Metal Phosphonates Research Articles

Metal phosphonate hybrid materials: from densely layered to hierarchically nanoporous structures

Inorganic–organic metal phosphonate hybrid materials with great diversity in structure and properties exhibit application potential in various fields.

Mesoporous non-siliceous inorganic–organic hybrids: a promising platform for designing multifunctional materials

An overview of the recent progress in the designed synthesis, modification and multifunctional applications of mesoporous non-siliceous inorganic–organic hybrid materials including metal phosphonates, carboxylates and sulfonates is presented.

The first route to highly stable crystalline microporous zirconium phosphonate metal-organic frameworks.

The first crystalline microporous zirconium phosphonate metal-organic framework (UPG-1) was synthesized using the novel tritopic ligand 2,4,6-tris(4-(phosphonomethyl)phenyl)-1,3,5-triazine. Its crystal structure was solved ab initio from laboratory powder X-ray diffraction data. UPG-1 displays remarkable thermal stability and hydrolysis resistance and has a good absorption affinity towards n-butane and CO2.

Syntheses, crystal structures, surface photovoltage, luminescence and molecular recognition properties of zinc(ii) and iron(ii) carboxyphosphonates with 2D and 3D supramolecular structures

Four new transition metal carboxyphosphonates with 2D and 3D supramolecular structures, namely, Fe2[(HL)(H2O)] (1), Fe(H4L)2 (2), Zn(H3L) (3) and Zn2(HL) (4) (H5L = 4-HO2C–C6H4–CH2N(CH2PO3H2)2), have been synthesized under hydrothermal conditions. For compound 1, {FeO5N} and {CPO3} polyhedra are interconnected into a 2D layer in the bc-plane via corner-sharing. Then the adjacent layers are further assembled into a 3D supramolecular structure through π–π stacking interactions. Compound 2 shows a 3D supramolecular structure. {FeO6} and {CPO3} polyhedra are interconnected into a 2D layer in the bc-plane via corner-sharing, which is further linked through π–π stacking interactions to form a 3D supramolecular structure. The overall structure of compound 3 can be described as a 2D supramolecular structure. The {ZnO4} polyhedra are interconnected by {CPO3} tetrahedra via corner-sharing to form a 1D chain. These neighboring metal phosphonate chains are connected through hydrogen bonding interactions to give rise to a 2D supramolecular structure in the ac-plane. In compound 4, {ZnO3N} and {ZnO4} polyhedra are interconnected by {CPO3} tetrahedra via corner-sharing and edge-sharing to form a 2D inorganic layer in the bc-plane, which is further linked through π–π stacking interactions to form a 3D supramolecular structure. The surface photovoltage properties of compounds 1–2 and luminescence properties of compounds 3–4 have been investigated. More interestingly, compound 4 is selective for sensing DMF and acetone.

Structure tuning of metal phosphonates: Syntheses, structures and characterizations of two new lead (II) trisphosphonates

Two lead (II) trisphosphonates, [Pb3(H3L1)2(H2O)] (1) and [Pb5(HL2)(H3L2)(H4L2)(H2O)2][(H2O)2] (2), have been synthesized from two trisphosphonate ligands and characterized by EA, IR, UV–vis, TGA, powder and single-crystal X-ray diffraction methods. The single-crystal X-ray diffraction analyses reveal that they both feature three-dimensional framework structures. The lead (II) ions are mainly five-coordinated, forming square pyramid coordination geometry. Although the two trisphosphonate ligands are very similar, different coordination modes and conformations are observed for them, suggesting that attachment of methyl groups to the central benzene ring has a major effect on the structure formation. They both absorb below 325nm and are thermally robust.

Layered Phosphonates in Colloidal Synthesis of Anisotropic ZnO Nanocrystals

We describe the role of phosphonic acids in the synthesis of anisotropic colloidal ZnO nanocrystals (nanorods) and, specifically, the discovery of an insoluble layered Zn–phosphonate intermediate. This compound is formed by the reaction of the molecular Zn precursor Zn(OAc)2 with phosphonic acids, and it acts as a heterogeneous Zn source during nanocrystal formation. Layered metal phosphonates have been studied extensively but have not been described in the context of nanocrystal synthesis. Layered Zn–octadecylphosphonate can be used as a sole precursor to obtain isotropic, soluble ZnO nanocrystals. However, for anisotropic rod-like shapes both the heterogeneous and the homogeneous (Zn(OAc)2) sources of Zn are necessary. The existence of a heterogeneous metal source described here is in contrast to the mechanisms of particle nucleation and growth from homogeneous molecular precursors often used to describe nanocrystal formation. Since many metals form layered phosphonates, our findings have implications f...

Enhancing Order and Porosity in a Highly Robust Tin(IV) Triphosphonate Framework

Metal organic frameworks (MOFs) are noted for crystallinity, stability, and porosity. For many industrial challenges though, beyond stability to pore activation, porous materials require high thermal and moisture stability. Here, we report a Sn(IV) triphosphonate framework, CALF-28, that is highly robust and porous. CALF-28 was designed based on the known structure of a divalent metal phosphonate that was 2-fold interpenetrated. It has strong sustaining interactions but consequently rapidly precipitates, compromising crystallinity. Using methods to enhance order, and by analogy to the M(II) analogue, insights to the structure are ascertained and corroborated by PXRD and gas sorption analysis. CALF-28 has a surface area >500 m(2)/g and is stable in water.

Hydrothermal Synthesis and Structural Characterization of Metal Organophosphonate Oxide Materials: Role of Metal-Oxo Clusters in the Self Assembly of Metal Phosphonate Architectures

Two new metal organophosphonate oxide materials with formulas [CuII4CuI2(L)2(2,2′-bpy)6(HPW12O40)]n·4nH2O (1) and [Cu(2,2′-bpy)VO2(OH)(H2L)]n (2) have been synthesized starting from the Cu(II) salt...

Cobalt 2-pyrazinephosphonates: syntheses, structures, and magnetic properties

Reactions of Co(ClO4)2·6H2O with 2-pyrazinephosphonic acid (2-paPO3H2) under two different hydrothermal conditions gave two new cobalt 2-pyrazinephosphonates, Co(2-paPO3H)2 (1) and Co(2-paPO3)(H2O) (2). Compound 1 was obtained at 160 °C, while 2 was obtained at 180 °C. In 1, two Co(II) units are bridged by two O–P–O’s into a dimer and the dimers are linked by pyrazinyl groups into a 1-D double chain. In 2, the {CoO4N2} and {CPO3} polyhedra are interconnected via edge and corner-sharing into a metal phosphonate layer, and the layers are pillared by pyrazinyl groups into a 3-D network. Variable-temperature magnetic susceptibility studies reveal that both complexes have weak antiferromagnetic coupling between Co(II) ions.

Effects of layered lanthanum phenylphosphonate on flame retardancy of glass-fiber reinforced poly(ethylene terephthalate) nanocomposites

Effects of layered metal phosphonate lanthanum phenylphosphonate (LaPP) on the thermal stability, flame retardancy and mechanical properties of glass-fiber reinforced poly(ethylene terephthalate) (PET/GF)/microencapsulated red phosphorus (MRP) systems were investigated. The result of transmission electron microscopy (TEM) measurements indicated that LaPP particles were homogenously dispersed in PET matrix and no obvious signs of LaPP aggregation were detected. Thermogravimetric (TG) analysis showed that incorporating LaPP into PET/GF-MRP enhanced the thermal stability and increased the char residue compared to the sample without LaPP. In the existence of LaPP, the PET/GF-MRP composites could pass the UL 94 V-0 rating test, and the limited oxygen index (LOI) could be enhanced. The structures of char residues observed by scanning electron microscopy (SEM) demonstrated that LaPP could promote to form the homogenous and compact char layer. What is more, the presence of LaPP improved the tensile strength and storage moduli of PET/GF-MRP composites.

Syntheses, structures and magnetic properties of two isostructural metal-phosphonate frameworks

A phosphonic acid, 4-(1,2,4-triazol-4-yl)phenylphosphonic acid (H2ptz) was used as a new ligand to construct magnetic materials, by which two 2-dimensional (2D) layered metal phosphonates, [M5(Hptz)2(ptz)4]n (where M=Co(II) (1) and Mn(II) (2)) have been hydrothermally synthesized. Both compounds were characterized by elemental analyses, infrared spectroscopy, powder X-ray diffraction and X-ray single-crystal diffraction. Structure analyses reveal that 1 and 2 are isostructures, where the metal and ptz ligands form M5(Hptz)2(ptz)4 subunits, which are further linked together into a 2-D layered structure. The magnetism studies over the temperature range 2–300K showed pronounced antiferromagnetic interactions between the combined oxo- and diazo-bridged metal centers in both 1 and 2.

Improving the flame retardancy and mechanical properties of high-density polyethylene-g-maleic anhydride with a novel organic metal phosphonate

Zinc N,N′-piperazinebis(methylenephosphonic acid) (PPMPA-Zn) was melt blended with high-density polyethylene-g-maleic anhydride (HDPE-MA) to fabricate flame-retardant HDPE-MA/PPMPA-Zn composites. The thermal stability and flame retardancy of the composites were investigated by thermogravimetric analysis (TGA) and cone calorimetry. The incorporation of PPMPA-Zn did not appreciably increase the thermal stability of HDPE-MA, but the residual char content increased to 18.7% when the content of PPMPA-Zn reached 25wt%. X-ray diffraction and Raman spectroscopy tests showed that the residual char was composed mainly of Zn(PO3)2, Zn11(HPO3)8(OH)6 and amorphous graphite. Scanning electron microscopy (SEM) images of samples collected after cone calorimetric tests also confirmed the formation of char in the sample with 25wt% PPMPA-Zn loading in HDPE-MA, and the char layer acted as a compact and intact physical barrier in the condensed phase. Even at a loading as low as 5wt% PPMPA-Zn, the peak value of the heat release rate (PHRR) was reduced by 38% compared with that of pure HDPE-MA. In contrast to other intumescent flame retardants, the introduction of PPMPA-Zn enhanced not only the flame retardancy but also the mechanical properties of HDPE-MA. For example, the yield strength and Young's modulus of HDPE-MA with 5wt% PPMPA-Zn were 125% and 128% higher, respectively, than those of the pure HDPE-MA matrix.

High-throughput microwave-assisted discovery of new metal phosphonates

A systematic study was carried out to investigate the influence of linker geometry, metal ionic radius as well as the nature of the counter ions on the structure formation of metal tetraphosphonates. Two tetraphosphonic acids p- and m-(H2O3PCH2)2N-CH2-C6H4-CH2-N(CH2PO3H2)2, six metal ions (Ca(2+), Mn(2+), Co(2+), Ni(2+), Zn(2+), and Cd(2+)) and two different counter ions (Cl(-) and NO3(-)) were employed using high throughput methods. Microwave (MW)-assisted heating led to the discovery of ten new metal-phosphonates which crystallize in three different crystal structures. The combination of direct methods and force field calculations allowed us to establish the crystal structures. The counter ion and the ionic radii of the metal ions have a profound influence on the crystallinity and the formed crystal structure. All compounds were characterized in detail by thermogravimetric analyses, IR spectroscopy and magnetic susceptibility measurements. The proton conductivity of two selected compounds is also reported.

Racemic metal phosphonates based on 1-phosphonomethyl-2-benzimidazol-piperidine

Based on racemic 1-phosphonomethyl-2-benzimidazol-piperidine (pbpH2), three metal phosphonate compounds with the formula M(pbp)(H2O)2·3H2O [M = Ni(1), Co(2)] and Cu(pbp)·2H2O (3) have been synthesised and structurally determined. All of the compounds contain chiral chains, in which adjacent M(II) ions are linked solely by O–P–O bridges. In compounds 1 and 2, linear chains of the opposite handedness are fused by hydrogen bonds forming racemic double chains. The double chains are further connected by hydrogen bond interactions into a three-dimensional (3D) supramolecular network structure. In compound 3, helical chains with the opposite helicity are arranged alternately in the structure leading to a racemic 3D network. π–π stacking and hydrogen bond interactions are found to exist between the chains. Magnetic studies reveal that dominant antiferromagnetic interactions are propagated in 1–3 between the magnetic centers via the O–P–O pathways.

Naphthalene-based linkers for metal phosphonates: synthesis, structure, and interesting conformational flexibility influence on final lanthanum hybrids

Two diphosphonic acids based on naphthalene scaffold, namely naphthalene-1,4-diphosphonic acid, C10H6(PO3H2)2 [1, H4NDP(1,4)] and 1-(phosphono)naphthalene-4-(methylphosphonic) acid, C10H6(PO3H2)(CH2PO3H2) [2, H4NDP(1,4C)] were obtained. Their supramolecular self-assembly were studied as well as solvent effect for the second one (2a, 2b). These potential building blocks in coordination polymer chemistry were engaged with a La3+ ion in a room temperature reaction to produce new single crystalline metal phosphonates: (I) [La{C10H6(PO3H)2}{C10H6(PO3H)(PO3H2)}(H2O)2]n·nH2O (3), a 2D coordination polymer with the I1O1 structure and {42.6}2{44.64.82} topology of the layer, and (II) [La{C10H6(PO3H1.5)(CH2PO3H)}2(H2O)7]·2H2O (4), a discrete complex. These drastic differences in hybrid material structures can be explained by ligand structures analysis including their conformational flexibility.

Phosphonates containing 8-hydroxyquinoline moiety and their metal complexes: structures, fluorescent and magnetic properties

Two kinds of solid-state structures of 5-phosphonomethyl-8-hydroxyquinoline (5pm8hqH3) have been obtained, namely 1·HCl·H2O and 1·H2O, involving different hydrogen bonds and/or aromatic stacking interactions. As a derivative of 5pm8hqH3, 5-phosphonomethyl-8-(carboxymethoxy)quinoline (5pm8cmoqH3) was synthesized. Based on 5pm8hqH3 and 5pm8cmoqH3, three new metal phosphonates have been hydrothermally prepared, including Zn(5pm8hqH)(H2O)·H2O (2), Cu(5pm8cmoqH)·2H2O (3) and Fe(5pm8cmoqH) (4), exhibiting layered structures for 2 and 4, and a three-dimensional open framework for 3. The 8-hydroxyquinoline moieties in 1·H2O and 2-4 exhibit three kinds of interesting aromatic stacking modes, including pyridine ring-pyridine ring stacking between a pair of moieties, double benzene ring-pyridine ring stacking between a pair of moieties and alternating benzene ring-benzene ring and pyridine ring-pyridine ring stacking among a number of moieties in the layered structure. The solid-state fluorescence measurements indicate the emissions of 1·HCl·H2O and 1·H2O are significantly different due to their distinct packing structures. Compound 2 exhibits both ligand-centered (LC) and ligand-to-metal charge transition (LMCT) emissions. Magnetic studies reveal dominant antiferromagnetic interactions in 3 and 4.

Syntheses, crystal structures, thermal stability, magnetism and luminescence of four new metal phosphonates

Hydrothermal reactions of Cd2+, Mn2+, Co2+ and Ni2+ ions with 4-pyridyl-CH2N(CH2COOH)(CH2PO3H2) (H3L) afforded four new metal phosphonates, namely, (H3O)4[Cd7(L)6]·16H2O (1), (H3O)4[Mn7(L)6]·17H2O (2), [Co(HL)(H2O)]·2H2O (3) and [Ni(HL)(H2O)]·2H2O (4). Compounds 1 and 3 are isomorphous with compounds 2 and 4, respectively. Solid 1 is a 3D open-framework consisting of heptanuclear cadmium clusters. The framework of solid 1 is thermally stable up to 250 °C under an air atmosphere. In 3, HL2− anions exhibit pentadentate modes to combine Co2+ ions into a 2D hybrid layer. It is interesting that solid 1 displays bright blue luminescence, which can be enhanced upon cooling to 10 K. Furthermore, after heat-treatment at 250 °C under an air atmosphere, solid 1-250 also gives off blue emission. And the magnetic properties of 2–4 have also been studied.

Cobalt phosphonates based on 4-(ethoxycarbonyl)naphthalen-1-yl)phosphonic acid

The first examples of metal phosphonates based on 4-(ethoxycarbonyl)naphthanen-1-yl)phosphonic acid (4-cnppH2) are reported, namely, Co(4-cnpp) (1), Co2(4-cnpp)2(dptz) (2) and Co2(4-cnpp)2(4,4'-bpy)(H2O) (3) (dptz = 3,6-di(pyridin-3-yl)-1,2,4,5-tetrazine, 4,4'-bpy = 4,4'-bipyridine). The cobalt atoms are four-coordinated with distorted tetrahedral geometries in both 1 and 2, while five-coordinated with a distorted trigonal bipyramidal environment in compound 3. Compound 1 shows a layer structure in which the inorganic layers made up of edge-sharing {CoNO3} dimers and {PO3C} linkages are separated by the organic groups of the 4-cnpp(2-) ligands. Compound 2 displays a different type of layer structure, where the ladder-like chains composed of corner-sharing {CoNO3} and {PO3C} tetrahedra are connected by dptz ligands with the organic groups of the 4-cnpp(2-) ligands pendent on the two sides of the layer. In 3, similar ladder-like chains of corner-sharing {CoNO4} and {PO3C} are also found except that the cobalt atoms within the chain are further bridged by a coordinated water molecule. The chains are cross-linked by 4,4'-bpy, leading to a three-dimensional open-framework structure. Magnetic studies reveal that dominant antiferromagnetic interactions are mediated between the Co(II) ions in all three cases.

Chiral one-dimensional O–P–O bridged MnIII-Schiff base complexes

Two couples of enantiomerically pure metal phosphonates are successfully synthesized by using chiral Mn(III)-Schiff base mononuclear precursors. Compounds [Mn((R,R)-5-Brsalcy)(2-FC(6)H(4)PO(3)H)]·3H(2)O (1) and [Mn((R,R)-5-Brsalcy)(4-CH(3)C(6)H(4)PO(3)H)]·CH(3)OH·H(2)O (3) [5-Brsalcy = N,N'-(1,2-cyclohexanediylethylene)bis(5-bromosalicylideneiminato) dianion] are isostructural and show similar one-dimensional chain structures where the Mn((R,R)-5-Brsalcy)(+) species are bridged by O-P-O units. Compounds 2 and 4 are (S,S)-enantiomers of 1 and 3, respectively. These compounds are all optically active, exhibiting second harmonic generation responses 0.3 times that of urea. The magnetic measurements of 1 and 3 reveal that dominant antiferromagnetic interactions are mediated between the Mn(III) centers.

Racemic metal phosphonates based on 2-phenyl-2-(phosphonomethylamino)acetate

The first examples of metal phosphonates based on 2-phenyl-2-(phosphonomethylamino)acetic acid (ppaH3) are reported, namely, Co3(ppa)2(4,4′-bpy)2(H2O)4·2H2O (1) and Ni4(ppaH)4(4,4′-bpy)2(H2O)2 (2). Compound 1 shows a three-dimensional framework structure in which the Co3(ppa)2 chains are cross-linked by 4,4′-bpy ligands. Within the chain, the equivalent Co2 atoms are doubly bridged by the O–P–O units from the R- and S-ppa(3−) ligands forming a racemic dimer of Co2(ppa)2. The dimers are connected by the Co1 atoms through O–P–O units to form an infinite racemic chain. Compound 2 displays a layer structure, where chains of Ni2(ppaH)2 are fused together by 4,4′-bpy. Within the chain, dimers of equivalent Ni atoms with O–P–O linkages are again observed. Unlike compound 1, however, the opposite handedness dimers are linked via O–C–O bridges into an infinite racemic chain. Magnetic studies reveal that dominant antiferromagnetic interactions are mediated between the magnetic centers in both cases.