Synthesis, X-ray powder structure, and magnetic properties of the new, weak ferromagnet iron(II) phenylphosphonate

Synthesis Strategy Guided by Decision Tree for Morphology Control of Metal Phosphonates

The morphology control of metal phosphonates is always a difficulty because there are many challenges derived from the complexity of crystallization and the multivariable synthesis system. Responding to challenges, we propose a synthesis strategy guided by a decision tree for morphology control of metal phosphonates, through which directional design of the morphology-controlled synthesis can be realized. Specifically, any one synthetic condition involving the synthesis of metal phosphonates can be regarded as a decision problem to construct a binary decision tree. By means of the classification principle of the binary decision tree, the samples synthesized under the boundary value of each synthesis condition are classified based on crystal phase and morphology. The key synthetic conditions determining crystal phase and morphology can be precisely screened out to serve as decision nodes for the binary decision tree and are also rapidly optimized by the recursion level by level, whereas others cannot. Here, the β-polymorph of copper phenylphosphonate (β-CuPP) is selected as an example to elaborate the decision-tree-guided synthesis strategy for morphology control of metal phosphonates. From the constructed binary decision tree, it is clear that the right amount of methanol in the solvent is vital to obtain β-phase of CuPP, whereas the reactant concentration, pH value, and reaction time are important for morphology and phase transformation. Under the optimal synthetic conditions screened out by the binary decision tree, β-CuPP can thus be controlled to be hierarchically flower-like microsphere morphology through either the direct synthesis route or the solid-to-solid phase transformation route. This research work confirms that the decision-tree-guided synthesis is highly efficacious for the morphology control of metal phosphonates. Furthermore, the morphology-controlled synthesis guided by a decision tree may provide some valuable inspiration for morphology control of metal-organic frameworks (MOFs) and even coordinate compounds.

The crystallisation of copper(ii) phenylphosphonates

The crystal structures and syntheses of four different copper(ii) phenylphosphonates, the monophenylphosphonates α-, β-, and γ-Cu(O₃PC₆H₅)·H₂O (α-CuPhPmH (1) β-CuPhPmH (2) and γ-CuPhPmH (3)), and the diphosphonate Cu(HO₃PC₆H₅)₂·H₂O (CuPhP2mH (4)), are presented. The compounds were synthesized from solution at room temperature, at elevated temperature, under hydrothermal conditions, and mechanochemical conditions. The structures of α-CuPhPmH (1) and CuPhP2mH (4) were solved from powder X-ray diffraction data. The structure of β-CuPhPmH (2) was solved by single crystal X-ray analysis. The structures were validated by extended X-ray absorption fine structure (EXAFS) and DTA analyses. Disorder of the crystal structure was elucidated by electron diffraction. The relationship between the compounds and their reaction pathways were investigated by in situ synchrotron measurements.

Divalent metal phosphonates – new aspects for syntheses, in situ characterization and structure solution

Divalent metal phosphonates are promising hybrid materials with a broad field of application. The rich coordination chemistry of the phosphonate linkers enables the formation of structures with different dimensionalities ranging from isolated complexes and layered structures to porous frameworks incorporating various functionalities through the choice of the building blocks. In brief, metal phosphonates offer an interesting opportunity for the design of multifunctional materials. Here, we provide a short review on the class of divalent metal phosphonates discussing their syntheses, structures, and applications. We present the advantages of the recently introduced mechanochemical pathway for the synthesis of divalent phosphonates as a possibility to generate new, in certain cases metastable compounds. The benefits of

Spontaneous Magnetization in Homometallic μ6-Oxalate Coordination Polymers

The reaction of 1,2,4-triazole and NaF with M(ox) (M = transition-metal dication; ox = oxalate dianion) under hydrothermal conditions has led to the isolation of a variety of hybrid organic-inorganic coordination polymers. Four structurally different 3D networks were obtained, depending on the transition metal, with stoichiometry [M2(H2O)(μ2-ox)][M2(μ3-trz)6] [M = Fe (1), Co (2), Ni (3)], [Zn2(H2O)(μ3-trz)2(μ2-ox)] (4), [Mn3(μ3-trz)2(μ6-ox)(μ3-F)2] (5), and [Fe3(μ3-trz)2(μ6-ox)(μ2-F)2] (6). In all cases, the magnetic behavior is dominated by antiferromagnetic exchange interactions between paramagnetic centers. Remarkably, 5 and 6 present a novel magnetic connectivity around the oxalate anion: a μ6-bridging mode. This magnetic geometry promotes multiple triangular arrangements among antiferromagnetically coupled spin carriers, resulting in a complex magnetic network because of the presence of competing interactions. These materials exhibit spontaneous magnetization below 9 and 66 K, respectively.

A distorted honeycomb motif in divalent transition metal compounds based on 4-phosphonbenzoic acid and exchange coupled Co(II) and Cu(II): synthesis, structural description and magnetic properties

The first example of a two-dimensional inorganic hybrid material with cobalt as an open-shell transition metal ion and 4-phosphonbenzoic acid as a linker is presented together with its copper analogue. For both metal ions the inorganic part consists of edge-sharing metal-oxygen octahedra leading to a metal honeycomb motif. The magnetic properties of the cobalt compound are reported together with those of the corresponding copper compound based on the remarkably six-coordinated copper(II) ions.

Hydrothermal synthesis and characterization of a layered cobalt phenylphosphonate, Co(PhPO3)(H2O)

We report the hydrothermal synthesis and characterization of a layered cobalt phenylphosphonate. Unlike most metal phosphonates reported to date, the structure was solved by single crystal X-ray diffraction (SC-XRD). Co(ii) centres are hexa-coordinated by oxygen and the octahedra corner-share into a layer. The layers are capped by phenylphosphonate groups, where the phenyl groups define a hydrophobic bilayer region. The material was also characterized by powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA) and SQUID (superconducting quantum interference device) magnetometry. The material undergoes an antiferromagnetic transition at a relatively low Néel temperature of 4.0 K, while the Curie-Weiss temperature of -76.5 K reflects the low-dimensionality of the magnetic structure. The effective magnetic moment of 5.01 micro(B) per Co(2+) verifies a high-spin configuration and an octahedral coordination of the metal centres. This layered material was correctly predicted in the literature from powder data, adds to the structural diversity of the cobalt phosphonates, and may be useful as an intercalation or exfoliation compound.

Dinuclear and layered copper 2-pyridylphosphonates with weak ferromagnetism observed in layer compound Cu(C5H4NPO3)

This paper reports the syntheses and structures of three new copper phosphonates based on 2-pyridylphosphonate, namely, Cu(C(5)H(4)NPO(3)H)2 (1), Cu3(OH)2(C(5)H(4)NPO(3))2.2H2O (2) and Cu(C(5)H(4)NPO(3)) (3). Compound 1 has a discrete dimeric structure in which the {CuO(4)N} square pyramids are linked by the {CPO(3)} tetrahedra through corner-sharing. The dimers are further connected into a chain through hydrogen bonds. In compound 2, edge-sharing {Cu(1)O(4)N} square pyramids and {Cu(2)O(4)} planes are found to form an infinite chain with composition {Cu(3)(mu-OH)(2)(mu-O)(4)}. Neighboring chains are linked by the phosphonate groups of the 2-pyridylphosphonate ligands, resulting in inorganic layers containing 4-, 8- and 12-membered rings. The pyridyl groups and the lattice water molecules occupy the inter-layer space. In compound 3, the {Cu(1)O(4)} and {Cu(2)O(2)N(2)} planes are each corner-shared with the {CPO(3)} tetrahedra, forming an inorganic layer containing 8- and 16-membered rings. The pyridyl groups reside between the layers. Crystal data for 1: space group P(-)1, a = 8.4045(19), b = 8.751(2), c = 10.632(2) A, alpha = 66.673(4), beta = 72.566(4), gamma = 70.690(4) degrees , V = 664.7(2) A(3), Z = 2. Crystal data for 2: space group P2(1)/c, a = 7.9544(17), b = 21.579(4), c = 5.0243(10) A, beta = 105.332(3) degrees , V = 831.7(3) A(3), Z = 2. Crystal data for 3: space group P2(1)/c, a = 4.7793(11), b = 15.319(3), c = 8.6022(19) A, beta = 97.156(4) degrees , V = 624.9(2) A(3), Z = 4. Magnetic measurements reveal that dominant antiferromagnetic interactions are propagated between the copper centers in compounds 1-3. For 3, spin canting is observed with a ferromagnetic transition occurring at 9 K.

Silver(I) Arylsulfonates: A Systematic Study of “Softer” Hybrid Inorganic−Organic Solids

The present study represents the first systematic examination of the effects on the layered structure of simple silver aryl-monosulfonates as the breadth of the pendant aryl group is increased beyond that where a simple "phosphonate-like" motif is sustainable. Five new silver arenesulfonates are reported. On the basis of comparison with Ag benzenesulfonate, a threshold of approximately 6.4 A is proposed and confirmed as the critical breadth of an aryl group for a simple layered motif to be observed in silver sulfonates. Ag 1,1'-biphenyl-4-sulfonate (1) and Ag 2-naphthalenesulfonate (2) are below this threshold and so form simple layered networks, termed type 1 solids. When the pendant group is broadened to a 1-naphthyl group, the layer incorporates coordinated water to maintain a layered structure giving Ag 1-naphthalenesulfonate hemihydrate (3a). This more diffuse structure is termed a type 2 solid. For anhydrous Ag 1-naphthalenesulfonate (3) and Ag 1-pyrenesulfonate (4), the additional breadth is compensated for by the formation of Ag-pi interactions and the formation of type 3 solids. Interactions between the pendant groups are observed to play a significant role in the packing of the solid. All frameworks are characterized by single crystal and powder X-ray diffraction, IR, DSC-TGA, and elemental analysis. The significance of this adaptable framework is discussed along with implications for design of stacked arene arrays.

Cr[(H3N−(CH2)2−PO3)(Cl)(H2O)]: X-Ray Single-Crystal Structure and Magnetism of a Polar Organic−Inorganic Hybrid Chromium(II) Organophosphonate

Cr[(H(3)N-(CH(2))(2)-PO(3))(Cl)(H(2)O)], a rare example of a polar organic-inorganic hybrid material containing Cr(2+), was prepared from CrCl(2), 2-aminoethylphosphonic acid, and urea in water and isolated as light-blue crystals. It crystallizes in the noncentrosymmetric monoclinic space group P2(1), with a = 5.249(1) A, b = 14.133(3) A, c = 5.275(1) A, and beta = 105.55(2) degrees. The inorganic layer of the hybrid network is formed by Cr(II) five-coordinated by three oxygen atoms from the phosphonates and one from the water molecule in a square pyramidal unit, whose apical position is occupied by the Cl(-) ion. Hydrogen bonds are established between the coordinating water molecule and the oxygen atoms of adjacent phosphonate ligands. The inorganic network is interspersed by ethylammonium groups, and the terminal ammonium moiety is linked to the apical Cl(-) ions through hydrogen bonds. Electrostatic interactions as well as hydrogen bonds and the coordinated chlorine atoms ensure the cohesion of the 3D structure. The lattice is polar (lack of inversion center), and this fact determines the magnetic behavior of the compound at low temperatures. The magnetic susceptibility data in the temperature range from 300 to 50 K show Curie-Weiss behavior, with C = 2.716 cm(3) K mol(-1) and the Weiss constant theta = -2.2 K. The corresponding effective magnetic moment of 4.7 mu(B) compares well with the expected value for Cr(2+) in d(4) high-spin configuration. A slight decrease of the chiT product versus T observed at temperatures below 50 K indicates nearest-neighbor antiferromagnetic exchange interactions. On cooling below T = 6 K, the magnetic susceptibility increases sharply up to a maximum at ca. 5 K and then decreases again. Below T = 6 K, hysteresis loops taken at different temperatures show that Cr[(H(3)N-(CH(2))(2)-PO(3))(Cl)(H(2)O)] behaves as a weak ferromagnet with the critical temperature T(N) at 5.5 K. The spin canting is responsible of the long-range magnetic ordering. The values of the coercive field, H(c), and of remnant magnetization, M(r), obtained from the hysteresis loop at T = 4.5 K (the lowest measured temperature) are 30 Oe and 0.08 mu(B), respectively.

Novel layered ruthenium diphosphonate containing a mixed valent diruthenium paddlewheel core

This paper reports the synthesis and crystal structure of a novel mixed valence ruthenium(II,III) compound, (NH(4))(3)Ru(2)(hedp)(2).2H(2)O (1), where hedp represents 1-hydroxyethylidenediphosphonate. It has a two-dimensional structure in which the paddlewheel diruthenium(II,III) units of Ru(2)(hedp)(2) are cross-linked through the phosphonate groups. The layers are stacked along the [100] direction with strong intra- and interlayer hydrogen bonds. Primary magnetic results are presented.

X-ray single-crystal structure and magnetic properties of Fe[CH(3)PO(3))] x H(2)O: a layered weak ferromagnet

The crystal and molecular structure of the layered weak-ferromagnet Fe[CH(3)PO(3)] x H(2)O has been solved by X-ray single-crystal diffraction techniques. Crystal data for Fe[CH(3)PO(3)] x H(2)O are the following: orthorhombic space group Pna2(1); a =17.538(2), b = 4.814(1), c = 5.719(1) A. The structure is lamellar, and it consists of alternating organic and inorganic layers along the a direction of the unit cell. The inorganic layers are made of Fe(II) ions octahedrally coordinated by five phosphonate oxygen atoms and one from oxygen of the water molecule. Each phosphonate group coordinates four metal ions, through chelation and bridging, making in this way a cross-linked Fe-O network. The resultant layers are then separated by bilayers of the methyl groups, with van der Waals contacts between them. The compound is air stable, and it dehydrates under inert atmosphere at temperatures above 120 degrees C. The oxidation state of the metal ion is +2, and the electronic configuration is d(6)( )()high spin (S = 2), as determined from dc magnetic susceptibility measurements from 150 K to ambient temperature. Below 100 K, the magnetic moment of Fe[CH(3)PO(3)] x H(2)O rises rapidly to a maximum at T(max) approximately equal to 24 K, and then it decreases again. The onset of peak at T = 25 K is associated with the 3D antiferromagnetic long-range ordering, T(N). The observed critical temperature, T(N), is like all the other previously reported Fe(II) phosphonates, and it appears to be nearly independent of the interlayer spacing in this family of hybrid organic-inorganic layered compounds. Below T(N), the compound behaves as a "weak ferromagnet", and represents the third kind of magnetic materials with a spontaneous magnetization below a finite critical temperature, ferromagnets and ferrimagnets being the other two types.