Polymorphism in intercluster salt system: two crystal structures of [Al13O4(OH)24(H2O)12][H2W12O40](OH) · nH2O

In this paper, we report the syntheses and crystal structures of two intercluster salt compounds, [Al₁₃O₄(OH)₂₄(H₂O)₁₂][H₂W₁₂O₄₀](OH) · 20H₂O (1) and [Al₁₃O₄(OH)₂₄(H₂O)₁₂][H₂W₁₂O₄₀](OH) · 24H₂O (2). The crystal structures of these compounds show that they are polymorphs to each other with different modes of packing of the and ions. The structures of 1 and 2 can be described as alternating arrangements of ionic clusters that optimize electrostatic interactions and hydrogen bonds between them. The structure of 1 is analogous to the PtS structure and that of 2 is similar to the β-BeO structure with the clusters forming tetrahedral or square planar coordination geometries to each other.     

Synthesis and characterization of a polyoxotungstate-supported metal compound [{Cu(enMe)2(H2O)}{Cu(enMe)2}3P2W18O62] · nH2O

A new polyoxotungstate formed by Wells-Dawson clusters and copper(II) complexes, [{Cu(enMe)₂(H₂O)}{Cu(enMe)₂}₃P₂W₁₈O₆₂] · nH₂O (enMe = 1,2-diaminopropane, n = 0.81) has been synthesized under hydrothermal conditions. Single-crystal X-ray diffraction revealed that one terminal and three bridging oxygen atoms of the Wells-Dawson cluster in the title compound are coordinated to copper(II) atoms, and forming a unique tetrasupporting polyoxometalate structure. Its cyclic voltammetric behavior in aqueous electrolyte demonstrated that its modified carbon paste electrode has a good stability. It was exhibited that the compound has catalytic activity in epoxidation of maleic anhydride.     

Syntheses and crystal structures of cyano-bridged cluster-metal layered coordination polymers [Cu(dien)]3[W4Te4(CN)12] · 9H2O and [Ni(en)(NH3)]3[W4Se4(CN)12] · 7.5H2O

Two new tetrahedral tungsten cyanide cluster compounds, [Cu(dien)]₃[W₄Te₄(CN)₁₂] · 9H₂O (1) (dien=diethylenetriamine) and [Ni(en)(NH₃)]₃[W₄Se₄(CN)₁₂] · 7.5H₂O (2) (en=ethylenediamine), were synthesized by treating aqueous solutions of the saltlike cluster compound K₆[W₄Te₄(CN)₁₂] · 5H₂O/K₆[W₄Se₄(CN)₁₂] · 6H₂O with copper(II)/nickel(II) chloride in aqueous ammonia containing dien/en. The cyano-bridged layered coordination polymeric compounds were characterized by single-crystal X-ray diffraction analysis: monoclinic, space group P2₁ for 1; trigonal, space group for 2. Structures of 1 and 2 consist of infinite neutral layers of cluster components {W₄Te₄(CN)₁₂}/{W₄Se₄(CN)₁₂} connected, one another by {Cu(dien)} or {Ni(en)(NH₃)} fragments, respectively.     

K2[Zn(CV)2(H2O)2] · 2H2O: The first Zn(II) complex structurally characterized containing the pseudo-oxocarbon Croconate Violet (CV)

The synthesis, thermal behavior, spectroscopic characterization and crystal and molecular structure of a Zn(II) complex containing the pseudo-oxocarbon Croconate Violet (CV²⁻) dianion, namely K₂[Zn(CV)₂(H₂O)₂] · 2H₂O are reported. Thermal analysis has shown that the complex structure presents coordination and lattice water molecules. According to vibrational spectroscopy the Croconate Violet dianion is coordinated to Zn(II) center through the vicinal oxygen atoms in a chelating fashion with no involvement of CN moieties. The complex structure has been confirmed by single crystal X-ray diffraction analysis. The dianionic units [Zn(CV)₂(H₂O)₂]²⁻ adopt an slight distorted octahedral geometry in which the metallic center is surrounded by six oxygen atoms. These discrete dianionic units are connected through intermolecular hydrogen bonding giving rise to a supramolecular array extended along the crystallographic a axis.     

3D hydrogen bonded metal-organic frameworks constructed from [M(H2O)6][M′(dipicolinate)2] · mH2O (M/M′ = Zn/Ni or Ni/Ni). Identification of intercalated acyclic (H2O)6/(H2O)10 clusters

New heterodinuclear Zn^II/Ni^II (1) and homodinuclear Ni^II/Ni^II (2) water-soluble and air stable compounds of general formula [M(H₂O)₆][M′(dipic)₂] · mH₂O have been easily prepared by self-assembly of the corresponding metal(II) nitrates with dipicolinic acid (H₂dipic) in water solution at room temperature.  The compounds have been characterized by IR, UV/Vis and atomic absorption spectroscopies, elemental and X-ray single crystal diffraction (for 1 · 4H₂O and 2 · 5H₂O) analyses.  3D infinite polymeric networks are formed via extensive hydrogen bonding interactions involving all coordinated and crystallization water molecules, and all dipicolinate oxygens, thus contributing to additional stabilization of dimeric units, metal-organic chains and 2D layers.  In 1 · 4H₂O, the latter represent a rectangular-grid 2D framework with multiple channels if viewed along the c crystallographic axis, while in 2 · 5H₂O intercalated crystallization water molecules are associated to form acyclic nonplanar hexameric water clusters and water dimers which occupy voids in the host metal-organic matrix, with a structure stabilizing effect via host-guest interactions.  The hexameric cluster extends to the larger (H₂O)₁₀ one with an unusual geometry (acyclic helical octamer with two pendent water molecules) by taking into account the hydrogen bonds to water ligands in [Ni(H₂O)₆]²⁺.  The obtained Zn/Ni compound 1 relates to the recently reported family of heterodimetallic complexes [M(H₂O)₅M′(dipic)₂] · mH₂O (M/M′ = Cu/Co, Cu/Ni, Cu/Zn, Zn/Co, Ni/Co, m = 2, 3), what now allows to establish the orders of the metal affinity towards the formation of chelates with dipicolinic acid (Co^II > Ni^II > Zn^II > Cu^II) or aqua species (Co^II < Ni^II < Zn^II < Cu^II).     

K2Fe(C2O4)(HPO4)(OH2) · H2O: A layered oxalatophosphate hybrid material

One novel layered oxalatophosphate structure K₂Fe(C₂O₄)(HPO₄)(OH₂) · H₂O (1) has been synthesized by hydrothermal method. X-ray crystallography reveals that the complex 1 possesses a 2D layered structure constructed from octahedral FeO₆, tetrahedral moieties and multidentate oxalate ligands with the K⁺ cations among the layers. It is noteworthy that the oxalate anion as a tetradentate ligand bonds to three iron atoms in bidentate-chelating mode on one side and in monodentate-bridging mode on the other, thus forming a neutral iron oxalate sheet. This new structural feature can be considered as the third role of the oxalate ions in metal oxalatophosphate chemistry.     

A new moisture-sensitive metal-coordination solids {[Cd(C4O4)(bipy)(H2O)2] · 3H2O}∞ (bipy=4,4-bipyridine)

A new mixed-ligands metal-coordination polymer, [Cd(C₄O₄)(bipy)(H₂O)₂] (1), (bipy=4,4^′-bipyridine), was synthesized under hydrothermal condition and characterized by X-ray diffraction method. A three-dimensional interpenetrating network with one-dimensional channels intercalating water molecules undergoes a reversible hydration-dehydration process upon a cooling-heating cycles associated with distinct color change and structural variation.     

Structure and magnetic properties of Ln2[Cu(opba)]3(DMSO)6(H2O) · (H2O) compounds with LnLa-Lu exhibiting ladder-like molecular motifs

The reaction of Ln(III) ions with the precursor [Cu(opba)]²⁻ in DMSO has afforded a series of isostructural compounds of general chemical formula Ln₂[Cu(opba)]₃(DMSO)₆(H₂O) · (H₂O), where Ln(III) stands for a lanthanide ion and opba stands for ortho-phenylenebis(oxamato). The crystal structure has been solved for the Gd(III) containing compound. It crystallizes in the orthorhombic system, space group Pbn2₁ (No. 33) with a = 9.4183(2) Å, b = 21.2326(4) Å, c = 37.9387(8) Å and Z = 4. The structure consists of ladder-like molecular motifs parallel to each other. To the best of our knowledge, this is the first Ln(III)Cu(II) coordination polymer family exhibiting the same crystal structure over the whole lanthanide series. The magnetic properties of the compounds have been investigated and the magnetic behavior of the Gd(III) containing compound was studied in more detail.     

Photocatalytical decomposition of hydrazine in K4[Mo(CN)8] solution: X-ray crystal structure of (PPh4)2[Mo(CN)4O(NH3)] · 2H2O

Ligand-field photolysis of K₄[Mo(CN)₈] · 2H₂O in 98% N₂H₄ · H₂O yields the catalytical decomposition of N₂H₄ into NH₃ and N₂. From irradiated solutions of octacyanomolybdate(IV) both in NH₃(aq) and 98% N₂H₄ · H₂O(l) as solvents, the salt of the formula (PPh₄)₂[Mo(CN)₄O(NH₃)] · 2H₂O was isolated. The salt is not formed by direct ligand replacement in tetracyanooxomolybdate(IV) ions derived from K₃Na[Mo(CN)₄O₂] · 6H₂O as the solute in similar conditions. The X-ray crystal structure and spectral properties of (PPh₄)₂[Mo(CN)₄O(NH₃)] · 2H₂O are described. The improved method of the synthesis of K₄[Mo(CN)₈] · 2H₂O is also presented.     

Synthesis, characterization, crystal structures and magnetic properties of dissymmetrical double schiff base heterotrinuclear complexes: [CuL(H2O)CoCuL] · H2O · CH3OH and [(CuL)2Ni] · 2H2O

A dissymmetrical double Schiff base Cu(II) mononuclear complex: CuHL (1) (where H₃L is N-3-carboxylsalicylidene-N^′-salicylaldehyde-1,2-diaminoethane) and two trinuclear complexes: [CuL(H₂O)CoCuL] · H₂O · CH₃OH (2) and [(CuL)₂Ni] · 2H₂O (3) have been synthesized and characterized by means of elemental analyses, IR and electronic spectra. The crystal structures of two heterotrinucler complexes were determined by X-ray analysis. Each dissymmetrical cell unit of the complex 2 contains two heterotrinucler neutral molecules. In each neutral molecule, the central Co²⁺ ion is located at the site of O₆ with a distorted octahedral geometry and one terminal Cu²⁺ ion at the four-coordination site of N₂O₂, but the other one at the square-pyramidal environment of N₂O₃. Each dissymmetrical unit of the complex 3 contains a heterotrinucler neutral molecule, whose structure is similar to that of 2 except two terminal Cu²⁺ ions both at the inner site of N₂O₂. The magnetic properties of two heterotrinucler complexes have been determined in the temperature range of 5-300 K, which indicate that the interaction between the central Co²⁺ ion or Ni²⁺ ion and the outer Cu²⁺ ions is antiferromagnetic. The exchange integrals are equal to −26.2 cm⁻¹ for 2 and −50.6 cm⁻¹ for 3.     

Syntheses, characterizations and crystal structures of two lead(II) diphosphonates: Pb2[NH(CH2PO3)2] · 2H2O and Pb3[HO2C(CH2)3NH(CH2PO3)2]2 · 2H2O

Hydrothermal reactions of lead(II) acetate and HO₂C(CH₂)₃N(CH₂PO₃H₂)₂ at 170 and 140 °C, respectively, resulted in two different lead diphosphonates, namely, Pb₂[NH(CH₂PO₃)₂] · 2H₂O (1), in which the butyric acid moiety of the HO₂C(CH₂)₃N(CH₂PO₃H₂)₂ has been cleaved and a novel layered compound, Pb₃[HO₂C(CH₂)₃NH(CH₂PO₃)₂]₂ · 2H₂O (2). Their crystal structures have been determined by single crystal X-ray diffraction. In compound 1, the interconnection of the lead(II) ions by bridging amino-diphosphonate ligands leads to the formation of a 3D network. Compound 2 features an unusual triple-layer structure with the non-coordinated butyric acid moieties as pendant groups between the layers.     

Hydrothermal synthesis and crystal structure of a novel one-dimensional arsenic vanadate decorated with organonitrogen ligand: [H3V3O26(AsO4)4(phen)8(H2O)2] · 2H2O (phen=phenanthroline)

A novel organic-inorganic hybrid vanadium arsenate [H₃V₃O₂₆(AsO₄)₄(phen)₈(H₂O)₂] · 2H₂O 1 (phen=phenanthroline) was synthesized by the hydrothermal reaction of V₂O₅, VOSO₄, Na₂HAsO₄ · 7H₂O, phen and water. Its structure was determined by elemental analyses, XPS spectra, EPR spectrum, TG analysis, IR spectrum and single-crystal X-ray diffraction.     

Hydrolytic stability of SnCl4 and GaCl3 in the formation of [cis-SnCl4(H2O)2] · 18-crown-6 · 2H2O and [[2,2,2]cryptand + 2H][GaCl4]2

The combination of anhydrous SnCl₄ with 18-crown-6 in aqueous conditions results in formation of the non-hydrolysed product [cis-SnCl₄(H₂O)₂] · 18-crown-6 · 2H₂O. The X-ray crystal structure shows extensive intermolecular hydrogen bonding involving the cis-octahedral SnCl₄(H₂O)₂ units, the uncoordinated water molecules and the crown ether. Similarly, [2,2,2]cryptand reacts with an aqueous solution formed by adding anhydrous GaCl₃ to slightly acidic water, affording [[2,2,2]cryptand + 2H⁺][GaCl₄]₂.     

Mn(II) complexes of monoanionic bidentate chelators: X-ray crystal structures of Mn(dha)2(CH3OH)2 (Hdha = dehydroacetic acid) and [Mn(ema)2(H2O)]2 · 2H2O (Hema = 2-ethyl-3-hydroxy-4-pyrone)

This report describes synthesis and characterization of bis-ligand Mn(II) complexes of bidentate chelators: maltol (3-hydroxy-2-methyl-4-pyrone), ethylmaltol (2-ethyl-3-hydroxy-4-pyrone), 1,2-dimethyl-3-hydroxy-4-pyridinone (DMHP) and dehydroacetic acid. All four Mn(II) complexes were characterized by elemental analysis, IR, UV/Vis, EPR, cyclic voltammetry, and X-ray crystallography in cases of Mn(dha)₂(CH₃OH)₂ and [Mn(ema)₂(H₂O)]₂ · 2H₂O. The bidentate chelator plays a significant role in the solid state structure of its Mn(II) complex. For example, dha forms the monomeric complex Mn(dha)₂(CH₃OH)₂ while ethylmaltol forms the dimeric complex [Mn(ema)₂(H₂O)]₂. Because of smaller size, maltol ligands in Mn(ma)₂ are able to bridge adjacent Mn(II) centers to give a polymeric structure in solid state. Despite of the difference in their solid state structures, both Mn(ema)₂ and Mn(ma)₂ exist in solution as monomeric Mn(II) species, Mn(ema)₂(H₂O)₂ and Mn(ma)₂(H₂O)₂. This assumption is supported by the similarity in their UV/Vis spectra, EPR data and electrochemical properties. Replacing maltol with DMHP results in a decrease (by ∼100 mV) in the redox potential for the Mn(II)/Mn(III) couple, suggesting that DMHP stabilizes Mn(III) better than maltol. Since Mn(DMHP)₂(H₂O)₂ is readily oxidized to form the more stable Mn(III) complex Mn(DMHP)₃, DMHP has the potential as a chelator for removal of excess Mn(II) from patients with chronic Mn toxicity.     

Preparation and characterization of the layered borophosphates M(H2O)2[B2P2O8(OH)2]·H2O (M = Fe, Co, Ni)

The isotypic layered transition metal borophosphates M^II(H₂O)₂[B₂P₂O₈(OH)₂]·H₂O (M^II = Fe, Co, Ni) were prepared under hydrothermal conditions. Their crystal structures were determined by single-crystal X-ray diffraction data and revealed an isotypic relationship to Mg(H₂O)₂[B₂P₂O₈(OH)₂]·H₂O, a structure containing wavy 6³ nets formed by tetrahedral phosphate and hydrogenborate groups interconnected in an alternating fashion by sharing common apices. The crystalline compounds were also characterized by chemical analyses, scanning electron microscopy, energy dispersive X-ray analyses, thermal analyses, IR-spectroscopy and magnetic susceptibility measurements.     

Long-range superexchanged magnetic interaction observed in heterometallic complex: {[Fe(Tpms)(CN)3][Mn(H2O)2(DMF)2]} · DMF

A new tri-cyanometalate building block for heterometallic complexes, [PPh₄]₂[Fe^II(Tpms)(CN)₃] (2) (PPh₄ = tetraphenylphosphonium; Tpms = tris(pyrazolyl) methanesulfonate), has been prepared. Using it as a building block, a one-dimensional chain compound, {[Fe^II(Tpms)(CN)₃][Mn^II(H₂O)₂( DMF)₂]} · DMF (3), has been synthesized and structurally characterized. The magnetic properties of 3 correspond to a ferromagnetic chain with weak long-range superexchanged magnetic interaction between the high-spin manganese(II) ions.     

Ln2(O2CCH2PO3)2(H2O)3 · H2O (Ln = La, Pr, Nd, Sm): Layered lanthanide phosphonoacetates containing two-dimensional -Ln-O- linkages

Four novel isostructural lanthanide phosphonate compounds with formula Ln₂(O₂CCH₂PO₃)₂(H₂O)₃ · H₂O [Ln = La (1), Pr (2), Nd (3), Sm (4)] have been prepared through hydrothermal reactions of phosphonoacetate acid and lanthanide nitrates. All show layered structures made up of {LnO₉} polyhedra and {CPO₃} tetrahedra with the lattice water molecules locating between the layers. Within the layer, chains of edge-sharing {LnO₉} polyhedra are connected via corner-sharing by phosphonate oxygens forming a two-dimensional -Ln-O- linkage. Thermal analyses and XRD measurements reveal that the framework structures can be maintained up to 400 °C.     

A trinuclear copper(II) complex with 2,5-pyridine-dicarboxylato bridges - [Cu3(2,5-pydc)2(Me5dien)2(H2O)2(BF4)2] · H2O: Synthesis, crystal structure and magnetic properties

A trinuclear copper(II) complex, [Cu₃(2,5-pydc)₂(Me₅dien)₂(BF₄)₂(H₂O)₂] · H₂O 1, has been constructed from 2,5-pyridine-dicarboxylato bridges (2,5-pydc²⁻) and N,N,N′,N″,N″-pentamethyl-diethylenetriamine (Me₅dien) acting as a blocking ligand. The copper ions, within the centrosymmetric trinuclear cations, are connected by two 2,5-pydc²⁻ bridges, with an intramolecular Cu···Cu separation of 8.432 Å. The central copper ion exhibits an elongated octahedral geometry, with semicoordinated ions, while the terminal ones are pentacoordinated (distorted square-pyramidal geometry). The cryomagnetic investigation of 1 reveals an antiferromagnetic coupling of the copper(II) ions (J = −5.9 cm⁻¹, H = −JS_Cu1S_Cu2 − JS_Cu2S_Cu1a).     

Zinc complexes of 6-methyl-2-pyridinecarboxylic acid. Crystal structure of [Zn(MeC5H3NCOO)2(H2O)] · H2O

Reaction of Zn(AcO)₂ · 2H₂O with 6-methyl-2-pyridinecarboxylic acid (L) yielded a new compound [Zn(MeC₅H₃NCOO)₂(H₂O)] · H₂O. This complex was characterised by elemental analyses, conductivity measurements, infrared, ¹H and ¹³C{¹H} NMR spectroscopies and single-crystal X-ray diffraction. The crystal structure consists of discrete molecules involving a pentacoordinated Zn atom with a geometry intermediate between a trigonal bipyramid and a square pyramid and with the two N_py atoms occupying the apical sites. Treatment of the complex [Zn(MeC₅H₃NCOO)₂(H₂O)] · H₂O with 2,2^′-bipyridine (bpy) produced [Zn(MeC₅H₃NCOO)₂(bpy)]. The metallic atom in this complex displays a distorted octahedral geometry and is coordinated to two ligands (L) via the pyridine nitrogen and the carbonyl oxygen atoms and to one 2,2^′-bypyridine (bpy).     

Two new supermolecular structures of organic-inorganic hybrid compounds: [Zn(phen)(SO4)(H2O)2]n and [Cu(phen)(H2O)2] · SO4 (phen = 1,10-phenanthroline)

Two new organic-inorganic hybrid compounds [Zn(phen)(SO₄)(H₂O)₂]_n (1) and [Cu(phen)(H₂O)₂] · SO₄ (2) have been prepared by conventional aqueous solution synthesis and characterized by single-crystal X-ray diffraction, IR spectroscopy, thermal gravimetric analysis (TGA) and fluorescent spectroscopy. In compound 1, the sulfate group adopts bidentate mode to coordinate with two Zn(II) ions to form one-dimensional polymer. The one-dimensional polymers are further linked together via the intermolecular hydrogen-bonding and π-π stacking interactions to form a 3D supramolecular framework. Compound 2 is build up of discrete [Cu(phen)(H₂O]²⁺ cations and SO₄²⁻ anions to form a three-dimensional framework via hydrogen-bonding and π-π stacking interactions. Furthermore, the luminescent properties of both 1 and 2 were studied. The complexes 1 and 2 excited at 280 nm wavelength produced characteristic luminescence features, arising maybe due to the π-π transitions.