Inorganics, Volume 3, Issue 2 (June 2015) – 15 articles , Pages 55-308

The transformation of three types of polyoxovanadates, {(n-C₄H₉)₄N}₃[H₃V₁₀O₂₈], {(n-C₄H₉)₄N}₄[V₁₂O₃₂] and {(n-C₄H₉)₄N}₃[V₁₃O₃₄] have been investigated according to the rational chemical equations, and the best transformation conditions were reported. By the reaction of [H₃V₁₀O₂₈]³⁻ with 0.33 equivalents of {(n-C₄H₉)₄N}OH in acetonitrile at 80 °C, [V₁₂O₃₂]⁴⁻ was formed with 92% yield. The reaction in nitroethane with 0.69 equivalents of p-toluenesulfonic acid gave [V₁₃O₃₄]³⁻ with 91% yield. The ⁵¹V NMR observation of each reaction suggests the complete transformations of [H₃V₁₀O₂₈]³⁻ to [V₁₂O₃₂]⁴⁻ and to [V₁₃O₃₄]³⁻ proceeded without the formation of any byproducts and it provides the reliable synthetic route. Decavanadates were produced by the hydrolysis of [V₁₂O₃₂]⁴⁻ or [V₁₃O₃₄]³⁻. While the direct transformation of [V₁₃O₃₄]³⁻ to [V₁₂O₃₂]⁴⁻ partly proceeded, the reverse one could not be observed. For the thioanisole oxidation, [V₁₃O₃₄]³⁻ showed the highest activity of the three. Full article

Hybrid organic-inorganic polyoxometalates (POMs) were synthesized in water by the reaction of a Mo^VI precursor with bisphosphonate ligands functionalized by pyridine groups. The fully oxidized POM [(Mo^VI₃O₈)₂(O)(O₃PC(O)(C₃H₆NH₂CH₂C₅H₄NH)PO₃)₂]⁴⁻ has been isolated as water insoluble pure Na salt (NaMo₆(Ale-4Py)₂) or mixed Na/K salt (NaKMo₆(Ale-4Py)₂) and their structure solved using single-crystal X-ray diffraction. The mixed-valent complex [(Mo^V₂O₄)(Mo^VI₂O₆)₂{O₃PC(O)(C₃H₆N(CH₂C₅H₄N)₂(Mo^VIO₃))PO₃}₂]⁸⁻ was obtained as an ammonium salt (NH₄Mo₆(AlePy₂Mo)₂), in the presence of a reducing agent (hydrazine). ³¹P NMR spectroscopic studies in aqueous media have allowed determining the pH stability domain of NH₄Mo₆(AlePy₂Mo)₂. NaMo₆(Ale-4Py)₂ and NaKMo₆(Ale-4Py)₂ exhibit remarkable solid-state photochromic properties in ambient conditions. Under UV excitation, they develop a very fast color-change from white to deep purple and proved to be the fastest photochromic organoammonium/POM systems. The coloration kinetics has been fully quantified for both salts and is discussed in light of the hydrogen-bonding networks. Full article

The 8-yttrium(III)-containing 81-tungsto-8-arsenate(III) [Y₈(CH₃COO)(H₂O)₁₈(As₂W₁₉O₆₈)₄(W₂O₆)₂(WO₄)]⁴³⁻ (1) has been synthesized in a one-pot reaction of yttrium(III) ions with [B-α-AsW₉O₃₃]⁹⁻ in 1 M NaOAc/HOAc buffer at pH 4.8. Polyanion 1 is composed of four {As₂W₁₉O₆₈} units, two {W₂O₁₀} fragments, one {WO₆} group, and eight Y^III ions. The hydrated cesium-sodium salt of 1 (CsNa-1) was characterized in the solid-state by single-crystal XRD, FT-IR spectroscopy, thermogravimetric and elemental analyses. Full article

A series of eight new materials based on the ionic association between 1-methyl-3-alkylimidazolium cations and the nanometric anionic Keplerate [Mo₁₃₂O₃₇₂(CH₃COO)₃₀(H₂O)₇₂]⁴²⁻ has been prepared and characterized in the solid state. The liquid crystal properties of these materials were investigated by the combination of Polarized Optical Microscopy, Differential Scanning Calorimetry and Small-angle X-Ray Diffraction showing a self-organization in lamellar (L) mesophases for the major part of them. From the interlamellar spacing h and the intercluster distance a_hex, we demonstrated that the cations are not randomly organized around the anionic cluster and that the alkyl chains of the cations are certainly folded, which limits the van der Waals interactions between the cations within the liquid crystal phase and therefore harms the quality of the mesophases. Full article

The interaction between human serum albumin (HSA) and a series of Zr(IV)-substituted polyoxometalates (POMs) (Lindqvist type POM ((ⁿBu₄N)₆[{W₅O₁₈Zr (μ-OH)}₂]·2H₂O, Zr2-L2), two Keggin type POMs ((Et₂NH₂)₁₀[Zr(PW₁₁O₃₉)₂]·7H₂O, Zr1-K2 and (Et₂NH₂)₈[{α-PW₁₁O₃₉Zr(μ-OH)(H₂O)}₂]·7H₂O, Zr2-K2), and two Wells-Dawson type POMs (K₁₅H[Zr(α₂-P₂W₁₇O₆₁)₂]·25H₂O, Zr1-WD2 and Na₁₄[Zr₄(P₂W₁₆O₅₉)₂(μ₃-O)₂(OH)₂(H₂O)₄]·10H₂O, Zr4-WD2) was investigated by tryptophan (Trp) fluorescence spectroscopy. The fluorescence data were analyzed using the Tachiya model, ideally suited for multiple binding site analysis. The obtained quenching constants have the same order of magnitude for all the measured POM:protein complexes, ranging from 1.9 × 10⁵ M⁻¹ to 5.1 × 10⁵ M⁻¹. The number of bound POM molecules to HSA was in the range of 1.5 up to 3.5. The influence of the ionic strength was studied for the Zr1-WD2:HSA complex in the presence of NaClO₄. The calculated quenching constant decreases upon increasing the ionic strength of the solution from 0.0004 M to 0.5004 M, indicating the electrostatic nature of the interaction. The number of POM molecules bound to HSA increases from 1.0 to 4.8. ³¹P NMR spectroscopy provided evidence for the stability of all investigated POM structures during the interaction with HSA. Full article

Metal-substituted hemoproteins have been examined by biochemists for decades, but their potential for diverse functionalities has not been thoroughly investigated. By replacing hemoproteins with non-native metals, heme-containing proteins could be capable of performing a range of chemistries not allowed for in the native protein. The metal within the heme of the oxygen-carrying hemoprotein, myoglobin, can readily be replaced with other first row transition metals such as cobalt, chromium and manganese. Upon oxidation with two-electron oxidants (ex. meta-chloroperbenzoic acid), an oxidizing intermediate is produced in manganese-substituted myoglobin. Electron paramagnetic resonance analyses confirm the oxidation of Mn(III) to Mn(IV). With the addition of weak C-H bonds of 1,4 cyclohexadiene, hydrogen atom abstraction is exhibited by the oxidizing intermediate that displays a second-order rate constant of 2.79 +/− 0.22 M⁻¹ s⁻¹ by the metal-oxo species. The replacement of the iron ion with a manganese ion at the active site of myoglobin displays oxidative capabilities that are not shown in native myoglobin. Full article

Three new hybrid inorganic-metalorganic compounds containing Keggin-type polyoxometalates, neutral copper(II)-picolinate complexes and guanidinium cations have been synthesized in bench conditions and characterized by elemental analysis, infrared spectroscopy and single-crystal X-ray diffraction: the isostructural [C(NH₂)₃]₄[{XW₁₂O₄₀}{Cu₂(pic)₄}]·[Cu₂(pic)₄(H₂O)]₂·6H₂O [X = Si (1), Ge (3)] and [C(NH₂)₃]₈[{SiW₁₂O₄₀}₂{Cu(pic)₂}₃{Cu₂(pic)₄(H₂O)}₂]·8H₂O (2). The three compounds show a pronounced two-dimensional character owing to the structure-directing role of guanidinium. In 1 and 3, layers of [{XW₁₂O₄₀}{Cu₂(pic)₄}]_n⁴ⁿ⁻ hybrid POM chains and layers of [Cu₂(pic)₄(H₂O)] complexes and [C(NH₂)₃]⁺ cations pack alternately along the z axis. The hydrogen-bonding network established by guanidinium leads to a trihexagonal tiling arrangement of all copper(II)-picolinate species. In contrast, layers of [C(NH₂)₃]⁺-linked [{SiW₁₂O₄₀}₂{Cu(pic)₂}₃]_n⁸ⁿ⁻ double chains where each Keggin cluster displays a {Cu₂(pic)₄(H₂O)} moiety pointing at the intralamellar space are observed in 2. The thermal stability of 1–3 has been studied by thermogravimetric analyses and variable temperature powder X-ray diffraction. Compounds 1 and 3 undergo single-crystal to single-crystal transformations promoted by reversible dehydration processes and the structures of the corresponding anhydrous phases 1a and 3a have been established. Despite the fact that the [Cu₂(pic)₄(H₂O)] dimeric complexes split into [Cu(pic)₂] monomers upon dehydration, the packing remains almost unaltered thanks to the preservation of the hydrogen-bonding network established by guanidinium and its associated Kagome-type lattice. Splitting of the dimeric complexes has been correlated with the electron paramagnetic resonance spectra. Full article

A novel hybrid nanocomposite, PMo₁₁V@N-doped few layer graphene, was prepared by a one-step protocol through direct immobilization of the tetrabutylammonium salt of a vanadium-substituted phosphomolybdate (PMo₁₁V) onto N-doped few layer graphene (N-FLG). The nanocomposite characterization by FTIR and XPS confirmed its successful synthesis. Glassy carbon modified electrodes with PMo₁₁V and PMo₁₁V@N-FLG showed cyclic voltammograms consistent with surface-confined redox processes attributed to Mo-centred reductions (Mo^VI→Mo^V) and a vanadium reduction (V^V→V^IV). Furthermore, PMo₁₁V@N-FLG modified electrodes showed good stability and well-resolved redox peaks with high current intensities. The observed enhancement of PMo₁₁V electrochemical properties is a consequence of a strong electronic communication between the POM and the N-doped few layer graphene. Additionally, the electro-catalytic and sensing properties towards acetaminophen (AC) and theophylline (TP) were evaluated by voltammetric techniques using a glassy carbon electrode modified with PMo₁₁V@N-FLG. Under the conditions used, the square wave voltammetric peak current increased linearly with AC concentration in the presence of TP, but showing two linear ranges: 1.2 × 10⁻⁶ to 1.2 × 10⁻⁴ and 1.2 × 10⁻⁴ to 4.8 × 10⁻⁴ mol dm⁻³, with different AC sensitivity values, 0.022 A/mol dm⁻³ and 0.035 A/mol dm⁻³, respectively (detection limit, DL = 7.5 × 10⁻⁷ mol dm⁻³). Full article

Starting very early, with the findings of Zeise, or Pope and Peachey, organoplatinum complexes were studied intensely in the 1970s and 1980s and were found to be quite stable and very versatile. From then on, the number of publications on organoplatinum complexes has more than doubled in each subsequent decade, and organoplatinum complexes have stretched into many fields of application today. This introduction to the Special Issue on “Organoplatinum Complexes” spans from the history of organoplatinum complexes to the seven manuscripts published in the frame of this Special Issue, representing some of these fields. Full article

Gold is emerging as a potential therapeutic agent in the treatment of arthritis, cancer and AIDS. The therapeutic mechanism of arthritic gold drugs and their modification in the presence of stomach hydrochloric acid, in the joints, and in the presence of mild and strong oxidizing agents is a matter of debate. It is believed that gold affects the entire immune response and reduces its potency and limits its oxidizing nature. DNA apparently is not the main target of gold in cancer treatment. Rheumatoid arthritis, cancer, heart diseases and recently AIDS have all been targeted with gold nanoparticles therapy. The era of gold nanoparticles started with cancer imaging and treatment studies. Gold nanoparticles have emerged as smart drug vehicles. Full article

The five coordinate organoplatinum complex [Pt(bpy)(cod)(Me)][SbF₆] (cod = 1,5-cyclooctadiene, bpy = 2,2’-bipyridine) was obtained reacting [Pt(cod)(Me)Cl] with Ag[SbF₆] and bpy and characterized by multiple spectroscopy (IR and NMR) and single crystal XRD. Although the application of the τ values for the discrimination between trigonal bipyramidal vs. square pyramidal coordination fails, the molecular structure can be unequivocally described as basally-distorted trigonal bipyramidal. Detailed multinuclear NMR spectroscopy in solution at ambient temperature gives strong evidence for the same structure; corresponding low-temperature measurements down to −70 °C revealed no marked dynamic processes. Full article

The synthesis of complex functional inorganic materials, such as oxides, can be successfully performed by using microwave irradiation as the source of heat. To achieve this, different routes and set-ups can be used: microwave-assisted synthesis may proceed in the solid state or in solution, aqueous or not, and the set ups may be as simple and accessible as domestic oven or quite sophisticated laboratory equipment. An obvious advantage of this innovative methodology is the considerable reduction in time—minutes rather than hours or days—and, as a consequence, energy saving. No less important is the fact that the particle growth is inhibited and the broad variety of different microwave or microwave-assisted synthesis techniques opens up opportunities for the preparation of inorganic nanoparticles and nanostructures. In this work, various microwave synthesis techniques have been employed: solid-state microwaves, single-mode microwaves using a TE_10p cavity and microwave-assisted hydrothermal synthesis. Relevant examples are presented and discussed. Full article

A new heteroaromatic thiophene containing organoimido functionalized hexamolybdate has been synthesized and characterized in both solid form and solution. Structural analysis shows successful introduction of the organoimido ligand through replacement of one terminal oxo site on [Mo₆O₁₉]²⁻ to yield the singly functionalized hexamolybdate. Spectroscopic and theoretical analysis indicates charge transfer between the inorganic and organic components, with a significantly red-shifted lowest lying transition of 399 nm vs. the parent Lindqvist ion of 325 nm. Additional characterization includes, thermal gravimetric analysis (TGA), infrared (IR), cyclic voltammetry (CV), nuclear magnetic resonance (NMR) and time-dependent density functional theory (TD-DFT) studies. Full article

Two pyridine-functionalized coumarins differing with respect to the site of pyridine attachment to the coumarin dye (3 in L1 or 7 in L2) and with respect to the presence (L1) or absence (L2) of a peripheral NMe₂ donor were prepared and used as cyclometalating ligands towards the Pt(acac) fragment. X-ray crystal structures of complexes 1 and 2 show strong intermolecular interactions by π-stacking and short Pt∙∙∙Pt or C-H∙∙∙O hydrogen bonding that result in the formation of sheetlike packing patterns. The NMe₂ donor substituent has a profound influence on the absorption and emission properties of the free coumarin dyes; L1 emits strongly while L2 is only weakly emissive. On binding to Pt(acac) the strong fluorescence of L1 is partially quenched while coumarin phosphorescence is observed from cyclometalated L1 and L2. The ligand-centered nature of the LUMO was confirmed by IR spectroelectrochemistry while the assignment of the phosphorescence emission as ligand-based rests on the vibrational structuring, the negligible solvatochromism, the small temperature-induced Stokes shifts on cooling to 77 K, the emission lifetimes, and strong oxygen quenching. (TD-)DFT calculations confirm our experimental results and provide an assignment of the electronic transitions and the spin density distributions in the T₁ state. Full article