Inorganics, Volume 5, Issue 1 (March 2017) – 17 articles

In recent years, the organometallic and coordination chemistry of the alkali and alkaline earth metals has experienced tremendous progress to tackle the needs of today’s society. Enhanced ecological awareness and global availability favor research on the chemistry of the essential s-block metals. Nowadays, the s-block metals are conquering new chemical fields based on sophisticated theoretical and preparative achievements. Recent investigations show a huge impact of the s-block elements on stoichiometric and catalytic processes. Full article

Synergistic relations between organic molecules and mineral precursors regulate biogenic mineralization. Given the remarkable material properties of the egg shell as a biogenic ceramic, it serves as an important model to elucidate biomineral growth. With established roles of complex anionic biopolymers and a heterogeneous organic scaffold in egg shell mineralization, the present study explores the regulation over mineralization attained by applying synthetic polymeric counterparts (polyethylene glycol, poly(acrylic acid), poly(aspartic acid) and poly(4-styrenesulfonic acid-co-maleic acid)) as additives during remineralization of decalcified eggshell membranes. By applying Mg²⁺ ions as a co-additive species, mineral retrosynthesis is achieved in a manner that modulates the polymorph and structure of mineral products. Notable features of the mineralization process include distinct local wettability of the biogenic organic scaffold by mineral precursors and mineralization-induced membrane actuation. Overall, the form, structure and polymorph of the mineralization products are synergistically affected by the additive and the content of Mg²⁺ ions. We also revisit the physicochemical nature of the biomineral scaffold and demonstrate the distinct spatial distribution of anionic biomolecules associated with the scaffold-mineral interface, as well as highlight the hydrogel-like properties of mammillae-associated macromolecules. Full article

Mesoporous titania (mp-TiO₂) has drawn tremendous attention for a diverse set of applications due to its high surface area, interfacial structure, and tunable combination of pore size, pore orientation, wall thickness, and pore connectivity. Its pore structure facilitates rapid diffusion of reactants and charge carriers to the photocatalytically active interface of TiO₂. However, because the large band gap of TiO₂ limits its ability to utilize visible light, non-metal doping has been extensively studied to tune the energy levels of TiO₂. While first-principles calculations support the efficacy of this approach, it is challenging to efficiently introduce active non-metal dopants into the lattice of TiO₂. This review surveys recent advances in the preparation of mp-TiO₂ and their doping with non-metal atoms. Different doping strategies and dopant sources are discussed. Further, co-doping with combinations of non-metal dopants are discussed as strategies to reduce the band gap, improve photogenerated charge separation, and enhance visible light absorption. The improvements resulting from each doping strategy are discussed in light of potential changes in mesoporous architecture, dopant composition and chemical state, extent of band gap reduction, and improvement in photocatalytic activities. Finally, potential applications of non-metal-doped mp-TiO₂ are explored in water splitting, CO₂ reduction, and environmental remediation with visible light. Full article

Photocatalytic hydrogen generation is considered to be attractive due to its combination of solar energy conversion and storage. Currently-used systems are either based on homogeneous or on heterogeneous materials, which possess a light harvesting and a catalytic subunit. The subject of this review is a brief summary of homogeneous proton reduction systems using sacrificial agents with special emphasis on non-noble metal systems applying convenient iron(0) sources. Iridium photosensitizers, which were proven to have high quantum yields of up to 48% (415 nm), have been employed, as well as copper photosensitizers. In both cases, the addition or presence of a phosphine led to the transformation of the iron precursor with subsequently increased activities. Reaction pathways were investigated by photoluminescence, electron paramagnetic resonance (EPR), Raman, FTIR and mass spectroscopy, as well as time-dependent DFT-calculations. In the future, this knowledge will set the basis to design photo(electro)chemical devices with tailored electron transfer cascades and without the need for sacrificial agents. Full article

Cancer stem cells (CSCs) are thought to be responsible for cancer relapse. CSCs are a subtype of cancer cells with the ability to differentiate, self-renew, and form secondary or tertiary tumors. Current cancer treatments—including chemotherapy, radiation, and surgery—effectively remove bulk cancer cells but are unable to eliminate CSCs. Here, we present the synthesis, characterization, and anti-CSC properties of a cobalt(III)–cyclam complex bearing two tolfenamic acid moieties, 3. Notably, 3 displays sub-micromolar potency towards breast CSCs and bulk breast cancer cells. Detailed mechanistic studies show that 3 is taken up readily by breast CSCs, enters the nucleus, causes DNA damage, and induces caspase-dependent apoptosis. Furthermore, 3 inhibits cyclooxygenase-2 (COX-2) expression in CSCs. The mechanism of action of 3 is similar to that of a naproxen-appended cobalt(III)–cyclam complex, 1 recently reported by our group. The advantage of 3 over 1 is that it has the potential to remove whole tumor populations (bulk cancer cells and CSCs) with a single dose. Full article

Mismatched complexes of the alkali metals cations Li⁺ and Na⁺ were synthesized from 1,2-disila[18]crown-6 (1 and 2) and of K⁺ from 1,2,4,5-tetrasila[18]crown-6 (4). In these alkali metal complexes, not all crown ether O atoms participate in the coordination, which depicts the coordination ability of the C-, Si/C-, and Si-bonded O atoms. Furthermore, the inverse case—the coordination of the large Ba²⁺ ion by the relatively small ligand 1,2-disila[15]crown-5—was investigated, yielding the dinuclear complex 5. This structure represents a first outlook on sandwich complexes based on hybrid crown ethers. Full article

We report the first magnetically coupled guanidinate, α-Eu(CN₃H₄)₂ (monoclinic, P2₁, a = 5.8494(3) Å, b = 14.0007(8) Å, c = 8.4887(4) Å, β = 91.075(6)°, V = 695.07(6) ų, Z = 4). Its synthesis, polymorphism, crystal structure, and properties are complemented and supported by density-functional theory (DFT) calculations. The α-, β- and γ-polymorphs of Eu(CN₃H₄)₂ differ in powder XRD, while the γ-phase transforms into the β-form over time. In α-Eu(CN₃H₄)₂, Eu is octahedrally coordinated and sits in one-dimensional chains; the guanidinate anions show a hydrogen-bonding network. The different guanidinate anions are theoretically predicted to adopt syn-, anti- and all-trans-conformations. Magnetic measurements evidence ferromagnetic interactions, presumably along the Eu chains. Finally, EuC(NH)₃ (isostructural to SrC(NH)₃ and YbC(NH)₃, hexagonal, P6₃/m, a = 5.1634(7) Å, c = 7.1993(9) Å, V = 166.23(4) ų, Z = 2) is introduced as a possible ferromagnet. Full article

Three members of the homologous series of manganese oxyselenides with the general formula La2n+2MnSen+2O2n+2 (n = 0–2) have been synthesized in a NaI/KI flux and characterized by single-crystalX-raydiffraction,powderX-raydiffractionandmagneticmeasurements. Thestructures consist of chains of edge-sharing MnSe4O2-octahedra along the b-axis which are linked together along the a-axis by edge-sharing OLa4- and/or OLa3Mn-tetrahedra forming infinite ribbons of increasing width. mC-La2MnSe2O2 (Pb2HgCl2O2-type, C2/m, a = 11.6621(5) Å, b = 3.9719(1) Å, c = 7.2049(3) Å, β = 121.655(2)◦) represents a new polymorph of this compound. La4MnSe3O4 (P2/m, a = 9.0055(4) Å, b = 4.0186(1) Å, c = 7.1946(3) Å, β = 109.715(2)◦) and La6MnSe4O6 (C2/m, a = 24.760(2) Å,b = 4.0359(3)Å,c=7.1850(6)Å, β =104.162(3)◦)exhibitnewstructuretypes. Magnetic measurements suggest antiferromagnetic order of the moments below about 15 K with effective magnetic moments of 5.53(1), 5.99(1) and 6.01(1) µB per formula unit for n = 1, 2 and 3, respectively. Full article

The reaction of [(OC)₅MnBr] with substituted 3-(2-pyridyl)pyrazoles) 2-PyPz^RH (1a-l) in methanol or diethyl ether yields the yellow to orange manganese(I) complexes [(OC)₃Mn(Br)(2-PyPz^RH)] (2a-l), the substituents R being phenyl (a), 1-naphthyl (b), 2-anthracenyl (c), 1-pyrenyl (d), 4-bromophenyl (e), 3-bromophenyl (f), duryl (g), 2-pyridyl (h), 2-furanyl (i), 2-thienyl (j), ferrocenyl (k), and 1-adamantyl (l). The carbonyl ligands are arranged facially, leading to three chemically different CO ligands due to different trans-positioned Lewis donors. The diversity of the substituent R demonstrates that this photoCORM backbone can easily be varied with a negligible influence on the central (OC)₃MnBr fragment, because the structural parameters and the spectroscopic data of this unit are very similar for all these derivatives. Even the ferrocenyl complex 2k shows a redox potential for the ferrocenyl subunit which is identical to the value of the free 5-ferrocenyl-3-(2-pyridyl)pyrazole (1k). The ease of variation of the starting 5-substituted 3-(2-pyridyl)pyrazoles) offers a modular system to attach diverse substituents at the periphery of the photoCORM complex. Full article

In the present paper, porous materials were prepared from the hydrothermal treatment of aqueous solutions of tannin, a renewable phenolic resource extracted from tree barks, containing dissolved salts of transition metals: V, Cr, Ni and Fe. Hydrothermal treatment produced carbonaceous particles doped with the aforementioned metals, and such materials were treated according to two different routes: (i) calcination in air in order to burn the carbon and to recover porous oxides; (ii) pyrolysis in inert atmosphere so as to recover porous metal/carbon hybrid materials. The nature of the metal salt was found to have a dramatic impact on the structure of the materials recovered by the first route, leading either to nano-powders (V, Cr) or to hollow microspheres (Ni, Fe). The second route was only investigated with iron, leading to magnetic Fe-loaded micro/mesoporous carbons whose texture, pore volumes and surface areas gradually changed with the iron content. Full article

My group developed a simple method to prepare copper nitride fine particles from copper carboxylate in a solvent of long-chain alcohols without the use of high temperatures or high pressures. By selecting copper acetate or copper decanoate as the copper source, my group demonstrated that the morphology of the copper nitride fine particles varied between cubic and plate-like, respectively. Although a hypothesis was proposed to explain the influence of the length of the alkyl chain on the copper decanoate, it is uncertain how much the chain length influences the shape of the fine particles. In this work, I demonstrated the effect of the length of the alkyl chain on particle shape by preparing fine particles from a series of copper sources with different alky chain lengths and characterizing the particles with x-ray diffractometry (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The main findings were as follows: (1) the fine particles were plate-like when the alkyl chain length exceeded 5; (2) the aspect ratio of the plate-like particles increased as the alkyl chain length increased; and (3) growth of the (110) and (111) planes of the copper nitride crystal were selectively inhibited. Full article

P-Fluorous phosphine (R₂PR_f), in which the perfluoroalkyl group is directly bonded to the phosphorus atom, is a promising ligand because it has a hybrid functionality, i.e., electron-poor and fluorous ligands. However, examples of P-fluorous phosphine–metal complexes are still rare, most probably because the P-fluorous group is believed to decrease the coordination ability of the phosphines dramatically. In contrast, however, we have succeeded in synthesizing a series of P-fluorous phosphine–coordinated metal complexes such as rhodium, iridium, platinum, and gold. Furthermore, the electronic properties of R₂PⁿC₁₀F₂₁ are investigated by X-ray analysis of PtCl₂(Ph₂PⁿC₁₀F₂₁)₂ and the infrared CO stretching frequency of RhCl(CO)(R₂PⁿC₁₀F₂₁)₂. IrCl(CO)(Ph₂PⁿC₁₀F₂₁)₂- and AuCl(R₂PⁿC₁₀F₂₁)-catalyzed reactions are also demonstrated. Full article

For more than 100 years metal complexes have been extensively used in therapy and since the discovery of cisplatin the research in this field has expanded exponentially. The scientific community is always in search of new alternatives to platinum compounds and a wide variety of metallodrugs based on other metals have been reported with excellent therapeutic results. This short review focuses on the work that our research group has carried out since 2007 in collaboration with others and centers on the preparation of organogallium(III) compounds, organotin(IV) derivatives, and titanocene(IV) complexes together with the study of their cytotoxic anticancer properties. Full article

The reaction of lanthanoid metal powders (Ln) with sulfur and cesium azide (CsN₃) as a nitrogen source in the presence of lanthanoid tribromides (LnBr₃) yields lanthanoid nitride sulfides with the composition Ln₄N₂S₃ (Ln = Ce–Nd) when appropriate molar ratios of the starting material are used. Additional cesium bromide (CsBr) as a flux secures quantitative conversion (7 days) at 900 °C in evacuated silica tubes as well as the formation of black single crystals. All compounds crystallize isotypically with the orthorhombic crystal structure of La₄N₂S₃ (Pnnm, Z = 2) and their structures were determined from single-crystal X-ray diffraction data (Ce₄N₂S₃: a = 644.31(4), b = 1554.13(9), c = 404.20(3) pm; Pr₄N₂S₃: a = 641.23(4), b = 1542.37(9), c = 400.18(3) pm; Nd₄N₂S₃: a = 635.19(4), b = 1536.98(9), c = 397.85(3) pm). Compared to La₄N₂S₃ the a-axes do not fulfill the expectation of the lanthanide contraction. The main feature of the crystal structure comprises N³⁻-centered (Ln³⁺)₄ tetrahedra arranging as pairs [N₂Ln₆]¹²⁺ of edge-shared [NLn₄]⁹⁺ units, which are further connected via four vertices to form double chains ${}_{\infty }^1${([NLn_4/2]₂)⁶⁺}. Bundled along [001] like a hexagonal rod packing, they are held together by two crystallographically different S²⁻ anions. Two compounds of a second modification (B-type La₄N₂S₃ and Pr₄N₂S₃) will also be presented and discussed for comparison. Full article

Molybdenum disulphide (MoS₂) is an earth-abundant material which has several industrial applications and is considered a candidate for platinum replacement in electrochemistry. Size-selected MoS₂ nanoclusters were synthesised in the gas phase using a magnetron sputtering, gas condensation cluster beam source with a lateral time-of-flight mass selector. Most of the deposited MoS₂ nanoclusters, analysed by an aberration-corrected scanning transmission electron microscope (STEM) in high-angle annular dark field (HAADF) mode, showed poorly ordered layer structures with an average diameter of 5.5 nm. By annealing and the addition of sulphur to the clusters (by sublimation) in the cluster source, the clusters were transformed into larger, crystalline structures. Annealing alone did not lead to crystallization, only to a cluster size increase by decomposition and coalescence of the primary clusters. Sulphur addition alone led to a partially crystalline structure without a significant change in the size. Thus, both annealing and sulphur addition processes were needed to obtain highly crystalline MoS₂ nanoclusters. Full article