Direct ring functionalisation of 1,4,7-trimethyl-1,4,7-triazacyclononane and its application in the preparation of functional [L2Mn2O3]-type complexes

Treatment of 1,4,7-trimethyl-1,4,7-triazacyclononane (metacn) with N-bromosuccinimide (NBS) gave a bicyclic ammonium intermediate, which was ring-opened to 2-cyano-1,4,7-trimethyl-1,4,7-triazacyclononane by reaction with potassium cyanide. Reduction to the amine followed by reaction with anhydrides gave amides, which could subsequently be converted to dinuclear tris-μ-oxo manganese complexes.     

Mercury macrocyclic complexes: The synthesis of [Hg([18]aneN2S4)] and [Hg(Me2[18]aneN2S4)]. The single crystal x-ray structure of [Hg([18]aneN2S4)](PF6)2·4/3H2O

Reaction of HgSO₄ with one molar equivalent of L{L = [18]aneN₂S₄ (1,4,10,13-tetrathia-7,16-diazacyclooctadecane) or Me₂[18]aneN₂S₄ (7,16-dimethyl-1,4,10,13-tetrathia-7,16-diazacyclooctadecane)} in refluxing MeOH-H₂O for 15 min affords a colourless solution containing the complex cation [Hg(L)]²⁺. Addition of excess PF₆⁻ counterion gives the complex [Hg([18]aneN₂S₄)](PF₆)₂·4/3H₂O as a cream coloured solid. A single crystal X-ray structure determination shows mercury(II) bound to a severely distorted octahedral arrangement of the six macrocyclic donor atoms, Hg---S = 2.655(5), 2.735(4), 2.751(4), 2.639(5) Å, Hg---N = 2.473(11), 2.472(17) Å. The cation is in a rac configuration with the two SCH₂CH₂NCH₂CH₂S linkages bound meridionally to the metal centre.     

Highly efficient oxidation of alcohols by the system "hydrogen peroxide-[lmn(o)3mnl](pf6)2 (l = 1,4,7-trimethyl-1,4,7-triazacyclononane)-oxalic acid"

Summary The dinuclear manganese(IV) complex [LMn(O)₃MnL](PF₆)₂ (1, L = 1,4,7-trimethyl-1,4,7-triazacyclononane) catalyzes the extremely efficient oxidation of alcohols with hydrogen peroxide at room temperature. Oxalic acid is an obligatory co-catalyst. The oxidation of isopropanol, for example, yields acetone with turnover numbers up to 40000 after 5-10 h in the absence of a solvent. 2-Cyanoethanol was oxidized by this system with somewhat lower efficiency (conversion 70%). The catalytically active cation from salt 1 was obtained in an insoluble form containing a heteropoly anion [Mn₂O₃(TMTACN)₂]₂[SiW₁₂O₄₀]. Oxidation of 2-cyanoethanol using this heterogenized catalyst and oxalic acid gave the oxo-products with the 54% total yield.     

Crystal Structures of Two New Monoprotonated Products of 1,4,7-trimethyl- 1,4,7-triazacyclononane: (Me3 [9] aneN3H ) (SO3CF3) and (Me3 [9] aneN3H) I

Two new monoprotonated products of macrocyclic polyamine 1,4,7-trimethyl- 1,4,7-triazacyclononane (Me3 [9]aneN3), (Me3 [9]aneN3H) (SO3CF3) 1 (C10H22N3O3SF3, Mr=321.36) and (Me3[9]aneN3H)I 2 (C9H22N3I, Mr=299.20) were obtained by the reactions of Me3[9]aneN3 and yttrium triflate or ytterbium diiodide as the unexpected products. The crystal structures of compounds 1 and 2 have been determined. Crystal 1is orthorhombic, space group P212121(#19), a =12. 609(3), b=13. 531(1), c=9.225(3) A, V=1573.9(7) A3, Z=4, Dc=1. 356g/cm3, μ=2.47cm- 1, F (000) = 680 and R= 0. 052, Rw= 0. 052 for 807 unique reflections with I＞ 2σ(I). Crystal 2 belongs to the orthorhombic system with space group P212121 (# 19), a=11.417(2), b=13.099(3), c=8.762(2) A, V=1310.5(4) A3, Z=4, Dc=1. 516 g/cm3, μ= 24.14 cm-1, F(000)=600 and R=0. 035, Rw=0. 042 for 1427 u-nique reflections with I＞3σ(I). The two structures contain the same cyclic framework in which the acid proton is bonded to an amine nitrogen. This proton exhibits strong intramolecular hydrogen bonds with the other two nitrogen atoms. The methyl groups are directed away from the ring cavity. The bond distance between acid proton and an amine nitrogen in compound 2 is extremely short. The bond angles for 1 and 2 also exhibit obvous diversity inside of triazacyclononae.     

Structural study on the organoantimony(III) NCN - Chelated compounds [2,6-(Me2NCH2)2C6H3]SbX2 - Influence of the polar group X

The reactions of organoantimony chloride LSbCl₂ (1) (L = [2,6-(Me₂NCH₂)₂C₆H₃]⁻) with the silver salts of selected carboxylic acids (1:2 molar ratio) resulted to the corresponding organoantimony carboxylates LSbX₂, where X = CH₃COO for (2); CF₃COO for (3). Similar reactions of 1 with the silver salt of the low nucleophilic anion (1:0.5 and 1:1 molar ratio) gave the ionic compounds [LSb(Cl)--Cl-Sb(Cl)L]⁺[CB₁₁H₁₂]⁻ (4), and [LSbCl]⁺[CB₁₁H₁₂]⁻ (5). All compounds were characterized by the help of the elemental analysis, ESI-MS, ¹H, ¹¹B, ¹³C NMR spectroscopy and IR spectroscopy. The solid state structure investigation using single crystal X-ray diffraction technique (3-5) revealed the presence of the strong Sb-N intramolecular dative connections in all cases and also significant differences in the shapes of the coordination polyhedra around the central antimony atoms was observed, i.e. a tetragonal pyramidal environment in 3 (CF₃COO groups are placed mutually in trans positions), an unusual chlorine bridged dinuclear cation consisting of one apex (Cl atom) sharing square pyramids in 4, and finally a vacant ψ-trigonal bipyramid around the central antimony atom in 5. Even more, crystallization of 5 from THF provided the single crystals of a THF aduct of 5 [LSbCl(THF)]⁺[CB₁₁H₁₂]⁻5a, where the central antimony atom is located in a tetragonal pyramidal environment. The solid state structures of 3-5 are retained in solution. Solution structure of the compound 2 was determined by the help of VT-¹H NMR spectroscopy and IR spectroscopy showing, that both carboxylates (CH₃COO) are unidentate and are placed mutually in cis positions in the coordination polyhedron around the central antimony atom. The whole coordination polyhedron in 2 might be best described as a biccaped - trigonal pyramid, due to the additional Sb-N intramolecular interactions.     

A novel three-dimensional cobalt (III) complex via hydrogen bonds: [Co(tacn)2] (ClO4)3 (tacn=1,4,7-triazacyclononane)

A novel cobalt (III) complex has been synthesized and its structure was determined. The structure consists of Co(tacn)₂³⁺ ions and ClO₄⁻, each cobalt (III) ion was six-coordinated with six nitrogen atoms of two tacns. Hydrogen bonds widely exist between the oxygen atoms of ClO₄⁻ and the nitrogen and carbon atoms of tacn, resulting in a unique three-dimensional network. The electronic spectra were measured and assigned in the strong-field approximation, giving the values of the parameter: Δ, B and C.     

Preparation of chiral diimino- and diaminodiphosphine ligands and their Cu and Ag complexes. X-ray crystal structures of [Cu(1S,2S-cyclohexyl-P2N2)][PF6] and [Ag(1R,2R-cyclohexyl-P2N2H4)][BF4]

The interaction of optically pure 1R,2R-diammoniumyclohexane mono-(+)-tartrate and 1S,2S-diammoniumcyclohexane mono-(−)-tartrate with 2 equiv. of o-(diphenylphosphino)benzaldehyde in the presence of 2 equiv. of potassium carbonate in a refluxing ethanol/water mixture gave the optically pure condensation products N,N′-bis[o-(diphenylphosphino)benzylidene]-1R,2R-diiminocyclohexane[1R,2R-cyclohexyl-P₂N₂, (R,R)-I] and N,N′-bis[o-(diphenylphosphino)benzylidene]-1S,2S-diiminocyclohexane [1S,2S-cyclohexyl-P₂N₂, (S,S)-I], respectively, in good yield. Reduction of optically pure (R,R)-I and (S,S)-I with NaBH₄ in ethanol gave the optically pure reduced products N,N′-bis[o-(diphenylphosphino)benzylidene]-1R,2R-diaminocyclohexane[1R,2R-cyclohexyl-P₂N₂H₄, (R,R)-II] and N,N′-bis[o-diphenylphosphine)benzylidene]-1S,2S-diaminocyclohexane[1S,2S-cyclohexyl-P₂N₂H₄, (S,S)-II], respectively, in good yield. The coordination behaviour of I and II toward salts of Cu^I and Ag^I have been examined. The interaction of [Cu(C)₃CN)₄][X] (X = ClO₄⁻, PF₆⁻) with 1 equiv. of optically pure L₄ [L₄ = (R,R)-I, (S,S)-I, (R,R)-II and (S,S)-II] gave the corresponding optically pure [CuL₄][X] complexes, III–VI IIIa, L₄ = (R,R)-I, X = PF₆⁻ IIIb, L₄ = (R,R)-I, X = ClO₄⁻ IV, X = PF₆⁻; Va, L₄ = (R,R)-II, X = PF₆⁻, Vb L₄ = (R,R)-II, X= ClO₄⁻, VI L₄ = (S,S)-II, X = PF₆⁻, in good yield. For the Cu^I complexes, the L₄ ligand acted as a tetradentate ligand. However, a variable-temperature ³¹P[¹H] NMR study of IIIb shows that at ambient temperature one of the imino groups of the tetradentate ligand undergoes rapid dissociation to form a tridentate ligand. The interaction of AgBF₄ with 1 equiv. of otpically pure L₄ [L₄ = (R,R)-I, (S,S)-I, (R,R)-II and (S,S)-II gave the corresponding optically pure [AgL₄][BF₄] complexes, VII–X VII L₄ = (R,R)-I; VIII, L₄ = (S,S)-I; IX,L₄ = (R,R)-II; X, L₄ = (S,S)-II], in good yield. For the Ag^I complexes, the L₄ ligand acted as a tetradentate ligand with the two amino groups coordinated unsymmetrically to the silver. A variable temperature ³¹P [¹H] NMR study of VII suggests that at high temperature the complex exists as a tri-coordinated complex. The structurers of IV and IX were established by X-ray diffraction studies.     

Tetrakis(triphenylphosphine oxide) complexes of the lanthanide nitrates; synthesis, characterisation and crystal structures of [La(Ph3PO)4(NO3)3]·Me2CO and [Lu(Ph3PO)4(NO3)2]NO3

The reaction of Ln(NO₃)₃·6H₂O (Ln=La, Ce, Pr or Nd) with a sixfold excess of Ph₃PO in acetone formed [Ln(Ph₃PO)₄(NO₃)₃]·Me₂CO. The crystal structure of the La complex shows a nine-coordinate metal centre with four phosphine oxides, two bidentate and one monodentate nitrate groups, and PXRD studies show the same structure is present in the other three complexes. In CH₂Cl₂ or Me₂CO solutions, ³¹P NMR studies show that the complexes are essentially completely decomposed into [Ln(Ph₃PO)₃(NO₃)₃] and Ph₃PO. Similar reactions in ethanol gave [Ln(Ph₃PO)₃(NO₃)₃] only. In contrast for Ln=Sm, Eu or Gd, only the [Ln(Ph₃PO)₃(NO₃)₃] are formed from either acetone or ethanol solutions. For the later lanthanides Ln=Tb–Lu, acetone solutions of Ln(NO₃)₃·6H₂O and Ph₃PO gave [Ln(Ph₃PO)₃(NO₃)₃] only, even with a large excess of Ph₃PO, but from cold ethanol [Ln(Ph₃PO)₄(NO₃)₂]NO₃ (Ln=Tb, Ho–Lu) were obtained. The structure of [Lu(Ph₃PO)₄(NO₃)₂]NO₃ shows an eight-coordinate metal centre with four phosphine oxides and two bidentate nitrate groups. In solution in CH₂Cl₂ or Me₂CO the tetrakis-complexes show varying amounts of decomposition into mixtures of [Ln(Ph₃PO)₃(NO₃)₃], [Ln(Ph₃PO)₄(NO₃)₂]NO₃ and Ph₃PO as judged by ³¹P{¹H} NMR spectroscopy. The [Ln(Ph₃PO)₃(NO₃)₃] also partially decompose in solution for Ln=Dy–Lu, forming some tetrakis(phosphine oxide) species.     

π-facial interactions between Cl and [S4N3]. X-ray crystal structure of [S4N3]Cl

The X-ray structure of [S₄N₃]Cl reveals three independent molecules, which all display π-facial interactions between the Cl⁻ and the pseudo-aromatic [S₄N₃]⁺ rings to produce a structure containing “inverse sandwich” systems.     

Rhodium macrocyclic complexes: The synthesis and single crystal X-ray structure of [Rh([18]aneN2S4)](PF6)3 · 3H2O ([18]aneN2S4 = 1,4,10,13-tetrathia-7,16-diazacyclooctadecane)

Reaction of[Rh(H₂O)₆]³⁺ with one molar equivalent of [18]aneN₂S₄ in refluxing MeOH-H₂O (1 : 1 v/v) for 12 h affords an orange solution from which the complex [Rh([18]aneN₂S₄)](PF₆)₃ can be isolated upon addition of NH₄PF₆. A single crystal X-ray structure determination shows a distorted octahedral geometry at rhodium(III) involving the four thioether and two aza-donors of the macrocycle. The complex cation adopts a rac-configuration via meridional coordination of the two SCH₂CH₂NCH₂CH₂S linkages.     

Oxidations by the system ‘hydrogen peroxide-[Mn2L2O3][PF6]2 (L=1,4,7-trimethyl-1,4,7-triazacyclononane)-carboxylic acid’. Part 10: Co-catalytic effect of different carboxylic acids in the oxidation of cyclohexane, cyclohexanol, and acetone

Hydrogen peroxide oxidation of cyclohexane in acetonitrile solution catalyzed by the dinuclear manganese(IV) complex [LMn(O)₃MnL](PF₆)₂ (L=1,4,7-trimethyl-1,4,7-triazacyclononane, TMTACN) at 25 °C in the presence of a carboxylic acid affords cyclohexyl hydroperoxide as well as cyclohexanone and cyclohexanol. A kinetic study of the reactions with participation of three acids (acetic acid, oxalic acid, and pyrazine-2,3-dicarboxylic acid, 2,3-PDCA) led to the following general scheme. In the first stage, the catalyst precursor forms an adduct. The equilibrium constants K₁ calculated for acetic acid, oxalic acid, and 2,3-PDCA were 127±8, (7±2)×10⁴, and 1250±50 M⁻¹, respectively. The same kinetic scheme was applied for the cyclohexanol oxidation catalyzed by the complex in the presence of oxalic acid. The oxidation of cyclohexane in water solution using oxalic acid as a co-catalyst gave cyclohexanol and cyclohexanone, which were rapidly transformed into a mixture of over-oxidation products. In the oxidation of cyclohexanol to cyclohexanone, varying the concentrations of the reactants and the reaction time we were able to find optimal conditions and to obtain the cyclohexanone in 94% yield based on the starting cyclohexanol. Oxidation of acetone to acetic acid by the system containing oxalic acid was also studied.     

Low-temperature single crystal X-ray diffraction and high-pressure Raman studies on [(CH3)2NH2]2[SbCl5]

The structure of bis(dimethylammonium) pentachloroantimonate(III), [(CH₃)₂NH₂]₂[SbCl₅], BDP, was studied at 15 K and ambient pressure by single-crystal X-ray diffraction as well as at ambient temperature and high pressures up to 4.87(5) GPa by Raman spectroscopy. BDP crystallizes in the orthorhombic Pnma space group with a=8.4069(4), b=11.7973(7), c=14.8496(7) Å, and Z=4; R₁=0.0381, wR₂=0.0764. The structure consists of distorted [SbCl₆]³⁻ octahedra forming zig-zag [{SbCl₅}_n]²ⁿ⁻ chains that are cross-linked by dimethylammonium [(CH₃)₂NH₂]⁺ cations. The organic and inorganic substructures are bound together by the N-H…Cl hydrogen bonds. The distortions of [SbCl₆]³⁻ units increase, partly due to the influence of the hydrogen bonds which became stronger, with decreasing temperature. The preliminary room temperature, high-pressure X-ray diffraction experiments suggest that BDP undergoes a first-order phase transition below ca. 0.44(5) GPa that destroys single-crystal samples. The transition is accompanied by changes in the intensities and positions of the Raman lines below 400 cm⁻¹.     

High-pressure high-temperature synthesis and crystal structure of the isotypic rare earth (RE)-thioborate-sulfides RE9[BS3]2[BS4]3S3, (RE=Dy-Lu)

Application of high-pressure high-temperature conditions (3.5 GPa at 1673 K for 5 h) to mixtures of the elements (RE:B:S=1:3:6) yielded crystalline samples of the isotypic rare earth-thioborate-sulfides RE₉[BS₃]₂[BS₄]₃S₃, (RE=Dy-Lu), which crystallize in space group P6₃ (Z=2/3) and adopt the Ce₆Al_3.33S₁₄ structure type. The crystal structures were refined from X-ray powder diffraction data by applying the Rietveld method. Dy: a=9.4044(2) Å, c=5.8855(3) Å; Ho: a=9.3703(1) Å, c=5.8826(1) Å; Er: a=9.3279(12) Å, c=5.8793(8) Å; Tm: a=9.2869(3) Å, c=5.8781(3) Å; Yb: a=9.2514(5) Å, c=5.8805(6) Å; Lu: a=9.2162(3) Å, c=5.8911(3) Å. The crystal structure is characterized by the presence of two isolated complex ions [BS₃]^3- and [BS₄]^5- as well as [□(S^2-)₃] units.     

Formation of [Cp2TiSbMe2]2, [Cp2TiSb(SiMe3)2]2 and [Cp2TiCl]2·2Mes4Sb2

Reactions of [Cp₂Ti(btmsa)] (btmsa = bis(trimethylsilyl)acetylene) with R₄Sb₂ (R = Me, Me₃Si) give [Cp₂TiSbMe₂]₂ (1) or [Cp₂TiSb(SiMe₃)₂]₂ (2) respectively. [Cp₂TiCl]₂·2Mes₄Sb₂ (3) is serendipitously formed from [Cp₂Ti(btmsa)] and Mes₂SbH containing NH₄Cl traces.     

Solvothermal synthesis and crystal structure of Sb(III) and Sb(V) thioantimonates: [Mn(en)3]2Sb2S5 and [Ni(en)3(Hen)]SbS4

Thioantimonate compounds of [Mn(en)₃]₂Sb₂S₅ (1) and [Ni(en)₃(Hen)]SbS₄ (2) (en=ethylenediamine) were prepared by reaction of transition metal chloride with Sb and S₈ powders under solvothermal conditions. Compound 1 consists of discrete [Sb₂S₅]⁴⁻ anion, which is formed by corner-sharing SbS₃ trigonal pyramids. Compound 2 is composed of discrete tetrahedral [SbS₄]³⁻ anion. The compounds 1 and 2 are charge compensated by [M(en)₃]²⁺ cations, whereas in the crystal of 2 there is another counter ion of [Hen]⁺. The results of the synthesis suggest that the temperature, the concentration and the existing states of the starting materials and so on are important for the structure and composition of the final products. In addition, the oxidation-state of antimony might be related to the molar ratio of the reactants. Excess amount of elemental S is beneficial to the higher oxidation-state of thioantimonate (V). Compound 1 decomposes from 150°C to 350°C, while compound 2 decomposes from 200°C to 350°C remaining Sb₂S₃ and NiSbS as residues.     

π-facial interactions between Cl and [S4N3]. X-ray crystal structure of [S4N3]Cl

The X-ray structure of [S₄N₃]Cl reveals three independent molecules, which all display π-facial interactions between the Cl⁻ and the pseudo-aromatic [S₄N₃]⁺ rings to produce a structure containing “inverse sandwich” systems.     

三维混合价态铜配位聚合物[Cu(Me_2dtc)_2(CuI)_3]_n的合成与晶体结构(英文)

A new three-dimensional copper dithiocarbamate-copper iodide coordination polymer [Cu(Me2dtc)2(CuI)3]n (Me2dtc=N,N-dimethyldithiocarbamate) was synthesized by reactions of Cu(OAc)2,NaI and Na(Me2dtc) in DMF solution,characterized by elemental analysis,IR spectrum,and single-crystal X-ray diffraction. The crystal belongs to the monoclinic system,space group C2/c with a=1.293 89(17) nm,b=1.077 61(11) nm,c=1.456 05(17) nm,β=115.585 (4)°,V=1.831 1 (4) nm3,Z=4,Dc=3.175 g·cm-3,Mr=875.28,λ (Mo Kα)=0.071 073 nm,μ=10.082 mm-1,F(000)=1 604,the final R=0.029 5 and wR=0.081 7. A total of 2 083 unique reflections were collected,of which 1 918 with I2σ(I) were observed. The Cu atoms are Cu(Ⅰ)/Cu(Ⅱ) mixed-valence and they have two different coordinate geometries,namely planar square and tetrahedron. This three-dimensional structure consists of individual Cu(Me2dtc)2 molecules linking together CuI polymeric chains which run parallel to the [001] direction vis Cu-S bonds.     

Triorganoantimony(V) carboxylates: Synthesis, characterization and crystal structure of [Me3Sb(O2C-C5H4N)2] · H2O

Reactions of [R₃Sb(OPrⁱ)₂] with N-heterocylic carboxylic acids gave compounds of the type [R₃Sb(O₂C-Ar)₂] (1) (R = Me, Et, Prⁱ, Ph; Ar = 2-C₅H₄N, 2-C₉H₆N). The mono-bromo compound [Me₃Sb(Br)(O₂C-C₅H₄N)] (2) exists in equilibrium with [Me₃Sb(O₂C-C₅H₄N)₂] and [Me₃SbBr₂]. All new compounds have been characterized by IR and NMR (¹H and ¹³C{¹H}) spectral data. X-ray structural analysis of one example, [Me₃Sb(O₂C-C₅H₄N)₂], isolated as its monohydrate, revealed an essentially trigonal bipyramidal geometry for the antimony atom defined by three equilaterally disposed methyl groups and two oxygen atoms from monodentate carboxylate groups, in apical positions. The crystal structure is consolidated into a three-dimensional network by cooperative O-H?O, O-H?N and C-H?O interactions.     

Diphenylbutadiene-bridged gadolinium complex [GdCl2(THF) 3]2(μ-Ph2C4H4) · 3THF: The synthesis and crystal structure

The diphenylbutadiene-bridged gadolinium complex [GdCl₂(THF)₃]₂(μ-Ph₂C₄H₄) · 3THF (1) has been obtained by the reaction of Gd(III) chloride with diphenylbutadienepotassium. The molecular structure of 1 was determined by X-ray diffraction. The complex 1 has a binuclear structure in which a bridging diphenylbutadiene ligand is η⁴-bonded to the Gd atoms connecting two GdCl₂(THF)₃ units. Both Gd atoms have a distorted octahedral environment. At the Gd atom the two Cl atoms are in trans positions and the four other coordination sites are occupied by the three O atoms of THF molecules and the η⁴-bonded C₄H₄ fragment of a diphenylbutadiene ligand. In the two η⁴-bonded GdC₄H₄ fragments one of the Gd-C η⁴-distances is significantly elongated (2.86(3) and 2.97(3) Å) compared with other three (2.65(3)–2.69(3) and 2.67(3)—2.77(3) Å). The magnetic moment of Gd, equal to 8.1 BM, is typical for Gd³⁺ compounds that is evidence for a formal charge of DPBD ligand of −2 in complex 1. However, the expected distribution of the C-C bond of the diene fragment as long—short—long is not realized.     

The crystal structure of CuSb2O3Br: Slabs from cubic Sb2O3 interspersed between puckered hexagonal CuBr-type layers

The new compound CuSb₂O₃Br crystallize in the monoclinic space group Cc. The unit cell parameters are , , , β=90°, Z=16. The crystal structure is solved from single crystal data, R=0.0490. The compound show a layered structure with slabs from cubic Sb₂O₃ interspersed in between puckered layers of CuBr. The Sb(III) atoms have tetrahedral [SbO₃E] coordination where E is the 5s² lone pair, these units build up Sb₄O₄E₆ cages. The CuBr layers resemble those in hexagonal CuBr but the Cu(I) ions have actually tetrahedral [CuBr₃O] coordination. The Cu-O bonds link the Sb₄O₆ cages with the CuBr layers.