Phosphonate Oxygen Research Articles

Linear chain aluminium(iii) carboxymethylphosphonate with encapsulated ammonium ions

An aluminium carboxymethylphosphonate of composition (NH(4))(2)Al(H(1/2)O(3)PCH(2)CO(2))(2) has been prepared hydrothermally. The aluminium cation is chelated by six membered rings formed from bonding by both the carboxylate and phosphonate oxygens. These chelate rings in turn form larger eight membered rings by connecting to similar chelate groups to form chains running along the a-axis.

Silver(i) pyrophosphonates: structural, photoluminescent and thermal expansion studies

The solvothermal reactions of silver(I) salts with mono-organophosphonic acids, i.e. 3-thienylphosphonic acid (3-TPA), phenylphosphonic acid (PPA), α-naphthylphosphonic acid (α-NPA) and cyclohexylphosphonic acid (CPA), yield four new silver(I) pyrophosphonates, namely: [Ag(2)(ptp)] (1), [Ag(2)(ppp)] (2), [Ag(3)(CH(3)CN)(pnp)(pnpH)] (3), and [Ag(3)(pcp)(pcpH)] (4) [ptp(2-) = pyro-3-thienylphosphonate, ppp(2-) = pyrophenylphosphonate, pnp(2-) = pyro-α-naphthylphosphonate, pcp(2-) = pyrocyclohexylphosphoante]. In all cases, the pyrophosphonate ligands are generated in situ from their relative mono-organophosphonic acids, mediated by silver(I) ions. Single crystal structural determinations reveal that compounds 1 and 2 display two-dimensional layer architectures, while 3 and 4 show one-dimensional chain structures. Structure 1 can be best described as a layer made up of Ag(4)O(P)(6) clusters linked by O-P-O units and AgAg contacts, with the organic groups grafted on the two sides of the inorganic layer. A similar layer structure is found in 2 except that the AgAg interactions are absent. Compound 3 shows a chain structure where the silver ions are bridged by the phosphonate oxygen atoms forming an infinite Ag-O(P) chain which is decorated by the pyrophosphonate ligand and CH(3)CN. Compound 4 has another type of chain structure made up of Ag-O(P) with extensive Ag···Ag argentophilic interactions. Solid state photoluminescent properties and thermal expansion behaviors are also investigated.

Supramolecular Hydrogen‐Bonded Frameworks from a New Bisphosphonic Acid and Transition Metal Ions

AbstractThe reaction of 2‐morpholinoethylimino‐bis(methylenephosphonic acid) (H4L) with cobalt(II), nickel(II) acetate, and cadmium(II) chloride in ethanol/water mixed solvents afforded three new crystal‐engineered supramolecular metal phosphonates, Co(H3L)2·2H2O (1), Ni(H3L)2·2H2O (2), and [Cd2Cl4(H2O)6]0.5[H4L] (3) by using a layering technique. The cobalt(II) ions in complex 1 are hexacoordinated by four phosphonate oxygen atoms and two imino nitrogen atoms. The mononuclear units of complex 1 are connected through hydrogen bonds to form a three dimensional supramolecular network. The structure of compound 2 is analogous to that of 1 except that the cobalt(II) ion in compound 1 is replaced by nickel(II) in compound 2. In the molecular structure of compound 3, cadmium is coordinated to three chloride ions and three aqua oxygen atoms to form a novel neutral dinuclear complex. Several hydrogen bonds connect the dinuclear complex and the neutral form of the ligand to build a supramolecular three dimensional structure.

High-Relaxivity Magnetic Resonance Imaging Contrast Agents Part 2

The observed relaxivity of gadolinium-based contrast agents has contributions from the water molecule(s) that bind directly to the gadolinium ion (inner-sphere water), long-lived water molecules and exchangeable protons that make up the second-sphere of coordination, and water molecules that diffuse near the contrast agent (outer-sphere). Inner- and second-sphere relaxivity can both be increased by optimization of the lifetimes of the water molecules and protons in these coordination spheres, the rotational motion of the complex, and the electronic relaxation of the gadolinium ion. We sought to identify new high-relaxivity contrast agents by systematically varying the donor atoms that bind directly to gadolinium to increase inner-sphere relaxivity and concurrently including substituents that influence the second-sphere relaxivity. Twenty gadolinium-1,4,7,10-tetraazacyclo-dodecane-N,N',N″,N'″-tetraacetato derivatives were prepared and their relaxivity determined in presence and absence of human serum albumin as a function of temperature and magnetic field. Data was analyzed to extract the underlying molecular parameters influencing relaxivity. Each compound had a common albumin-binding group and an inner-sphere donor set comprising the 4 tertiary amine N atoms from cyclen, an α-substituted acetate oxygen atom, 2 amide oxygen atoms, an inner-sphere water oxygen atom, and a variable donor group. Each amide nitrogen was substituted with different groups to promote hydrogen bonding with second-sphere water molecules. Relativities at 0.47 and 1.4 T, 37°C, in serum albumin ranged from 16.0 to 58.1 mM(-1)s(-1) and from 12.3 to 34.8 mM(-1)s(-1), respectively. The reduction of inner-sphere water exchange typical of amide donor groups could be offset by incorporating a phosphonate or phenolate oxygen atom donor in the first coordination sphere, resulting in higher relaxivity. Amide nitrogen substitution with pendant phosphonate or carboxylate groups increased relaxivity by as much as 88% compared with the N-methyl amide analog. Second-sphere relaxivity contributed as much as 24 and 14 mM(-1)s(-1) at 0.47 and 1.4 T, respectively. Water/proton exchange dynamics in the inner- and second-coordination sphere can be predictably tuned by choice of donor atoms and second-sphere substituents, resulting in high-relaxivity agents.

A one-dimensional copper(II) phenylenediphosphonate:catena-poly[[(1,10-phenanthroline-κ2N,N′)copper(II)]-μ3-[m-phenylenediphosphonato-κ3O:O′:O′′

The title compound, [Cu(1,3-HO3PC6H4PO3H)(C12H8N2)]n, is a coordination polymer of the metal–diphospho­nate family. The chain structure is constructed from ‘4+1’ square-py­rami­dally coordinated copper(II) atoms bonded to chelating phenanthroline (phen) ligands and linked through 1,3-phenyldihydrogendiphospho­nate ligands. The basal plane of the Cu(II) site is defined by the phen nitro­gen donors and phospho­nate oxygen atoms from two diphospho­nate ligands, while the apical position is occupied by an oxygen donor from a third diphospho­nate ligand. The chains propagate along the a-axis direction. Inversion-related phen groups engage in π-π stacking with a mean distance of 3.376 (2) Å between the ring planes. O—H⋯O hydrogen-bonding inter­actions between the protonated {P—OH} groups of one chain and the {P=O} groups of adjacent chains stabilize the crystal packing.

Facile Proton Conduction via Ordered Water Molecules in a Phosphonate Metal−Organic Framework

A new phosphonate metal-organic framework (MOF) with a layered motif but not that of the classical hybrid inorganic-organic solid is presented. Zn(3)(L)(H(2)O)(2)·2H(2)O (L = [1,3,5-benzenetriphosphonate](6-)), henceforth denoted as PCMOF-3, contains a polar interlayer lined with Zn-ligated water molecules and phosphonate oxygen atoms. These groups serve to anchor free water molecules into ordered chains, as observed by X-ray crystallography. The potential for proton conduction via the well-defined interlayer was studied by (2)H solid-state NMR spectroscopy and AC impedance spectroscopy. The proton conductivity in H(2) was measured as 3.5 × 10(-5) S cm(-1) at 25 °C and 98% relative humidity. More interestingly, an Arrhenius plot gave a low activation energy of 0.17 eV for proton transfer, corroborating the solid-state NMR data that showed exchange between all deuterium sites in the D(2)O analogue of PCMOF-3, even at -20 °C.

Room temperature assembly of a uranyl carboxyphosphonate: Synthesis, characterization and UO22+ hydrolysis

Abstract A novel 1-dimensional U(VI) phosphonoacetate, UO2(O3PCH2CO2H)(H2O)·2H2O (1), has been synthesized from the room temperature reaction of uranium nitrate and phosphonoacetic acid (H3PPA) in water. The compound crystallizes in a monoclinic space group (P21, a = 8.3517(5) A, b = 7.0013(4) A, c = 8.3728(5) A, β = 107.310(1)°, Z = 2) and exhibits bonding to the UO22+ through both phosphonate and carboxylate oxygen atoms of the acid unit. The crystal structure, thermal and fluorescent behaviors, and role of UO22+ hydrolysis in the context of ambient versus hydrothermal syntheses are discussed.

Platinum(II) complexes of 8-quinolylmethylphosphonates: Synthesis, characterization and antitumour activity

A series of novel platinum(II) complexes of diethyl (8-dqmp) and monoethyl (8-Hmqmp) ester of 8-quinolylmethylphosphonic acid has been prepared and studied. It was shown that molecular or ionic complexes could be isolated by reaction of these organophosphorus ligands with [PtX 4] 2− (X = Cl, Br), depending on the acidity of the reaction solution. In the neutral medium diester formed dihalide adducts, trans-[Pt(8-dqmp) 2X 2] ( 1 and 2), with N-bonded ligand through the quinoline nitrogen. Under acidic conditions (pH < 3) both ligands gave the quinolinium salt complexes [LH] 2[PtX 4] ( 3 and 4, L = 8-dqmp; 7 and 8, L = 8-Hmqmp), with protonated quinoline ligand as cation and tetrahalidoplatinate complex as anion. By heating in methanol complexes 3 and 4 were converted into the corresponding dimeric hexahalidodiplatinum complexes, [8-Hdqmp] 2[Pt 2X 6] ( 5 and 6). The chelate complex [Pt(8-mqmp) 2] ( 9), with monoester ligand bonded through the quinoline nitrogen and the deprotonated phosphonic acid oxygen and forming two seven-membered {N, O} chelate rings, was obtained in neutral and basic media by reaction of platinum(II) halides either with sodium or hydrochloride salt of this monoester. The complexes were identified and characterized by elemental and thermogravimetric analyses, conductometric measurements, and by spectroscopic studies. In vitro antitumour activity of complexes was evaluated against the human epidermoid KB and murine leukaemia L1210 cell lines. These results were compared with those obtained for the palladium(II) complexes of the same phosphonate ligands and with those of platinum(II) and palladium(II) complexes of diethyl and monoethyl 2-quinolylmethylphosphonate, in order to correlate the structural and biological properties of quinoline-based aminophosphonate compounds.

Organic‐Inorganic Hybrid Materials: Syntheses, X‐ray Diffraction Study, and Characterisations of Manganese, Cobalt, and Copper Complexes of Modified Bis(phosphonates)

AbstractFour new cobalt, manganese, and copper bis(phosphonates), [Co2{Cl2C(PO3)2}(H2O)7·4H2O] (1), [Co{Cl2C(PO2O(C(O)C6H5))2(H2O)5}·2H2O{Cl2C(PO2O(C(O)C6H5))2}{Co(H2O)6}] (2), [Mn{[Cl2C(PO2O(C(O)C6H5))2](H2O)3}] (3), and [Cu{(CH2C5H5N)C(OH)(PO3H)2}2·4H2O] (4), were prepared by gel, liquid, and evaporation crystallisation methods. Compounds 1–4 were characterised by X‐ray single‐crystal diffraction, elemental analysis, infrared spectroscopy, and thermogravimetric analysis. The effects of metal and various substituted groups in bis(phosphonate) ligands on the structure formation of bis(phosphonates) were studied. In the structure of 1, the clodronic acid ligand (L1) is in bischelating bonding mode, and the dinuclear units of 1 are surrounded by two‐dimensional water cluster patterns. The hydrogen bond network of compound 1 is extended to a three‐dimensional framework when the phosphonate oxygen atoms serve as hydrogen‐bond acceptors. In complex 2, the CoO6 octahedron shares a corner of one PCO3 tetrahedron of the dibenzoyl derivative of clodronic acid ligand (L2), and forms a two‐dimensional hydrogen bonding network, which consists of [Co(H2O)6}]2+ cations, lattice water molecules and L2 ligand molecules. Compound 3, in turn, consists of dimeric building blocks built up of PCO3 tetrahedra of the ligand L2, which connect the corner‐sharing MnO6 octahedra and form an overall 2D structure through hydrogen bonds of coordinated and crystal water molecules and phosphonate oxygen atoms. Complex 4 is among the first metal complexes of risedronic acid (L3). In compound 4, two L3 ligand molecules chelate tridentately the CuII atom at the center of symmetry, and the monomeric units of 4 are connected to a 3D structure through hydrogen bonding of coordinated and lattice water molecules to both protonated and deprotonated phosphonate oxygen atoms and protonated nitrogen atoms in the pyridine ring.

Synthesis and Characterization of 1‐, 2‐, and 3‐Dimensional Bimetallic UO22+/Zn2+ Phosphonoacetates

AbstractFour bimetallic UO22+/Zn2+ phosphonoacetates have been prepared from hydrothermal reactions of uranyl nitrate, zinc nitrate, and triethyl phosphonoacetate. These compounds, (UO2)2(PPA)2(H2O)2·Zn(H2O)6·4H2O (1), (UO2)4(PPA)2(HPPA)2·Zn(H2O)6·5H2O·(2), (UO2)2(H2O)2(PPA)2Zn(H2O)4 (3), and (UO2)2(PPA)2(HPPA)Zn2(H2O)2·3(H2O) (4), adopt 1‐, 2‐, and 3‐dimensional architectures wherein the UO22+ cation exhibits coordination preference for the phosphonate over the carboxylate oxygen atoms. The Zn2+ metal centers show an increased degree of ligand coordination with increasing reaction temperature. At 120 °C, compounds 1 and 2 are formed. These structures are 1‐ and 2‐dimensional, respectively, and contain fully hydrated [Zn(H2O)6]2+ cations. At 150 °C and 180 °C, the HPPA ligand displaces H2O molecules from the inner Zn2+ hydration sphere and binds to the metal centers via a –CO2H oxygen atom in 3 and both carboxylate and phosphonate oxygen atoms in 4. The overall Zn2+ reaction can be expressed by the equation Zn(H2O)62+ + HPPA [rlarr2] Zn(H2O)5(HPPA) + H2O. Presented here are the syntheses, structures, and characterization of these materials.

Supramolecular networks of polymethylphosphonic acid groups bonded to aromatic platforms: biphenyldiyl-2,2′-bis(methylphosphonic acid) and benzenetriyl-1,3,5-tris(methylphosphonic acid)

Biphenyldiyl-2,2'-bis(methylphosphonic acid) (BBMP) and benzenetriyl-1,3,5-tris(methylphosphonic acid) (BTMP) as ligands have been synthesized from diphenic acid and trimesic acid, respectively. Cu, Mn and Co complexes of BBMP have been prepared but similar complexes of BTMP did not crystallize. However, a copper compound with added 4,4'-bipyridyl was obtained. This copper complex is dimeric in which the dimers are linked into a supramolecular compound through the bipyridyl groups. Interestingly, the structure was solved in P1 with an unusual correlation between the ligand oxygen bond distances and the copper bond distances to water molecules. The Mn and Co BBMP complexes are isostructural in which the BBMP ligands phenyl groups rotate around each other to bridge the metal atoms forming 1:1 linear chains. There are four water molecules bonded to Co that can be removed reversibly. In the case of the Cu compound, one Cu is square planar bonded to four phosphonate oxygen atoms from two BBMP molecules. The second copper is six coordinate adding two water molecules in the axial positions. The two copper ions alternate forming a one dimensional chain but with ligands bonding the chain on both sides. The four coordinate copper atoms are chelated by two BBMP ligands utilizing one oxygen atom from the two phosphonate groups of each ligand and a second oxygen atom from these groups that bridge across the Cu atoms to bond to the six coordinate copper ion. A detailed synthetic procedure for each of the two ligands is supplied as ESI.

Stepwise Topotactic Transformations (1D to 3D) in Copper Carboxyphosphonate Materials: Structural Correlations

In this report, we demonstrate a topotactic transformation of a [Cu(HPAA)(H2O)2]·H2O one-dimensional (1D) hybrid (HPAA = HO3PCH(OH)CO2, hydroxyphosphonoacetate dianion) to an anhydrous Cu(HPAA) three-dimensional (3D) framework, via the 1D intermediate Cu(HPAA)(H2O)2. Removal of lattice water from 1D [Cu(HPAA)(H2O)2]·H2O yields 1D Cu(HPAA)(H2O)2 and results in alterations in hydrogen bonding interactions (chain···H2O···chain), and, in turn, compaction of the chains as well as “slipping”. These changes are accompanied by creation of a new hydrogen bonding scheme (chain···chain) involving the phosphonate groups and the hydroxyl/carboxy moieties. The initial zigzag 1D chain is retained throughout the dehydration process. In 3D Cu(HPAA) the resulting vacant sites on Cu (generated by removal of both Cu-bound waters) are occupied by phosphonate oxygens from neighboring chains. All three materials have been characterized by X-ray diffraction and a variety of other techniques and their structures have been determined.

Exceptional Ion-Exchange Selectivity in a Flexible Open Framework Lanthanum(III)tetrakisphosphonate

The flexible, anionic, open-framework material NaLa[(PO(3)H)(2)CH-C(6)H(4)-CH(PO(3)H)(2)].4H(2)O (NaLa(H(4)L)) exhibits an exceptional selectivity for monovalent metal cations. This study elucidates the relationship between the ion-exchange behavior and the framework flexibility of this recently discovered material. The exchange of the Na(+) ions in NaLa(H(4)L) with alkaline-earth, alkaline, and selected transition metal ions was studied. EDX and ICP-OES elemental analysis revealed that ion exchange was successful with monovalent ions, while higher-valent ions were rejected. An explanation for this charge selectivity could be found in the site-specific role of the guest cation. X-ray diffraction and thermogravimetric studies on the reversible hydration and dehydration behavior demonstrate that NaLa(H(4)L) has a flexible framework. Contraction of the channels upon dehydration leads to a decrease in the cell volume of 15%. Rietveld refinement of the structure of the dehydrated form NaLa(H(4)L)(dehyd) revealed the key role played by the guest cation in the channel-shrinking mechanism. In the hydrated, expanded form, each Na(+) ion guest shares three phosphonate oxygens with a La(3+) ion in a lanthanum phosphonate chain that defines part of the wall of a rhombic channel. The Na(+) ion completes its octahedral coordination sphere with two water molecules and a weaker bond to a fourth phosphonate oxygen. In the dehydrated, contracted form, the Na(+) ion loses the two water molecules and moves toward a second La(3+) ion, which is located in an adjacent lanthanum phosphonate chain, to share two more phosphonate oxygens, and becomes 5-coordinate. This results in the formation of an -La-O-Na-O-La- chain and a concomitant shrinking of the channels. A comparison of the monovalent metal (M(I)) ion-exchanged compounds, M(I)La(H(4)L), reveals that both the ionic radius and the enthalpy of hydration of the guest cation affect the equilibrium between the expanded and the contracted forms, and that the framework adapts specifically to the size of the guest cation.

Sodium and potassium benzeneazophosphonate complexes with crown ethers: Solid-state microwave synthesis, characterization and biological activity

The eco-friendly synthesis, spectroscopic (IR, MS, 1H and 13C NMR) study and biological (cytostatic, antiviral) activity of sodium and potassium benzeneazophosphonate complexes, obtained by reaction in the solid state under microwave irradiation of the alkali salts of ethyl [α-(4-benzeneazoanilino)- N-benzyl]phosphonic acid and [α-(4-benzeneazoanilino)- N-4-methoxybenzyl]phosphonic acid with crown ethers containing 18-membered (dibenzo-18-crown-6 and bis(4′-di- tert-butylbenzo)-18-crown-6), 24-membered (dibenzo-24-crown-8) and 30-membered (dibenzo-30-crown-10) macrocyclic rings, have been described. The simple work-up solvent free reaction is an efficient green procedure for the formation of mononuclear crown ether complexes in which the sodium/potassium ion is bound to oxygen atoms of the macrocycle and the phosphonic acid oxygen. The free crown ethers, alkali benzeneazophosphonate salts and their complexes were evaluated for their cytostatic activity in vitro against murine leukemia L1210, murine mammary carcinoma FM3A and human T-lymphocyte CEM and MT-4 cell lines, as well as for their antiviral activity against a wide variety of DNA and RNA viruses. The investigated compounds showed no specific antiviral activity, whereas all the free crown ethers and their complexes demonstrated cytostatic activity, which was especially pronounced in the case of bis(4′-di- tert-butylbenzo)-18-crown-6 and its complexes.

New Types of Luminescent Lanthanide Squarato-Aminophosphonates

Hydrothermal reactions of lanthanide nitrates with aminodiphosphonate ligand (H2O3PCH2)2−N−CH2−C6H4−COOH, H5L1) and squaric acid afforded a series of isostructural lanthanide(III) squarato-phosphonates, namely, Ln(HL2) (Ln = La, 1; Pr, 2; Nd, 3; Eu, 4; Gd, 5; Tb, 6; Er, 7) (H4L2 = HOOC−C6H4−CH2−N(C4O3H)(CH2PO3H2)), in which a new multifunctional squarato-phosphonate ligand (H4L2) was formed by in situ condensation reaction between the two types of organic ligands. The seven-coordinated lanthanide(III) ions in these compounds are bridged by the squarato-aminophosphonate moieties of the {HL2}3− anions into a double layer. Each {HL2}3− anion acts as septadentate metal linker, bridging with seven lanthanide ions by using one carboxylate oxygen, three squarato, and three phosphonate oxygens. These double layers are further cross-linked via the coordination of the carboxylate groups into a pillared layered architecture. The Eu, Tb, and Nd compounds exhibit strong luminescence in red light, green light, and near-IR regions, respectively.

STUDY OF THEORETICAL VIBRATIONAL SPECTRA AND THEIR ASSIGNMENTS FOR VINYLPHOSPHONIC AND VINYLTHIOPHOSPHONIC ACIDS

The structures and conformational stability of vinylphosphonic and vinylthiophosphonic acids were investigated using calculations mostly at DFT/6-311G** level and ab initio ones at MP2/6-311G** level. From the calculations the molecules were predicted to exist in a nonplanar near-cis (nc) to trans -gauche (tg) conformational equilibrium with nc (phosphonic oxygen or sulfur nearly eclipses the vinyl group) being the predominant conformer at ambient temperature, at least on the basis of Gibbs free energy (in the case of the thio compound the potential energy of tg is slightly lower than that of nc). The antisymmetric potential function for the internal rotation was determined for each one of the molecules. However, when starting optimizations from a structure too close to the full cis symmetry, the cis form results as an extremum on the potential hyper-surface. Consequently cis was reported in the literature several times as minimum. However, when we calculated the vibrational frequencies the cis form turned out to have an imaginary frequency, and thus cis is a local maximum along one of the normal coordinates. The true minimum, with only real frequencies, actually is an nc one with a very low barrier to rotation. The rotational angle out of cis is rather small; however, HOPX dihedral angles are quite away from real cis. This holds true not only with DFT but also with MP2. The vibrational frequencies were computed and the spectra were plotted as a prediction. Normal coordinate calculations were carried out and potential energy distributions were calculated for the molecules in the nc and the tg conformations. From our results and their analysis, we conclude, in agreement with results from the literature based on localized orbitals, that conjugation effects are absent – or at least negligible – as compared with electrostatic or steric ones in determining the structures of the stable conformers in the vinyl derivatives.

Ln 2(O 2CCH 2PO 3) 2(H 2O) 3 · H 2O (Ln = La, Pr, Nd, Sm): Layered lanthanide phosphonoacetates containing two-dimensional –Ln–O– linkages

Four novel isostructural lanthanide phosphonate compounds with formula Ln 2(O 2CCH 2PO 3) 2(H 2O) 3 · H 2O [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 {LnO 9} polyhedra and {CPO 3} tetrahedra with the lattice water molecules locating between the layers. Within the layer, chains of edge-sharing {LnO 9} 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.

Hydrothermal synthesis and crystal structures of Mn(II) and Cd(II) aminophosphonates with a layered structure

Two new divalent metal aminodiphosphonates with a layered structure, Mn2[(HL)(H2O)F]·H2O (1) and Cd3.5[(HL)L] (2) (H4L = CH3CH2CH2N(CH2PO3H2)2), have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction as well as with infrared spectroscopy, elemental analysis and thermogravimetric analysis. In 1, two MnO4F2 and two MnO5F polyhedra are interconnected via edge-sharing into a tetramer, and such tetramers are bridged by the diphosphonate ligands into a Mn(II) phosphonate layer in the ab-plane. The structure of 2 also features a 2D layered structure, in which the CdO5N and CdO6 polyhedra are interconnected into a 1D chain. The chains are then cross-linked via phosphonate oxygen atoms to form Cd(II) phosphonate layers in the ab-plane.

Coordination properties of some nickel(II) monophosphono dipeptides species in aqueous solution: The role of phosphonic oxygen in complex stabilization and ligand-fields analysis

Equilibrium studies on the nickel(II) complexes of oxygen and nitrogen donor ligand (monophosphono dipeptides: 1- ( N- l-leucylamino)methylphosphonic acid – Leu-Gly(P), and a thioether sulfur donor ligands (monophosphono dipeptides: 1- N-(glycyloamino)-2-( S-benzylthio)ethanephosphonic acid – Gly-(Bz)Cys(P), d(−) and Gly-(Bz)Cys(P), d(+) were performed by potentiometric titration and NIR–Vis spectroscopy. Additionally, the ligand-field parameters (CFM/AOM) were estimated and discussed in the tetragonal distortion framework. The lowest tetragonal distortion was observed in the case of the [NiHL] species, whereas the strongest in the case of [NiL 2] species. In the latter species the ligand-field analysis confirms the coordination of the deprotonated phosphonic groups to the metal ions in both axial positions. In the case of nickel(II) complexes with Gly-(Bz)Cys(P), d(−) or Gly-(Bz)Cys(P), d(+) additional interaction between sulfur donor atom and nickel(II) was suggested.

Synthesis, crystal structures, and luminescent properties of two types of lanthanide phosphonates

Hydrothermal reactions of different lanthanide(III) salts with an amino-diphosphonate ligand (H 4L=C 6H 5CH 2N(CH 2PO 3H 2) 2) led to two series of lanthanide phosphonates, namely, Ln(H 2L)(H 3L) ( Ln=La, 1; Pr, 2; Nd, 3; Sm, 4; Eu, 5; Gd, 6; Tb, 7). Compounds 1–5 feature a one-dimensional (1D) chain structure in which dimers of two edge-sharing LnO 8 polyhedra are interconnected by bridging phosphonate groups, such 1D arrays are further interlinked via strong hydrogen bonds between non-coordinated phosphonate oxygen atoms into a two-dimensional (2D) layer with the phenyl groups of the ligands orientated toward the interlayer space. Compounds 6 and 7 also show a different 1D array in which the LnO 6 octahedra are bridged by phosphonate groups via corner-sharing, such chains are also further interlinked by hydrogen bonds into a 2D supramolecular layer. Compounds 5 and 7 emit red and green light with a lifetime of 2.1 and 3.7 ms, respectively.