Two metal-organic frameworks with infinite indium hydroxide chains connected through tetradentate carboxylate linkers

Two indium-based metal-organic framework have been hydrothermally synthesized by using 1,2,4,5-benzenetetracarboxylate (pyromellitate) or 3,3′,4,4′-benzophenonetetracarboxylate as linkers. Their structures have been characterized by means of single-crystal X-ray diffraction analysis and reveal closely related networks consisting of identical infinite chains of indium-centered trans-connected octahedra, linked to each other through the tetradentate carboxylate linkers. The structure of the indium pyromellitate (MIL-60) delimits a 3D frameworks with one-dimensional 4.0 × 2.7 Å² channels running along [001] encapsulating water. The second compound (MIL-119) is built up from the compact stacking of the 3,3′,4,4′-benzophenonetetracarboxylate molecules connected to four distinct inorganic chains. In the latter, water species are found to be trapped between two indium hydroxide chains or in terminal positions, bonded to the indium cations. Strong hydrogen interactions are observed between these types of water molecules. Both compounds do not exhibit any significant porosity.Crystal data: In₂(OH)₂[C₁₀O₈H₂]·2H₂O (MIL-60): monoclinic, C2/m, a = 7.1854(7) Å, b = 17.1940(17) Å, c = 6.5167(7) Å, β = 100.639(2)°, V = 791.27(14) Å³, Z = 2. In₂(OH)₂(H₂O)[C₁₇O₉H₆]·H₂O (MIL-119), monoclinic, P2₁/c, a = 14.2530(11) Å, b = 14.4024(10) Å, c = 11.7027(9) Å, β = 93.018(2)°, V = 2399.0(3) Å³, Z = 4.     

Structure and magnetic properties of a novel copper diphosphonate with pillared layered structure:: Cu2(H2O)2{O3PCH2N(C2H4)2NCH2PO3}

Compound Cu₂(H₂O)₂{O₃PCH₂N(C₂H₄)₂NCH₂PO₃} (1) has a pillared layered structure in which the organic groups of N,N′-piperazinebis(methylenephosphonate) are sandwiched between the inorganic layers. Compared with other copper phosphonates with layered or pillared layered structures, the inorganic layer in 1 is unique in that each {CPO₃} tetrahedron is corner-shared with three {CuO₄N} square pyramids through three oxygen donors. Ferromagnetic interactions are mediated between the metal centers. Crystal data: Pbca, a=10.0830(16) Å, b=9.4517(15) Å, c=13.218(2) Å, V=1259.7(3) Å³, Z=4.     

Two novel Keggin tungstocobaltates grafted by cobaltII complex group(s): K[Co(phen)2(H2O)]2[HCoW12O40]·2H2O and [Co(2,2′-bipy)3]1.5{[Co(2,2′-bipy)2(H2O)][HCoW12O40]}·0.5H2O

Two novel inorganic–organic hybrid compounds composed of Keggin tungstocobaltate framework and cobalt(II)–N coordination complexes, K[Co(phen)₂(H₂O)]₂[HCoW₁₂O₄₀]·2H₂O (1) (phen = 1,10-phenanthroline) and [Co(2,2′-bipy)₃]_1.5{[Co(2,2′-bipy)₂(H₂O)][HCoW₁₂O₄₀]·0.5H₂O (2) (bipy = bipyridine), have been synthesized under hydrothermal conditions by directly using Keggin POMs as starting materials, which were characterized by elemental analyses, IR, TG analyses and X-ray single crystal diffraction. Crystal data for compound 1: C₄₈H₄₁Co₃KN₈O₄₄W_12, triclinic, space group P-1, a = 10.918(5) Å, b = 13.401(5) Å, c = 13.693(5) Å, α = 69.291(5)°, β = 71.568(5)°, γ = 78.421(5)°, V = 1768.9(12) Å³, Z = 1; for compound 2: C₁₃₀H₁₀₄Co₇N₂₆O₈₃W_24, orthorhombic, space group, C2/c, a = 46.839(9) Å, b = 14.347(3) Å, c = 26.147(5) Å, α = β = γ = 90°, V = 17,570(6) Å³, Z = 4. Compound 1 exhibits a pseudo-1D chainlike structure, in which potassium ions act as linkages of Keggin unit doubly grafted by [Co(phen)₂(H₂O)] complex. Compound 2 represents a [Co(2,2′-bipy)₂(H₂O)]²⁺ mono-grafted Keggin tungstocobaltate derivative with 1.5[Co(2,2′-bipy)₃]²⁺ countercations. The cyclic voltammetric behavior of 1-CPE is similar to the parent 3-CPE, but the cyclic voltammetric behavior of Co^II shows a little difference. Variable-temperature magnetic susceptibility measurement of compound 1 demonstrates the presence of antiferromagnetic interactions.     

Synthesis and structure of a new scorpionate-dithio carboxyl oxovanadium complex and an organic dithio carboxyl compound

A new complex of oxovanadium(IV), V₂O₂[(HB(pz)₃)₂(pyrro)₂ (1) and a dimer-dithio carboxyl compound (C₅H₈NS₂)₂ (2) have been synthesized by the reaction of VOSO₄·nH₂O with NaHB(pz)₃ and pyrrolidine dithio carboxylic acid ammonium salt. They were characterized by element analysis, IR spectra, UV–vis spectra and X-ray diffraction. Structural analyses of 1 and 2 gave the following parameters: 1, triclinic, P-1, a = 7.732(4) Å, b = 14.285(8) Å, c = 17.802(9) Å, α = 101.314(8)°, β = 92.682(9)°, γ = 92.228(9)°, V = 1923.6(18) Å³, and Z = 4; 2, monoclinic, C2/c, a = 13.857(2) Å, b = 10.4213(18) Å, c = 9.436(2) Å, β = 97.099(2), V = 1352.1(4) Å³, and Z = 4. In complex 1, vanadium atom adopts a distorted tetragonal bipyramid structure, which is typical for oxovanadium(IV) complexes. Compound 2 is a dimer-dithio carboxyl compound with S–S bond. In addition, thermal analysis was performed for analyzing the stabilization of the complexes.     

Copper and cadmium phosphonates based on 2-quinolinephosphonate

Hydrothermal reactions of 2-quinolinephosphonic acid (1) and CuSO₄ or CdSO₄ result in two new compounds with formula Cu(2-C₉H₆NPO₃) (2) and Cd(2-C₉H₆NPO₃)(H₂O) (3). Compound 2 has a layer structure in which dimers of edge-sharing {CuO₄N} square-pyramids are linked by {CPO₃} tetrahedra through corner sharing. Compound 3 shows a new type of layer structure where chains of corner sharing {CdO₅N} octahedra are connected by {CPO₃} tetrahedra into an inorganic layer. The quinoline groups fill in the inter-layer spaces in both cases. Crystal data for 1: monoclinic, space group P2₁/c, a = 10.270(2) Å, b = 13.566(3) Å, c = 6.9818(16) Å, β = 101.916(4)°, V = 951.8(4) Å³, Z = 4. For 2: monoclinic, space group P2₁/c, a = 13.976(3) Å, b = 7.9398(18) Å, c = 7.8687(18) Å, β = 101.150(5)°, V = 856.7(3) Å³, Z = 4. For 3: monoclinic, space group P2₁/c, a = 17.164(4) Å, b = 5.4870(12) Å, c = 10.850(2) Å, β = 101.557(4)°, V = 1001.1(4) Å³, Z = 4. The magnetic measurement on 2 reveals a dominant antiferromagnetic exchange coupling between the Cu(II) centers. A quasi-reversible electrochemical reaction is observed for complex 2 immobilized on the surface of GC electrode, corresponding to the redox couple Cu²⁺/Cu⁺. The fluorescent properties of 1–3 are also investigated.     

Ce(H2O)(PO4)3/2(H3O)1/2(H2O)1/2, a second entry in the structural chemistry of cerium(IV) phosphates

A cerium(IV) phosphate has been prepared using precipitation methods and its structure has been solved by single crystal X-ray diffraction (R₁ = 0.0292 for 3092 reflections with I>2σ(I) and wR₂ = 0.0540). Ce(H₂O)(PO₄)_3/2(H₃O)_1/2(H₂O)_1/2 crystallises in the monoclinic space group C2/c (a = 15.7058(17) Å, b = 9.6261(9) Å, c = 10.1632(4) Å, ß = 121.623(7)°, and V = 1308.4 (2) Å³). Its structure is based on a negatively charged 3D framework, made of cerium atoms connected by PO₄ tetrahedra. There are two types of PO₄ units; one shares only corners with the cerium coordination polyhedra while the other one shares edges and corners. This structure also includes hydronium cations, to balance the framework charge, and water molecules. One special feature of this 3D framework is the formation of interconnected tunnels which extend along the c axis and contain the hydronium cations and the water molecules. This open framework and the presence of cationic species in the tunnels are in perfect agreement with the previously reported ion exchange properties.     

Synthesis,structure and fluorescence of a novel three-dimensional inorganic–organic hybrid polymer constructed from trimetallic clusters and mixed carboxylate ligands

A new inorganic–organic hybrid framework coordination polymer, Cd₃(BDC)_0.5(BTC)₂(DMF)(H₂O)·3DMF·H₃O·H₂O 1, in which two carboxylate ligands, 1,4-benzenedicarboxylic acid (H₂BDC) and 1,3,5-benzenetricarboxylic acid (H₃BTC), coordinate with cadmium ions, has been synthesized under mild conditions and its structure solved by single-crystal X-ray diffraction (XRD) analysis. Polymer 1 crystallizes in the monoclinic system, space group P2₁/c (No. 14) with a=15.750(3) Å, b=14.501(3) Å, c=19.363(4) Å, β=113.67(3)°, V=4050.4(14) Å³, Z=4, R1=0.0374 and wR2=0.1148. Its structure revealed that the nine vertices of the secondary building units are linked by benzene rings from both H₃BTC and H₂BDC ligands to form a 3D network with 10×10 Å channels along [001] direction. Complex 1 is characterized by inductively coupled plasma analysis, powder XRD, infrared spectroscopy and thermogravimetric analysis. Polymer 1 exhibits intense fluorescence at 358 and 377 nm with λ_excitation=208 nm in the solid state at room temperature.     

Syntheses,structures and single-molecule magnetic behaviors of two dicubane Mn4 complexes

The reaction of MnX₂ · 4H₂O (X = Cl or Br) with 2,6-bis(hydroxymethyl)-4-methylphenol (H₃L) and NaOH in methanol solution yielded two tetranuclear manganese complexes, [Mn₄(HL)₄(MeOH)₄Cl₂] (1) and [Mn₄(HL)₄(MeOH)₄Br₂] (2). Both compounds crystallize in the monoclinic space group C₂/c with cell parameters: a = 26.0945(19) Å, b = 11.4999(8) Å, c = 21.2188(16) Å, β = 121.050(1)° and z = 4 for 1 · 2Et₂O; a = 25.8145(3) Å, b = 11.6734(2) Å, c = 21.3956(3) Å, β = 120.1277(6)° and z = 4 for 2 · 2Et₂O. Both complexes consist of a mixed-valence dicubane structure, which comprises two Mn^II and two Mn^III ions. Magnetic susceptibilities and magnetization of complexes 1 and 2 in the solid state indicate that two clusters have an S = 9 ground state. Frequency-dependent out-of-phase signals of alternating current magnetic susceptibilities were observed in the low temperature range (<3 K) for both complexes indicating a slow magnetic relaxation.     

Electrochemical and magnetic properties of inorganic polymers constructed from Mn(II)/Co(II)-substituted heteropolymolybdates

Two inorganic polymers constructed from transition metal-substituted heteropolymolybdates, [(CH₃)₃NH]_5n[PMo₁₁MO₃₉]_n·xH₂O (M = Mn²⁺, x = n (1); M = Co²⁺, x = 2n (2)), have been synthesized in aqueous solutions and characterized by IR, TGA, and single-crystal X-ray diffraction analysis. Crystal data: 1, monoclinic, C2/c, a = 17.1322(7) Å, b = 17.6062(7) Å, c = 17.6459(7) Å, β = 103.2220(10)°, V = 5181.5(4) Å³ and Z = 4; 2, triclinic, P-1, a = 12.1986(7) Å, b = 13.0973(7) Å, c = 16.7736(9) Å, α = 97.1810(10)°, β = 98.5040(11)°, γ = 96.3920(10)°, V = 2606.5(2) Å³ and Z = 2. The cyclic voltammograms of 1 and 2 show irreversible redox peaks in DMF solution and there are three reversible couples after addition of 0.1 M H₂SO₄ aqueous solutions. The cyclic voltammograms of 1/2-modified carbon paste electrode (1-CPE/2-CPE) show two consecutive reversible two-electron redox processes. Especially, 2-CPE shows good electrocatalytic activity toward the reduction of nitrite and hydrogen peroxide. The magnetic properties of the two complexes have also been investigated.     

Synthesis,structure and property of a new inorganic–organic hybrid compound [Cu(phen)2][Cu(phen)H2O]2[Mo5P2O23]·3.5H2O

A new polyoxomolybdophosphate 1, formulated as [Cu(phen)₂][Cu(phen)H₂O]₂[Mo₅P₂O₂₃]·3.5H₂O (phen = 1,10-phenanthroline) has been synthesized under hydrothermal conditions. Compound 1 crystallizes in the triclinic space group P-1 with a = 12.2429(5) Å, b = 14.3543(5) Å, c = 20.0814(8) Å, α = 80.023 (1)°, β = 74.283 (1)°, γ = 66.452(1)°, V = 3105.8(2) Å³, R₁ = 0.0375, wR₂ = 0.0885, Z = 2 and GOF = 1.009. Compound 1 is constructed from diphosphopentamolybdate clusters coordinated to Cu(II)-phen units, and free water molecules, which are connected to a three-dimensional framework via π–π stacking interactions from the phen ligands. The single-crystal X-ray diffraction, FT-IR, TG-DTA, XPS, EPR and fluorescent spectra for this compound were determined. The electrochemical properties of compound 1 are studied using cyclic voltammogram, the results indicated that the compound 1 shows good electrocatalytic activity to NO₂^?.     

Copper(II)-methylmalonate complexes with unidentate N-donor ligands: Syntheses,structural characterization and magnetic properties

Two new methylmalonate-bridged copper(II) complexes with the formulas [Cu(3-Ipy)(Memal)(H₂O)] (1) and [Cu(2,4′-bpy)(Memal)(H₂O)] · 3H₂O (2) [Memal = methylmalonate dianion, 3-Ipy = 3-iodopyridine, 2,4′-bpy = 2,4′-bipyridine] have been synthesized and characterized by X-ray diffraction. Both compounds crystallize in the monoclinic space group P2₁/n and Z = 4, with unit cell parameters a = 8.5874(13) Å, b = 7.1738(14) Å, c = 19.093(5) Å, β = 99.509(15)° in 1 and a = 17.375(4) Å, b = 7.3305(14) Å, c = 14.247(3) Å, β = 111.409(15)° in 2. The structures of 1 and 2 consist of zigzag chains of anti-syn carboxylate-bridged copper(II) ions running along the b direction. The pyridine-like ligands occupy one equatorial position of the copper environment avoiding the formation of the sheet-like arrangement observed in previously reported Memal complexes. The chains are grouped together in hydrophilic layers through hydrogen bonds and the layers are pillared through the 3-Ipy (1) and 2,4′-bpy (2) ligands which are stacked through π–π interactions involving alternatively aromatic ligands from two adjacent chains. Magnetic susceptibility measurements of both compounds in the temperature range 2–290 K show the occurrence of intrachain ferromagnetic interactions between the copper(II) ions [J = +2.66(2) cm^?1 (1) and J = +2.62(2) cm^?1 (2)].     

Two fumarato-bridged Co(II) coordination polymers: syntheses,crystal structures and properties of Co(H2O)4L and [Co3(H2O)4(OH)2L2]·2H2O with H2LHOOCCHCHCOOH

Two fumarato-bridged Co(II) coordination polymers Co(H₂O)₄L 1 and [Co₃(H₂O)₄(OH)₂L₂]·2H₂O 2 with H₂LHOOCCH CHCOOH were prepared. Complex 1 consists of polymeric chains _∞¹[Co(H₂O)₄(C₄H₂O₄)_2/2], which result from octahedrally coordinated Co atoms bridged by bis-monodentate fumarate anions and are assembled by interchain hydrogen bonds. Within 2, the edge-shared Co₂O₁₀ bi-octahedra are connected to the CoO₆ octahedra to form 1D cobalt oxide chains and 3D open framework generated from the chains inter-linked by bis-bidentate fumarate anions displays rhombic tunnels, which are filled with the lattice H₂O molecules. Thermal and magnetic behaviors of both the title coordination polymers are discussed. Crystal data: (1) monoclinic, P2₁/c, Z=4, a=7.493(1) Å, b=14.377(1) Å, c=7.708(1) Å, β=99.54(1)°, V=818.9(2) Å³, R₁=0.0304, and wR₂=0.0669 for 1487 observed reflections (I⩾2σ(I)) out of 1877 unique reflections; (2) monoclinic, P2₁/c, Z=2, a=6.618(1) Å, b=8.172(2) Å, c=15.578(3) Å, β=96.30(3)°, V=837.4(3) Å³, R₁=0.0360 and wR₂=0.0663 for 1442 observed reflections (I⩾2σ(I)) out of 1927 unique reflections.     

Synthesis and characterization of a novel three-dimensional open-framework: Metal diphosphonate,Zn[HO3PCH2(C6H4)CH2PO3H]

A novel zinc diphosphonate, Zn[HO₃PCH₂(C₆H₄)CH₂PO₃H] (1) was synthesized from tetraethyl para-xylylenediphosphonate, Et₂O₃PCH₂C₆H₄CH₂PO₃Et₂, and Zn (AcO)₂·2H₂O under solvothermal conditions. The structure of compound 1 was determined by single-crystal X-ray diffraction, which reveals that the structure crystallizes in the monoclinic space group C2/c (No. 15), with a = 22.4844(19) Å, b = 6.4361(5) Å, c = 8.1194(7) Å, β = 102.595(2)°, V = 1146.70(16) Å³, T = 298(2) K, Z = 8. The novel three-dimensional (3D) construction is simply built up from linear inorganic chains of corner-sharing four-rings of tetrahedral [ZnO₄] and [PO₃C] which connected adjacent chains by the organophosphorus ligand para-xylylenediphosphonate. The framework has 10 Å × 4 Å (containing the van der Waals radii of atoms) channels running along the b-axis.     

New transition metal sulfates templated by 1,4-butanediamine, (C4H14N2)[MII(H2O)6](SO4)2·4H2O (MII: Co,Ni): Structure,reactivity and thermal decomposition

Two new hybrid materials, (C₄H₁₄N₂)[M^II(H₂O)₆](SO₄)₂·4H₂O (M^II: Co (I), Ni (II)), have been synthesised by slow evaporation method at room temperature and crystallographically characterized. They crystallise isotypically in the monoclinic system, space group P2₁/n, with the following unit-cell parameters a = 9.2285(3), b = 11.3333(4), c = 10.6693(4) Å, β = 109.004(2)°, Z = 2 and V = 1055.07(6) Å³ for I and a = 9.2127(2), b = 11.3182(2), c = 10.6434(2) Å, β = 109.094(1)°, Z = 2 and V = 1048.74(4) Å³ for II. The structure of the two supramolecular compounds consists of metallic cation octahedrally coordinated to six water molecules, sulfate anions, 1,4-butanediammonium cation and water molecules linked together via two types of hydrogen bonds, O–H?O and N–H?O. The two compounds are not stable at room temperature and their partial dehydration depends on the humidity of the environment. The thermal decomposition of precursors, studied by thermogravimetric analysis (TG) and temperature-dependent X-ray diffraction (TDXD), shows successive intermediate hydrates and crystalline anhydrous compounds upon dehydration.     

Syntheses and structures of the MOF-type series of metal 1,4,5,8,-naphthalenetetracarboxylates M2(OH)2[C14O8H4] (Al,Ga, In) with infinite trans-connected M–OH–M chains (MIL-122)

Three new isostructural MOF-type compounds (named MIL-122) have been obtained from the hydrothermal reaction at 210 °C for 24 h of the 1,4,5,8-naphthalenetetracarboxylic acid with aluminum, gallium or indium source in water. The structures of the compounds M₂(OH)₂[C₁₄H₄O₈] (M = Al, Ga, In) have been solved ab initio from powder X-ray diffraction analysis using the synchrotron radiation (Soleil; station CRISTAL). The three-dimensional organic–inorganic framework exhibits infinite straight chains of metal-centered octahedra sharing trans corners linked to each other through the 1,4,5,8-naphthalenetetracarboxylate ligand. The cations Al, Ga or In, are coordinated by four oxygen atoms coming from the carboxyl groups and two bridging hydroxyl groups μ₂-OH, located in trans position in the octahedral surrounding. The compounds characterized by thermogravimetric and thermodiffraction analyses are thermally stable up to 440, 460 and 380 °C, for Al, Ga and In, respectively. Crystal data: monoclinic cell; P2₁/c (n°14); for MIL-122 (Al): a = 9.5174(2), b = 10.0706(1), c = 6.6465(2) Å, β = 91.2614(5)°, V = 636.878(2) Å³, Z = 2; for MIL-122 (Ga): a = 9.6501(1), b = 10.0585(1), c = 6.75069(9) Å, β = 92.4786(9)°, V = 654.65(1) Å³, Z = 2; for MIL-122 (In): a = 9.92359(5), b = 10.19765(7), c = 7.19357(4) Å, β = 727.034(8)°, V = 727.034(8)ų, Z = 2.     

Synthesis,structure and solid state NMR analysis of a new templated titanium(III/IV) fluorophosphate

The title compound MIL-131 (MIL stands for Material from Institut Lavoisier) was prepared hydrothermally (4 days, 473 K, autogenous pressure) in the presence of an organic base (N((CH₂)₂NH₂)₃). The structure of MIL-131 or Ti^IIITi^IV(OH)F₄(HPO₄)·(PO₄)·(N((CH₂)₂NH₃)₃) has been determined ab initio from X-Ray synchrotron powder diffraction data using simulated annealing methods and was refined in the triclinic space group P-1 (no. 2). MIL-131 exhibits a one-dimensional structure built up from inorganic chains of corner sharing TiO₅(OH) titanium(III) octahedra and PO₄ and HPO₄ phosphate tetrahedra, related to TiO₂F₄ titanium octahedra. Protonated triamine cations are located between the inorganic motifs, and interact strongly with the mineral network through hydrogen bondings both with terminal fluorine atoms and hydroxo or oxo groups. Multinuclear solid state NMR has allowed a clear attribution of the protons, fluoride, and phosphate groups environment within the framework of MIL-131. The large values of chemical shift anisotropy together with the absence of any ¹³C NMR response confirmed the presence of paramagnetic titanium(III) species deduced from the crystal structure. Finally, 2D MAS ¹H-³¹P CP-HETCOR NMR correlation experiment gives some insight on the nature of the intra-framework hydrogen bonding.Crystal data for MIL-131: a = 14.109(1) Å, b = 8.462(3) Å, c = 7.179(1) Å, α = 93.772(1)°, β = 96.566(2)°, γ = 98.004(1)°, V = 840.36(2) ų, z = 2.     

Synthesis,crystal structure and thermal behaviour of [La(hfa)3(Phen)2] (hfa = hexafluoroacetylacetonate,Phen = o-phenanthroline)

The mixed ligand complex [La(hfa)₃(Phen)₂] (I) was obtained by the interaction of La(hfa)₃ and Phen; its composition does not depend on the stoichiometry of the reagents. According to the X-ray single crystal analysis data, complex I crystallizes in the monoclinic space group P2₁/n, with a = 13.583(3) Å, b = 16.959(3) Å, c = 18.860(4) Å, β = 94.71(3)° and Z = 4. The structure of I consists of isolated mononuclear molecules, the coordination number of La being 10. Thermal behaviour and composition of the vapor phase have been studied for I by thermal analysis and mass-spectrometry using a Knudsen cell. The mixed ligand complex I was found to sublime congruently in the temperature range 370–460 K: [La(hfa)₃(Phen)₂]_(s) = [La(hfa)₃(Phen)]_(g) + Phen_(g), Δ_rH⁰(T) = 316.2 ± 1.8 kJ/mol.     

Hybrid inorganic–organic frameworks containing magnesium: Synthesis and structures of magnesium squarate,diglycolate, and glutarate,and potassium magnesium cyclobutanetetracarboxylate

Four new magnesium containing metal–organic hybrid compounds have been synthesized in an effort to prepare low-density materials for hydrogen storage. The compounds were prepared hydrothermally and characterized using single crystal X-ray diffraction. Three of these compounds are analogs of known transition metal structures with squarate (I, Pn-3n, a = 16.276(5) Å), diglycolate (II, P2₁2₁2₁, a = 6.860(1) Å, b = 9.993(1) Å, c = 10.884(1) Å, R₁ = 0.0341), and glutarate (III, R-3, a = 10.744(2) Å, c = 28.677(5) Å, R₁ = 0.0554) ligands; the fourth is a novel structure using cyclobutanetetracarboxylate (IV, Pccn, a = 9.382(1) Å, b = 14.410(2) Å, c = 8.725(1) Å, R₁ = 0.0465) which contains potassium as well as magnesium cations.