Bond Valence Sum Calculations Research Articles

Mongrel synthesis of tin (IV) based 3-aminopyridine with hydrogen halides: Structural, optical, thermal analysis, DFT, Hirshfeld surface analysis and antibacterial investigations

The novel organic-inorganic hybrid materials (C5H7N4)2 [SnCl6] 2- (1) and (C5H7N4)2 [SnBr6]2-(2) have been synthesized and characterized by single-crystal X-ray diffraction at room temperature. Both compounds demonstrate the crystal system was triclinic with Pī space group. Hirshfeld surface analysis investigate the intermolecular interactions and crystal packing derived by single-crystal XRD data reveals the closer contacts associated with strong interactions. Infrared spectrum of both compounds shows the NH stretching band at 3396 cm−1 which indicates a protonated amine group. The product crystals optical characteristics were inspected using UV–visible and photoluminescence spectroscopy. The thermal characteristics were evaluated simultaneously using thermogravimetric (TG) and differential thermal analysis. Tin formal oxidation state was determined as +4 through bond valence sum calculations and CSM shows the ideal octahedral geometry of the anions. DFT calculations utilizing the B3LYP method with the LanL2DZ basis set provide optimized geometries and molecular electrostatic potential maps. We explored the energy difference between (HOMO) and (LUMO) orbitals to understand molecular electrical transport capabilities. The biological activity of the investigated compounds are examined against pathogens which indicates efficacy against bacterial strains.

Synthetic V(V)-peroxido-zwitterionic species catalyze benzene oxidation under mild reaction conditions

A series of dinuclear complexes were synthesized, involving vanadium with N-methylglycine (sarcosine)/N,N’-dimethylglycine in aqueous media and H2O2, capable of exerting catalytic activity. Specifically, the ternary V(V) tetraperoxido dinuclear species (NH4)2[V2O2(O2)4(CH3NH2CH2COO)] (symmetric conformer) (1), (NH4)2[V2O2(O2)4(CH3NH2CH2COO)] (asymmetric conformer) (2), K2(Η2Ο)[V2O2(O2)4(CH3NH2CH2COO)] . H2O (3) (asymmetric conformer), and K2(Η2Ο)2[V2O2(O2)4{(CH3)2NHCH2COO)}] (4) (asymmetric conformer) were synthetically isolated in crystalline form. Compounds 1 and 2 are the same, whilst with profound conformational differences exemplified through pH-specific chemistries. The new materials 1–4 were characterized by elemental analysis, FT-IR, Raman, NMR, and UV–Visible spectroscopy, cyclic voltammetry, thermogravimetric analysis (TGA-DTG), and X-ray crystallography. Further support of the spectroscopic and structural profile was achieved through Bond Valence Sum (BVS) and Hirshfeld molecular mapping calculations. In all of the studied compounds, pH appears to be a crucial factor in the synthesis and isolation. The physicochemical characterization of the hybrid materials justified further use of compound 3 as a potential hydroxylation catalyst of benzene under a variable set of mild reaction conditions. The products of the catalytic reaction systems investigated were identified and quantified by gas chromatography–mass spectrometry (GC-MS) and gas chromatography–flame ionization detection (GC-FID), respectively. The results a) exemplify the involvement of the hybrid dinuclear vanadium compounds in the pursued benzene transformations, and b) distinctly demonstrate the structural and chemical characteristics justifying the emergence of catalytic action of vanadium under mild conditions (40 °C) in reactions toward organic substrates (e.g. benzene) as the basis for the pursuit of selective industrial applications, affording readily available useful compounds.

Synthesis, structure and characterization of two new silver-iron based phosphates AgFe2(PO4)2F(H2O)2 and Ag3Fe2(PO4)(HPO4)3

Two new silver-iron based phosphates AgFe2(PO4)2F(H2O)2 (1) with monoclinic P21/n and Ag3Fe2(PO4)(HPO4)3 (2) with triclinic P-1 were synthesized by a conventional hydrothermal method, featuring a dimer structure and a twisted honeycomb-like lattice, respectively. XPS and BVS (Bond Valence Sum) calculations indicated only Fe3+ ions in both compounds, while FT-IR spectra proved the presence of [H2O] in 1 and [OH] groups in 2. Solid-state UV–vis–NIR diffuse reflectance spectra suggested their wide optical band gaps of 2.31 eV and 1.94 eV, respectively. Magnetic measurements indicated that both compounds display a long-range antiferromagnetic ordering at low temperature, showing the change of magnetic entropy of 9.59 J mol−1 K−1 in 1 and that of 14.87 J mol−1 K−1 in 2, respectively.

Investigation of optical and magnetic properties of 3d-4d transition metal ion based double Perovskite: Sr2MnRuO6

Investigation of physical properties in double perovskites, A2B′B″O6, containing 3d/4d transition metal ions at the B sites is an interesting avenue of research. In this study, we focus on Sr2MnRuO6, exploring its structural, morphological, optical and magnetic properties. Sr2MnRuO6 was synthesized in single phase using solid-state reaction route. It crystallizes in a tetragonal structure (space group I4/mcm, #140) with lattice parameters a = 5.4633 (2) Å, c = 7.9419 (1) Å. X-ray diffraction analysis revealed no super lattice reflections, indicating disorder in the B-site cations.The Jahn-Teller distortion in Mn-O6 octahedra,as revealed by XRD results, indicates a high spin state for the Mn3+ ion. The stoichiometric ratio of Sr: Mn: Ru (∼2:1:1), as determined by bond valence sum calculations and confirmed by energy dispersive x-ray spectroscopy agree well with the nominal composition of Sr2MnRuO6. Diffuse reflectance spectroscopy showed strong absorption throughout the visible region with a direct band gap of ∼3 eV, indicating Sr2MnRuO6 is a potential candidate for optical applications. Huge photoluminescence emission observed in the visible region is attributed to Mn3+ ions. The temperature dependence of molar susceptibility data indicates a paramagnetic to antiferromagnetic transition around 195 K. The possible super exchange paths for antiferromagnetic interaction are Ru5+- 4d3 (t2g3eg0) − O1 − Ru5+- 4d3 (t2g3eg0) along the z axis, or Ru5+- 4d3 (t2g3eg0) − O2 − Ru5+- 4d3 (t2g3eg0) in the xy-plane, with the angles between these orbitals being nearly 180°. At low temperatures under a 10,000 Oe field, spin glass type magnetic behaviour is observed. The effective magnetic moment (6.17 μB) obtained from the Curie-Weiss fit from 260 K to 290 K nearly matched with the theoretical resultant effective moment (6.24 μB) by considering Mn3+ ions in HS state and Ru5+ ions.Specific heat measurements revealed no long-range magnetic ordering down to 2 K, further suggesting the role of cationic disorder in the magnetic behaviour of Sr2MnRuO6.

Structural Analysis, Characterization, and First-Principles Calculations of Bismuth Tellurium Oxides, Bi6Te2O15

A single crystal of Bi6Te2O15 was obtained from the melt of the solid-state reaction of Bi2O3 and TeO3. Bi6Te2O15 crystallizes in the Pnma space group (No. 62) and exhibits a three-dimensional network structure with a =10.5831(12) Å, b = 22.694(3) Å, c = 5.3843(6) Å, α = β = γ = 90°, V = 1293.2(3) Å3, and Z = 4. The structure was determined using single-crystal X-ray diffraction. An asymmetric unit in the unit cell, Bi3Te1O7.5, uniquely composed of four Bi3+ sites, one Te6+ site, and nine O2− sites, was solved and refined. As a bulk phase, Bi6Te2O15 was also synthesized and characterized using powder X-ray diffraction (XRD), infrared (FT-IR) spectrometry, and the thermogravimetric analysis (TGA) method. Through bond valence sum (BVS) calculations from the single crystal structure, Bi and Te cations have +3 and +6 oxidation numbers, respectively. Each Bi3+ cation forms a square pyramidal structure with five O2− anions, and a single Te6+ cation forms a six-coordinated octahedral structure with O2− anions. Since the lone-pair electron (Lp) of the square pyramidal structure, [BiO5]7−, where the Bi+ cation occupies the center of the square base plane, exists in the opposite direction of the square plane, the asymmetric environments of all four Bi3+ cations were analyzed and explored by determining the local dipole moments. In addition, to determine the extent of bond strain and distortion in the unit cell, which is attributed to the asymmetric environments of the Bi3+ and Te6+ cations in Bi6Te2O15, bond strain index (BSI) and global instability index (GII) were also calculated. We also investigated the structural, electronic, and optical properties of the structure of Bi6Te2O15 using the full potential linear augmented plane wave (FP-LAPW) method and the density functional theory (DFT) with WIEN2k code. In order to study the ground state properties of Bi6Te2O15, the theoretical total energies were calculated as a function of reduced volumes and then fitted with the Birch–Murnaghan equation of state (EOS). The band gap energy within the modified Becke–Johnson potential with Tran–Blaha parameterization (TB-mBJ) revealed a value of 3.36 eV, which was higher than the experimental value of 3.29 eV. To explore the optical properties of Bi6Te2O15, the real and imaginary parts of the dielectric function, refraction index, optical absorption coefficient, reflectivity, the real part of the optical conductivity extinction function, and the energy loss function were also calculated.

Hydrothermal assembly strategy for the construction of oxygen‐bridging lanthanide‐substituted bilacunary Keggin‐type germanotungstate tetramers encapsulating [W3O12]6− connector

AbstractUnder the hydrothermal condition and presence of organic amines, incorporating lanthanide (Ln) ions into monolacunary Keggin‐type germanotungstate precursor resulted in the formation of two new complex clusters formulated as H17(H2en)5[K3(H2O)(GeW10O37TbOTb)4(μ6‐W3O12)] ⋅ 45H2O (GeW‐Tb) and H22(H2en)3[K2(GeW10O37EuOEu)4(H2O)(μ6‐W3O12)] ⋅ 44H2O (GeW‐Eu) (en=ethylenediamine), which have been structurally characterized by elemental analyses, ICP analysis, IR spectra, thermogravimetric analysis, bond valence sum calculations and single‐crystal X‐ray diffraction. The most prominent structural feature of GeW‐Eu and GeW‐Tb revealed an unprecedented oxygen‐bridging Ln‐substituted bilacunary Keggin‐type germanotungstate tetramers encapsulating [W3O12]6− connector. What's more interesting is that a versatile library of linkable units including bilacunary germanotungstate [α‐GeW10O37]10−, internal oxo group between two Ln ions, as well as central tritungstate intermediate [W3O12]6− are all generated in situ thanks to the potential promotion of hydrothermal reaction system. In particular, the possible assembly mechanism for the complex clusters is proposed, and their solid‐state photoluminescence properties are also discussed in detail. To our knowledge, both [α‐GeW10O37]10− and [W3O12]6− intermediates are the highly robust POM building blocks that were first discovered. The studies highlight the structural diversity of Ln‐substituted germanotungstates and provide a new direction in the design of other functional germanotungstate based POMs in the future.

First principle calculation of electronic structures and hole concentration of YBCO family compounds

Yttrium barium copper oxide (YBCO) family compounds are similar in structure but have different superconducting temperatures. It is well known that superconducting properties arise from the crystal lattice and electronic structure of compounds. This work reveals and discusses the electronic structures of YBCO family compounds (YBa2Cu3O6, YBa2Cu3O6.5, YBa2Cu3O7, and YBa2Cu4O8) based on density functional theory (DFT). The electronic structure results show that Cu–O chains are the trigger components for conduction, and only Cu–O chains and Cu-O2 planes play important roles in electronic and superconducting properties. The results also reveal that additional hole doped will be non-trivially distributed between the Cu–O chains and the Cu-O2 planes, and hence a more comprehensive method is required to calculate the hole concentration in the Cu-O2 plane. This work also demonstrates the calculation of hole concentrations using DFT. By DFT calculation, the Y1236 has hole concentration of 0.5 and the hole doped of Y12365, Y1237 and Y124 are 0.09, 0.16 and 0.10, respectively. The results are consistent with the cuprate-superconductor phase diagram and the bond-valence sum (BVS) calculations.

Crystal structure, electronic structure, and optical properties of Cu4ZnGe2S7 and Cu4CdGe2S7: Polar diamond-like semiconductors exhibiting second harmonic generation

The novel I4-II-IV2-VI7 quaternary diamond-like semiconductors (DLSs), Cu4ZnGe2S7 and Cu4CdGe2S7, were prepared from the constituent elemental powders at elevated temperatures. Cu4ZnGe2S7 crystallizes in the polar, chiral space group C2 and adopts the Cu4NiSi2S7 structure-type, which can be considered a derivative of the cubic diamond structure. The cadmium analog takes on the Cu5Si2S7 structure-type, which is related to the hexagonal diamond structure, and displays polar, Cc space group symmetry. Both compounds contain [Ge2S7]6- anions created by corner-sharing GeS4 tetrahedra. The crystal structures were carefully evaluated using: 1) extended connectivity tables, 2) minimum bounding ellipsoid analysis, and 3) bond valence sum (BVS) and global instability index (G) calculations. Both compounds are thermally stable up to temperatures exceeding 950 °C and melt incongruently. As assessed using diffuse reflectance spectroscopy, Cu4ZnGe2S7 and Cu4CdGe2S7 possess optical bandgaps of 1.65 eV and 1.90 eV, respectively, which are narrower than the analogous I2-II-IV-VI4 DLSs. Electronic structure calculations show that both compounds are direct-bandgap semiconductors with significant contributions of Cu-d and S-p orbitals to the states at the top of the valence band. While Cu4CdGe2S7 displays a weak second harmonic generation (SHG) response, the second-order nonlinear optical susceptibility, χ(2), of Cu4ZnGe2S7 is 14.8 ± 1.5 pm V-1, assessed using the Kurtz-Perry powder method and an optical-grade AgGaSe2 (AGSe) reference. Both compounds exhibit laser-induced damage threshold values similar to AGSe, ∼0.1 GW cm-2, for λ = 1.064 µm using picosecond laser pulses. Most importantly, Cu4ZnGe2S7 exhibits a phase-matching behavior at λ = 3.1 µm. These results suggest that Cu4ZnGe2S7 holds potential for use in low-powered laser applications involving efficient wave mixing in the mid-IR region.

Experimental and computational studies of two binuclear Co(II) and Ni(II) bis(salamo)‐like complexes

Acetate‐bridged binuclear Co(II) and Ni(II) complexes, [Co2(L)(μ‐OAc)(EtOH)] (1) and [Ni2(L)(μ‐OAc)(EtOH)] (2) were synthesized via the reaction of a new bis(salamo)‐like ligand with two different metal(II) acetates. X‐ray single crystal diffraction analyses showed that two metal(II) ions (Co or Ni) occupy two sets of N2O2 cavities, respectively. The acetate group bridges the two metals, and the ethanol oxygen atom participates in the coordination. Furthermore, UV–vis titration experiments clearly indicated that the complexation between H3L and M(II) ions leads to the 1:2 complexes [(L)M2]+ through a highly synergistic process. Bond valence sum (BVS) calculations exhibited that the Co(II) and Ni(II) ions are divalent. Secondly, the ligand H3L highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO‐LUMO) gap analysis and surface electrostatic potential were theoretically analyzed by theoretical calculation (density functional theory), and the reactivity of M(II) ions and the ligand in the complex formation process was demonstrated. Finally, the microscopic properties of the complexes were deeply understood through the calculation of the weak intramolecular interactions and the unstressed regions outside the complexes.

Tetra-Face-Capped Octahedra in a Tetrahedra Network - Structure Determination and Scanning Transmission Electron Microscopy of SrAl5 P4 N10 O2 F3.

Tetrahedra-based nitridophosphates show a rich structural chemistry, which can be further extended by incorporating cations in higher coordinated positions, for example, in octahedral voids or by substituting the nitrogen atoms in the network with other anions. Following this approach, SrAl5 P4 N10 O2 F3 was synthesized at high-temperature and high-pressure conditions using a multianvil press (1400 °C, 5 GPa) starting from Sr(N3 )2 , c-PON, P3 N5 , AlN, and NH4 F. SrAl5 P4 N10 O2 F3 crystallizes in space group with a=11.1685(2) and c=7.84850(10) Å. Atomic-resolution EDX mapping with scanning transmission electron microscopy (STEM) indicates atom assignments, which are further corroborated by bond-valence sum (BVS) calculations. Ten Al3+ -centered octahedra form a highly condensed tetra-face-capped octahedra-based unit that is a novel structure motif in network compounds. A network of vertex-sharing PN4 tetrahedra and chains of face-sharing Sr2+ -centered cuboctahedra complement the structure. Eu2+ -doped SrAl5 P4 N10 O2 F3 shows blue emission (λem= 469 nm, fwhm=98 nm; 4504 cm-1 ) when irradiated with UV light.

Bi-layered calcium vanadium oxide as a cathode material for wet organic electrolyte-based rechargeable Zn-ion batteries

Zn-ion batteries attract considerable attention as a promising option for large-scale energy storage owing to their many benefits, including safety, high abundance of zinc, low fabrication costs, and ease of handling in air. However, to improve their effectiveness, three key technical challenges must be overcome: low electrolyte performance, metal dendrite formation, and a limited choice of host materials. This study introduces a new cathode material for Zn-ion batteries — double-layered Ca0.26V2O5·H2O — that exhibits outstanding performance in a wet organic electrolyte. The cathode material demonstrates an initial discharge capacity of 268.76 mAh g−1 at a rate of 0.2C and average operating voltage of 0.82 V (vs. Zn2+/Zn) with excellent capacity retention. A reversible Zn intercalation/crystal water extraction reaction is confirmed by conducting elemental and structural analyses, including powder X-ray diffraction. Furthermore, the results of bond valence sum calculations support the formation of a two-dimensional network of Zn-ion conduction pathways along the a-axis and b-axis, illustrating the electrochemical zinc intercalation into the wet organic electrolyte. Overall, this study not only introduces double-layered Ca0.26V2O5·H2O as a new cathode material for Zn-ion batteries but also provides valuable insights into the electrochemical zinc intercalation/crystal water extraction in wet organic electrolytes.

Structure and Ionic Conductivity of Li-Disordered Bismuth o-Thiophosphate Li60-3xBi16+x(PS4)36.

The structure of the first lithium-containing bismuth ortho (o)-thiophosphate was determined using a combination of powder X-ray, neutron, and electron diffraction. Li60-3xBi16+x(PS4)36 with x in the range of 4.1-6.5 possesses a complex monoclinic structure [space group C2/c (No. 15)] and a large unit cell with the lattice parameters a = 15.4866 Å, b = 10.3232 Å, c = 33.8046 Å, and β = 85.395° for Li44.4Bi21.2(PS4)36, in agreement with the structure as observed by X-ray and neutron pair distribution function analysis. The disordered distribution of lithium ions within the interstices of the dense host structure and the Li ion dynamics and diffusion pathways have been investigated by solid-state nuclear magnetic resonance (NMR) spectroscopy, pulsed field gradient NMR diffusion measurements, and bond valence sum calculations. The total lithium ion conductivities range from 2.6 × 10-7 to 2.8 × 10-6 S cm-1 at 20 °C with activation energies between 0.29 and 0.32 eV, depending on the bismuth content. Despite the highly disordered nature of lithium ions in Li60-3xBi16+x(PS4)36, the underlying dense host framework appears to limit the dimensionality of the lithium diffusion pathways and emphasizes once more the necessity of a close inspection of the structure-property relationships in solid electrolytes.

Novel Co5 Cluster Based Triazole Bridged Cobalt‐Fluorophosphate: Synthesis, Structure, Magnetic and Heterogeneous Catalytic Epoxidation Studies

AbstractA novel triazole bridged cobalt fluorophosphate coordination polymer with the formula {Co5(1,2,4‐triazole)2(OH)2(PO3F)4}n has been synthesized. Single crystal X‐ray studies reveal that the compound comprises of Co5 clusters which ultimately build the whole framework, here all cobalt centers are in octahedral geometry established from continuous shape analysis. All the cobalt centers are in Co(II) oxidation state and the results are supported by the bond valence sum (BVS) calculation. The sample has been characterized by single crystal X‐ray, powder X‐ray, FTIR and TGA analysis. The compound was tested for olefin catalysis performance and magnetism. Magnetization measurements reveal overall antiferromagnetic interactions among the Co(II) ions. The compound is very active in the catalytic transformation of olefins to their corresponding epoxides. Catalytic epoxidation studies reveal that cyclohexene and styrene can be converted up to 97 % with almost 65 % selectivity of products with higher TON numbers.

High entropy effect on double exchange interaction and charge ordering in half doped Nd0.5Sr0.5MnO3 manganite

The entropy stabilized oxides i.e., the so-called high-entropy oxides are of great interest in recent time due to their intriguing physical properties. This new category of advanced materials is stabilized by the high configurational entropy of randomly mixed elements, where a specific lattice site is populated by five or more elements. The present study is devoted to explore the high entropy effect in well-known charge ordered manganite Nd0.5Sr0.5MnO3 where a delicate balance exists between the ferromagnetic double exchange and the antiferromagnetic superexchange interactions. Powder X-ray diffraction analyses confirm phase purity of the samples. FE-SEM imaging revealed the microstructure and elemental mapping confirmed the chemical homogeneity of the samples as well as nominal cationic composition. Bond valence sum (BVS) calculation using refinement parameters supports the expected cationic valence in all the samples. Replacement of Nd3+ by five trivalent cations as in (La0.1Pr0.1Nd0.1Gd0.1Bi0.1)Sr0.5MnO3 with larger average A-site ionic radius,<rA>and smaller size variance, σ2 compared with Nd0.5Sr0.5MnO3 dramatically suppressed the ferromagnetic double exchange interaction. This observation is in contrast with the expected variation in<rA>and σ2. In (La0.1Nd0.1Gd0.1Bi0.1Y0.1)Sr0.5MnO3 with smaller<rA> and marginally higher σ2 the ferromagnetic state ceases to exist. In both the multicationic compositions, a long-range antiferromagnetic state is evolved around 200 K with the retention of charge ordering. In the high entropy (La1/6Nd1/6Dy1/6Ca1/6Ba1/6Sr1/6)MnO3 composition with nominal<rA> and larger σ2 values the high temperature long-range ordering is completely suppressed and a new antiferromagnetic state is evolved at 45 K without manifestation of any charge ordering. This composition also avoids magnetic frustration unlike the dopant variant with larger σ2. The present investigation thus highlights the role of local lattice distortion or high entropy effect apart from the<rA>and σ2 in manganites.

Sodalite‐type Ga16/3[P12N24]O2: Synthesis, Electron Crystallography and Powder X‐ray Diffraction

AbstractThe gallium(III) nitridophosphate‐oxide Ga16/3[P12N24]O2 was synthesized by metathesis reaction between GaF3 and LiPN2. The crystal structure was elucidated by electron crystallography and powder X‐ray diffraction, comparing both approaches. This reveals a partially collapsed sodalite‐type structure (space group I 3m, a=8.1585(2) Å) with a tilt angle ϕ of ∼33°. Vertex‐sharing PN4 tetrahedra build up a sodalite network that hosts gallium(III) cations and oxide anions. Gallium forms bonds to further three N atoms. The structure model is confirmed by EDX analyses, IR spectroscopy and bond valence sum calculations.

Flux crystal growth of Ba2[(UO2)2Ti2O8]: Structures, spectroscopies and implications

AbstractWe report a flux crystal growth of Ba2[(UO2)2Ti2O8] and subsequent structural and spectroscopic studies using multiple techniques. The layered crystal structure, built up with sheets of edge‐sharing dimeric uranyl pentagonal bipyramids and dimeric TiO5 square pyramids with interlayer Ba(II) ions, was revealed by synchrotron single crystal x‐ray diffraction and confirmed with electron diffraction using a transmission electron microscope. The presence of only hexavalent uranium was confirmed by both diffuse reflectance and x‐ray absorption near‐edge structure spectroscopies, consistent with the bond valence sum calculations. Its vibrational modes were revealed by Raman spectroscopy. In addition, its implications as a potential hexavalent uranium waste form for the immobilization of uranium‐rich radioactive wastes were discussed.

A Cyclen-Functionalized Cobalt-Substituted Sandwich-Type Tungstoarsenate with Versatility in Removal of Methylene Blue and Anti-ROS-Sensitive Tumor Cells.

Oxidative degradation by using reactive oxygen species (ROS) is an effective method to treat pollutants. The synthesis of artificial oxidase for the degradation of dyes is a hot spot in molecular science. In this study, a nanoscale sandwich-type polyoxometalate (POM) on the basis of a tetra-nuclear cobalt cluster and trivacant B-α-Keggin-type tungstoarsenate {[Co(C8H20N4)]4}{Co4(H2O)2[HAsW9O34]2}∙4H2O (abbreviated as CAW, C8H20N4 = cyclen) has been synthesized and structurally examined by infrared (IR) spectrum, ultraviolet–visible (UV–Vis) spectrum, X-ray photoelectron spectrum (XPS), single-crystal X-ray diffraction (SXRD), and bond valence sum (Σs) calculation. According to the structural analysis, the principal element of the CAW is derived from modifying sandwich-type polyanion {Co4(H2O)2 [HAsW9O34]2}8– with four [Co(Cyclen)]2+, in which 1,4,7,10-tetraazacyclododecane (cyclen) is firstly applied to modify POM. It is also demonstrated that CAW is capable of efficiently catalyzing the production of ROS by the synergistic effects of POM fragments and Co–cyclen complexes. Moreover, CAW can interfere with the morphology and proliferation of sensitive cells by producing ROS and exhibits ability in specifically eliminating methylene blue (MB) dyes from the solution system by both adsorption and catalytic oxidation.

From high‐pressure β‐V2O5 to κ‐NaxV2O5 (x = 0.4 − 0.55): A structural, chemical, and kinetic insight into a sodiated phase with a large interlayer space

AbstractVanadium pentoxide polymorphs are attracting much interest due to their remarkable electrochemical performance as positive electrodes for rechargeable metal‐ion batteries. High‐pressure β‐V2O5 is an interesting positive electrode material for Na‐ion batteries able to intercalate 1 Na+/formula unit delivering a capacity of 147 mAh g−1. The sodium intercalation of 0.4 Na+ has been described in the literature as a two‐phase domain involving an important structural rearrangement yielding NaxV2O5, but details about the structural changes upon sodium intercalation and structure of intercalated Na0.4V2O5 have not been elucidated so far. In this work, we performed operando synchrotron X‐ray diffraction measurements on sodium batteries on discharge. A full crystal structure determination for such phase, which we have called κ‐Na0.4V2O5, was carried out for the first time directly from operando measurements in monoclinic space group C2/m. Structural analysis was completed with bond valence sum calculations revealing the sites of intercalated sodium in κ‐NaxV2O5 and the structure was further optimized by means of density functional theory calculations. Operando X‐ray absorption spectroscopy and ex situ X‐ray photoelectron spectroscopy allowed to unveil the redox changes upon the phase transformation from β‐V2O5 into κ‐NaxV2O5, providing information about the reduction of vanadium from V5+ to V4+. The phase transformation also produced enhanced charge transfer and sodium diffusion processes, as deduced from both impedance and kinetic study.

Barrel-Shaped-Polyoxometalates Exhibiting Electrocatalytic Water Reduction at Neutral pH: A Synergy Effect.

Two copper-based barrel-shaped polyoxometalates (POMs), namely, [{H3O}4{Na6(H2O)22}][{CuI (H2O)3}2{CuII (H2O)}3{B-α-BiIIIWVI9O33}2]·7H2O (NaCu-POM) and Li4[{NH4}2{H3O}3{Li(H2O)5}][{CuII(SH)}{(CuIICuI1.5)(B-α-BiIIIWVI9O33)}2]·9H2O (LiCu-POM) have been synthesized and structurally characterized. The single-crystal X-ray diffraction analyses of NaCu-POM and LiCu-POM reveal the presence of penta- and hexa-nuclear copper wheels per formula units, respectively; these copper wheels are sandwiched between two lacunary Keggin anions {B-α-BiIIIWVI9O33}9- (BiW9) to form the barrel-shaped title POM compounds. In both the compounds NaCu-POM and LiCu-POM, the mixed-valent copper centers are present in their respective penta- and hexa-nuclear copper wheels, established by X-ray photoelectron spectroscopy (XPS) as well as by bond valence sum (BVS) calculations. Compound LiCu-POM additionally shows the presence of a sulfhydryl ligand (SH-), coordinated to one of the copper centers of its {Cu6}-wheel, that is expected to be generated from the in situ reduction of sulfate anion present in the concerned reaction mixture (lithium-ion in ammonia solution may be the reducing agent). Interestingly, the title compounds, NaCu-POM and LiCu-POM exhibit an efficient electrocatalytic hydrogen evolution reaction (HER) by reducing water at neutral pH. Detailed electrochemical studies including controlled experiments indicate that the active sites for this electrocatalysis are the W(VI) centers of the title compounds, not the copper centers. However, a relevant tri-lacunary Keggin cluster anion {PVWVI9O33}7- (devoid of copper ion) does not show comparable HER as shown by the title compounds. The intra-cluster cooperative interactions of the mixed-valent copper centers (CuII/CuI) with the tungsten centers (W6+) make the overall system electrocatalytically active toward water reduction to molecular hydrogen at neutral pH. High Faradaic efficiencies (89 and 92%) and turnover frequencies (1.598 s-1 and 1.117 s-1) make the title compounds NaCu-POM and LiCu-POM efficient catalysts toward electrochemical water reduction to molecular hydrogen.

Tetrazole-Containing Triphenylamine-Based MOF as a Sensitive Sensor for Food Inspection.

A new metal-organic framework (MOF) with tetrazole-derived triphenylamine (TPA) as the ligand, namely Mn-TPA, has been successfully prepared and thoroughly characterized via thermogravimetric analysis, IR spectroscopy, elemental analysis, UV-vis absorption, fluorescence analysis, bond valence sum calculations, and single-crystal and powder X-ray diffraction analysis. The undulating monolayer of Mn-TPA can hinder the interaction and tight stacking among analytes, which creates a bionic microenvironment for the electrochemical recognition process. Mn-TPA exhibits high specific surface area, stable film-forming capacity, excellent electrochemical activity, and good biocompatibility. Furthermore, the developed Mn-TPA-based immunosensing system exhibits an excellent limit of detection of 0.50 pg·mL-1 toward vomitoxin, which is more outstanding than that of the reported vomitoxin-sensing system. Thus, this work shows the great potential of a well-designed MOF as an easy-to-make and highly sensitive electrochemical platform for biosensing in food safety detection and other fields.