range elucidated the homogeneity field of YPtxB6-2x (0.90 ≤ x ≤ 1.40) and revealed the existence of three more ternary phases at 780 °C: YPt2B (space group P6222), YPt3B (space group P4mm), and YPt5B2 (space group C2/m).

Synthesis, Characterization, and Antibacterial Activity of Ni-Substituted Krebs-type Sandwich-Tungstobismuthates Functionalized with Amino Acids.

Four new Ni-substituted Krebs-type sandwich-tungstobismuthates, K4Ni2[{Ni(ß-ala)(H2O)2}2{Ni(H2O)}2{Ni(H2O)(η2-ß-ala)}2(B-ß-BiW9O33)2]·49H2O {(ß-ala)4(Ni3)2(BiW9)2}, K3.5Na6.5[{Ni(η3-L-asp)}2(WO2)2(B-ß-BiW9O33)2]·36H2O·L-asp {(L-asp)2(NiW)2(BiW9)2}, K4Na6[{Ni(gly)(H2O)2}2(WO2)2(B-ß-BiW9O33)2]·86H2O {(gly)2(NiW)2(BiW9)2}, and K2Na8[{Ni(η2-serinol) (H2O)}2{Ni(H2O)2}2(B-ß-BiW9O33)2]·42H2O {(serinol)2Ni4(BiW9)2} have been synthesized by one-pot solution methods. All compounds have been characterized in the solid state by single-crystal X-ray diffraction (SXRD), powder X-ray diffraction (PXRD), elemental and thermogravimetric analyses, and infrared spectroscopy (IR), as well as by UV-vis spectroscopy in solution. The antibacterial activity of all compounds was studied against four bacterial strains by the determination of the minimum inhibitory concentration (MIC). The results showed that only {(ß-ala)4(Ni3)2(BiW9)2} demonstrates antibacterial activity (MIC is in the range from 8 to 256 µg/mL) compared to three other Ni-Krebs sandwiches.

Synthesis and characterization of the `Japanese rice-ball'-shaped Molybdenum Blue Na4[Mo2O2(OH)4(C6H4NO2)2]2[Mo120Ce6O366H12(OH)2(H2O)76]∼200H2O.

The hybridized lanthanide-containing molybdenum blue (Ln-MB) wheel Na4[Mo2O2(OH)4(C6H4NO2)2]2[Mo120Ce6O366H12(OH)2(H2O)76]∼200H2O ({Mo2(C6H4NO2)2}2{Mo120Ce6}) was assembled in an aqueous one-pot synthesis. The Ln-MB was hybridized with 2-picolinic acid through the generation of the organometallic counter-ion [Mo2O2(OH)4(C6H4NO2)2]2+. Control experiments demonstrated that the position of the carboxylic acid group (2-position to the N atom) in the hybridization component is critical in yielding single crystals of Ln-MB. In addition to single-crystal X-ray diffraction (XRD) analysis, which revealed a `Japanese rice-ball'-shaped Ln-MB as the anion, elemental analyses, IR spectroscopy, and thermogravimetric analysis (TGA) were performed to confirm its structure and composition. Bond-valence-sum calculations (BVS) revealed that {Mo2(C6H4NO2)2}2{Mo120Ce6} is composed of a 24-electron reduced anionic ring, which was confirmed by Vis-NIR spectroscopy.

Thermoacidophilic Bioleaching of Industrial Metallic Steel Waste Product.

The continuous deposition of hazardous metalliferous wastes derived from industrial steelmaking processes will lead to space shortages while valuable raw metals are being depleted. Currently, these landfilled waste products pose a rich resource for microbial thermoacidophilic bioleaching processes. Six thermoacidophilic archaea (Sulfolobus metallicus, Sulfolobus acidocaldarius, Metallosphaera hakonensis, Metallosphaera sedula, Acidianus brierleyi, and Acidianus manzaensis) were cultivated on metal waste product derived from a steelmaking process to assess microbial proliferation and bioleaching potential. While all six strains were capable of growth and bioleaching of different elements, A. manzaensis outperformed other strains and its bioleaching potential was further studied in detail. The ability of A. manzaensis cells to break down and solubilize the mineral matrix of the metal waste product was observed via scanning and transmission electron microscopy. Refinement of bioleaching operation parameters shows that changes in pH influence the solubilization of certain elements, which might be considered for element-specific solubilization processes. Slight temperature shifts did not influence the release of metals from the metal waste product, but an increase in dust load in the bioreactors leads to increased element solubilization. The formation of gypsum crystals in course of A. manzaensis cultivation on dust was observed and clarified using single-crystal X-ray diffraction analysis. The results obtained from this study highlight the importance of thermoacidophilic archaea for future small-scale as well as large-scale bioleaching operations and metal recycling processes in regard to circular economies and waste management. A thorough understanding of the bioleaching performance of thermoacidophilic archaea facilitates further environmental biotechnological advancements.

Crystal structure of hexa-sodium tetra-serinolium paratungstate B deca-hydrate, [Na6{(CH2OH)2CHNH3}4][W12O40(OH)2]·10H2O.

The title polyoxometalate-based organic-inorganic hybrid compound, [Na6(C3H10NO2)4][W12O40(OH)2]·10H2O, consists of a di-µ 3-hydroxido-tetra-µ 3-oxido-octa-deca-µ-oxido-octa-deca-oxidododeca-tungstate (para-do-deca-tungstate B) anion, [W12O40(OH)2]10-, and six sodium cations coordinated by the oxygen ions of the polyanions, serinol ligands protonated at the N atom, and water mol-ecules. The centrosymmetric paratungstate B anion shows characteristic features in terms of bond lengths and angles. The three-dimensional framework structure is established by bonding of the sodium cations with oxygen ions of the paratungstate B anions and a network consisting of N-H⋯O and O-H⋯O hydrogen bonds of medium strength between the protonated serinol cations, water mol-ecules and the paratungstate B anions. The title compound was also characterized by means of elemental analysis, IR spectroscopy and thermogravimetric analysis.

Speciation of Transition-Metal-Substituted Keggin-Type Silicotungstates Affected by the Co-crystallization Conditions with Proteinase K.

We report on the synthesis of the tetrasubstituted sandwich-type Keggin silicotungstates as the pure Na salts Na14[(A-α-SiW10O37)2{Co4(OH)2(H2O)2}]·37H2O (Na{SiW10Co2}2) and Na14[(A-α-SiW10O37)2{Ni4(OH)2(H2O)2}]·77.5H2O (Na{SiW10Ni2}2), which were prepared by applying a new synthesis protocol and characterized thoroughly in the solid state by single-crystal and powder X-ray diffraction, IR spectroscopy, thermogravimetric analysis, and elemental analysis. Proteinase K was applied as a model protein and the polyoxotungstate (POT)-protein interactions of Na{SiW10Co2}2 and Na{SiW10Ni2}2 were studied side by side with the literature-known K5Na3[A-α-SiW9O34(OH)3{Co4(OAc)3}]·28.5H2O ({SiW9Co4}) featuring the same number of transition metals. Testing the solution behavior of applied POTs under the crystallization conditions (sodium acetate buffer, pH 5.5) by time-dependent UV/vis spectroscopy and electrospray ionization mass spectrometry speciation studies revealed an initial dissociation of the sandwich POTs to the disubstituted Keggin anions HxNa5-x[SiW10Co2O38]3- and HxNa5-x[SiW10Ni2O38]3- ({SiW10M2}, M = CoII and NiII) followed by partial rearrangement to the monosubstituted compounds (α-{SiW11Co} and α-{SiW11Ni}) after 1 week of aging. The protein crystal structure analysis revealed monosubstituted α-Keggin POTs in two conserved binding positions for all three investigated compounds, with one of these positions featuring a covalent attachment of the POT anion to an aspartate carboxylate. Despite the presence of both mono- and disubstituted anions in a crystallization mixture, proteinase K selectively binds to monosubstituted anions because of their preferred charge density for POT-protein interaction.

Synthesis and characterization of the Anderson-Evans tungstoantimonate [Na5(H2O)18{(HOCH2)2CHNH3}2][SbW6O24].

A novel tungstoantimonate, [Na5(H2O)18{(HOCH2)2CHNH3}2][SbVWVI6O24] (SbW6), was synthesized from an aqueous solution and structurally characterized by single-crystal X-ray diffraction, which revealed C2/c symmetry. The structure contains two serinol [(HOCH2)2CHNH3]+ and five Na+ cations, which are octahedrally surrounded by 18 water molecules, and one [SbVWVI6O24]7- anion. The serinol molecules also play a critical role in the synthesis by acting as a mild buffering agent. Each of the WVI and SbV ions is six-coordinated and displays a distorted octahedral motif. A three-dimensional supramolecular framework is formed via hydrogen-bonding interactions between the tungstoantimonates and cations. Powder X-ray diffraction, elemental analysis, thermogravimetric analysis and IR spectroscopy were performed on SbW6 to prove the purity, to identify the water content and to characterize the vibrational modes of the crystallized phase.

Phosphate-Templated Encapsulation of a {CoII 4 O4 } Cubane in Germanotungstates as Carbon-Free Homogeneous Water Oxidation Photocatalysts.

The ever-growing interest in sustainable energy sources leads to a search for an efficient, stable, and inexpensive homogeneous water oxidation catalyst (WOC). Herein, the PO4 3- templated synthesis of three abundant-metal-based germanotungstate (GT) clusters Na15 [Ge4 PCo4 (H2 O)2 W24 O94 ] ⋅ 38H2 O (Co4 ), Na2.5 K17.5 [Ge3 PCo9 (OH)5 (H2 O)4 W30 O115 ] ⋅ 45H2 O (Co9 ), Na6 K16 [Ge4 P4 Co20 (OH)14 (H2 O)18 W36 O150 ] ⋅ 61H2 O (Co20 ) with non-, quasi-, or full cubane motifs structurally strongly reminiscent of the naturally occurring {Mn4 Ca} oxygen evolving complex (OEC) in photosystem II was achieved. Under the conditions tested, all three GT-scaffolds were active molecular WOCs, with Co9 and Co20 outperforming the well-known Na10 [Co4 (H2 O)2 (PW9 O34 )2 ] {Co4 P2 W18 } by a factor of 2 as shown by a direct comparison of their turnover numbers (TONs). With TONs up to 159.9 and a turnover frequency of 0.608 s-1 Co9 currently represents the fastest Co-GT-based WOC, and photoluminescence emission spectroscopy provided insights into its photocatalytic WOC mechanism. Cyclic voltammetry, dynamic light scattering, UV/Vis and IR spectroscopy showed recyclability and integrity of the catalysts under the applied conditions. The experimental results were supported by computational studies, which highlighted that the facilitated oxidation of Co9 was due to the higher energy of its highest occupied molecular orbital electrons as compared to Co4 .

Bifunctional Fe(II) spin crossover-complexes based on ω-(1H-tetrazol-1-yl) carboxylic acids.

To increase the supramolecular cooperativity in Fe(ii) spin crossover materials based on N1-substituted tetrazoles, a series of ω-(1H-tetrazol-1-yl) carboxylic acids with chain-lengths of C2-C4 were synthesized. Structural characterization confirmed the formation of a strong hydrogen-bond network, responsible for enhanced cooperativity in the materials and thus largely complete spin-state transitions for the ligands with chain lenghts of C2 and C4. To complement the structural and magnetic investigation, electronic spectroscopy was used to investigate the spin-state transition. An initial attempt to utilize the bifunctional coordination ability of the ω-(1H-tetrazol-1-yl) carboxylic acids for preparation of mixed-metallic 3d-4f coordination polymers resulted in a novel one-dimensional gadolinium-oxo chain system with the ω-(1H-tetrazol-1-yl) carboxylic acid acting as µ2-η2:η1 chelating-bridging ligand.

Triapine Derivatives Act as Copper Delivery Vehicles to Induce Deadly Metal Overload in Cancer Cells.

Thiosemicarbazones continue to attract the interest of researchers as potential anticancer drugs. For example, 3-aminopyridine-2-carboxaldehyde thiosemicarbazone, or triapine, is the most well-known representative of this class of compounds that has entered multiple phase I and II clinical trials. Two new triapine derivatives HL1 and HL2 were prepared by condensation reactions of 2-pyridinamidrazone and S-methylisothiosemicarbazidium chloride with 3-N-(tert-butyloxycarbonyl) amino-pyridine-2-carboxaldehyde, followed by a Boc-deprotection procedure. Subsequent reaction of HL1 and HL2 with CuCl2·2H2O in 1:1 molar ratio in methanol produced the complexes [CuII(HL1)Cl2]·H2O (1·H2O) and [CuII(HL2)Cl2] (2). The reaction of HL2 with Fe(NO3)3∙9H2O in 2:1 molar ratio in the presence of triethylamine afforded the complex [FeIII(L2)2]NO3∙0.75H2O (3∙0.75H2O), in which the isothiosemicarbazone acts as a tridentate monoanionic ligand. The crystal structures of HL1, HL2 and metal complexes 1 and 2 were determined by single crystal X-ray diffraction. The UV-Vis and EPR spectroelectrochemical measurements revealed that complexes 1 and 2 underwent irreversible reduction of Cu(II) with subsequent ligand release, while 3 showed an almost reversible electrochemical reduction in dimethyl sulfoxide (DMSO). Aqueous solution behaviour of HL1 and 1, as well as of HL2 and its complex 2, was monitored as well. Complexes 1-3 were tested against ovarian carcinoma cells, as well as noncancerous embryonic kidney cells, in comparison to respective free ligands, triapine and cisplatin. While the free ligands HL1 and HL2 were devoid of antiproliferative activity, their respective metal complexes showed remarkable antiproliferative activity in a micromolar concentration range. The activity was not related to the inhibition of ribonucleotide reductase (RNR) R2 protein, but rather to cancer cell homeostasis disturbance-leading to the disruption of cancer cell signalling.

Cation-Directed Synthetic Strategy Using 4f Tungstoantimonates as Nonlacunary Precursors for the Generation of 3d-4f Clusters.

The first synthetic pathway using a series of four nonlacunary 4f-heterometal-substituted polyoxotungstate clusters Na21[(Ln(H2O)(OH)2(CH3COO))3(WO4)(SbW9O33)3]·nH2O (NaLnSbW9; Ln = TbIII, DyIII, HoIII, ErIII, YIII) as precursors for the directed preparation of nine new 3d-4f heterometallic tungstoantimonates K5Na12H3[TM(H2O)Ln3(H2O)5(W3O11)(SbW9O33)3]·nH2O (KTMLnSbW9; TM = CoII, NiII; Ln = TbIII, DyIII, HoIII, ErIII, YIII) has been developed. Systematic studies revealed an increased K content in the aqueous acidic reaction mixture to be the key step in the cation-directed preparation of 3d-4f compounds; among those, the Co-containing members represent the first examples of KCoLnSbW9 (Ln = TbIII, DyIII, HoIII, ErIII, YIII) heterometallic tungstoantimonates exhibiting the SbW9 building block. All 13 compounds have been characterized thoroughly in the solid state by powder and single-crystal X-ray diffraction (XRD), revealing a cyclic trimeric polyoxometalate architecture with three SbW9 units encapsulating a planar triangle of LnIII ions in the case of NaLnSbW9 and a heterometallic core of one TMII and three LnIII for KTMLnSbW9 (TM = CoII, NiII; Ln = TbIII, DyIII, HoIII, ErIII, YIII). The results obtained by XRD are supplemented by complementary characterization methods in the solid state such as IR spectroscopy, thermogravimetric analysis, and elemental analysis as well as in solution by UV-vis spectroscopy. Detailed magnetic studies on the representative compounds KTMDySbW9 (TM = CoII, NiII) and KCoYSbW9 of the series revealed field-induced slow magnetic relaxation.

Incorporation of CrIII into a Keggin Polyoxometalate as a Chemical Strategy to Stabilize a Labile {CrIIIO4} Tetrahedral Conformation and Promote Unattended Single-Ion Magnet Properties.

Polyoxometalates (POMs) provide rigid and highly symmetric coordination sites and can be used as a strategy for the stabilization of magnetic ions. Herein, we report a new member of the Keggin archetype, the Cr-centered Keggin anion [α-CrW12O40]5- (CrW12), with the unusual tetrahedral coordination of CrIII reported for the first time in POMs conferring unattended magnetic properties. POM chemistry has recently presented excellent examples of single-molecule and single-ion magnets (SMMs and SIMs) as well as molecular spin qubits; however, the majority of POM-based SIMs reported to date contain lanthanoid ions. CrW12, as the first example of a chromium(III) SIM, exhibits slow relaxation of magnetization and quantum tunneling with a single-ion magnetic behavior even above 10 K with an energy barrier for the reversal of the magnetization of 3.0 K. The first 3d-metal SIM based on a nonlacunary Keggin anion is the foundation for a new research area in POM chemistry.

Synthesis, characterization, and POM-protein interactions of a Fe-substituted Krebs-type Sandwich-tungstoantimonate.

ABSTRACT: The novel iron-substituted Krebs-type polyoxotungstate (C12N4H11)4Na2H5[(Fe(H2O)3)2((FeO2)0.5(WO2)0.5)2(ß-SbW9O33)2] (Fe-1) has been synthesized using ortho-phenylenediamine (opda) as a precursor for the in situ formation of the counter cation 2,3-diaminophenazinium (C12N4H11)+ (2,3-DAP). Fe-1 has been thoroughly characterized in the solid state by single-crystal X-ray diffraction (SXRD), powder X-ray diffraction (PXRD), IR spectroscopy, and elemental analysis as well as in solution by UV-Vis spectroscopy. The crystal structure of Fe-1 reveals π-π-interactions between the aromatic systems of the unconventional 2,3-DAP counter cation. POM-protein interaction studies using SDS-PAGE revealed a non-proteolytic behavior of Fe-1 towards Human Serum Albumin (HSA) as a model protein.

Inhibition of Na+/K+- and Ca2+-ATPase activities by phosphotetradecavanadate.

Polyoxometalates (POMs) are promising inorganic inhibitors for P-type ATPases. The experimental models used to study the effects of POMs on these ATPases are usually in vitro models using vesicles from several membrane sources. Very recently, some polyoxotungstates, such as the Dawson anion [P2W18O62]6-, were shown to be potent P-type ATPase inhibitors; being active in vitro as well as in ex-vivo. In the present study we broaden the spectrum of highly active inhibitors of Na+/K+-ATPase from basal membrane of epithelial skin to the bi-capped Keggin-type anion phosphotetradecavanadate Cs5.6H3.4PV14O42 (PV14) and we confront the data with activity of other commonly encountered polyoxovanadates, decavanadate (V10) and monovanadate (V1). The X-ray crystal structure of PV14 was solved and contains two trans-bicapped α-Keggin anions HxPV14O42(9-x)-. The anion is built up from the classical Keggin structure [(PO4)@(V12O36)] capped by two [VO] units. PV14 (10 µM) exhibited higher ex-vivo inhibitory effect on Na+/K+-ATPase (78%) than was observed at the same concentrations of V10 (66%) or V1 (33%). Moreover, PV14 is also a potent in vitro inhibitor of the Ca2+-ATPase activity (IC50 5 µM) exhibiting stronger inhibition than the previously reported activities for V10 (15 µM) and V1 (80 µM). Putting it all together, when compared both P-typye ATPases it is suggested that PV14 exibited a high potential to act as an in vivo inhibitor of the Na+/K+-ATPase associated with chloride secretion.

First crystal structures of metal complexes with a 4-nitropyrazole-3-carboxylic acid ligand and the third crystal form of the ligand.

Pyrazole (pz)-derived ligands can, besides exhibiting a strong coordination ability toward different metal ions, exhibit a great diversity in their coordination geometry and nuclearity, which can be achieved by varying the type and position of the pz substituents. The present study reports the synthesis and crystal structure of two binuclear complexes, namely bis(µ-4-nitro-1H-imidazol-1-ide-5-carboxylato)-κ3N1,O:N2;κ3N2:N1,O-bis[aqua(dimethylformamide-κO)copper(II)], [Cu2(C4HN3O4)2(C3H7NO)2(H2O)2], (II), and bis(µ-4-nitro-1H-imidazol-1-ide-5-carboxylato)-κ2N1,O:N2;κ2N2:N1,O-bis[triaquacobalt(II)] dihydrate, [Co2(C4HN3O4)2(H2O)6]·2H2O, (III). These compounds represent rare examples of metal complexes comprising 3,4-substituted pz derivatives as a bridging ligand and also the first crystal structures of transition-metal complexes with ligands derived from 4-nitropyrazole-3-carboxylic acid. Recently, the crystal structures of the same ligand in the neutral and mixed neutral/anionic forms have been reported. We present here the third form of this ligand, where it is present in a fully deprotonated anionic form within a salt, i.e. ammonium 4-nitropyrazole-3-carboxylate, NH4+·C4H2N3O4-, (I). Single-crystal X-ray diffraction revealed that in the present complexes, the CuII and CoII centres adopt distorted square-pyramidal and octahedral geometries, respectively. In both cases, the N,N',O-coordinated pz ligand shows simultaneously chelating and bridging coordination modes, leading to the formation of a nearly planar six-membered M2N4 metallocycle. In all three crystal structures, the supramolecular arrangement is controlled by strong hydrogen bonds which primarily engage the carboxylate O atoms as acceptors, while the nitro group adopts the role of an acceptor only in structures with an increased number of donors, as is the case with CoII complex (III). The electrostatic potential, as a descriptor of reactivity, was also calculated in order to examine the changes in ligand electrostatic preferences upon coordination to metal ions.

Direct Single- and Double-Side Triol-Functionalization of the Mixed Type Anderson Polyoxotungstate [Cr(OH)3W6O21]6.

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)3W6O21]6- leading to the single-side grafted anions [Cr(OCH2)3CRW6O21]6- (CrW6-tris-R, R = -C2H5, -NH2, -CH2OH) and the unprecedented double-side functionalized anion [Cr((OCH2)3CC2H5)2W6O18]3- (CrW6-(tris-C2H5)2), despite the lack of protons in the parent anion in the solid state. CrW6-(tris-C2H5)2 demonstrates the first example of double-side functionalized Anderson POT with the partially one-side protonated corresponding parent anion. The new heteropolytungstates were characterized by single-crystal X-ray diffraction, elemental analysis, Fourier-transform infrared spectroscopy, thermal gravimetric analysis, cyclic voltammetry, and electrospray ionization mass spectrometry. Density functional theory calculations were performed to investigate and compare the stability among the different isomers of the parent anion [Cr(OH)3W6O21]6-.

Synthesis and characterization of hybrid Anderson hexamolybdoaluminates(III) functionalized with indometacin or cinnamic acid.

The single-side Al-centred tris-functionalized hybrid organic-inorganic Anderson polyoxomolybdates (C16H36N)3[Al(OH)3Mo6O18(OCH2)3CNH(C10H8O)]·C9H7N·4CH3OH·5H2O (AlMo6-NH-Cin; Cin is cinnamic acid, C10H9O2) and (C16H36N)3[Al(OH)3Mo6O18(OCH2)3CNH(C19H15ClNO3)]·9H2O (AlMo6-NH-Indo; Indo is indometacin, C19H16ClNO4) have been prepared in a mild three-step synthesis and structurally characterized by single-crystal X-ray diffraction, 1H NMR and IR spectroscopies and elemental analysis. Both AlMo6-NH-Cin and AlMo6-NH-Indo crystallize in the orthorhombic space group Pbca. The antibacterial activities of AlMo6-NH-Cin and AlMo6-NH-Indo against the Gram-negative human mucosal pathogen Moraxella catarrhalis were investigated by determination of the minimum inhibitory concentration, which is 32 µg ml-1 for AlMo6-NH-Cin and 256 µg ml-1 for AlMo6-NH-Indo.

Synthesis of the first Zn6-hexagon sandwich-tungstoantimonate via rearrangement of a non-lacunary Krebs-type polyoxotungstate.

A novel synthetic pathway to obtain the first Zn6 hexagon tungstoantimonate [(Zn(H2O))6(B-α-SbW9O33)2]6- ([Zn6-α-SbW9] (1)) via rearrangement of a non-lacunary Krebs-POM precursor (C12N4H11)4K4[(Mn(H2O)3)2((Mn0.5W0.5)O2)2(B-ß-SbW9O33)2] ([Mn-ß-SbW9]) has been developed. Addition of ortho-phenylenediamine (opda) in order to optimize the synthesis of [Mn-ß-SbW9] led to the crystallization of a novel Krebs-type Zn-POM (C12N4H11)4Na5[((Zn0.8W0.2)(H2O)3)2((Zn0.2W0.8)O2)2(B-ß-SbW9O33)2] ([(Zn/W)2-ß-SbW9] (2)) comprising four disordered Zn-centers after replacement of MnCl2 with ZnCl2. The compounds were characterized in the solid state by single-crystal and powder X-ray diffraction (XRD), IR spectroscopy, thermogravimetric analysis (TGA) and elemental analysis and in solution by UV-vis spectroscopy and ESI-mass spectrometry. The Krebs-POM archetype and the Zn6 hexagon tungstoantimonate have been investigated towards their interactions with Human Serum Albumin (HSA) as a model protein using SDS-PAGE and trypthophan fluorescence quenching.

Structure and properties of a novel boride: ThNi12B6.

Investigation of the system Th-Ni-B prompted a novel ternary compound ThNi12B6. X-ray structure analysis of single crystals obtained by the mechanical fragmentation of an as-cast sample revealed a fully ordered CeNi12B6-type structure (space group Cmc21, no. 36; a = 0.95638(1) nm, b = 0.73852(1) nm, c = 1.10195(1) nm; RF2 = 0.0305). Density functional theory (DFT) calculations have been performed comprising heat of formation, electronic band structure and density of states, Fermi surface via Wannier functions, phonon band structure and density of states, phonon and electronic contributions to specific heat and elastic constants Cij. Comparing the parameters evaluated from DFT with the experimental data, an overall satisfactory agreement has been achieved. Measurements of electrical resistivity, magnetic susceptibility and specific heat manifest a Pauli paramagnetic, metallic behaviour for ThNi12B6 without any anomalies, in close match with the isotypic homologue LaNi12B6. Static and dynamic hardness data show rather high values; Young's modulus is in the range of 240 GPa. The Debye temperature, θD = 490 K, gained via elastic constants, is slightly higher than the values extracted from specific heat or electrical resistivity data. A rather low coefficient of thermal expansion, α = 5.5 × 10-6 K-1, was derived from the temperature dependent length change.