Inorganics — Open Access Journal

The presence of hazardous chemicals in wastewater produced by industrial activities and human metropoles is threating the availability of safe drinking water. The development of a multifunctional material coupling adsorption and photocatalytic activity is hereby particularly promising for the removal of pollutants. We have proved the adsorption and catalytic activity of NiFe₂O₄-layered double hydroxide (LDH) composite through the degradation of methyl orange (MO) at room temperature under visible light. This degradation is enhanced by using a set of small light-emitting diodes (LEDs) providing a uniform 405 nm UV light. The remediation process is based on a first-step rapid adsorption of MO molecules by the LDH structures followed by the photocatalytic oxidation of the pollutant by the (·OH) radicals produced by the NiFe₂O₄ semiconductor nanoparticles (NPs). The magnetic properties of the ferrite NPs allow a facile separation of the composite from the liquid media via a simple magnet. NiFe₂O₄-LDH composite could find wide application as a highly effective adsorbent/oxidizing catalyst operating under visible or near UV light. Full article

The synthesis and characterization of three metalla-rectangles of the general formula [Ru₄(η⁶-p-cymene)₄(μ₄-clip)₂(μ₂-L_anthr)₂][CF₃SO₃]₄ (L_anthr: 9,10-bis(3,3’-ethynylpyridyl) anthracene; clip = oxa: oxalato; dobq: 2,5-dioxido-1,4-benzoquinonato; donq: 5,8-dioxido-1,4-naphthoquinonato) are presented. The molecular structure of the metalla-rectangle [Ru₄(η⁶-p-cymene)₄(μ₄-oxa)₂(μ₂-L_anthr)₂]⁴⁺ has been confirmed by the single-crystal X-ray structure analysis of [Ru₄(η⁶-p-cymene)₄(μ₄-oxa)₂(μ₂-L_anthr)₂][CF₃SO₃]₄ · 4 acetone (A₂ · 4 acetone), thus showing the anthracene moieties to be available for reaction with oxygen. While the formation of the endoperoxide form of L_anthr was observed in solution upon white light irradiation, the same reaction does not occur when L_anthr is part of the metalla-assemblies. Full article

Novel pillared-layered framework materials were synthesized by high-throughput or microwave-assisted methodology that contain Mg²⁺ and the zwitterionic linker HDTMP (hexamethylenediamine-N,N,N′,N′-tetrakis(methylenephosphonic acid)). Three compounds were structurally characterized by X-ray powder diffraction. In the compound {Mg[(HO₃PCH₂)₂N(CH₂)₆N(CH₂PO₃H₂)₂]·(H₂O)}_n(1), obtained at 140 °C by hydrothermal or microwave-assisted reaction, the layers are built by isolated Mg²⁺ octahedra coordinated by oxygen atoms from six different zwitterionic HDTMP ligands. Each amino-bis(methylenephosphonate) moiety links three Mg²⁺ ions, bridging two of them through one phosphonate group and connecting the third polyhedron in a monodentate fashion. In Compound 2, {Mg[(HO₃PCH₂)₂N(CH₂)₆N(CH₂PO₃H₂)₂]}_n, hydrothermally synthesized at 180 °C, the layers are composed of bidentate amino-bis(methylenephosphonate) moieties connected to three Mg²⁺ ions, with one of the phosphonate groups acting as a bridging ligand. Various subtle structural changes are noted for the other two compounds. Thermodiffraction of 1 reveals that a crystalline-to-crystalline phase transformation occurs concomitantly with its dehydration, leading to a new anhydrous phase, namely, {Mg[(HO₃PCH₂)₂N(CH₂)₆N(CH₂PO₃H₂)₂]}_n(1deh). This process is fully reversible upon equilibrating the solid at room temperature. The reported compounds can adsorb ammonia and CO₂. Compound 1 exhibits a moderate proton conductivity, ~1.5 × 10⁻⁵ S·cm⁻¹ at 80 °C and 95% RH, that increases a half order of magnitude after experiencing a complete dehydration/rehydration process, 1→1deh→1. Full article

Ferrocenediyl systems offer a motif that incorporates multiple functionality and redox-active centers, enabling these units to be used as molecular scaffolds in linear and cyclic compounds. Herein, we discuss a new modular methodology for the synthesis and incorporation of ferrocenediyl motifs within extended conjugated systems. We have synthesized a family of compounds featuring ferrocenediyl-ethynyl units with various para-substituted aromatic linkages. Extended linear, open-chain species have been isolated and understanding towards the analogous cyclic compounds gained. The new compounds have been probed using NMR, mass spectrometry, cyclic voltammetry and X-ray crystallography to gain further understanding of their structural and electronic properties. Full article

The results are reported on a precise crystal structure and microstructure determination of new mixed YVO₄-based orthovanadates of Y_0.5R_0.5VO₄ (R = Sm, Tb, Dy, Ho, Tm, Yb, Lu) as well as some Bi³⁺-doped RVO₄ (R = La, Gd, Y, Lu) nano- (submicro-) materials. The formation of continuous solid solutions in the YVO₄–RVO₄ pseudo-binary systems (R = Sm, Tb, Dy, Ho, Tm, Yb, Lu) has been proved. The lattice constants and unit cell volumes of the new mixed orthovanadates were analyzed as a function of R³⁺ cation radius. The impact of crystal structure parameters on the energy band gap of the materials was studied by means of photoluminescence studies of the Bi³⁺-doped compounds. Full article

A new Co(II) phosphonate, Co(H₂O)₂PO₃C–C₁₂H₉·H₂O, has been synthesized under hydrothermal conditions. The monoclinic P2₁/c structure of this organic–inorganic hybrid consists of isolated perovskite-type chains of corner-shared CoO₄(H₂O)₂ octahedra interconnected via phosphonate groups. The unique one-dimensional structure of this phase is closely related to the single-chain magnet (SCM) phosphonate Co(H₂L)(H₂O), with L = 4-Me-C₆H₄-CH₂N(CPO₃H₂)₂, that contains isolated chains of CoO₅N octahedra. Like the latter, this hybrid exhibits 1D antiferromagnetic interactions and the possibility of an effective pseudo spin contribution due to spin canting at low temperature, but, in contrast, is not an SCM. This different magnetic behavior is explained by the different geometry of the octahedral chains and by the possible existence of weak antiferromagnetic interactions between the chains. This opens the route to the investigation of a large series of compounds by tuning the chemical composition and structure of the phosphonic acid used as organic precursor of hybrid materials. Full article

9,9-dimethylfluorenyl-2-phosphonic acid 1 was reacted with manganese nitrate tetrahydrate to produce under hydrothermal conditions the crystalline manganese phosphonate Mn(H₂O)₂[O₂(OH)PC₁₅H₁₃]₂·2H₂O which crystallize in the P2₁/c space group. This compound is a rare example of Mn-phosphonate material featuring isolated chains. The interactions between these chains containing the 9,9-dimethylfluorenyl moieties, result from Van der Waals interactions involving the fluorene ligands and C···H–C hydrogen bonds as revealed by Hirshfeld Surfaces. This material features antiferromagnetic exchange interactions as revealed by the magnetic susceptibility as a function of the temperature. Full article

Storage of renewable energy remains a key obstacle for the implementation of a carbon free energy system. There is an urgent need to develop a variety of energy storage systems with varying performance, covering both long-term/large-scale and high gravimetric and volumetric densities for stationary and mobile applications. Novel materials with extraordinary properties have the potential to form the basis for technological paradigm shifts. Here, we present metal hydrides as a diverse class of materials with fascinating structures, compositions and properties. These materials can potentially form the basis for novel energy storage technologies as batteries and for hydrogen storage. Full article

The SiO₂@α-Fe₂O₃/ZnO metal oxide nanocomposites employed in this study were obtained using the sol-gel method. Their photocatalytic activities were enhanced by photo-Fenton reactions. The metal oxide composite of ZnO and α-Fe₂O₃ nanoparticles were deposited on the SiO₂ nanospheres intended for visible light photocatalysis. Further, the as-synthesized SiO₂@α-Fe₂O₃/ZnO nanocomposites exhibited a robust crystallinity and a high adsorption of dye molecules when compared to SiO₂@ZnO and SiO₂@α-Fe₂O₃ nanocomposites, respectively. The experimental results demonstrated a rapid Methylene Blue (MB) degradation among these catalysts within short intervals of time with the addition of α-Fe₂O₃/ZnO mixed metal oxide catalysts on the SiO₂ nanospheres. Finally, a photo-Fenton reaction was implemented to confirm the presence of the hydroxyl (OH) radicals, which are powerful agents used for the degradation of organic pollutants. Full article

Compounds Sr_3−xPr_xFe_1.25Ni_0.75O_7−δ with 0 ≤ x ≤ 0.4 and Ruddlesden–Popper n = 2 type structures were synthesized and investigated by X-ray and neutron powder diffraction, thermogravimetry, and Mössbauer spectroscopy. Both samples, prepared at 1300 °C under N₂(g) flow and samples subsequently air-annealed at 900 °C, were studied. The structures contained oxygen vacancies in the perovskite layers, and the Fe/Ni cations had an average coordination number less than six. The oxygen content was considerably higher for air-annealed samples than for samples prepared under N₂, 7 − δ = ~6.6 and ~5.6 per formula unit, respectively. Mössbauer data collected at 7 K, below magnetic ordering temperatures, were consistent with X-ray powder diffraction (XRD) and neutron powder diffraction (NPD) results. The electrical conductivity was considerably higher for the air-annealed samples and was for x = 0.1~30 S·cm⁻¹ at 500 °C. The thermal expansion coefficients were measured in air between room temperature and 900 °C and was found to be 20–24 ppm·K⁻¹ overall. Full article

The electronic structures of a series of uranium hexahalide and uranyl tetrahalide complexes were simulated at the density functional theoretical (DFT) level. The resulting electronic structures were analyzed using a novel application of the Quantum Theory of Atoms in Molecules (QTAIM) by exploiting the high symmetry of the complexes to determine 5f- and 6d-shell contributions to bonding via symmetry arguments. This analysis revealed fluoride ligation to result in strong bonds with a significant covalent character while ligation by chloride and bromide species resulted in more ionic interactions with little differentiation between the ligands. Fluoride ligands were also found to be most capable of perturbing an existing electronic structure. 5f contributions to overlap-driven covalency were found to be larger than 6d contributions for all interactions in all complexes studied while degeneracy-driven covalent contributions showed significantly greater variation. σ-contributions to degeneracy-driven covalency were found to be consistently larger than those of individual π-components while the total π-contribution was, in some cases, larger. Strong correlations were found between overlap-driven covalent bond contributions, U–O vibrational frequencies, and energetic stability, which indicates that overlap-driven covalency leads to bond stabilization in these complexes and that uranyl vibrational frequencies can be used to quantitatively probe equatorial bond covalency. For uranium hexahalides, degeneracy-driven covalency was found to anti-correlate with bond stability. Full article

The Pfeiffer effect is observed when an optically active compound such as an amino acid is introduced to a solution containing a labile racemic metal complex, and an equilibrium shift is obtained. The “perturbation” results in an excess of one enantiomer over the other. The shift is a result of a preferential outer sphere interaction between the introduced chiral species and one enantiomeric form (Λ or ∆) of a labile metal complex. Speculations regarding the mechanism of the Pfeiffer effect have attributed observations to a singular factor such as pH, solvent polarity, or numerous other intermolecular interactions. Through the use of the lanthanide(III) complexes [Tb(DPA)₃]³⁻ and [Eu(DPA)₃]³⁻ (where DPA = 2,6-pyridinedicarboxylate) and the amino acids l-serine and l-proline; it is becoming clear that the mechanism is not so simply described as per the preliminary findings that are discussed in this study. It appears that the true mechanism is far more complicated than the attribute just a singular factor. This work attempts to shine light on the fact that understanding the behavior of the solvent environment may hypothetically be the key to offering a more detailed description of the mechanism. Full article

The 2,2′:6′:2″-terpyridine ligand has literally shaped the coordination chemistry of transition metal complexes in a plethora of fields. Expansion of the ligand bite by amine functionalities between the pyridine units in the tridentate N,N’-dimethyl-N,N’-dipyridine-2-yl-pyridine-2,6-diamine ligand (ddpd) modifies the properties of corresponding transition metal complexes, comprising redox chemistry, molecular dynamics, magnetism and luminescence. The origins of these differences between ddpd and tpy complexes will be elucidated and comprehensively summarized with respect to first row transition metal complexes with d²–d¹⁰ electron configurations. Emerging applications of these ddpd complexes complementary to those of the well-known terpyridine ligand will be highlighted. Full article

Titanocene bis-arylthiolates [(C₅H₄X)(C₅H₄Y)Ti(SC₆H₄R)₂] (X,Y = H, Cl; R = H, Me) can be prepared from the corresponding titanocene dichlorides by reacting with the thiols in the presence of DABCO as a base. They react with n-butyl lithium to give unstable Ti(III) radical anions. While the unsubstituted thiolates (X = Y = R = H) react with lithium Di-isopropylamide by decomposing to dimeric fulvalene-bridged and thiolate-bridged Ti(III) compounds, the ring-chlorinated compounds can be deprotonated with LDA and give appropriate electrophiles di-substituted and tri-substituted titanocene dithiolates. Full article

Since the invention of fluorescent light sources, there is strong interest in Eu³⁺ activated phosphors as they are able to provide a high color rendering index (CRI) and luminous efficacy, which will also hold for phosphor converted light emitting diodes. Due to an efficient U⁶⁺ to Eu³⁺ energy transfer in Gd₃Li₃Te₂O₁₂:U⁶⁺,Eu³⁺, this inorganic composition shows red photoluminescence peaking at 611 nm. That means Eu³⁺ photoluminescence can be nicely sensitized via excitation into the U⁶⁺ excitation bands. Therefore, photoluminescence properties, such as temperature dependent emission and emission lifetime measurements, are presented. Charge transfer bands were investigated in detail. Additionally, density functional theory calculations reveal the band structure of the pure, i.e., non-doped host material. Obtained theoretical results were evaluated experimentally by the aid of diffuse UV reflectance spectroscopy. Full article

A novel exsolution process was used to fabricate complex all-oxide nanocomposite cathodes for Protonic Ceramic Fuel Cells (PCFCs). The nanocomposite cathodes with La_0.5Ba_0.5Co_1/3Mn_1/3Fe_1/3O_3−δ-BaZr_1−zY_zO_3−δ nominal composition were prepared from a single-phase precursor via an oxidation-driven exsolution mechanism. The exsolution process results in a highly nanostructured and intimately interconnected percolating network of the two final phases, one proton conducting (BaZr_1−zY_zO_3−δ) and one mixed oxygen ion and electron conducting (La_0.5Ba_0.5Co_1/3Mn_1/3Fe_1/3O_3−δ), yielding excellent cathode performance. The cathode powder is synthesized as a single-phase cubic precursor by a modified Pechini route followed by annealing at 700 °C in N₂. The precursor phase is exsolved into two cubic perovskite phases by further heat treatment in air. The phase composition and chemical composition of the two phases were confirmed by Rietveld refinement. The electrical conductivity of the composites was measured and the electrochemical performance was determined by impedance spectroscopy of symmetrical cells using BaZr_0.9Y_0.1O_2.95 as electrolyte. Our results establish the potential of this exsolution method where a large number of different cations can be used to design composite cathodes. The La_0.5Ba_0.5Co_1/3Mn_1/3Fe_1/3O_3−δ-BaZr_0.9Y_0.1O_2.95 composite cathode shows the best performance of 0.44 Ω·cm² at 600 °C in 3% moist synthetic air. Full article

Small molecule activation is a topic of growing importance and the use of low-valent f-elements to perform these reactions is nowadays well established. The complex Cp^tt₂Sm(thf) (1, Cp^tt = 1,3-(^tBu)₂Cp) is shown to activate the alkyne C–H bond of phenylacetylene to form the Cp^tt₂Sm(C≡C–Ph)(thf) complex. The subsequent reaction of this Sm(III) complex with CO₂ leads to the CO₂ insertion, yielding a dimeric [Cp^tt₂Sm(O₂C–C≡C–Ph)]₂ complex (2), in which the carbon dioxide has been inserted in the Sm–C bond. Along with the experimental chemical structure analysis, theoretical calculations have been performed in order to rationalize the formation of 1 and 2. Full article

This short review outlines the main results obtained by our research group over the last 15 years in the field of porphyrins and metal porphyrins for second order nonlinear optics (NLO). This overview aims to provide a general framework of the key factors which affect the second order NLO response of porphyrin chromophores. The pivotal role of the porphyrin ring as π-conjugated linker, the nature of the metal center, the substitution pattern which features the geometrical arrangement of donor and acceptor substituents in the different classes of porphyrin NLO-phores, as well as the aggregation phenomena and the role of solvents are addressed in detail. Full article

Much attention has recently focused on helical structures that can change their helicity in response to external stimuli. The requirements for the invertible helical structures are a dynamic feature and well-defined structures. In this context, helical metal complexes with a labile coordination sphere have a great advantage. There are several types of dynamic helicity controls, including the responsive helicity inversion. In this review article, dynamic helical structures based on oligo(salamo) metal complexes are described as one of the possible designs. The introduction of chiral carboxylate ions into Zn₃La tetranuclear structures as an additive is effective to control the P/M ratio of the helix. The dynamic helicity inversion can be achieved by chemical modification, such as protonation/deprotonation or desilylation with fluoride ion. When (S)-2-hydroxypropyl groups are introduced into the oligo(salamo) ligand, the helicity of the resultant complexes is sensitively influenced by the metal ions. The replacement of the metal ions based on the affinity trend resulted in a sequential multistep helicity inversion. Chiral salen derivatives are also effective to bias the helicity; by incorporating the gauche/anti transformation of a 1,2-disubstituted ethylene unit, a fully predictable helicity inversion system was achieved, in which the helicity can be controlled by the molecular lengths of the diammonium guests. Full article