Tetrahedral Coordination Research Articles

Unexpected formation of two different coordination polymers from the reaction of Zn(HCOO)2·2H2O with 1,2-bis(4-pyridyl)ethylene

Zn(HCOO)2·2H2O reacts with 1,2-bis(4-pyridyl)ethylene (bpe) yielding two new coordination polymers [Zn4(HCOO)8(bpe)2(H2O)]∞ (1) and [Zn2(HCOO)4(bpe)]∞ (2) which were structurally characterized by IR spectroscopy and single crystal X-ray diffraction study. The hydrate species 1 is a 3D polymer where four different zinc sites are present, the first of them, four-coordinated, being linked by three bridging formate and one bridging bpe, the second six-coordinated, with a ZnNO5 coordination environment, almost regular, due to three bridging formate groups and one monodentate formate, one water molecule and one bpe. The third zinc center in 1 is always tetrahedral with three bridging formate ligands and one bridging bpe whereas the fourth Zn site is coordinated by five bridging formate ligands and one bridging bpe. The anhydrous species 2, obtained upon recrystallisation from DMF at 278 K is a zig-zag 1D polymer with a tetrahedral N2O2 zinc coordination environment due to two monodentate formate groups and two bridging bpe. Thermal analysis of 1 show a weight loss due to water elimination followed by formate and bpe decomposition, whereas in the case of 2 only a decomposition between 210 and 240 °C was observed.

Zinc borosilicate glasses doped with Co2+ ions: Synthesis and optical properties

New promising optical glasses containing cobalt ions in tetrahedral coordination have been synthesized, their mechanical and optical properties, as well as their characteristic temperatures, have been studied. High-quality glasses of the composition (70-x)ZnO–10SiO2-(20 + x)B2O3 (x = 0; 5; 10 wt%) doped with 0.1, 0.3, and 0.6 wt% CoO have been synthesized for the first time. The selected glass compositions were close to the eutectic one in the ZnO–SiO–B2O3 system. This made it possible to reduce the glass synthesis temperature from the 1350–1500 °C, described in the literature for similar zinc borosilicate glasses, to the 1170 °C. The presence of tetrahedral cobalt ions (CoO4) was identified by the absorption bands at 17000 cm−1 (4A2(4F) → 4T1(4P)) and at 6954 cm−1 (4A2(4F) → 4T1(4F)). Then the intense absorption bands in the visible region have been attributed to the 4A2(4F) → 2A1(2G), 4A2(4F) → 4T1(4P), 4A2(4F) → 2T2(2G), 4A2(4F) → 2T1(2G) and 4A2(4F) → 2E(2G) transitions. The most intense absorption band of octahedral cobalt ions (CoO6) corresponds to the 4T1(F) → 4T1(P) transition and is located in the region of 18000–20000 cm−1. According to analysis of Co2+ absorption spectra, the tetrahedral Co2+ ions concentration increased with increasing the CoO concentration in glasses. To study the nature of the bond between cobalt ion and ligands, the values of the splitting force of the ligand field (10Dq) and Racah parameter B were determined.

Lead-free scintillators based on pyridine manganese halide for X-ray imaging

Metal halide with high luminescence property have emerged as the novel candidate materials for X-ray detection and imaging. However, the toxicity of some metal cations, such as Pb2+, limits its further widespread application. In this work, a new of lead-free pyridine manganese halide (C5H6N)2MnBr4 was synthesized by the solution-processed method in room temperature. The research results show (C5H6N)2MnBr4 has a typical structure of tetrahedral coordination related to d-d transition, which has a strong green emission at 520 nm with a full width at half maximum (FWHM) of 45 nm. (C5H6N)2MnBr4 exhibits high photoluminescence quantum yields (PLQYs) of 59.36%, appreciable light yield of 15400 photons/MeV which is much higher than lead halide, relative short PL decay lifetime (247 μs) which is shorter than previous reported manganese halide and ultrashort RL decay time (12.24 ns). Finally, the performance of (C5H6N)2MnBr4 Scintillators was verified via X-ray imaging, and clear X-ray image was obtained. (C5H6N)2MnBr4 scintillators are eco-friendly and easy-synthesize while it has many superior performances: large stokes shift to reduce self-absorption of light; high PLQY to enhance scintillation performances; short decay lifetime to improve response. Thus, (C5H6N)2MnBr4 shows great potential as next generation of scintillators and this work provides a new way for the preparation of simple and low-cost metal halide scintillators.

ZIF-Based Metal-Organic Frameworks for Cantilever Gas Sensors

Among the different gas sensing platforms, cantilever-based sensors have attracted considerable interest in recent years thanks to their ultra-sensitivity and high-speed response. The gas sensing mechanism in a dynamic cantilever sensor is based on its resonance frequency shift upon adsorption of a gas molecule on the sensor. In order to sensitize the surface of a cantilever, a sensitive receptor material with large surface area is required. Metal-organic frameworks (MOFs) are a class of nanoporous crystalline materials composed of metal ions coordinated to organic linkers. MOFs are promising for gas sensing applications as they have large surface area, rich porosity with adjustable pore size and excellent selective adsorption capability for various gasses.[1] Zeolite imidazole frameworks (ZIFs) are a class of MOFs where metals with tetrahedral coordination (i.e. Zn, Co, Fe, Cu) are the central node and the ligands are imidazolate-based organic molecules.In this work, we developed a ZIF-based thin film for dynamic cantilever gas-sensing applications. We employed a novel atmospheric pressure spatial atomic layer deposition (AP-SALD)[2][3] technique to deposit a ZnO sacrificial layer on the silicon cantilevers. This technique allows the deposition of high-quality films at atmospheric pressure, faster than conventional ALD. The ZnO layer was then converted to a particular ZIF film with desired porosity and size, through a MOF-CVD process.[4] A gas-sensing bench setup was developed for the cantilever actuation and read-out. We present the chemical and morphological properties of the ZIF, as well as the frequency response of the sensor to various gases. The device showed reliable sensitivity to humidity, CO2 and several VOCs.

Construction of a 3D Metal-Organic Framework and Its Composite for Water Remediation via Selective Adsorption and Photocatalytic Degradation of Hazardous Dye.

In this work, a new bimetallic Na(I)–Zn(II) metal–organic framework (MOF), formulated as [Na2Zn3(btc)2(μ-HCOO)2(μ-H2O)8]n (1) (H3btc = benzene tricarboxylic acid), and its composite (ZnO@1) have been successfully synthesized using solvothermal and mechanochemical solid grinding methods. 1 and ZnO@1 were characterized by diffraction [single-crystal X-ray diffraction (XRD) and powder XRD], spectroscopic (ultraviolet–visible diffuse reflectance spectroscopy and Fourier transform infrared spectroscopy), microscopic (transmission electron microscopy), and thermal (thermogravimetric analysis) methods. The surface area and porosity of 1 were determined using a Brunauer–Emmett–Teller analyzer. Single-crystal diffraction of 1 confirms that Na1 and Zn2 have octahedral coordination environments, whereas Zn1 has a tetrahedral coordination geometry. Topological simplification of 1 shows a 3,6-connected kgd net. Na(I)–Zn(II) MOF (1) is crystallized with slight porosity and exhibits good tendency toward the encapsulation of zinc oxide nanoparticles (ZnO NPs). The photocatalytic behaviors of 1 and its composite (ZnO@1) were investigated over MB dye under sunlight illumination with promising degradation efficiencies of 93.69% for 1 and 97.53% for ZnO@1 in 80 min.

The structure of sc16 GaP obtained at 17.5 GPa and 1400 K

ABSTRACT Using a laser-heated diamond anvil cell, a powdered sample of gallium phosphide was compressed to 17.5 GPa and heated up to 1400 K. The material obtained was characterized at room temperature using synchrotron x-ray diffraction. Experimental results were compared with first-principles calculations. The polymorph observed assumes the simple cubic structure (sc16) initially reported for GaAs at high pressures. Microdiffraction mapping showed variable grain sizes of the synthesized phase, with the largest grains located in the middle of the heated spot. Structural refinements were performed on selected grains. The structure predicted based on first-principles calculations is in close agreement with the experiments. The two Ga–P bonds show similar lengths in sc16-GaP; however, the bond angles differ, resulting in a distorted tetrahedral coordination geometry.

Studies on the catalytic hydrothermal liquefaction of sugarcane bagasse to bio-oil, over cobalt oxide

Sugarcane bagasse, a by-product of sugar industry is a potential lignocellulose biomass for bio-oil production by hydrothermal liquefaction (HTL). The catalyst and the reaction parameters are important for the higher bio-oil yield. Hence, by the sol-gel method, cobalt oxide catalyst was synthesized, characterized by FTIR, X-ray diffraction, nitrogen adsorption and studied for the HTL of sugarcane bagasse with varying reaction time, catalyst/biomass weight ratio and water/biomass weight ratio. Formation of face-centered cubic spinel of Co3O4 was confirmed from the XRD peaks at 2Θ positions of 18, 31, 37, 45, and 65° and FTIR absorption bands at 558 and 654 cm−1 attributed to stretching vibrations of Co-O, having the Co3+ in octahedral and tetrahedral coordination respectively. A high BET surface area of 413.63 cm2/g obtained may be attributed to the citric acid added during sol-gel synthesis, which got decomposed off during the calcination. The highest yield of bio-oil was found to be 57.6% at the reaction time of 120 min, catalyst/biomass ratio of 0.4, water/biomass ratio of 28, 250°C and initial CO pressure of 45 bars, compared to 35.2% for non-catalytic HTL, confirmed its catalytic activity.

Heteronuclear metal–organic framework‐based fluorescent sensor for the detection of tetracycline antibiotics

The residues of tetracycline antibiotics (TCs) have caused serious environmental pollution due to the multi‐field application. In order to rapidly detect TCs, there is an urgent need to design new fluorescence sensor. Herein, a heterometallic metal‐organic framework (HNU‐61) is constructed and used as a fluorescence sensor for detecting the TCs. InHNU‐61, both Zn2+and Li+ions are assembled into the crystal structure, in which Zn2+adopts tetrahedral coordination mode, and can be served as the potential coordination site. The 3D structure ofHNU‐61is formed by the connection between Zn2+/Li+and isophthalic acid (m‐BDC2−) ligand with the 1D channel alongaaxis. Among the six categories of antibiotics,HNU‐61can effectively detect TCs, including tetracycline hydrochloride (TCY), chlortetracycline hydrochloride (CTE), doxycycline hydrochloride (DOX), and oxytetracycline hydrochloride (OXY) with the detection limits of 6.5 × 10−8 M, 9.2 × 10−8 M, 4.5 × 10−7 M, and 3.9 × 10−7 M, respectively. Furthermore,HNU‐61enables a rapid and sensitive detection of TCs with good anti‐interference and circulation. The detection mechanism can be attributed to the interaction between Zn2+inHNU‐61and TCs.

Prevention and mechanism effect of Zn(II) coordination complex on oral implant restoration

In this study, by reaction of Zn(NO3)2·6H2O with HL ligand under a slow evaporation reaction condition, a novel mononuclear Zn(II) complex [Zn(L)2]·C2H5OH (1) with tetrahedral coordination geometry has been created by employment of an adamantan-type Schiff-base ligand 2-(adamantan-1-ylimino)methyl-4-methylphenol (HL). Its application values against the recurrent infection after oral implants were evaluated with ELISA assay and real time RT-PCR assay. The Zn(II) complex toxicity was evaluated in this research with CCK-8 assay. The molecular docking simulation confirmed that the adamantane functional group applied a hindrance effect on the connected nitrogen atom and therefore, the oxygen atom on the hydroxyl functional group could form binding interaction with receptor as expected.

Octahedral oxide glass network in ambient pressure neodymium titanate

Rare-earth titanates form very fragile liquids that can be made into glasses with useful optical properties. We investigate the atomic structure of 83TiO2-17Nd2O3 glass using pair distribution function (PDF) analysis of X-ray and neutron diffraction with double isotope substitutions for both Ti and Nd. Six total structure factors are analyzed (5 neutron + 1 X-ray) to obtain complementary sensitivities to O and Ti/Nd scattering, and an empirical potential structure refinement (EPSR) provides a structural model consistent with the experimental measurements. Glass density is estimated as 4.72(13) g cm−3, consistent with direct measurements. The EPSR model indicates nearest neighbor interactions for Ti-O at overline{r}_{TiO} = 1.984(11) Å with coordination of n_{TiO} = 5.72(6) and for Nd-O at overline{r}_{NdO} = 2.598(22) Å with coordination of n_{NdO} = 7.70(26), in reasonable agreement with neutron first order difference functions for Ti and Nd. The titanate glass network comprises a mixture of distorted Ti-O5 and Ti-O6 polyhedra connected via 71% corner-sharing and 23% edge-sharing. The O-Ti coordination environments include 15% nonbridging O-Ti1, 51% bridging O-Ti2, and 32% tricluster O-Ti3. This structure is highly unusual for oxide glasses melt-quenched at ambient pressure, as it consists of Ti-Ox predominantly in octahedral (with nearly no tetrahedral) coordination.

Influence of inversion level on the optical absorption spectra of Ti‐doped transparent MgGa2O4 ceramics

AbstractTi‐doped (0.08, 0.30, and 1.00 atomic% [at.%]) transparent MgGa2O4 ceramics (possessing a high inversion level; i up to 0.8) were fabricated by pulsed electric current sintering, at 950°C, under vacuum for 30–90 min. Optical transmission, emission, and electron paramagnetic resonance spectra were recorded. The maximal transmission level was ∼70% (820 nm), for a thickness of ∼1 mm, which, while not very high, permitted the observation of the optical absorption bands location and profile.Interpretation of the fluorescence spectra suggests that some Ti4+ cations (mostly hexacoordinated) were accommodated by the host despite the scarcity of oxygen in the atmosphere during the sintering process. The Ti3+ cations substitute native ions located in tetrahedral sites, distorting the original Td symmetry toward a D2d symmetry. Comparing the Ti‐doped MgGa2O4 (high inversion) and MgAl2O4 (low inversion) spinels, spectral characteristics revealed that a significant increase in the inversion level drives Ti3+ cations from octahedral toward tetrahedral sites. This is reflected in the optical absorption spectra by the disappearance of the band at ∼20 000 cm−1 (detectable in MgAl2O4) in MgGa2O4; the two d–d bands, of MgA2O4, in MgGa2O4 are reduced to a single one, located at 11 800 cm−1. These results, for MgGa2O4, strongly support a similar assignment—of the strong band at 12 800 cm−1, in Ti‐doped MgAl2O4—to a tetracoordinated Ti3+. Thus, while in MgAl2O4, Ti3+ appears in both octahedral and tetrahedral coordination and in MgGa2O4 only the latter state is stable. In both spinels, Ti dopant speciates into Ti3+ and Ti4+ cations.

Hydrothermal synthesis of bulk Ni impregnated WO3 2D layered structures as catalysts for the desulfurization of 3-methyl thiophene

Unsupported Ni/W catalysts were synthesized using a hydrothermal method to form WO3. The WH-x and WN-x (x is the hydrothermal time) samples were impregnated with Ni and calcined at 450 ºC. The X-Ray diffraction, Raman spectroscopy, and UV–vis results showed that the monoclinic tungsten oxide phase forms the WOx phase in tetrahedral and octahedral coordination. Only in the Ni/WN-x series was detected the octahedral Ni species responsible for promoting the active phase. The XPS analysis revealed that 70% of the Ni promotes the WS2 active phase, forming the NiWS phase and 90% of W formed the WS2 phase. The catalysts tested in the 3-methylthiophene hidrodesulfurization reaction showed good activity under low pressure conditions. The largest activity of the Ni/WN-24 catalyst correlates well with the shorter WS2 slab lengths and the Ni-promoting the active phase. Interestingly, isoprene was obtained as the main product, indicating that the reaction mechanism followed the direct desulfurization (DDS) pathway.

Synthesis, X-ray, Hirshfeld, and AIM Studies on Zn(II) and Cd(II) Complexes with Pyridine Ligands

The synthesis and crystal structures of three heteroleptic complexes of Zn(II) and Cd(II) with pyridine ligands (ethyl nicotinate (EtNic), N,N-diethylnicotinamide (DiEtNA), and 2-amino-5-picoline (2Ampic) are presented. The complex [Zn(EtNic)2Cl2] (1) showed a distorted tetrahedral coordination geometry with two EtNic ligand units and two chloride ions as monodentate ligands. Complexes [Zn(DiEtNA)(H2O)4(SO4)]·H2O (2) and [Cd(OAc)2(2Ampic)2] (3) had hexa-coordinated Zn(II) and Cd(II) centers. In the former, the Zn(II) was coordinated with three different monodentate ligands, which were DiEtNA, H2O, and SO42−. In 3, the Cd(II) ion was coordinated with two bidentate acetate ions and two monodentate 2Ampic ligand units. The supramolecular structures of the three complexes were elucidated using Hirshfeld analysis. In 1, the most important interactions that governed the molecular packing were O···H (15.5–15.6%), Cl···H (13.6–13.8%), Cl···C (6.3%), and C···H (10.3–10.6%) contacts. For complexes 2 and 3, the H···H, O···H, and C···H contacts dominated. Their percentages were 50.2%, 41.2%, and 7.1%, respectively, for 2 and 57.1%, 19.6%, and 15.2%, respectively, for 3. Only in complex 3, weak π-π stacking interactions between the stacked pyridines were found. The Zn(II) natural charges were calculated using the DFT method to be 0.8775, 1.0559, and 1.2193 for complexes 1–3, respectively. A predominant closed-shell character for the Zn–Cl, Zn–N, Zn–O, Cd–O, and Cd–N bonds was also concluded from an atoms in molecules (AIM) study.

Structural evolution of transition metal orthoborates (Zn3B2O6−Co3B2O6) with the Kotoite mineral structure: Synthesis, structure and properties

AbstractWe describe the synthesis, structure, optical, magnetic, and dielectric properties of Zn3B2O6 and Co3B2O6 systems with the detailed investigation of the structural transition along with the evolution of color. The compounds (Zn3‐xCox)B2O6 (0≤x≤3) were synthesised by high temperature solid‐state reactions. Rietveld refinements of the powder X‐ray diffraction (PXRD) patterns on (Zn2.25 Co0.75)B2O6 and (Co2.25Zn0.75)B2O6 samples indicate uniform distribution of Zn and Co in their respective crystallographic sites. UV‐Vis absorption spectra on the samples can be explained based on the electronic transitions of Co2+ ions in tetrahedral and octahedral coordination. NIR reflectivity studies on Zn3B2O6 was found to be better than that of TiO2, which suggests possible use of this compound for reflective coatings. The temperature dependent magnetic susceptibility studies indicate antiferromagnetic behaviour. The compounds exhibit low dielectric loss across the investigated frequencies.

New bioactive 1D Ag(I) coordination polymers with pyrazole and triazine ligands; Synthesis, X-ray structure, Hirshfeld analysis and DFT studies

The two new Ag(I) complexes [Ag(4BrPyz)2(NO3)]n(1) and [Ag2(2ClDAT)2(NO3)2(H2O)]n (2) of 4-bromo-1H-pyrazole (4BrPyz) and 2-chloro-4,6-diamino-1,3,5-triazine (2ClDAT) were synthesized and characterized using elemental analysis, FTIR and NMR spectroscopic techniques. Single crystal X-ray diffraction revealed that both complexes are 1D coordination polymers but differ in their nitrate anion coordination modes. Complex 1 contains silver atom in a distorted tetrahedral coordination environment, while complex 2 shows two different coordination modes for the silver atoms, a trigonal and a distorted square pyramidal environments. Hirshfeld surface analysis predicted many intermolecular contacts affecting the molecular packing, particularly the N···H and O···H hydrogen bonds, which are the most important. The charge transferences from ligand molecules to Ag(I), and also the interaction strength of the coordinate bonds, were determined using natural bond orbital (NBO) analysis. The anticancer activity of 1 and 2 was screened against breast (MCF-7) and lung (A-549) carcinoma cell lines which demonstrated superior substantial growth inhibition against both cell lines, particularly complex 2, which exhibits significantly higher activity against lung and breast carcinoma cell lines with IC50 of 1.85 μg/mL and 3.01 μg/mL, respectively compared to cis-platin (IC50 = 2.46 and 3.23 μg/mL, respectively). The two complexes along with the free ligands were examined for their antimicrobial and antioxidant activities. Complex 1 (DPPH; 273.6 ± 11.84 µg/mL) has a slightly improved antioxidant activity compared to 4BrPyz (DPPH; 355.5 ± 20.93 µg/mL). The Ag(I) complexes have no antifungal activity at the applied concentration against A. fumigatus and C. albicans but could be considered as a broad spectrum antibacterial agents.

Low‐Coordinated Iron(II) Siloxide Complexes – Structural Diversity and Reactivity Towards O2 and Oxygen Atom Transfer Reagents

AbstractThe coordination chemistry of Fe2+ ions in combination with a monodentate siloxide ligand Ph3SiO− (L) was investigated. Using a Fe/L stoichiometry of 1 : 3 the complex [Na(DME)][FeL3], 2, with the iron center in a trigonal ligand environment was isolated and through decreasing the siloxide amount fraction 2 was shown to form via a unique example of a dinuclear complex, where one of the iron ions has a quasi‐trigonal and the other one a tetrahedral coordination sphere, namely [Na(DME)][Fe2L5], 1. If, however, 4 equivalents of L are employed, the tetrasiloxido ferrate(II) anion with a tetrahedral structure is generated, so that the product [Na(DME)]2[FeL4], 3, can be isolated. 2 reacts instantly with O‐atom transfer reagents, also at low temperatures, but no reaction intermediate could be identified. From the product mixture the iron(III) siloxide complex [Na(DME)3][FeL4], 4, could isolated by crystallization as the main product. Likewise, the reaction with dioxygen proceeded rather fast and added substrates did not intercept any intermediate upon its formation. However, in the presence of cyclohexene oxidation products were observed. They correspond to the typical radical‐chain‐derived products of cyclohexene suggesting, that initially a reactive FeOx species is generated that via an H atom abstraction from cyclohexene triggers its autoxidation.

A series of coordination polymers constructed by 2-phenylsuccinic acid and flexible bis(imidazole) ligands: Syntheses, structures, and photoluminescent properties

Eight coordination polymers (CPs), namely, [Co(μ-phsuc)(μ-obix)]n(1), {[Co2(μ-phsuc)2(μ-pbix)1.5]⋅2H2O}n(2), [Zn(μ-phsuc)(μ-obix)]n(3), {[Zn(μ-phsuc)(μ-mbix)]⋅H2O}n(4), {[Zn(μ-phsuc)(μ-pbix)]⋅H2O}n(5), {[Zn(μ-phsuc)(μ-pbix)]⋅1.5H2O⋅CH3OH}n(6), [Cd(μ-phsuc)(μ-obix)]n(7) and [Cd(μ3-phsuc)(μ-pbix)0.5]n(8) (phsucH2 = 2-phenylsuccinic acid, obix = 1,2-bis((imidazol-1-yl)methyl)benzene, mbix = 1,3-bis((imidazol-1-yl)methyl)benzene, pbix = 1,4-bis((imidazol-1-yl)methyl)benzene), were solvothermally synthesized and characterized by IR spectroscopy, elemental analysis, single-crystal X-ray diffraction, powder X-ray diffraction (PXRD), and thermal analyses. The structural analyses revealed that the compounds were 2D coordination polymers, in which metal ions were in tetrahedral coordination geometries in 1-6 and in octahedral coordination geometries in 2, 7 and 8. Compounds 1, 3, 4, 5, 7 and 8 displayed 4-connected 2D wave sheets with the point symbol of {44.62}. Compound 2 was rare example exhibiting a 2D polyrotaxane structure. Compound 6 showed a two-fold interpenetrated 2D structure with hcb topology (the point symbol of {63}). In the compounds, the neighboring 2D layers were further assembled by π⋅⋅⋅π stacking and weak C–H⋅⋅⋅π interactions into the 3D supramolecular framework. The effects of the bis(imidazole) linkers and metals ions on the framework assemblies have been discussed. In addition, thermal and photoluminescent and optical properties of the compounds were investigated.

Local Atomic Configuration Control of Superconductivity in the Undoped Pnictide Parent Compound BaFe2As2

Emergent superconductivity is strongly correlated with the symmetry of local atomic configuration in the parent compounds of iron-based superconductors. While chemical doping or hydrostatic pressure can change the local geometry, these conventional approaches do not provide a clear pathway in tuning the detailed atomic arrangement predictably, due to the parent compounds complicated structural deformation in the presence of the tetragonal-to-orthorhombic phase transition. Here, we demonstrate a systematic approach to manipulate the local structural configurations in BaFe2As2 epitaxial thin films by controlling two independent structural factors orthorhombicity (in-plane anisotropy) and tetragonality (out-of-plane/in-plane balance) from lattice parameters. We tune superconductivity without chemical doping utilizing both structural factors separately, controlling local tetrahedral coordination in designed thin film heterostructures with substrate clamping and bi-axial strain. We further show that this allows quantitative control of both the structural phase transition, associated magnetism, and superconductivity in the parent material BaFe2As2. This approach will advance the development of tunable thin film superconductors in reduced dimension.

Guite, the spinel-structured Co2+Co3+2O4, a new mineral from the Sicomines copper–cobalt mine, Democratic Republic of Congo

AbstractGuite (IMA2017-080), Co3O4, is a new mineral species and an important economic mineral found in the Sicomines copper-cobalt mine, located ~11 km southwest of Kolwezi City, Democratic Republic of Congo. The mineral occurs as a granular agglomerate, 50 to 500 μm in size, and is associated closely with heterogenite in a quartz matrix. Guite is opaque, has a dark grey colour with metallic lustre and a black streak. In reflected light microscopy, it is white with no internal reflections. The reflectance values (in air,Rin %) are: 27.0 (470 nm); 25.6 (546 nm); 25.2 (589 nm), and 24.6 (650 nm). The average of 20 electron-microprobe analyses is Co 71.53, Cu 0.58, Mn 0.67, Si 0.25, O 26.78, total 99.82 wt.%, corresponding to the empirical formula calculated on the basis of 4 O apfu: (Co2+0.92Cu2+0.02Si4+0.02)Σ0.96(Co3+1.98Mn3+0.03)Σ2.01O4.00, with Co2+and Co3+partitioned using charge balance. The ideal formula is Co2+Co3+2O4. Guite is cubic with space groupFd$\bar{3}$m. The unit cell parameters refined from the single crystal X-ray diffraction data are:a= 8.0898(1) Å,V= 529.436(11) Å3andZ= 8. The calculated density of guite is 6.003 g/cm3. The eight strongest observed powder X-ray diffraction lines [din Å (I/I0) (hkl)] are: 4.6714 (16.7) (111), 2.8620 (18.4) (220), 2.4399 (100) (311), 2.3348 (10.4) (222), 2.0230 (24.8) (400), 1.5556 (26.3) (511, 333), 1.4296 (37.7) (440) and 1.0524 (10.1) (731, 553). The crystal structure of guite was determined by single-crystal X-ray diffraction and refined toR= 0.0132 for 3748 (69 unique) reflections. Guite has a typical spinel-type structure with Co2+in tetrahedral coordination with a Co2+–O bonding length of 1.941(1) Å, and Co3+in octahedral coordination with a Co3+–O bonding length of 1.919(1) Å. The structure is composed of cross-linked framework of chains of Co3+–O6octahedra sharing the equilateral triangle edges (2.550 Å) in three directions [0 1 1], [1 1 0], [1 0 1] with Co2+filling the tetrahedral interstices among the chains. Guite is named in honour of Prof. Xiangping Gu (1964–).

Complexes of zinc halides with amide ligands having a high dipole moment

Complexes [Zn(C6H5CONH2)2Br2] and [Zn((NH2)2CO)2Br2] were synthesized and characterized by elemental analysis, IR spectroscopy, and X-ray diffraction and compared to other complexes of zinc halides with benzamide and urea. In all complexes, the zinc ion has a tetrahedral coordination environment of two halide ligands and two oxygen atoms of two amide ligands. The structure of [Zn(C6H5CONH2)2Br2] (orthorhombic, Pna21, a = 29.207(6), b = 7.5826(14), c = 14.753(3) Å, Z = 8) is not isostructural to the chloride and iodide compounds. The [Zn((NH2)2CO)2Br2] complex (triclinic, P-1, a = 6.4435(9), b = 7.096(1), c = 11.7079(18) Å, α = 88.119(9)°, β = 77.005(9)°, γ = 66.320(8)°, Z = 2) is isostructural to [Zn((NH2)2CO)2Cl2], and they both differ from [Zn((NH2)2CO)2I2]. Dipole moments of complexes of various zinc halides with benzamide, urea, and dimethylformamide were calculated; they vary in the 9–13 D range. Complexes of zinc halides with amides were used to prepare films with the use of cellulose diacetate as a polymer matrix. Dielectric measurements showed the presence of a pronounced electret effect.