Positions Of Ions Research Articles

Comparison of bismuth ferrites for chloride removal: Removal efficiency, stability, and structure

The chloride (Cl−) ions in wastewater are difficult to remove, since there is a lack of effective and recyclable chloride removal agents. In this study, the bismuth ferrites (BFO) are first explored as chloride removal agents, and their oxidation or precipitation effects on the Cl− removal are studied. In the BFO samples, the crystal phases of BiFeO3 and Bi2FeO4 have very limited contributions to the Cl− removal, while the enhanced removal ability is exhibited with the increase of Bi25FeO40. When the mass percentage of Bi25FeO40 reaches 70%, high Cl− removal efficiencies of 80–90% are achieved, which even exceeds 95% for pure Bi25FeO40. The morphology and structure characterizations reveal that the excellent Cl− removal performance of Bi25FeO40 is determined by its unstable chemical structure due to the sharing of Bi5+ and Fe3+ ions in the tetrahedral positions. The density of states and electron localization function of Bi25FeO40 demonstrate that its Fe and O bonding is weaker than those of BiFeO3 and Bi2FeO4, resulting in the easier breaking of the Fe3+/Bi5+-O bonds to release Bi5+ ions, which have oxidation ability for the formation of OH and Cl radicals to enhance the Cl− removal efficiency.

Mineralogy and mineral chemistry of quartz: A review

AbstractQuartz (trigonal, low-temperature α-quartz) is the most important polymorph of the silica (SiO2) group and one of the purest minerals in the Earth crust. The mineralogy and mineral chemistry of quartz are determined mainly by its defect structure. Certain point defects, dislocations and micro-inclusions can be incorporated into quartz during crystallisation under various thermodynamic conditions and by secondary processes such as alteration, irradiation, diagenesis or metamorphism. The resulting real structure is a fingerprint of the specific physicochemical environment of quartz formation and also determines the quality and applications of SiO2raw materials. Point defects in quartz can be related to imperfections associated with silicon or oxygen vacancies (intrinsic defects), to different types of displaced atoms, and/or to the incorporation of foreign ions in lattice sites and interstitial positions (extrinsic defects). Due to mismatch in charges and ionic radii only a limited number of ions can substitute for Si4+in the crystal lattice or can be incorporated in interstitial positions. Therefore, most impurity elements in quartz are present at concentrations below 1 ppm. The structural incorporation in a regular Si4+lattice site has been proven for Al3+, Ga3+, Fe3+, B3+, Ge4+, Ti4+, P5+and H+, of which Al3+is by far the most common and typically the most abundant. Unambiguous detection and characterisation of defect structures in quartz are a technical challenge and can only be successfully realised by a combination of advanced analytical methods such as electron paramagnetic resonance (EPR) spectroscopy, cathodoluminescence (CL) microscopy and spectroscopy as well as spatially resolved trace-element analysis such as laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and secondary-ion mass spectrometry (SIMS). The present paper presents a review of the state-of-the-art knowledge concerning the mineralogy and mineral-chemistry of quartz and illustrates important geological implications of the properties of quartz.

Enhancement of the Luminescence Properties of Eu (III) Containing Paramagnetic Saponite Clays

In this study, 1,10-phenanthroline molecules were introduced in the interlayer space of a paramagnetic synthetic saponite clay containing both Eu3+ and Gd3+ ions in structural positions. Two samples with different loading of phenanthroline dye were prepared. The resulting hybrid materials possessed improved optical emission properties due to an efficient antenna effect from the phenanthroline to the Eu3+ centers; this effect was demonstrated to be higher than the metal-to-metal Gd3+-Eu3+ energy transfer previously studied. Insights on the relaxometric properties in aqueous solution of the solids after incorporation of the antenna groups were also obtained through NMR relaxometric analyses.

Collision dynamics of cytosine under proton irradiation

In the framework of the time-dependent density-functional theory, applied to valence electrons, coupled non-adiabatically to molecular dynamics of ions, the collision dynamics of cytosine impacted by proton is studied. We especially focus on the effect of the collision orientations on the damage of cytosine by choosing two collision orientations taking the oxygen atom on the double bond CO as the collision site with the incident energy of proton ranging from 150 eV to 1000 eV. First, two collision dynamical processes are explored by analyzing the molecular ionization, the ionic position and the kinetic energy, the energy loss of proton and the electronic density evolution. The results show that the damage process of cytosine induced by proton impact is mainly the capture of electrons by proton, the departments of ions and groups as well as the opening of ring. It is found that the orientation has little effect on the loss of the kinetic energy of proton, which is about 21.5[Formula: see text] of the incident energy of proton. Although the scattering angle [Formula: see text] has a polynomial relationship with [Formula: see text] in both cases, it is greatly affected by the orientation. When [Formula: see text] eV, the scattering angle of proton colliding with O along the [Formula: see text]-axis is greater than that of proton colliding with O along the [Formula: see text]-axis. The orientation also has a great effect on the mass distribution of the fragments and the fragmentation route. When proton moves along the [Formula: see text]-axis, the fragmentation route is that O leaves the cytosine and the rest keeps on vibration, while products are not only related to the incident kinetic energy, but also show diversity when proton moves along the [Formula: see text]-axis.

Insights to the hydrothermal synthesis of highly crystalline aluminum-free Na[Co]ZSM-5 zeolites and their CO2 adsorption performance

In this work, MFI-type cobaltosilicates as inorganic polymers consisting of tetrahedral TO4 (T = Si and Co) building units were synthesized by utilization of a novel pretreatment method aimed for the silicon precursor activation. Crystallization of zeolites was carried out using a conventional hydrothermal method. The effect of various parameters such as Co/Si molar ratio, crystallization time and pH of initial gel on the crystallization process was studied to provide the optimal conditions for crystallization. The prepared zeolites were characterized using XRD, FT-IR, UV–vis, SEM, TEM, N2 adsorption, and TGA techniques. The XRD patterns confirmed the formation of pure crystalline ZSM-5 zeolites without any cobalt oxide impurities. A small shift towards lower diffraction angles in the XRD patterns of the samples was detected by increasing cobalt content in the initial gel, which validated the incorporation of Co2+ ions into the zeolites’ framework. The presence of Co2+ ions in the tetrahedral positions of zeolites’ framework was also proved by FT-IR and UV–vis spectra. EDX-mapping images exhibited a more uniform dispersion of Co2+ ions in the structure of ZSM-5 zeolite synthesized at pH = 9.5 compared to its analogous counterpart synthesized at higher pH. The results of N2 adsorption analysis revealed that the specific surface area of Na[Co]ZSM-5 zeolites was comparable to aluminosilicate ZSM-5 zeolites. The synthesized zeolites were examined for CO2 adsorption. The adsorption capacities measured at 298 K and 1 bar were approximately 2.19 and 5.33 mmol g−1 for samples prepared at pH = 9.5 and 10.5, respectively.

Bifunctional Paramagnetic and Luminescent Clays Obtained by Incorporation of Gd3+ and Eu3+ Ions in the Saponite Framework.

A novel bifunctional saponite clay incorporating gadolinium (Gd3+) and europium (Eu3+) in the inorganic framework was prepared by one-pot hydrothermal synthesis. The material exhibited interesting luminescent and paramagnetic features derived from the co-presence of the lanthanide ions in equivalent structural positions. Relaxometry and photoluminescence spectroscopy shed light on the chemical environment surrounding the metal sites, the emission properties of Eu3+, and the dynamics of interactions between Gd3+ and the inner-sphere water placed in the saponite gallery. The optical and paramagnetic properties of this solid make it an attractive nanoplatform for bimodal diagnostic applications.

Dielectric Relaxation Dynamics and Polaronic Tunneling Conduction Mechanism of Electrical Conductivity of Fe2O3‐Doped PbO–ZrO2–SiO2 Glass Ceramics

This study consists of comprehensive investigations on dielectric permittivity (ε′), electric moduli (M′, M″), impedance (Z), and conductivity (σac) spectra over broad regions of frequency and temperature of lead zirconium silicate glass ceramics mixed with different concentrations of Fe2O3. The observed increase in dielectric permittivity with the content of Fe2O3 is attributed to the increasing presence of iron ions in octahedral positions. Electric moduli plots with frequency (ω) and temperature (T) exhibit dipolar effects. These effects are quantitatively analyzed by Cole–Cole plots; the analysis indicates the distribution of relaxation times. Probable dipoles for these effects are identified and discussed. AC conductivity (σac) shows a rising trend with an increase in Fe2O3 beyond 0.2 mol%, and this increase is attributed to the polaron exchange among Fe2+ and Fe3+ ions. The conduction mechanism is well explained using a polaron tunneling model in the middle‐frequency and high‐temperature regions.

Double single-channel Kondo coupling in graphene with Fe molecules

We study the interaction between graphene and a single-molecule-magnet, [Fe 4(L)2(dpm)6]. Focusing on the closest Iron ion in a hollow position with respect to the graphene sheet, we derive a channel selective tunneling Hamiltonian, that couples different d orbitals of the Iron atom to precise independent combinations of sublattice and valley degrees of freedom of the electrons in graphene. When looking at the spin-spin interaction between the molecule and the graphene electrons, close to the Dirac point the channel selectivity results in a channel decoupling of the Kondo interaction, with two almost independent Kondo systems weakly interacting among themselves. The formation of magnetic moments and the development of a full Kondo effect depends on the charge state of the graphene layer.

An electrospray ionization study on complexes of amylin with Cu(II) and Cu(I).

Human amylin (hIAPP) is one of a number of different peptides known to be responsible for the formation of amyloid fibrils in the pancreas of subjects with Type 2 diabetes mellitus. It was recognized that metal ions such as Cu(II) are implicated in the aggregation process of amyloidogenic peptides. However, the role of Cu(II) ions in the aggregation and dyshomeostasis of amylin has been controversial. Considering that most of the research reported in the literature pertain to the interactions between Cu(II) and amylin, we thought of interest to compare the interactions of Cu(II) and Cu(I) ions with amylin by electrospray ionization (ESI) mass spectrometry and collisional experiments, to elucidate possible differences in structural aspects of the complexes so formed. The ESI mass spectra of solutions containing hIAPP and Cu(I) or Cu(II) ions show the formation of hIAPP-Cu complexes. In both cases, M + Cu ions with three and four positive charges are detected. However, a series of fragment ions, absent in the ESI spectrum of untreated hIAPP, become detectable. Some of them are common for both Cu(I) and Cu(II) complexes, whereas others are specific for the complexes containing Cu in different oxidation states. Some fragments imply the involvement of residues His18, Ser19, Ser20, Asn21, and Asn22 in the complex formation, but the detection of the fragment b22 3+ indicates the presence of copper ions in a different position. This suggests different interaction sites between Cu(II) and Cu(I) and hIAPP. In contrast to Cu(II) complex, in the Cu(I) complex, some peculiar structures are present, corresponding to the cleavage of Asn-Asn peptidic bond and to [b30 + Cu(I)]4+ and [b28 + Cu(I)]4+ species. These results are in agreement with the coordination vacancy in [Cu(I)-(peptide)] species, which promotes Cu(I) interaction with additional neighboring donors (mainly N-histidine, and also S-methionine or other groups depending on the peptide conformation) through formation of trigonal T-shaped intermediates.

Effects of Ni-doping on microstructure, magnetic and microwave absorption properties of CoFe2O4

In this paper, the Co1−xNixFe2O4 (x = 0, 0.1, 0.3, 0.5) ferrite material sample was successfully synthesized by the sol–gel combustion method. Using XRD to detect the phase, it was found that a pure sample was prepared, and the corresponding unit cell model was established using XRD data. At the same time, using Raman spectroscopy analysis, the change of the T2g(1) peak in the Raman spectrum indicates that the doping of Ni2+ ions replaces the Co2+ ions in the tetrahedral position, and the high-frequency shoulder-like characteristics also indicate that the octahedral position has been replaced. The substitution of Ni2+ ions for Co2+ ions causes lattice distortion, which leads to the destruction of the ferromagnetic sequence and thus changes in magnetic properties. Microscopic observation was performed with SEM to observe the structure. It was found that with the doping of Ni2+ iron, the grain size gradually decreased, and the decrease of the grain size would have an impact on the space charge polarization. At the same time, the phenomenon of electronic polarization was found in the analysis of the microwave absorption mechanism. To explain the occurrence of this phenomenon, Raman detection was performed on the sample. The Raman detection is combined with the bond length and bond angle changes in the unit cell to analyze the Ni element. The reason for doping electron polarization. When the Ni doping amount is 0.1, the reflection loss of Co1−xNixFe2O4 at 16.24 GHz is 37.66 dB, the corresponding thickness is 2.1 mm, and the effective frequency band is 2.64 GHz, which meets the requirements of light, thin and wide microwave absorbing materials.

DNA interactions, antitubercular and cytotoxic activity of heteroleptic CuII complexes containing 1,10-phenanthroline

Herein, we describe the synthesis and characterization of novel heteroleptic copper(II) complexes, [Cu(2-HNA)(phen)ClO4]•1•5H2O I, [Cu(6-HNA)(phen)ClO4]•H2O II, [Cu(QNA)(phen)ClO4]•0•5H2O III and [Cu(2-MNA)(phen)ClO4]•0•5H2O IV, where 2-HNA = 2-hydroxynicotinic acid, 6-HNA = 6-hydroxynicotinic acid, QNA = 2-quinolinecarboxylic acid, 2-MNA = 2-mercaptonicotinic acid and phen = 1,10-phenanthroline. The spectral data indicate a square-pyramidal geometry around the copper(II) ion in the solid state, with an acid derivative and 1,10-phenanthroline (N–N) acting as bidentate ligands. A perchlorate ion in the apical position completes the metal coordination sphere. All these complexes exhibited potent activity against the Mycobacterium tuberculosis H37Rv strain, with MIC values in the range of few µM. The cytotoxic activity of these compounds was also investigated toward tumor cell lines (MDA-MB-231 and MCF-7) and in a non-tumorigenic cell line (MCF-10A). Complex I was the most active (IC50 = 4.2 μM) and selective (SI > 3) toward MDA-MB-231 cells. DNA binding studies performed by circular dichroism (CD) and UV–Vis spectroscopic methods, using a Hoechst 33258 displacement assay, indicated that these complexes can efficiently bind to ct-DNA, with Kb values in the range of 103 M‒1.

Lattice dynamics of cobalt orthoborate Co3(BO3)2 with kotoite structure

Transition metal oxyborates M3(BO3)2 (M = Mn, Co, Ni) belong to a group of materials with the kotoite structure and many of them demonstrate complex magnetic behavior as a result of competing interactions between magnetic ions in nonequivalent crystallographic positions. In this paper, we report results of the detailed infrared and Raman spectroscopic studies of a Co3(BO3)2 single crystal. Most of the phonons are observed and identified. Unusually large phonon shifts, in comparison to isostructural compound Ni3(BO3)2, were registered in the low- and mid-infrared frequency range (100–700 cm−1) of the spectra. The experimental findings are supported by the ab initio simulations of the lattice dynamics, which allow us to propose the normal-mode assignments. We argue that the large phonon shift between cobalt and nickel compounds are associated with changes of force constants induced by the changes of M–O bond lengths within the two types of octahedral MO6 groups. In addition to the first-order Raman scattering, intense second-order Raman scattering was detected due to the resonant enhancement regime. Furthermore, we performed the single crystal XRD experiments which did not show any detected evidences of magneto-structural phase transition previously observed in Ni3(BO3)2.

The synergistic mechanisms of apo-ferritin structural transitions and Au(iii) ion transportation: molecular dynamics simulations with the Markov state model.

Due to its unique structure, recent years have witnessed the use of apo-ferritin to accumulate various non-natural metal ions as a scaffold for nanomaterial synthesis. However, the transport mechanism of metal ions into the cavity of apo-ferritin is still unclear, limiting the rational design and controllable preparation of nanomaterials. Here, we conducted all-atom classical molecular dynamics (MD) simulations combined with Markov state models (MSMs) to explore the transportation behavior of Au(iii) ions. We exhibited the complete transportation paths of Au(iii) from solution into the apo-ferritin cage at the atomic level. We also revealed that the transportation of Au(iii) ions is accompanied by coupled protein structural changes. It is shown that the 3-fold axis channel serves as the only entrance with the longest residence time of Au(iii) ions. Besides, there are eight binding clusters and five 3-fold structural metastable states, which are important during Au(iii) transportation. The conformational changes of His118, Asp127, and Glu130, acting as doors, were observed to highly correlate with the Au(iii) ion's position. The MSM analysis and Potential Mean Force (PMF) calculation suggest a remarkable energy barrier near Glu130, making it the rate-limiting step of the whole process. The dominant transportation pathway is from cluster 3 in the 3-fold channel to the inner cavity to cluster 5 on the inner surface, and then to cluster 6. These findings provide inspiration and theoretical guidance for the further rational design and preparation of new nanomaterials using apo-ferritin.

Study on the mechanism of tunable ferromagnetic composites with different rare earth ions.

Size-controlled Fe3O4 nanoparticles doped with rare earth (RE) ions (La3+, Ce3+, and Dy3+) varying from 15 nm to 30 nm were successful synthesized by a hydrothermal method for potential applications in the fields of biomedicine, environmental protection and magnetic memory devices. They possessed good dispersibility, adjustable particle size and nearly spherical shape. The particle grain size was uniformly distributed and showed a low degree of agglomeration in comparison with undoped Fe3O4 nanoparticles. The FTIR results showed that the RE elements partially replaced Fe2+, occupied the octahedral position, and enhanced the vibration of the Fe–O bond. The XPS study further revealed that the valence states of La, Ce, and Dy are both positive trivalent. The XPS Fe 2p valence band spectra observed a shift in the peak position toward higher binding energy after RE doping, confirming the existence of RE ions in the octahedral position. This paper explains the mechanism of rare earth doping with Fe3O4, and clarifies the influence of the doping of different RE ions on its magnetic properties. The detailed analysis of RE-doped ferrite materials can open a new perspective in designing biomedical and spintronics materials with tailored properties by choosing suitable cation substitution.

Synthesis and Investigation of Magnesium–Aluminum Nanopowders and Ceramics Activated by Copper

Nanopowders of two crystalline phases, magnesium–aluminum spinel (98 wt %), and cuprite (2 wt %) have been obtained by laser evaporation of a solid target, which is a mechanical mixture of simple oxides (MgO, Al2O3, CuO). These nanopowders have been used to prepare test samples of transparent Cu:MgAl2O4 ceramics, the IR transmission spectra of which revealed two new strong absorption bands at λ1 ≈ 1.55 (1.45) μm and λ2 ≈ 3.45 (3.03) μm, corresponding to transitions between the Stark levels 2E( $${\text{t}}_{2}^{6}$$ e3) and 2T2 ( $${\text{t}}_{2}^{5}$$ e4) of Cu2+ ions in octahedral and tetrahedral positions, respectively.

Calorimetry of DyxY3−xAl5O12 garnet solid solutions in magnetic field

We report the caloric and magnetocaloric properties of the DyxY3−xAl5O12 garnet single crystals (x = 0, 0.15, 0.5, 1, 1.5, 2.25, 3) studied within a large temperature range at magnetic fields up to 70 kOe. Heat capacity at zero field revealed that the Schottky anomalies ascribed to magnetic splitting the ground Kramers doublet of Dy3+ ions induced by neighbor ions. The low-temperature heat capacity was fitted by a sum of the Debye and Schottky contributions. The antiferromagnetic transition above 1.9 K was observed only for the pure dysprosium aluminum garnet. The shifts of the Schottky anomalies in magnetic fields agreed with strong anisotropy of the g-factor of Dy3+ ions in the c-sites. The Dy3+ ions in the non-stoichiometric positions caused additional weak anomalies in the heat capacity. The heat capacity for the garnet with x = 1 demonstrated strong clustering for this particular composition. The results obtained showed that the measurements of the heat capacity in magnetic field can be used to get information on substitutional disorder and non-stoichiometry in solid solutions. The magnetic entropy was evaluated for the dysprosium-comprising garnets. The pronounced magnitude of the magnetic entropy owing to the Schottky anomalies shows the applicability of the mixed dysprosium yttrium garnets to adiabatic refrigerators.

Synthesis and structural analysis of complexes based on α-amino ketone derived from benzimidazole

Two cobalt (II) and nickel (II) coordination compounds have been synthesized starting from 2-(1H-benzimidazol-1-yl)-1-phenylethanone, an α-amino ketone with the N atom belonging to an imidazole ring. The newly synthesized compounds have been characterized by spectral methods (IR, UV-Vis-NIR), thermal analysis, magnetic data and single-crystal X-ray diffraction. The single-crystal X-ray structure of the cobalt (II) complex shows a tetragonal octahedral geometry with four organic ligands in the equatorial plane and two nitrate ions in the axial positions. An interesting feature is the dynamic disordering of the distortions inside the coordination units, due to one intra-molecular hydrogen bond traveling between one nitrate axial ligand and each of the four organic ligands. The electronic structure calculations, in the frame of Density Functional Theory (DFT), are sustaining this hypothesis, revealing optimized molecular geometries less symmetrical than the experimental shape, which is an average over equivalent distortions. The modeled reaction coordinate gave a shallow barrier, 2.36 kcal/mol, for the transformation between the four equivalent geometries corresponding to the intramolecular floppy hydrogen bonding. Entering methodological issues, we showed that the Time Dependent (TD) routines for computing electronic spectra in the DFT frame cannot account completely for ligand field driven d-d transitions. However, with dedicated analysis, useful information on the ligand field scheme can be extracted.

Influence of Antisite Defects in Yttrium–Aluminum Garnet on Paramagnetic Centers of Ce3+ and Tb3+

In yttrium aluminum garnet (YAG) crystals containing terbium and cerium impurities, along with the main EPR signals of Tb3+ and Се3+ ions located in the dodecahedral sites of the YAG lattice in a regular environment, EPR lines with a lower (several percent) intensity were observed. They also belong to the paramagnetic centers of terbium and cerium, but are characterized by slightly altered parameters—the initial level splitting for non-Kramers Tb3+ ions and g-factors for Се3+ ions. It is shown that the nature of such centers and their number can be explained by the presence of YAl antisite defects, i.e. yttrium ions in the octahedral aluminum positions, in the environment of Tb3+ and Се3+.

Evaluation of Co/SSZ-13 Zeolite Catalysts Prepared by Solid-Phase Reaction for NO-SCR by Methane.

Co/SSZ‐13 zeolites were prepared by heating the finely dispersed mixture of NH4‐SSZ‐13 and different cobalt salts up to 550 °C. Investigations by thermogravimetry – differential scanning calorimetry – mass spectrometry provided new insight into details of the solid‐state reaction. Formation of Co carrying hydrate melt or volatile species was shown to proceed from chloride, nitrate, or acetylacetonate Co precursor salts upon thermal treatment. This phase change allows the transport of the Co species into the zeolite pores. The reaction of the NH4 + or H+ zeolite cations and the mobile Co precursors generates vapor or gas products, readily leaving the zeolite pores, and cobalt ions in lattice positions suggesting that solid‐state ion‐exchange is the prevailing process. The obtained catalysts are of good activity and N2 selectivity in the CH4/NO‐SCR reaction. The thermal treatment of acetate or formate salts give solid intermediates that are unable to get in contact and react with the cations in the zeolite micropores. These catalysts contain mainly Co‐oxide clusters located on the outer surface of the zeolite crystallites and have poor catalytic performance.

Formation of a nona-nuclear copper(II) cluster with 3,5-di-methyl-pyrazolate starting from an NHC complex of copper(I) chloride.

The complete nona-nuclear cluster in bis-[1,3-bis-(2,6-di-methyl-phen-yl)imid-azol-ium] di-μ-chlorido-tetra-chlorido-octa-kis-(μ-3,5-di-methyl-pyrazolato)hexa-μ3-hydroxido-nona-copper(II) chloro-form disolvate, [HIXy]2[Cu9(μ-pz*)8(μ3-OH)6(μ2-Cl)2Cl4]·2CHCl3 or (C19H21N2)2[Cu9(C5H7N2)8Cl6(OH)6]·2CHCl3, where pz* is the 3,5-di-methyl-pyrazolyl anion, C5H7N2 -, and HIXy is the 1,3-bis-(2,6-di-methyl-phen-yl)imidazolium cation, C19H21N2 +, is generated by a crystallographic centre of symmetry with a square-planar CuII ion bound to four μ3-OH ions lying on the inversion centre. Of the four remaining unique CuII atoms, three adopt CuN2O2Cl square-pyramidal coordination geometries with the chloride ion in the apical position and one has a distorted CuN2OCl tetra-hedral geometry. The dianionic nona-nuclear core can be described as a 24-membered [CuNN]8 ring that contains a Cu9O6Cl6 core. The cluster features three intra-molecular O-H⋯Cl hydrogen bonds. In the crystal, weak C-H⋯N and C-H⋯Cl inter-actions link the components. Polynuclear paramagnetic clusters of this type are of considerable inter-est due to their relevance to both the bioinorganic and single-mol-ecule magnets research fields.