Thermal decomposition of lithium-inserted NbO2F

The thermal decomposition of lithium-inserted NbO₂F was studied by differential scanning calorimetry. Samples of Li_xNbO₂F (O ⩽ x ⩽ 1.8) were heated to 800 and 950 K. The thermograms revealed that decomposition started within the temperature range 640–780 K followed by a second step at approximately 900 K. The products were characterized by X-ray powder diffraction and electron diffraction patterns and by high resolution electron microscopy. The following phases were obtained at 800 K: LiF, NbO₂F, the low pressure form of Nb₃O₇F, and lithium-enriched forms of PNb₂O₅, NbO₂ and LiNbO₃. At 950 K, NbO₂F disappeared, and LiNb₃O₈ and the high pressure form of Nb₃O₇F coexisted with the other phases obtained at 800 K. The formation of structures built up of approximately hexagonally close-packed anion arrangements is discussed, as well as the role of lithium as a stabilizing component.     

NH4Ag3(PO3F)2, a layered monofluorophosphate(V) with seven different Ag sites

Single crystals of ammonium trisilver bis[fluorophosphate(V)], NH₄Ag₃(PO₃F)₂, were obtained from an aqueous solution and the structure was refined from a racemically twinned crystal. The asymmetric unit contains seven crystallographically distinct Ag atoms (two of which are located on twofold axes), four PO₃F tetrahedra and two ammonium cations. The layered structure is composed of silver–monofluorophosphate sheets, [Ag₃(PO₃F)₂]⁻, that extend parallel to (100). The F atoms of the PO₃F tetrahedra point towards the ammonium cations, which are located in the interlayer space and stabilize the structure via moderate N—H...O and N—H...F hydrogen bonds.     

Li(+) ion conductivity in rock salt-structured nickel-doped Li(3)NbO(4)

Two mechanisms of doping Li(3)NbO(4), which has an ordered, rock salt superstructure, have been established. In the "stoichiometric mechanism", the overall cation-to-anion ratio is maintained at 1:1 by means of the substitution 3Li(+) + Nb(5+) --> 4Ni(2+). In the "vacancy mechanism", Li(+) ion vacancies are created by means of the substitution 2Li(+) --> Ni(2+). Solid solution ranges have been determined for both mechanisms and a partial phase diagram constructed for the stoichiometric join. On the vacancy join, the substitution mechanism has been confirmed by powder neutron diffraction; associated with lithium vacancy creation, a dramatic increase in Li(+) ion conductivity occurs with increasing Ni content, reaching a value of 5 x 10(-4) Omega(-1) cm(-1) at 300 degrees C for composition x= 0.1 in the formula Li(3-2x)Ni(x)NbO(4). This is the first example of high Li(+) ion conductivity in complex oxides with rock salt-related structures.     

Neue Komplexe Fluoride mit Ag2+ und Pd2+: NaMIIZr2F11 (MII = Ag,Pd) und AgPdZr2F11

New Complex Fluorides with Ag²⁺ and Pd²⁺: NaM^IIZr₂F₁₁ (M^II = Ag, Pd) and AgPdZr₂F₁₁ For the first time single crystals of NaAgZr₂F₁₁, NaPdZr₂F₁₁ and AgPdZr₂F₁₁ have been obtained and investigated by X-ray methods. The isotypic compounds NaM^IIZr₂F₁₁ (M^II = Ag, Pd) crystallize triclinic, spcgr. P1 ? C (No. 2) with a = 780.9, b = 570.0, c = 583.2 pm, α = 106.1°, β = 112.2°, γ = 97.9° (NaPdZr₂F₁₁), AgPdZr₂F₁₁ is monoclinic, spcgr. C2/m? C_2h (No. 12) with a = 935.1, b = 699.1, c = 780.1 pm, β = 115.7°, Z = 2 (Four circle diffractometer data, Siemens AED 2). Their structure is closeley related to the Ag₃Hf₂F₁₄-type of structure.     

Characteristic of the Ag(bipy) 2 2+ /Ag(bipy) 2 + and Ag(phen) 2 2+ /Ag(phen) 2 + systems in acetonitrile

The values of standard potentials of redox systems formed by the complexes of Ag(II) and Ag(I) with 2,2-bipyridine and 1,10-phenanthroline in acetonitrile have been determined. The properties of the above systems in water and acetonitrile are compared. The possibility of application of these systems for the construction of electrodes with a constant potential in different solvents is discussed.

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Charakteristik der Systeme Ag(bipy) ₂ ²⁺ /Ag(bipy) ₂ ⁺ und Ag(phen) ₂ ²⁺ /Ag(phen) ₂ ⁺ in Acetonitril

Zusammenfassung Die Standardpotentialwerte der Redoxsysteme, die durch Komplexbildung von Ag(II)- und Ag(I)-Ionen mit 2,2-Bipyridin und 1,10-Phenantrolin gebildet werden, wurden in Acetonitril bestimmt. Die Eigenschaften dieser Redoxsysteme in Wasser und Acetonitril wurden verglichen.Es wurde weiterhin die Möglichkeit der Anwendung dieser Systeme zur Konstruktion einer Elektrode mit unveränderbarem Potential in verschiedenen Lösungsmitteln diskutiert.

     

Remediation of Wastewater with Ultraviolet Irradiation Using a Novel Titanium (IV) Oxide Photocatalyst

Photocatalysis has become common and nanomaterials having photocatalytic functions have been widely characterized. At present, among the many candidates for photocatalysis, TiO₂ is almost the only material suitable for industrial use. In this paper, we present a TiO₂ synthesis starting from Ti sheets put in contact with a mixture of 0.1 N NaOH and acetone for 72?hours under ambient conditions. The obtained sheets were washed with distilled water and ethanol, and the surface was analyzed for its structural and morphological properties. Thus, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) investigations indicated the formation of TiO₂ on the edges of nanometer circles on the surface of the Ti sheets. For characterizing the photocatalytic capacity for wastewater treatment, Ti sheets with TiO₂ on the surface contacted with methylene blue solutions at room temperature under ultraviolet light. The degradation of the methylene blue concentration was measured by ultraviolet–visible spectroscopy, demonstrating 99.94% efficiency for wastewater treatment using the obtained material.     

可见光催化剂Ag/Ag_2O制备及其对染料脱色降解

介绍了一个简单易行的综合化学实验——Ag/Ag_2O可见光催化剂的制备及其对染料的脱色降解,以及其教学设计思路。通过液相沉淀法制备Ag_2O,光还原沉积银制备Ag/Ag_2O,借助场发射扫描电子显微镜(FESEM)、X射线衍射(XRD)对催化剂进行表征,并以甲基橙降解为模型反应研究其可见光催化降解性能。结果显示,Ag/Ag_2O具有优异的可见光光催化性能。该综合实验运用了大学化学基本知识及学生在基础化学实验阶段学习的材料合成、仪器分析等基本技能,将前沿学术发展、最新研究成果和实践技能融入实验教学,使学生了解化学与材料、环境等学科交叉融合的同时,学生的综合能力得到训练,有助于培养学生的创新思维和分析问题、解决问题的能力。     

A new sensitive reagent for identifying Ag(+) and Hg(2+)

This paper describes the synthesis of a new reagent: N,N′-difuroyl thiourea for the purpose of improving coordination capacity of thiourea compounds. It has been characterized by IR, UV, MS and ¹H-NMR as well as elemental analytical data. According to the studies on its analytical performance, it is found that this reagent can be used to identify Ag⁺ and Hg²⁺. Both of their sensitivities and selectivities are the best in all methods for the time being. The new methods are simple and convenient, and can provide satisfactory results on synthetic and standard samples.     

Silver Complexes with Cyanoguanidine: Preparation and Crystal Structures of [Ag(cgn)2]F and [Ag(cgn)2][BF4]

The silver cyanoguanidine complexes [Ag(cgn)₂]F ( 1 ), [Ag(cgn)₂][BF₄] ( 2 ), [Ag(cgn)₂][ClO₄] ( 3 ) and [Ag(cgn)][NO₃] ( 4 ) were obtained from aqueous solutions of the corresponding silver salts and cyanoguanidine. The crystal structures of 1 and 2 have been determined by single crystal X‐ray diffraction. 1 : Space group P1¯, Z = 2, cell constants at —65 °C: a =618.18(3), b = 761.49(8), c = 971.2(1) pm; α = 93.56(1), β = 97.439(8), γ = 97.376(9)β; R₁ = 0.0218 2 : Space group P1¯, Z = 2, cell constants at —65 °C: a = 549.79(9), b = 958.17(17), c = 1121.04(12) pm; α = 90.026(13), β = 102.520(11), γ = 95.937(14)°; R₁ = 0.0283.     

A Novel 3‐D Heterobimetallic Cyano‐bridged Coordination Polymer Incorporating Ag···Ag Interaction: [Cu(dien)Ag(CN)2]2[Ag2(CN)3][Ag(CN)2]

A three‐dimensional cyano‐bridged copper(II) complex, [Cu(dien)Ag(CN)₂]₂[Ag₂(CN)₃][Ag(CN)₂] ( 1 ) (dien = diethylenetriamine), has been prepared and characterized by X‐ray crystallography. Complex 1 crystallized in the monoclinic space group P2₁/n with a = 6.988(2), b = 17.615(6), c = 12.564(4) Å, β = 90.790(5)°. The crystal consists of cis‐[Cu(dien)]²⁺ units bridged by [Ag(CN)₂]^— to form a zig‐zag chain. The Ag atoms of the free and bridging [Ag(CN)₂]^— link together to form additional infinite zig‐zag chains with short Ag···Ag distances. The presence of Ag···Ag interactions effectively increases the dimensionality from a 1‐D chain to a 3‐D coordination polymer.     

Real and Hypothetical Intermediate-Valence Ag(II)/Ag(III) and Ag(II)/Ag(I) Fluoride Systems as Potential Superconductors

With the aim of gauging their potential as conducting or superconducting materials, we examine the crystal structures and magnetic properties of the roughly one hundred binary, ternary, and quaternary Ag(II) and Ag(III) fluorides in the solid state reported up to date. The Ag(II) cation appears in these species usually in a distorted octahedral environment, either in an [AgF](+) infinite chain or as [AgF(2)] sheets. Sometimes one finds discrete square-planar [AgF(4)](2-) ions. The Ag(III) cation occurs usually in the form of isolated square-planar [AgF(4)](-) ions. Systems containing Ag(III) (d(8)) centers are typically diamagnetic. On the other hand, the rich spectrum of Ag(II) (d(9)) environments in binary and ternary fluorides leads to most diverse magnetic properties, ranging from paramagnetism, through temperature-independent paramagnetism (characteristic for half-filled band and metallic behavior) and antiferromagnetism, to weak ferromagnetism. Ag(II) and Ag(III) have the same d-electron count as Cu(II) (d(9)) and Cu(III) (d(8)), respectively. F(-) and O(2-) ions are isoelectronic, closed-shell (s(2)p(6)) species; both are weak-field ligands. Led by these similarities, and by some experimental evidence, we examine analogies between the superconducting cuprates (Cu(II)/Cu(III)-O(2-) and Cu(II)/Cu(I)-O(2-) systems) and the formally mixed-valence Ag(II)/Ag(III)-F(-) and Ag(II)/Ag(I)-F(-) phases. For this purpose we perform electronic-structure computations for a number of structurally characterized binary and ternary Ag(I), Ag(II), and Ag(III) fluorides and compare the results with similar calculations for oxocuprate superconductors. Electronic levels in the vicinity of the Fermi level (x(2)-y(2) or z(2)) have usually strongly mixed Ag(d)/F(p) character and are Ag-F antibonding, thus providing the potential of efficient vibronic coupling (typical for d(9) systems with substantially covalent bonds). According to our computations this is the result not only of a coincidence in orbital energies; surprisingly the Ag-F bonding is substantially covalent in Ag(II) and Ag(III) fluorides. The electron density of state at the Fermi level (DOS(F)) for silver fluoride materials and frequencies of the metal-ligand stretching modes have values close to those for copper oxides. The above features suggest that properly hole- or electron-doped Ag(II) fluorides might be good BCS-type superconductors. We analyze a comproportionation/disproportionation equilibrium in the hole-doped Ag(II) fluorides, and the possible appearance of holes in the F(p) band. It seems that there is a chance of generating an Ag(III)-F(-)/Ag(II)-F(0) "ionic/covalent" curve crossing in the hole-doped Ag(II)-F(-) fluorides, significantly increasing vibronic coupling.     

Improved Photocatalytic Activity and Stability of Nano‐sized Ag/Ag2CO3 Plasmonic Photocatalyst by Surface Modification of Fe(III) Nanocluster

The surface modification of Ag/Ag₂CO₃ with Fe(III) ions has been achieved through simply photoreduction‐impregnation method. The obtained products were characterized by means of X‐ray diffraction (XRD), scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), and UV‐vis absorption spectroscopy. Under visible‐light irradiation (γ>420 nm), the Fe(III)/Ag/Ag₂CO₃ sample displays a higher photocatalytic activity and stability than pure Ag₂CO₃ and Ag/Ag₂CO₃ samples for the degradation of methyl orange (MO). The improved photocatalytic activity and stability of this ternary system could be ascribed to the synergetic effect between Ag nanoparticles and Fe(III) nanocluster. The metallic Ag nanoparticles cause an obviously enhanced visible‐light absorption to produce more photogenerated charges, while the Fe(III) works as an active site for the following oxygen reduction to reduce the recombination rate of photogenerated electrons and holes.     

The short N [bond] F bond in N(2)F(+) and how Pauli repulsion influences bond lengths. Theoretical study of N(2)X(+), NF(3)X(+), and NH(3)X(+) (X [double bond] F, H)

Exceptionally short N [bond] F bond distances of only 1.217 A (crystal) and 1.246 A (gas phase) have been reported for N(2)F(+), making it the shortest N [bond] F bond ever observed. To trace the origin of this structural phenomenon, we have analyzed the model systems N(2)X(+), NF(3)X(+), and NH(3)X(+) (X [double bond] F, H) using generalized gradient approximation density functional theory at BP86/TZ2P. In good agreement with experiment, the computations yield an extremely short N [bond] F bond for N(2)F(+): we find N [bond] F bond distances in N(2)F(+), NF(4)(+), and NH(3)F(+) of 1.245, 1.339, and 1.375 A, respectively. The N [bond] X bonding mechanisms are quantitatively analyzed in the framework of Kohn-Sham MO theory. At variance with the current hypothesis, reduced steric and other Pauli repulsion (of substituents or lone pairs at N with F) rather than the extent of s [bond] p hybridization of N (i.e., sp versus sp(3)) are responsible for the much shorter N [bond] F distance in N(2)F(+) compared to NF(4)(+). The results for our nitrogen compounds are furthermore discussed in the more general context of how bond lengths are determined by both bonding and repulsive orbital interactions.     

CCl3(+) and CBr3(+) salts with the [Al(OR(F))4]- and [((F)RO)3Al-F-Al(OR(F))3]- anions (R(F) = C(CF3)3)

The CX3(+) salts [CCl(3)](+)[Al(OR(F))(4)](-)1, [CCl(3)](+)[(R(F)O)(3)Al-F-Al(OR(F))(3)](-)2, [CBr(3)](+)[Al(OR(F))(4)](-)3, [CBr(3)](+)[(R(F)O)(3)Al-F-Al(OR(F))(3)](-)4 (R(F) = C(CF(3))(3)) were prepared in 56 to 85% yield from CX(4) (X = Cl, Br) and the corresponding silver salts (weight balance, NMR, IR, X-ray structure of 1). The most convenient solvent for the preparation of 1 and 2 is SO(2)ClF but for 3 and 4 it is SO(2). The reactions are complete after about three days stirring at -30 to -40 °C. The salts are stable for weeks in solution at -40 °C and stable for a few hours at RT in the solid state. In SO(2)ClF (1, 2) or SO(2) (3, 4) solution they decompose slowly at -20 °C and within several hours at RT; in general the CBr3(+) salts are more stable than the CCl3(+) homologues. The decomposition products were assigned as CCl(3)F and primarily CBr(2)F(2) (which likely forms as a Lewis acid induced disproportionation product of the initial CBr(3)F). The C-X vibrations of the salts were found in the expected range and the assignments were made based on experimental and calculated data. The IR spectrum of a CBr3(+) salt is for the first time reported here.     

新型含2-噁唑啉基三角架配体-银(I)一维配位聚合物的合成与结构

通过含2-噁唑啉基三角架配体1,3,5-三(2-噁唑啉基)苯(L)与三氟醋酸银反应合成了配合物[Ag₄(L)₂(CH₃CN)₂(CF₃CO₂)₄]_n (1), 并利用元素分析、电喷雾质谱、X射线单晶衍射等方法对其进行了表征. 晶体结构解析结果显示配合物1属三斜晶系, 空间群P-1, a＝0.83731(6) nm, b＝1.22828(9) nm, c＝1.33997(10) nm, α＝102.9760(10)°, β＝107.3050(10)°, γ＝93.8600(10)°, Z＝1, R＝0.0365, wR₂＝0.0929. 该配合物是由[Ag₄(L)₂(CF₃CO₂)₂]^2＋笼状结构单元通过另外两个三氟醋酸根双桥连形成的一维链状结构. 相邻的链间通过C—H…O氢键进一步扩展为二维网状结构. 电喷雾质谱研究结果显示在实验条件下, 溶液中配合物1是以聚合状态存在的.     

Ag2Hg2(TeO4)3

Red single crystals of disilver(I) dimercury(II) tris­[tetra­oxo­tellurate(VI)], Ag₂Hg₂(TeO₄)₃, were obtained under hydro­thermal conditions at 523 K. The structure is built up of _∞¹[(TeO_2/1O_4/2)({TeO_2/1O_2/2}₂O_4/2)] chains, with an overall composition [TeO₄]²⁻, that run parallel to the crystallographic a axis. Distorted AgO₆ and HgO₆ polyhedra (the latter with two short and nearly collinear Hg—O bonds) link the tellurate chains into a three‐dimensional network. Except for one Te atom situated on an inversion center, all atoms occupy general positions.     

Ag(nic)2 (nic = nicotinate): a spin-canted quasi-2D antiferromagnet composed of square-planar S = 1/2 Ag(II) ions

Square-planar S = 1/2 Ag(II) ions in polymeric Ag(nic)(2) are linked by bridging nic monoanions to yield 2D corrugated sheets. Long-range magnetic order occurs below T(N) = 11.8(2) K due to interlayer couplings that are estimated to be about 30 times weaker than the intralayer exchange interaction.     

The Osmium(VIII) Oxofluoro Cations OsO(2)F(3)(+) and F(cis-OsO(2)F(3))(2)(+): Syntheses, Characterization by (19)F NMR Spectroscopy and Raman Spectroscopy, X-ray Crystal Structure of F(cis-OsO(2)F(3))(2)(+)Sb(2)F(11)(-), and Density Functional Theory Calculations of OsO(2)F(3)(+), ReO(2)F(3), and F(cis-OsO(2)F(3))(2)(+)

Osmium dioxide tetrafluoride, cis-OsO(2)F(4), reacts with the strong fluoride ion acceptors AsF(5) and SbF(5) in anhydrous HF and SbF(5) solutions to form orange salts. Raman spectra are consistent with the formation of the fluorine-bridged diosmium cation F(cis-OsO(2)F(3))(2)(+), as the AsF(6)(-) and Sb(2)F(11)(-) salts, respectively. The (19)F NMR spectra of the salts in HF solution are exchange-averaged singlets occurring at higher frequency than those of the fluorine environments of cis-OsO(2)F(4). The F(cis-OsO(2)F(3))(2)(+)Sb(2)F(11)(-) salt crystallizes in the orthorhombic space group Imma. At -107 degrees C, a = 12.838(3) ?, b = 10.667(2) ?, c = 11.323(2) ?, V = 1550.7(8) ?(3), and Z = 4. Refinement converged with R = 0.0469 [R(w) = 0.0500]. The crystal structure consists of discrete fluorine-bridged F(cis-OsO(2)F(3))(2)(+) and Sb(2)F(11)(-) ions in which the fluorine bridge of the F(cis-OsO(2)F(3))(2)(+) cation is trans to an oxygen atom (Os-O 1.676 ?) of each OsO(2)F(3) group. The angle at the bridge is 155.2(8) degrees with a bridging Os---F(b) distance of 2.086(3) ?. Two terminal fluorine atoms (Os-F 1.821 ?) are cis to the two oxygen atoms (Os-O 1.750 ?), and two terminal fluorine atoms of the OsO(2)F(3) group are trans to one another (1.813 ?). The OsO(2)F(3)(+) cation was characterized by (19)F NMR and by Raman spectroscopy in neat SbF(5) solution but was not isolable in the solid state. The NMR and Raman spectroscopic findings are consistent with a trigonal bipyramidal cation in which the oxygen atoms and a fluorine atom occupy the equatorial plane and two fluorine atoms are in axial positions. Density functional theory calculations show that the crystallographic structure of F(cis-OsO(2)F(3))(2)(+) is the energy-minimized structure and the energy-minimized structures of the OsO(2)F(3)(+) cation and ReO(2)F(3) are trigonal bipyramidal having C(2)(v)() point symmetry. Attempts to prepare the OsOF(5)(+) cation by oxidative fluorination of cis-OsO(2)F(4) with KrF(+)AsF(6)(-) in anhydrous HF proved unsuccessful.