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1.
Eux(NH4)2‐2xTi3O7 nanoporous phosphor was prepared by ion exchange method. (NH4)2Ti3O7 nanotubes were employed as the host structure by treating H2Ti3O7 with NH4OH solution and the activator, Eu2+, was introduced into the host via ion exchange. This is an easy and feasible way to prepare a phosphor. The synthesized samples were characterized using TEM, XRD, N2 adsorption‐desorption isotherm, TPR, and fluorescence spectrophotometer. Experimental results showed that a portion of Eu2+ ions was oxidized into Eu3+ ions during ion exchange, resulting in the present phosphor with blue‐emitting and red‐emitting. Moreover, the tubular structure of Eux(NH4)2‐2xTi3O7 was distorted as Eu2+ was placed into the host structure. This distortion is attributed to the electrostatic interaction between Eu2+ and the electric field of the host structure.  相似文献   

2.
2‐Amino‐3‐hydroxypyridinium dioxido(pyridine‐2,6‐dicarboxylato‐κ3O2,N,O6)vanadate(V), (C5H7N2O)[V(C7H3NO4)O2] or [H(amino‐3‐OH‐py)][VO2(dipic)], (I), was prepared by the reaction of VCl3 with dipicolinic acid (dipicH2) and 2‐amino‐3‐hydroxypyridine (amino‐3‐OH‐py) in water. The compound was characterized by elemental analysis, IR spectroscopy and X‐ray structure analysis, and consists of an anionic [VO2(dipic)] complex and an H(amino‐3‐OH‐py)+ counter‐cation. The VV ion is five‐coordinated by one O,N,O′‐tridentate dipic dianionic ligand and by two oxide ligands. Thermal decomposition of (I) in the presence of polyethylene glycol led to the formation of nanoparticles of V2O5. Powder X‐ray diffraction (PXRD) and scanning electron microscopy (SEM) were used to characterize the structure and morphology of the synthesized powder.  相似文献   

3.
The monovanadium‐substituted polyoxometalate anion [VMo7O26]5?, exhibiting a β‐octamolybdate archetype structure, was selectively prepared as pentapotassium [hexaikosaoxido(heptamolybdenumvanadium)]ate hexahydrate, K5[VMo7O26]·6H2O ( VMo7 ), by oxidation of a reduced vanadomolybdate solution with hydrogen peroxide in a fast one‐pot approach. X‐ray structure analysis revealed that the V atom occupies a single position in the cluster that differs from the other positions by the presence of one doubly‐bonded O atom instead of two terminal oxide ligands in all other positions. The composition and structure of VMo7 was also confirmed by elemental analyses and IR spectroscopy. The selectivity of the synthesis was inspected by a 51V NMR investigation which showed that this species bound about 95% of VV in the crystallization solution. Upon dissolution of VMo7 in aqueous solution, the [VMo7O26]5? anion is substantially decomposed, mostly into [VMo5O19]3?, α‐[VMo7O26]4? and [V2Mo4O19]4?, depending on the pH.  相似文献   

4.
The crystal structure of the title compound, poly­[bis‐[copper(I)‐μ‐(4,4′‐bipyridyl)‐N:N′]‐μ‐dimolybdato‐O:O′],[Cu2(C10H8N2)2{Mo2O7}]n, consists of {Mo2O7}2? units (with the central O atom lying on twofold symmetry axes) and [Cu(4,4′‐bipy)]nn+ chains (bipy = bipyridyl); the chains are generated by a c‐glide‐plane operation. The {Mo2O7}2? units are covalently bridged to two [Cu(4,4′‐bipy)]nn+ chains, forming a complex with a bridged double‐chain structure. The Cu—O and Cu—N distances are 2.191 (3) and 1.933 (3) Å, respectively.  相似文献   

5.
Low‐temperature (200 °C) hydrothermal synthesis of the ruthenium oxides Ca1.5Ru2O7, SrRu2O6, and Ba2Ru3O9(OH) is reported. Ca1.5Ru2O7 is a defective pyrochlore containing RuV/VI; SrRu2O6 is a layered RuV oxide with a PbSb2O6 structure, whilst Ba2Ru3O9(OH) has a previously unreported structure type with orthorhombic symmetry solved from synchrotron X‐ray and neutron powder diffraction. SrRu2O6 exhibits unusually high‐temperature magnetic order, with antiferromagnetism persisting to at least 500 K, and refinement using room temperature neutron powder diffraction data provides the magnetic structure. All three ruthenates are metastable and readily collapse to mixtures of other oxides upon heating in air at temperatures around 300–500 °C, suggesting they would be difficult, if not impossible, to isolate under conventional high‐temperature solid‐state synthesis conditions.  相似文献   

6.
Chemical Vapor Transport of Solid Solutions. 11 Mixed Phases and Chemical Vapor Transport in the Systems CrIII/InIII/GeIV/O, GaIII/InIII/GeIV/O, MnIII/InIII/GeIV/O und FeIII/InIII/GeIV/O By means of chemical vapor transport methods the following mixed phases have been prepared: Cr0, 18In1, 82Ge2O7 (Cl2, 950 → 850 °C), (Ga0, 6In1, 4)2Ge2O7 (Thortveitit‐type, Cl2, 1050 → 950 °C), (Ga1, 9In0, 1)2Ge2O7 (Ga2Ge2O7‐type, 1050 → 950 °C), (In1, 9Mn0, 1)2Ge2O7 (Thortveiti‐type, Cl2, 1000 → 800 °C), mixed phase crystallizing in the Mn2Ge2O7‐structure showing a composition near MnInGe2O7 (Cl2, 1000 → 800 °C), Mn6, 5In0, 5GeO12 (Braunit‐type, Cl2, 1000 → 800 °C), (FexIn1‐x)Ge2O7 (Thortveitit‐type with x = 0…0, 94; Cl2, 840 → 780 °C). Changing the compositions of the starting materials showed no effect on the composition of the deposit except for the system Fe2O3‐In2O3‐GeO2.  相似文献   

7.
Coordination polymers (CPs) have attracted increasing interest in recent years. In this work, two new CPs, namely poly[[aquabis(2,2′‐bipyridine‐κ2N,N′){μ3‐5‐[(4‐carboxylatophenoxy)methyl]benzene‐1,3‐dicarboxylato‐κ4O1,O1′:O3:O5}(μ‐formato‐κ3O:O,O′)dicadmium(II)] monohydrate], {[Cd2(C16H9O7)(HCO2)(C10H8N2)2(H2O)]·H2O}n ( 1 ), and poly[[(2,2′‐bipyridine‐κ2N,N′){μ3‐5‐[(4‐carboxylphenoxy)methyl]benzene‐1,3‐dicarboxylato‐κ4O1,O1′:O3:O5}manganese(II)] sesquihydrate], {[Mn(C16H10O7)(C10H8N2)]·1.5H2O}n ( 2 ), have been prepared using the tricarboxylic acid 5‐[(4‐carboxyphenoxy)methyl]benzene‐1,3‐dicarboxylic acid and 2,2′‐bipyridine under hydrothermal conditions. CP 1 displays a two‐dimensional layer structure which is further extended into a three‐dimensional (3D) supramolecular structure via intermolecular π–π interactions, while CP 2 shows a different 3D supramolecular structure extended from one‐dimensional ladder chains by intermolecular π–π interactions. In addition, the solid‐state luminescence spectra of 1 and 2 were studied at room temperature.  相似文献   

8.
The crystal structures of hydrothermally synthesized aluminium dihydrogen arsenate(V) dihydrogen diarsenate(V), Al(H2AsO4)(H2As2O7), gallium dihydrogen arsenate(V) dihydrogen diarsenate(V), Ga(H2AsO4)(H2As2O7), and diindium bis[dihydrogen arsenate(V)] bis[dihydrogen diarsenate(V)], In2(H2AsO4)2(H2As2O7)2, were determined from single‐crystal X‐ray diffraction data collected at room temperature. The first two compounds are representatives of a novel sheet structure type, whereas the third compound crystallizes in a novel framework structure. In all three structures, the basic building units are M 3+O6 octahedra (M = Al, Ga, In) that are connected via one H2AsO4 and two H2As2O72− groups into chains, and further via H2As2O72− groups into layers. In Al/Ga(H2AsO4)(H2As2O7), these layers are interconnected by weak‐to‐medium–strong hydrogen bonds. In In2(H2AsO4)2(H2As2O7)2, the H2As2O72− groups link the chains in three dimensions, thus creating a framework topology, which is reinforced by weak‐to‐medium–strong hydrogen bonds. The three title arsenates represent the first compounds containing both H2AsO4 and H2As2O72− groups.  相似文献   

9.
Two isostructural diarsenates, SrZnAs2O7 (strontium zinc diarsenate), (I), and BaCuAs2O7 [barium copper(II) diarsenate], (II), have been synthesized under hydrothermal conditions and characterized by single‐crystal X‐ray diffraction. The three‐dimensional open‐framework crystal structure consists of corner‐sharing M2O5 (M2 = Zn or Cu) square pyramids and diarsenate (As2O7) groups. Each As2O7 group shares its five corners with five different M2O5 square pyramids. The resulting framework delimits two types of tunnels aligned parallel to the [010] and [100] directions where the large divalent nine‐coordinated M1 (M1 = Sr or Ba) cations are located. The geometrical characteristics of the M1O9, M2O5 and As2O7 groups of known isostructural diarsenates, adopting the general formula M1IIM2IIAs2O7 (M1II = Sr, Ba, Pb; M2II = Mg, Co, Cu, Zn) and crystallizing in the space group P21/n, are presented and discussed.  相似文献   

10.
The structures of two ammonium salts of 3‐carboxy‐4‐hydroxybenzenesulfonic acid (5‐sulfosalicylic acid, 5‐SSA) have been determined at 200 K. In the 1:1 hydrated salt, ammonium 3‐carboxy‐4‐hydroxybenzenesulfonate monohydrate, NH4+·C7H5O6S·H2O, (I), the 5‐SSA monoanions give two types of head‐to‐tail laterally linked cyclic hydrogen‐bonding associations, both with graph‐set R44(20). The first involves both carboxylic acid O—H...Owater and water O—H...Osulfonate hydrogen bonds at one end, and ammonium N—H...Osulfonate and N—H...Ocarboxy hydrogen bonds at the other. The second association is centrosymmetric, with end linkages through water O—H...Osulfonate hydrogen bonds. These conjoined units form stacks down c and are extended into a three‐dimensional framework structure through N—H...O and water O—H...O hydrogen bonds to sulfonate O‐atom acceptors. Anhydrous triammonium 3‐carboxy‐4‐hydroxybenzenesulfonate 3‐carboxylato‐4‐hydroxybenzenesulfonate, 3NH4+·C7H4O6S2−·C7H5O6S, (II), is unusual, having both dianionic 5‐SSA2− and monoanionic 5‐SSA species. These are linked by a carboxylic acid O—H...O hydrogen bond and, together with the three ammonium cations (two on general sites and the third comprising two independent half‐cations lying on crystallographic twofold rotation axes), give a pseudo‐centrosymmetric asymmetric unit. Cation–anion hydrogen bonding within this layered unit involves a cyclic R33(8) association which, together with extensive peripheral N—H...O hydrogen bonding involving both sulfonate and carboxy/carboxylate acceptors, gives a three‐dimensional framework structure. This work further demonstrates the utility of the 5‐SSA monoanion for the generation of stable hydrogen‐bonded crystalline materials, and provides the structure of a dianionic 5‐SSA2− species of which there are only a few examples in the crystallographic literature.  相似文献   

11.
Reaction of cadmium nitrate with diphenylphosphinic acid in dimethylformamide solvent yielded the one‐dimensional coordination polymer catena‐poly[[bis(dimethylformamide‐κO)cadmium(II)]‐bis(μ‐diphenylphosphinato‐κ2O:O′)], [Cd(C12H10O2P)2(C3H7NO)2]n, (I). Addition of 4,4′‐bipyridine to the synthesis afforded a two‐dimensional extended structure, poly[[(μ‐4,4′‐bipyridine‐κ2N:N′)bis(μ‐diphenylphosphinato‐κ2O:O′)cadmium(II)] dimethylformamide monosolvate], {[Cd(C12H10O2P)2(C10H8N2)]·C3H7NO}n, (II). In (II), the 4,4′‐bipyridine molecules link the CdII centers in the crystallographic a direction, while the phosphinate ligands link the CdII centers in the crystallographic b direction to complete a two‐dimensional sheet structure. Consideration of additional π–π interactions of the phenyl rings in (II) produces a three‐dimensional structure with channels that encapsulate dimethylformamide molecules as solvent of crystallization. Both compounds were characterized by single‐crystal X‐ray diffraction and FT–IR analysis.  相似文献   

12.
Fluorooxoborates, benefiting from the large optical band gap, high anisotropy, and ever‐greater possibility to form non‐centrosymmetric structures activated by the large polarization of [BOxF4?x](x+1)? building blocks, have been considered as the new fertile fields for searching the ultraviolet (UV) and deep‐UV nonlinear optical (NLO) materials. Herein, we report the first asymmetric alkaline‐earth metal fluorooxoborate SrB5O7F3, which is rationally designed by taking the classic Sr2Be2B2O7 (SBBO) as a maternal structure. Its [B5O9F3]6? fundamental building block with near‐planar configuration composed by two edge‐sharing [B3O6F2]5? rings in SrB5O7F3 has not been reported in any other borates. Solid state 19F and 11B magic‐angle spinning NMR spectroscopy verifies the presence of covalent B?F bonds in SrB5O7F3. Property characterizations reveal that SrB5O7F3 possesses the optical properties required for deep‐UV NLO applications, which make SrB5O7F3 a promising crystal that could produce deep‐UV coherent light by the direct SHG process.  相似文献   

13.
Two polymorphs of tripotassium erbium disilicate, K3ErSi2O7, were synthesized by high‐temperature flux crystal growth during the exploration of the flux technique for growing new alkali rare‐earth elements (REE) containing silicates. Their crystal structures were determined by single‐crystal X‐ray diffraction analysis. One of them (denoted 1 ) crystallizes in the space group P63/mmc and is isostructural with disilicates K3LuSi2O7, K3ScSi2O7 and K3YSi2O7, while the other (denoted 2 ) crystallizes in the space group P63/mcm and is isostructural with disilicates K3NdSi2O7, K3REESi2O7 (REE = Gd–Yb), K3YSi2O7, K3(Y0.9Dy0.1)Si2O7 and K3SmSi2O7. In the crystal structure of polymorph 1 , the Er cations are in an almost perfect octahedral coordination, while in the crystal structure of polymorph 2 , part of the Er cations are in a slightly distorted octahedral coordination and the other part are in an ideal trigonal prismatic coordination environment. Sharing six corners, disilicate Si2O7 groups in the crystal structure of polymorph 1 link six ErO6 octahedra, forming a three‐dimensional network and nine‐coordinated potassium cations are located in its holes. In the crystal structure of polymorph 2 , the disilicate Si2O7 groups connect four ErO6 octahedra, as well as one ErO6 trigonal prism. Three differently coordinated potassium cations are situated between them. Different site symmetries of the erbium cations in the crystal structures of polymorphs 1 and 2 affect their photoluminescence properties. Only polymorph 2 exhibits luminescence. Intense narrow lines in the emission spectrum are a result of the 4f–4f transition. The green emission line at 560 nm is the result of the Er3+ transition 4S3/24I15/2, and the luminescence line at 690 nm is the result of a 4F9/24I15/2 transition. The crystal morphologies of the two polymorphs are similar. Crystals of polymorph 1 are in the form of a hexagonal prism in combination with a hexagonal base, while crystals of polymorph 2 contain a dihexagonal prism in combination with a hexagonal base, although poorly developed faces of the dihexagonal pyramid can also be noticed.  相似文献   

14.
The title compound, catena‐poly[[[heptaaqualanthanum(III)]‐μ‐1,3‐dioxo‐2‐oxa‐1H,3H‐phenalene‐6,7‐dicarboxylato‐κ2O6:O7] hemi(4,8‐dicarboxynaphthalene‐1,5‐dicarboxylate) dihydrate], {[La(C14H4O7)(H2O)7](C14H6O8)0.5·2H2O}n, is a dihydrate of a coordination polymer between the dianion of naphthalene‐1,4,5,8‐tetracarboxylic 1,8‐anhydride and the heptahydrated lanthanum(III) ion, charge balanced by an additional 4,8‐dicarboxynaphthalene‐1,5‐dicarboxylate dianion that is located on an inversion centre and is not coordinated to the metal ion. The linear polymeric arrays adopt a comb‐like structure, and these pack in pairs with one chain interpenetrating another, like two parts of a zip, to optimize stacking interactions between their ligand fragments. All the components of this compound are further interlinked by an extensive pattern of O—H...O hydrogen bonds throughout the crystal structure. The main scientific significance of the results reported here is that they demonstrate for the first time the feasibility of coordination polymerization of the above organic ligand with lanthanide ions. The resulting polymer has a unique architecture. Finally, the reported structure is a rare example where the tetraacid and the diacid anhydride ligand species co‐exist in the same crystal.  相似文献   

15.
Sm2As4O9: An Unusual Samarium(III) Oxoarsenate(III) According to Sm4[As2O5]2[As4O8] Pale yellow single crystals of the new samarium(III) oxoarsenate(III) with the composition Sm4As8O18 were obtained by a typical solid‐state reaction between Sm2O3 and As2O3 using CsCl and SmCl3 as fluxing agents. The compound crystallizes in the triclinic crystal system with the space group (No. 2, Z = 2; a = 681.12(5), b = 757.59(6), c = 953.97(8) pm, α = 96.623(7), β = 103.751(7), γ = 104.400(7)°). The crystal structure of samarium(III) oxoarsenate(III) with the formula type Sm4[As2O5]2[As4O8] (≡ 2 × Sm2As4O9) contains two crystallographically different Sm3+ cations, where (Sm1)3+ is coordinated by eight, but (Sm2)3+ by nine oxygen atoms. Two different discrete oxoarsenate(III) anions are present in the crystal structure, namely [As2O5]4? and [As4O8]4?. The [As2O5]4? anion is built up of two Ψ1‐tetrahedra [AsO3]3? with a common corner, whereas the [As4O8]4? anion consists of four Ψ1‐tetrahedra with ring‐shaped vertex‐connected [AsO3]3? pyramids. Thus at all four crystallographically different As3+ cations stereochemically active non‐binding electron pairs (“lone pairs”) are observed. These “lone pairs” direct towards the center of empty channels running parallel to [010] in the overall structure, where these “empty channels” being formed by the linkage of layers with the ecliptically conformed [As2O5]4? anions and the stair‐like shaped [As4O8]4? rings via common oxygen atoms (O1 – O6, O8 and O9). The oxygen‐atom type O7, however, belongs only to the cyclo‐[As4O8]4? unit as one of the two different corner‐sharing oxygen atoms.  相似文献   

16.
The X‐ray structure analysis of the title compound, chloro[1‐cyclopropyl‐6‐fluoro‐1,4‐dihydro‐4‐oxo‐7‐(piperazin‐4‐ium‐1‐yl)‐3‐quinolinecarboxylate‐κ2O3,O4](1,10‐phenanthroline‐κ2N,N′)copper chloride dihydrate, [CuCl(C17H18FN3O3)(C12H8N2)]Cl·2H2O or [CuCl(cfH)(phen)]Cl·2H2O, where cfH is 1‐cyclopropyl‐6‐fluoro‐1,4‐dihydro‐4‐oxo‐7‐(piperazin‐4‐ium‐1‐yl)‐3‐quinolinecarboxylate and phen is 1,10‐phenanthroline, shows that the geometry around the Cu ion is a slightly distorted square pyramid. Two O atoms of the carbonyl and carboxyl groups of ciprofloxacin and two N atoms of 1,10‐phenanthroline are coordinated to the metal centre in the equatorial plane, and a Cl ion is coordinated at the apical position. Extensive intermolecular hydrogen bonding produces a supramolecular structure that consists of alternating six‐ and 12‐membered rings.  相似文献   

17.
The morpholinium (tetrahydro‐2H‐1,4‐oxazin‐4‐ium) cation has been used as a counter‐ion in both inorganic and organic salt formation and particularly in metal complex stabilization. To examine the influence of interactive substituent groups in the aromatic rings of benzoic acids upon secondary structure generation, the anhydrous salts of morpholine with salicylic acid, C4H10NO+·C7H5O3, (I), 3,5‐dinitrosalicylic acid, C4H10NO+·C7H3N2O7, (II), 3,5‐dinitrobenzoic acid, C4H10NO+·C7H3N2O6, (III), and 4‐nitroanthranilic acid, C4H10NO+·C7H5N2O4, (IV), have been prepared and their hydrogen‐bonded crystal structures are described. In the crystal structures of (I), (III) and (IV), the cations and anions are linked by moderately strong N—H…Ocarboxyl hydrogen bonds, but the secondary structure propagation differs among the three, viz. one‐dimensional chains extending along [010] in (I), a discrete cyclic heterotetramer in (III), and in (IV), a heterotetramer with amine N—H…O hydrogen‐bond extensions along b, giving a two‐layered ribbon structure. With the heterotetramers in both (III) and (IV), the ion pairs are linked though inversion‐related N—H…Ocarboxylate hydrogen bonds, giving cyclic R44(12) motifs. With (II), in which the anion is a phenolate rather than a carboxylate, the stronger assocation is through a symmetric lateral three‐centre cyclic R12(6) N—H…(O,O′) hydrogen‐bonding linkage involving the phenolate and nitro O‐atom acceptors of the anion, with extension through a weaker O—H…Ocarboxyl hydrogen bond. This results in a one‐dimensional chain structure extending along [100]. In the structures of two of the salts [i.e. (II) and (IV)], there are also π–π ring interactions, with ring‐centroid separations of 3.5516 (9) and 3.7700 (9) Å in (II), and 3.7340 (9) Å in (IV).  相似文献   

18.
Owing to a parity allowed 4f6(7F)5d1→4f7(8S7/2) transition, powders of the nominal composition Sr0.25Ba0.75Si2O2N2:Eu2+ (2 mol % Eu2+) show surprising intense blue emission (λem=472 nm) when excited by UV to blue radiation. Similarly to other phases in the system Sr1?xBaxSi2O2N2:Eu2+, the described compound is a promising phosphor material for pc‐LED applications as well. The FWHM of the emission band is 37 nm, representing the smallest value found for blue emitting (oxo)nitridosilicates so far. A combination of electron and X‐ray diffraction methods was used to determine the crystal structure of Sr0.25Ba0.75Si2O2N2:Eu2+. HRTEM images reveal the intergrowth of nanodomains with SrSi2O2N2 and BaSi2O2N2‐type structures, which leads to pronounced diffuse scattering. Taking into account the intergrowth, the structure of the BaSi2O2N2‐type domains was refined on single‐crystal diffraction data. In contrast to coplanar metal atom layers which are located between layers of condensed SiON3‐tetrahedra in pure BaSi2O2N2, in Sr0.25Ba0.75Si2O2N2:Eu2+ corrugated metal atom layers occur. HRTEM image simulations indicate cation ordering in the final structure model, which, in combination with the corrugated metal atom layers, explains the unexpected and excellent luminescence properties.  相似文献   

19.
Several bis‐triazolium‐based receptors have been synthesized and their anion‐recognition capabilities have been studied. The central chiral 1,1′‐bi‐2‐naphthol (BINOL) core features either two aryl or ferrocenyl end‐capped side arms with central halogen‐ or hydrogen‐bonding triazolium receptors. NMR spectroscopic data indicate the simultaneous occurrence of several charge‐assisted aliphatic and heteroaromatic C?H noncovalent interactions and combinations of C?H hydrogen and halogen bonding. The receptors are able to selectively interact with HP2O73?, H2PO4?, and SO42? anions, and the value of the association constant follows the sequence: HP2O73?>SO42?>H2PO4?. The ferrocenyl end‐capped 72+?2 BF4 ? receptor allows recognition and differentiation of H2PO4? and HP2O73? anions by using different channels: H2PO4? is selectively detected through absorption and emission methods and HP2O73? by using electrochemical techniques. Significant structural results are the observation of an anion???anion interaction in the solid state (2:2 complex, 62+? [ H2P2O7 ] 2? ), and a short C?I???O contact is observed in the structure of the complex [ 8 2+][SO4]0.5[BF4].  相似文献   

20.
CuAl2F2(Si2O7) has been prepared by hydrothermal synthesis and its crystal structure was determined by single crystal X‐ray diffraction: space group Pnma, a = 8.8697(9), b = 14.084(2), c = 4.7553(5) Å, wR2 = 0.056, R = 0.022. Cu2+ shows elongated square pyramidal coordination. Edge‐ and corner‐sharing [AlO4F2] octahedra with fluorine atoms in cis position form layers parallel to the ac plane. Along b these layers are linked by Si2O7 groups to form a three‐dimensional framework [Al2F2(Si2O7]2–. In addition, the [CuO5] pyramides connect two Al octahedra of neighbouring layers. The crystal structure is discussed as a derivative from topaz structure. The modular (or polysomatic) approach is used for this purpose, and for modelling hypothetical related compounds.  相似文献   

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