Tetravalent Ions Research Articles

Elucidating trends in synthesis and structural periodicity in a series of tetravalent actinide–oxo hexamers

Differences in synthetic conditions and structural systematics in a series of actinide–oxo clusters reflect trends in the hydrolysis behavior of the tetravalent metal ions, Th–Pu.

Effect of multivalent ion doping on magnetic, electrical, and dielectric properties of nickel ferrite nanoparticles

The nanoscale spinel structured ferrites co-doped with multi-valence ions are of great interest and proving to be promising for numerous applications. In light of this, herein we report tetravalent titanium ions (Ti4+) and divalent zinc ions (Zn2+) co-doped nickel ferrites with generic formula of NiFe2 − 2xTixZnxO4 (x = 0.00 ≤ x ≤ 0.20 in step of 0.05). The sol gel self combustion method in assistance with citric acid as fuel was employed to prepare the samples. The X-ray diffraction (XRD) analysis with Rietveld refinement was performed to confirm the single-phase cubic spinel structure. The sphere type grain morphology of the samples was revealed by SEM images. The compositional studies carried out by EDAX showed desired formation of the composition with absence of impurities in the samples. The characteristics bands belonging to the spinel ferrites were appeared in IR spectra confirming the successive sample forming. The different surface parameters including surface area and pore volume was estimated using Brunauer-Emmett-Teller (BET) analysis. The low coercive nature with soft magnetism was observed with the co-doping as revealed by M-H plots. The electric and dielectric parameters showed decrementing behaviour with increment in Ti4+-Zn2+ co-doping. This study outcome signifies that the Ti4+-Zn2+ co-doping in nickel ferrites could be a prominent for many nanoelectronics applications.

Synthesis, characterization, biological activity, and modelling protein docking of divalent, trivalent, and tetravalent metal ion complexes of new azo dye ligand (N,N,O) derived from benzimidazole

The ligand 2-[2′-(benzimidazole)azo]-4,6-dimethyl benzoic acid (BADMB) was employed to create coordination complexes with Pd(II), Co(III), and Pt(IV) ions. A variety of analytical methods were utilized to verify the structures of the synthesized chelates, including microanalysis, 1H NMR, 13C NMR, UV–Vis spectroscopy, FT-IR, mass spectrometry, magnetic susceptibility, molar conductivity, X-ray diffraction (XRD), and thermal analysis. The stoichiometry of the metal complexes was 1:1 [M:L] in the case of both Pd(II) and Pt(IV) complexes while that of the Co(III) complex was 1:2 [M:L]. The results of molar conductivity measurements confirmed that all of the complexes are electrolytes and that they fall within the range 15.74–40.11 Ω−1 cm2 mol−1. The findings indicated that the Co(III) and Pt(IV) complexes adopt an octahedral geometry, with the formulas [Co(BADMB)2]Cl·H2O and [Pt(BADMB)Cl3]·H2O, respectively. In contrast, the Pd(II) complex, represented by the general formula [Pd(BADMB)Cl]·H2O, has a square planar geometry. BADMB acts as a trident (N,N,O) ligand through two nitrogen atoms from the benzimidazole ring and an azo group and one oxygen atom of the carboxyl group. The antimicrobial activity of these compounds was evaluated against a variety of microorganisms, including Streptococcus, Staphylococcus aureus, Penicillium spp., and Aspergillus, as well as multidrug resistance. In addition, all compounds were active against Penicillium spp. fungi compared to the other microorganisms examined. Moreover, the cytotoxic effects of the BADMB, Pd(II), and Pt(IV) complexes were evaluated in a human hepatocellular carcinoma cell line (HepG2) and a normal cell line (WRL68). A molecular docking study was performed using MOE 2015 software and the PDBsum online server. The compounds showed a binding free energy greater than 5 kcal/mol and an RMSD value was present in the range of 1.41 to 2.01 Å, indicating their potential as ligands for further molecular studies with selected targets.

Transition-Metal Substitution Effects on Ionic Conduction Properties of Solid Electrolyte LiTa2PO8

All-solid-state lithium-ion batteries are increasing in interest as the next-generation battery due to their safety, high energy density, and long lifetime in achieving a decarbonized society. However, all-solid-state lithium-ion batteries, using inorganic solid electrolytes instead of liquid electrolytes, face challenges in charging/discharging rates and capacity due to their much lower ion conductivity[1]. Therefore, it is essential to explore novel solid electrolytes with high ionic conductivity.Solid electrolytes with particularly high ion conductivity are called superionic conductors, such as Li10GeP2S12 (LGPS)[2]and Li1.3Al0.3Ti1.7(PO4)3 (LATP)[3]. Theoretical studies suggest that their fast ionic conduction is governed by a non-trivial conduction mechanism, simultaneous multiple-ion hopping, which is driven by Coulomb interactions of lithium ions instead of classical single-ion hopping[4]. Multiple-ion hopping, namely concerted migration, results in a lower energy barrier for ion migration than single-ion hopping. Thus, triggering concerted migration would be crucial to achieving high ionic conductivity.To induce concerted migration, chemical substitution may be effective, as seen in LATP. LATP is a superionic conductor with a NASICON-type structure in which the Ti4+ site of the parent compound LiTi2(PO4)3 is partly substituted with Al3+. Though the parent compound has a low ionic conductivity of 3.13×10–6 S/cm, the ionic conductivity in LATP of 5.1×10–3 S/cm increases by approximately three orders of magnitude[5]. A theoretical study suggests the conduction mechanism of LATP is governed by concerted migration, meaning a chemical substitution leads to concerted migration, resulting in such a significant enhancement.To find ionic conductors with high ionic conductivity, we focused on LiTa2PO8 [6]for the following reasons: First, its ionic conductivity (1.6×10–3 S/cm) is comparable to that of LATP without chemical substitutions. Second, theoretical calculations predict that a substantially weaker Li-Li interaction is expected in LiTa2PO8 [7] than in LATP[4], implying that the conduction mechanism may be classical. Given the increase in ionic conductivity in LATP, high ionic conductivity might be achieved when concerted migration is induced/enhanced in LiTa2PO8. Though the substitutions of Ta5+/P5+ sites with tetravalent ions of typical elements such as Te4+ [8]and Si4+[9] have been studied, no drastic increase in ionic conductivity has been achieved, and the highest ionic conductivity is 1.6×10–3 S/cm. In this study, we performed chemical substitutions of Ta5+ with transition metal ions, Ti4+ and W6+.Polycrystalline powder of Li1±xTa2–xMxPO8 (M = Ti4+, W6+) (x = 0 ~ 0.2) was prepared by solid-state reaction. The lattice parameters determined by XRD patterns decreased as the substitution amount x increased, indicating successful substitutions of Ti4+ and W6+ since Ti4+ and W6+ have smaller ionic radii than Ta5+. The x dependence of the lattice constants indicates the solubility limit is xTi = 0.08 for the case of Ti4+, while the linear decrease of the lattice constants in the case of W6+ indicates the solubility limit is above xW = 0.20. Elemental analysis via SEM/EDX also supports the above results. The ionic conductivity of xTi = 0.08 and xW = 0.20 was measured by the AC impedance method in the range of 1.0×102~5.0×107 Hz. The results showed that Ti4+ substitution increases ion conductivity, while W6+ substitution decreases compared with non-doped LiTa2PO8, meaning the increase in the number of Li ions is effective in enhancing the ionic conductivity in LiTa2PO8. However, unlike LATP, the increase in ionic conductivity is at most twice as large.

Application of the flexible and polarisable hydration ion model to study Th(IV) aqueous solutions

Th(IV) hydration in aqueous solution is studied by means of molecular dynamics simulations based on a polarisable Th(IV)- H 2 O interaction potential developed in the framework of the hydrated ion concept. Molecular Dynamics (MD) simulations provide as the only in-solution representative motif the ennea-aqua ion, [ Th ( H 2 O ) 9 ] 4 + , with first shell water molecules at an average distance of 2.47 Å from the ion, in accordance with most of the experimental estimates. A well-defined second hydration shell is also identified, hosting ca. 19 solvent molecules at 4.65 Å. Non-structural aspects of the Th(IV) hydration phenomenon, such hydration enthalpy and ion diffusion are well reproduced by the simulation results. The analysis of the O-Th-O angle distribution suggests that the capped square antiprism arrangement prevails over the trigonal tricapped prism. The well-balanced definition of the ion–water and water–water interactions in such a demanding ion neighbourhood is confirmed by the EXAFS and XANES spectroscopies. The theoretical spectra, computed from the MD trajectory, are in fine agreement with some of the experimentally recorded. The sensitivity of the XAS spectroscopy to structural changes confirms how the presented potential manages in a proper way the response of the water molecules to the highly polarising electric field generated by the tetravalent ion.

Effect of branching in the alkyl chain of diglycolamide on the sequestration of tetravalent actinides: solvent extraction and theoretical studies.

DGA (diglycolamide) ligands show a different extraction behavior of trivalent metal ions by changing the branching alkyl chain length as well as the branching at the methylene position. There are no studies of these factors on the extraction efficiency of these DGA derivatives for the extraction of tetravalent actinides. We have evaluated four different DGA derivatives for the extraction of Np, Pu, and Th from molecular diluents. The n-butyl derivative shows enhanced extraction efficiency and branching gives rise to a reduction in the extraction efficiency of tetravalent ions. The distribution ratios are higher in pure octanol than in a mixture of 30% octanol and 70% n-dodecane. This behavior is in marked difference to that of the extraction of trivalent ions where the addition of an alcohol generally decreases the distribution ratio of trivalent ions due to the ligand-modifier intercation, poor aggregation or micelle formation tendency of DGAs in polar solvents. This suggests that micelle-mediated extraction may not be the dominating factor for the extraction of tetravalent metal ions. Slope analysis suggests the involvement of only two DGA molecules in the extracted species suggesting no/poor possibility of micelle formation in the present system. The higher extraction in pure octanol may be due to a better solubility of the extracted complexes in this polar medium compared to the mixture of octanol and n-dodecane. The water and acid uptake, the back extraction, and the radiation stability of the solvent systems were also investigated. DFT studies were performed to get a better insight into the extraction and complexation of the different DGA solvent systems.

Textural and chemical variations in cassiterite from the Yuanlinzi Sn-Cu deposit, NE China: Insights into ore-forming processes

Microtextural, U–Pb isotopic, and trace element analyses were conducted on magmatic and hydrothermal cassiterites from the Yuanlinzi Sn–Cu deposit (NE China) to determine the timing of mineralization and investigate the ore-forming process. Magmatic cassiterites are disseminated in pegmatite, while hydrothermal cassiterites can be classified into three types: cassiterite-bearing stockworks in pegmatite, disseminated cassiterite in wall rock, and cassiterite-quartz-feldspar veins. U–Pb dating of the four types of cassiterite yields a similar age of ∼ 139 Ma, which is consistent with the ages of regional tin mineralization and granites within the mining district. These results suggest a strong association between Early Cretaceous magmatism and tin mineralization. The four types of cassiterite exhibit comparable textural features, characterized by alternating oscillatory CL zonation and dark homogeneous bands, with the latter commonly enriched in W, Nb, Ta, and U. The direct substitution of tetravalent ions, including Zr, Hf, Ti, and V, with Sn4+ and the coupled substitutions of Fe3+ + OH– = Sn4+ + O2– or Fe3+ + H+ = Sn4+, 2Sb3+ + U6+ = 3Sn4+ and Sc3+ + V5+ = 2Sn4+ are responsible for the incorporation of these elements in cassiterite. The enrichment of W, Nb, Ta, and U in the dark domains of cassiterite is related to the coupled substitution of W + U and Nb + Ta, while the excess of Nb and Ta in the oscillatory-zoned domains may be attributed to the substitution of 4(Nb, Ta)5+ + □ = 5Sn4+. The trace element variations observed in the four types of cassiterite, particularly Al, Sc, Ti, V, and Fe, reflect the ongoing enhancement of the water–rock reaction during the mineralization process. The examination of redox-sensitive elements such as Fe, U, and V suggested that tin mineralization in the Yuanlinzi deposit occurred in an oxidizing environment where oxygen fugacity gradually increased. Additionally, we proposed that the Sc/V ratio of cassiterite could serve as an indicator of the redox state of the associated melt/fluid.

Arsenazo III-spectrophotometry for the determination of thorium content

ABSTRACT The complexation interaction between arsenazo III chromogenic agent and tetravalent thorium ion (Th4+) is the theoretical basis for the determination of thorium by spectrophotometry. In this paper, the effects of the acidity, temperature, interfering ions and Th4+ concentration on the absorbance and stability of arsenazo III-Th4+ solution by spectrophotometry were systematically studied. The results showed that the solutions to be tested had high absorbance values and stability only when the concentration of hydrochloric acid was greater than 6 mol·L−1. The absorbance decreased only 0.02 when the temperature was changed from 15°C to 40°C. The absorbance of arsenazo III-Th4+ solution at 662 nm showed a good linear relationship with the concentration of Th4+ under the same experimental environment (R2 = 0.9986), and the apparent molar absorption coefficient was 9.95 × 104 L·mol−1·cm−1, showing that thorium can be accurately quantitatively measured according to the Lambert-Beer law under these conditions.

Micrometric patterning of a borogermanate glass containing terbium by thermal poling to manage luminescence and second order optical properties

Borogermanate glasses containing terbium ions are interesting materials due to their luminescent and magnetic properties. Terbium can present two different oxidation states and the thermal poling technique can be a pertinent way to modulate spatially the oxidation state of these ions. In this work, we demonstrate using a thermo-electrical imprinting process the transfer of micro scaled motifs on the surface of a borogermanate glass containing Tb3+ resulting in a micrometric structuring of the oxidation state of Tb3+/Tb4+ ions. A large change in absorption and luminescence optical properties is observed, arising from the distinct properties of trivalent and tetravalent terbium ions. Correlative micro luminescence, Raman and second harmonic generation measurements were carried out on the patterned poled glass surface. This has demonstrated an accurate concomitant modification of the glass structure accompanying large luminescence changes and the appearance of a second order optical response which could be attributed to a localized space charge implantation. These original results demonstrate how a simple electrical process allows managing multi optical properties but also paves the way to induce static electrical functionalities in a magnetic optical glassy system.

Crystal structure, composition and valence state of cations in mixed-valence A1-xCdxMnO3 (A=Pr, La) ceramics

Abstract Complex manganites A1−xCdxMnO3 (A = Pr, La) are synthesized by solid state reaction method. X-ray diffraction, scanning electron microscopy and energy-dispersive analysis are applied to study their crystal structure, surface morphology, elemental and phase composition. X-ray photoelectron spectroscopy (XPS) methods are used to study the charge states of Pr and La cations, as well as to quantify the fractions of coexisting Mn3+ and Mn4+ ions. La3d-, La4d-, Pr4d- и Mn2p-spectra of La3+, Pr3+, Mn3+ and Mn4+ ions are calculated in the isolated–ion approximation with accounting for multiplet splitting and charge transfer effect. Good agreement with the experiment is obtained. The relative fractions of trivalent and tetravalent manganese ions in La0.45Cd0.78Mn0,9O2.86 and Pr0.50Cd0.76Mn0.86O2.88 samples are determined by fitting the Mn2p spectra by superposition of experimental spectra containing only Mn3+, and only Mn4+ ions; they were found to be 0.71Mn3+/0.29Mn4+ and 0.54Mn3+/0.46Mn4+, respectively.

Li3V2(PO4)3 Cathode Material: Synthesis Method, High Lithium Diffusion Coefficient and Magnetic Inhomogeneity.

Li3V2(PO4)3 cathodes for Li-ion batteries (LIBs) were synthesized using a hydrothermal method with the subsequent annealing in an argon atmosphere to achieve optimal properties. The X-ray diffraction analysis confirmed the material's single-phase nature, while the scanning electron microscopy revealed a granular structure, indicating a uniform particle size distribution, beneficial for electrochemical performance. Magnetometry and electron spin resonance studies were conducted to investigate the magnetic properties, confirming the presence of the relatively low concentration and highly uniform distribution of tetravalent vanadium ions (V4+), which indicated low lithium deficiency values in the original structure and a high degree of magnetic homogeneity in the sample, an essential factor for consistent electrochemical behavior. For this pure phase Li3V2(PO4)3 sample, devoid of any impurities such as carbon or salts, extensive electrochemical property testing was performed. These tests resulted in the experimental discovery of a remarkably high lithium diffusion coefficient D = 1.07 × 10-10 cm2/s, indicating excellent ionic conductivity, and demonstrated impressive stability of the material with sustained performance over 1000 charge-discharge cycles. Additionally, relithiated Li3V2(PO4)3 (after multiple electrochemical cycling) samples were investigated using scanning electron microscopy, magnetometry and electron spin resonance methods to determine the extent of degradation. The combination of high lithium diffusion coefficients, a low degradation rate and remarkable cycling stability positions this Li3V2(PO4)3 material as a promising candidate for advanced energy storage applications.

Preliminary study of novel all‐solid‐state tin‐graphite battery based on composite solid electrolyte

AbstractThis study primarily focuses on utilizing tin as the primary electrode material. Tin is chosen for its exceptional theoretical capacitance and cost‐effectiveness, attributed to its tetravalent ions carrying a high charge. Tin also exhibits desirable soft material characteristics, ensuring superior stability and adhesion. The experimental methodology involves thermal evaporation and vacuum heat treatment to create Sn, Sn‐9 wt.%Zn, Sn‐40wt.%Zn alloy negative electrodes. For the solid electrolyte, we opt for magnesium silicate processed battery cloth deposition combined with a polymer, offering flexibility. The positive electrode incorporates a graphite film modified with a stable and conductive phosphate, referred to as GFN. This approach enables the development of an all‐solid‐state Sn‐C ion secondary battery while prioritizing safety and environmental friendliness. The experimental findings encompass microscopic structural insights into various electrode materials, elucidation of the metallurgical mechanism of alloy films, exploration of ion transport pathways, and confirmation of the charge and discharge mechanism.

Triply Bonded Pancake π-Dimers Stabilized by Tetravalent Actinides.

Aromatic π-stacking is a weakly attractive, noncovalent interaction often found in biological macromolecules and synthetic supramolecular chemistry. The weak nondirectional nature of π-stacking can present challenges in the design of materials owing to their weak, nondirectional nature. However, when aromatic π-systems contain an unpaired electron, stronger attraction involving face-to-face π-orbital overlap is possible, resulting in covalent so-called "pancake" bonds. Two-electron, multicenter single pancake bonds are well known, whereas four-electron double pancake bonds are rare. Higher-order pancake bonds have been predicted, but experimental systems are unknown. Here, we show that six-electron triple pancake bonds can be synthesized by a 3-fold reduction of hexaazatrinaphthylene (HAN) and subsequent stacking of the [HAN]3- triradicals. Our analysis reveals a multicenter covalent triple pancake bond consisting of a σ-orbital and two equivalent π-orbitals. An electrostatic stabilizing role is established for the tetravalent thorium and uranium ions in these systems. We also show that the electronic absorption spectrum of the triple pancake bonds closely matches computational predictions, providing experimental verification of these unique interactions. The discovery of conductivity in thin films of triply bonded π-dimers presents new opportunities for the discovery of single-component molecular conductors and other spin-based molecular materials.

Studies on electromagnetic properties of lithium based ferrimagnetic spinel oxides prepared with different additives and microwave sintering

Soft ferrimagnetic spinel lithium based oxides were prepared with additives like V2O5 and Na2SiO3 and sintered with the efficient microwave sintering technique. Tetravalent metal ions substituents like Mn+4, Ti+4 were used to enhance the important properties like D. C. resistivity, saturation magnetization, permeability, hysteresis and dielectric behavior. The ferrites were sintered at different sintering temperatures viz., 900, 950 and 1000 °C for 10 min by microwave technique and by conventional technique at 1050 °C for 4h. X-ray diffraction (XRD) studied the structural behavior which confirmed the spinel characteristics, Scanning electron microscopy (SEM) and EDAX revealed the microstructural and elemental compositions respectively of the ferrites. The use of additives and the microwave sintering significantly influencing the microstructural behavior and subsequently on the electromagnetic properties could be observed. Studies of initial permeability and initial permeability loss found to remain nearly constant with change in frequency until at certain frequency they showed resonance behavior. The resonance frequency’s dependence on the microstructures of the ferrites could be observed. Temperature dependence behavior of the dielectric parameters and the B-H loop traced from torroidal samples of the ferrites were studied.

Chemical expansion of La3+ and Yb3+ incorporated Zr-doped ceria ceramics for concentrated solar energy-driven thermochemical production of fuels

Redox studies on Zr, La, Yb doped ceria (Ce0.9M3+/4+0.1O2-x, M3+/4+ = Zr4+, La3+, Yb3+ and CeZr0.05 M3+0.05O1.95, M3+ = La3+, Yb3+) ceramics were performed using dilatometry and mass change measurements to analyze the chemical and thermal volume changes depending on reduction state which can have dramatic effects on the long-term stability of these ceramics in Concentrated Solar Energy (CSE)–driven applications relevant to the synthesis of fuels. The reduction extents determined by both methods under vacuum (p = 2×10−5 mbar) are similar up to 1673 K. At higher temperatures, CeO2, which has a higher vapor pressure than the oxides of the dopant ions, evaporates. As a result, there is an accumulation of doping ions, which leads to a porous surface zone. Surface enrichment of dopants, especially that of Zr4+, is crucial for re-oxidation kinetics. Co-doping with trivalent doping ions such as La3+ and Yb3+ reduces the extent of selective evaporation materializing it into a thinner porous surface layer. Trivalent dopants and their additional oxygen vacancies also influence the chemical expansion/contraction of the Zr4+ doped ceria crystal lattice during the redox reaction and thus lead to a reduction of mechanical stresses. We assume that additional oxygen vacancies from trivalent dopant ions promote the disordering of intrinsic oxygen vacancies, while smaller tetravalent ions such as Zr4+ compensates this effect. This explains that doped ceria with trivalent and tetravalent ions show almost the same chemical expansion as pure ceria. The new results on alteration, thermal and chemical expansions/contractions at high temperature are particularly important for the development of metal oxide ceramic components exposed to cyclic reducing and oxidizing atmospheres at elevated temperatures achieved via CSE.

Structure and size of complete hydration shells of metal ions and inorganic anions in aqueous solution.

The structures of nine hydrated metal ions in aqueous solution have been redetermined by large angle X-ray scattering to obtain experimental data of better quality than those reported 40-50 years ago. Accurate M-OI and M-(OI-H)⋯OII distances and M-OI(H)⋯OII bond angles are reported for the hydrated magnesium(II), aluminium(III), manganese(II), iron(II), iron(III), cobalt(II), nickel(II), copper(II) and zinc(II) ions; the subscripts I and II denote oxygen atoms in the first and second hydration sphere, respectively. Reported structures of hydrated metal ions in aqueous solution are summarized and evaluated with emphasis on a possible relationship between M-OI-OII bond angles and bonding character. Metal ions with high charge density have M-OI-OII bond angles close to 120°, indicative of a mainly electrostatic interaction with the oxygen atom in the water molecule in the first hydration shell. Metal ions forming bonds with a significant covalent contribution, as e.g. mercury(II) and tin(II), have M-OI-OII bond angles close to 109.5°. This implies that they bind to one of the free electron pairs in the water molecule. Comparison of M-O bond distances of hydrated metal ions in the solid state with one hydration shell, and in aqueous solution with in most cases at least two hydration shells, shows no significant differences. On the other hand, the X-O bond distance in hydrated oxoanions increases by ca. 0.02 Å in aqueous solution in comparison with the corresponding X-O distance in the solid state. A linear correlation is observed between volume, calculated from the van der Waals radius of the hydrated ion, and the ionic diffusion coefficient in aqueous solution. This correlation strongly indicates that monovalent metal ions, except lithium and silver(I), and singly-charged monovalent oxoanions have a single hydration shell. Divalent metal ions, bismuth(III) and the lanthanoid(III) and actinoid(III) ions have two hydration shells. Trivalent transition and tetravalent metal ions have two full hydration shells and portion of a third one. Doubly charged oxoanions have one well-defined hydration shell and an ill-defined second one.

Amine-directed synthesis, valence state control, and optical properties of two new organic-inorganic tin chlorides.

Two organic-inorganic tin chlorides, namely (C9H26N3Cl)SnCl4 (1) and (C9H26N3Cl)SnCl6 (2), were prepared via valence state control using N,N,N',N'',N''-pentamethyldiethylenetriamine as a structure-directing agent. The two compounds have zero-dimensional structures crystallized in non-centrosymmetric orthorhombic space group Cmc21 and P212121, respectively. In compound 1, the divalent tin ion forms a seesaw coordination configuration with four chloride ions, whereas in compound 2, the tetravalent tin ion forms an octahedral coordination configuration with six chloride ions. The two compounds show a moderate second-harmonic generation response under 1064 nm laser irradiation. Notably, compound 2 displays a bright orange luminescence with a photoluminescence quantum yield of 19.67%. Theoretical calculations were performed to gain insights into the optical properties of the two compounds.

Structures of Th4+ aqueous solutions: insights from AIMD and metadynamics simulations.

Solution chemistry of actinide ions is critical to understanding the solvation behaviors and hydrolysis process. Using tetravalent thorium ion Th4+ as a representative example, we investigate the local structures and dynamic behaviors of hydrated Th4+ ions by ab initio molecular dynamics (AIMD) simulations using the recently developed norm-conserving pseudopotentials and basis sets optimized for actinides (J.-B. Lu et al., J. Chem. Theory Comput. 2021, 17, 3360-3371). AIMD simulations reveal two distinct solvation shells, with the first shell comprising 9 water molecules at approximately rTh-O = 2.50 Å and exhibiting a tricapped trigonal prism geometry. These conclusions are confirmed through metadynamics simulations and further structural analysis. AIMD simulations also show the slight effect of temperature and counterions on the structure of the solution. The structured solvation shells of the highly charged Th4+ ion with the specific geometry, distinct from the structure of liquid water, lead to corresponding structural changes in the hydrogen bond network in water. Additionally, beyond the solvent-shared ion pair (SIP) state observed in the unbiased AIMD simulations, the metadynamics simulations reconstruct a two-dimensional free energy surface that clearly indicates the potential stability of the contact ion pair (CIP) state in the system with Cl- as a counterion. The findings in this work provide insights into the solution chemistry of actinides and serve as a reference for studying other actinide solution systems.

A tetravalent praseodymium complex with field-induced slow magnetic relaxation.

Herein the synthesis, structural characterization, and magnetic properties of a Pr(IV) complex [Pr(OSiPh3)4(L)] (1, L = 4,4'-dimethoxy-2,2'-bipyridine) are reported. The stability of the Pr(IV) complex significantly enhanced with the use of the bidentate ligand L. Slow magnetic relaxation was observed at low temperatures, indicating that the complex may be the first single-ion magnet with a tetravalent lanthanide ion being the magnetic center.

Doping of large amount tetravalent Ge ions into Fe2O3 structure and experimental results on modified structural, optical and electronic properties

We report the doping of high concentration of tetravalent Ge4+ ions (5 mol % for x = 0.05–30 mol % for x = 0.30) at the Fe3+ sites of Fe2-xGexO3 system by chemical coprecipitation route. The charge state of Fe and Ge ions has been modified into lower values, in addition to their normal +3 and + 4 states, to stabilize the rhombohedral phase of hematite (α-Fe2O3) structure. X-ray photoelectron spectra and optical band gap measurements indicated a combination of ionic and covalence character of metal-oxygen bonds as an effect of Ge doping in the hematite structure. The Ge doped hematite samples have exhibited semiconductor properties with band gap of 1.50–4.70 eV and remarkably enhanced electrical conductivity (σ ∼ 10−4 S/m) in comparison to α-Fe2O3 (10−11 S/m). The results confirmed the strategy of enhancing electrical conductivity in hematite structure by doping of tetravalent cations. The thermo-conductivity measurements using warming and cooling modes showed highly irreversible feature at higher temperatures. Some of the samples indicated metal-like state at lower temperature, in addition to semiconductor state at higher temperatures. It has been understood that combination of ionic and covalence character of the metal-oxygen bonds has played an important role in modifying the semiconductor properties in Ge doped Fe2O3 system.