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A family of alkali metal-based frameworks containing the tetraphosphonate ligand hexamethylenediamine- N,N,N′,N′-tetrakisIJmethylenephosphonic acid), HDTMP, is reported. A cation size-induced structural diversity, from monodimensional solids (Li+ and Na+) through layered (K+) to pillared-layered (Rb+ and Cs+) structures, was found. The proton conductivity properties of the Li compounds (hydrated and dehydrated) are reported and the influence of dehydration/rehydration processes in enhancing proton transfer processes is highlighted. Reversible changes in the dimensionality occurred upon full dehydration/rehydration with minor rearrangements in the framework, implying variations in the Li+–ligand connectivity but preserving the tetracoordination of the metal ion. The reversibly dehydrated–rehydrated sample displayed the highest proton conductivity (5 × 10−3 S cm−1 at 80 °C and 95% RH), a behavior attributed to reversible formation/ reformation of P–OIJH)–Li bonds that, in turn, provoked changes in the acidity of acid groups and water mobility in the temperature range of impedance measurements. Proyecto MAT2016-77648-R del ministerio y proyecto P12-FQM-1656 de la Junta de Andalucía Ministerio de Economía y Competitividad por el contrato Ramon y Cajal (RyC2015-17870).

This chapter focuses on polymeric gel drug delivery systems used for initial immobilization and subsequent controlled release of active pharmaceutical ingredients. The primary focus is on phosphonate-based drugs, which are extensively used for a variety of medicinal applications and pathological conditions. Their most recognizable use is for osteoporosis drugs with the common names: medronate, chlodronate, etidronate, alendronate, zoledronate, obadronate, ibandronate, neridronate, etc. Herein, we present a concise literature overview of this research field, presenting research results on immobilization of phosphonates onto silica-based polymeric gels, with the goal to achieve controlled release of these ingredients into biological fluids.

In our effort to develop new synthetic strategies for the isolation of new phosphonate frameworks, we exploited the possibility of simultaneously utilizing benzene-1,3,5-triphosphonic acid (H(6)btp) and di-2-pyridyl ketone (py(2)CO), which is a major player in the field of polynuclear metal complexes. This ligand blend in Cu-II chemistry afforded a 2D framework comprising tetranuclear [Cu-4(II)] secondary building units. A thorough investigation of the Cu-II/di-2-pyridyl ketone/benzene-1,3,5-triphosphonic acid reaction system also revealed a hydrogen-bonded framework. The structure of the latter comprises the cationic [Cupy(2)C(OH)(2)(2)](2+) complex [py(2)C(OH)(2) is the hydrate of py(2)CO], the dianion of benzene-1,3,5-triphosphonic acid (H(4)btp(2-)) and water solvates. The magnetic properties of the coordination polymer were rationalized on the basis of magnetically isolated [Cu-4(II)] units dominated by antiferromagnetic interactions.

Colloidal/amorphous silica (SiO2nH2O, n is variable) is considered as the most undesirable inorganic precipitate that forms during various processes in silica-supersaturated industrial waters. In this paper we present how certain polymeric chemical additives can prevent silicic acid polymerization to form colloidal silica, which may lead to deposition onto industrial equipment. More specifically, stabilization of silicic acid is accomplished by using a cationic polymer, polyallylamine hydrochloride (PALAM), in supersaturated silica solutions (starting silica concentration in the form of silicate 500 ppm, or 8.3 mM sodium orthosilicate, Na2SiO3·5H2O, expressed as SiO2) at pH = 7. PALAM is a linear homopolymer that carries one amine side functional group every two carbon atoms, so it becomes protonated at circumneutral pH, rendering the molecule cationic. Its blends with anionic polymers such as carboxymethylinulin (CMI), poly(acrylamide-co-acrylic acid) (PAM-co-AA) and phosphonomethylated chitosan (PCH) are also studied for their silica scale inhibition efficiency.

Stabilization of mono- and disilicic acids is accomplished by using a cationic polymeric chemical additive, polyethyleneimine (PEI), in supersaturated silica solutions (the starting solution contained 500 ppm/8.3 mM sodium orthosilicate, Na2SiO3·5H2O, expressed as SiO2) at pH = 7. The PEI polymeric system contains an excess of amine groups (~25% primary amines, ~50% secondary amines and ~25% tertiary amines) that become protonated at circumneutral pH, hence charging the molecules positively. PEI was found to be efficient as a silica scale inhibitor only at the low dosage of 10 ppm. Its inhibitory activity was found to drop as its concentration increased. It was hypothesized that PEI is entrapped into the colloidal silica matrix and deactivated. Thus, one way to maintain its activity was to create blends of PEI and anionic polymers. Anionic polyelectrolytes that were tested included polyacrylic acid (PAA), phosphonated polyacrylic acid (PAA(PO3H2)2), carboxymethylinulin (CMI), poly(acrylamide-co-acrylic acid) (PAM-coAA), phosphonomethylated chitosan (PCH) are also studied for their silica scale inhibition efficiency. It is observed that the silica inhibitory activity of PEI was improved upon its combination with anionic polyelectrolytes.

Numerous publications report the existence of intracellular “Si” storage pools in diatoms representing intracellular concentrations of ca. 19–340 mM depending on the species. “Si” storage pools in diatom cells, if present, are supposed to accumulate “Si” for the production of new valves. The accumulated “Si” is then transported into the silicon deposition vesicle (SDV) where the new cell wall is synthesized. Interestingly, the reported concentrations of intracellular “Si” within the storage pool sometimes strongly exceed the solubility of monosilicic acid (ca. 2 mM pH in situ supramolecular assemblies that can also affect the condensation of silicic acid. Possible mechanisms for their effect on the condensation reaction are presented, with an eye towards their relevance to the “Si pools,” from a bioinspired/biomimetic point of view.

We have developed a series of pH- and temperature-stimuli-sensitive vinyl hydrogels, bearing α-amino acid residues ( l -phenylalanine, l -valine) and incorporating magnetic nanoparticles of different chemical compositions (CoFe2O4 and Fe3O4). The goal was to study the potential applications of these nanocomposites in the controlled release of doxorubicin (DOXO), a potent anticancer drug. The strength of the electrostatic interaction between the protonated nitrogen of the DOXO molecule and the ionized carboxylic groups of the hydrogel allowed effective control of the drug release rate in saline solutions. The embedded magnetic nanoparticles were an additional remote control of the drug release under the stimulus of an appropriate external alternating magnetic field (AMF). Data showed that the controlled release of DOXO proceeded for months and followed a diffusion-controlled release mechanism, while maintaining the amount of released drug within acceptable therapeutic windows. The amount of the released DOXO was found in all cases substantially higher than the “control” because the application of the AMF augments in stimulating the nanoparticles within the DOXO-loaded hydrogel. In vitro experiments have shown that the released DOXO is able to induce cell death to cervix adenocarcinoma cells (HeLa cells).

This paper focuses on scale control approaches using a number of “green” silica scale inhibitors. These findings may be of interest to chemists and engineers in the fields of cooling and boiler water, pulp and paper, detergents, oil, gas, etc. In light of increasing environmental concerns, this research acquires significant interest. Also, in this paper, the effects of biological and synthetic polymers on the formation of amorphous silica are discussed. The importance of synergies between polyelectrolytes on silica inhibition is also discussed. A specific example of a zwitterionic polymer phosphonomethylated chitosan (PCH) is further analyzed for its inhibitory activity. Specifically, the ability of PCH to retard silicic acid condensation at circumneutral pH in aqueous supersaturated solutions is explored. Furthermore, the effects of either purely cationic (polyethyleneimine, PEI) or purely anionic (carboxymethylinulin) polyelectrolytes on the inhibitory activity of PCH are systematically studied....

Increased interest in the area of metal phosphonate inorganic–organic frameworks is exemplified with a high range of applications and a rich synthetic and structural chemistry of these compounds. The synthesis and potential applications of a novel metal phosphonate, namely Cu(II) phenylvinylphosphonate (PVP) is described in this paper. Syntheses were performed starting from a 1:1 molar ratio of a Cu(NO3)2·6H2O or CuSO4·5H2O and 1-phenylvinylphosphonic acid under hydrothermal conditions at pH values ranging between 2.8 and 3.1. The influence of different counterion for the copper salt used as the Cu(II) source on the structure and crystallinity of the final product was studied. The obtained copper(II) phenylvinylphosphonate compounds were characterized by X-ray powder diffraction, FT-IR spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and energy-dispersive X-ray spectrometry (EDAX). A possible crystal structure for the copper (II) phenylvinylphosphonate products ...

Mono- and disilicic acids were stabilized by uncharged polyethylene glycols (PEGs) in silica-supersaturated solutions (the starting solution contained 500 ppm/8.3 mM sodium orthosilicate, Na2SiO3·5H2O, expressed as SiO2) at pH = 7, most likely by hydrogen bonding between the silanol groups and -CH2-CH2-O-ether moieties. The stabilization was monitored by measuring molybdate-reactive silica and also by a combination of liquid- and solid-state (29)Si NMR spectroscopy. It depends on PEG concentration (20-100 ppm) and molecular weight (1550-20,000 Da). Two narrow (29)Si NMR signals characteristic for monosilicic acid (Q(0)) and disilicic acid (Q(1)) can be observed in (29)Si NMR spectra of solutions containing PEG 10000 with intensities distinctly higher than the control, that is, in the absence of PEG. Silica-containing precipitates are observed in the presence of PEG, in contrast to the gel formed in the absence of PEG. These precipitates exhibit similar degrees of silica polycondensation as found in the gel as can be seen from the (29)Si MAS NMR spectra. However, the (2)D HETCOR spectra show different (1)H NMR signal shifts: The signal due to H-bonded SiOH/H2O, which is found at 6 ppm in the control, is shifted to ~7 ppm in the PEG-containing precipitate. This indicates the formation of slightly stronger H-bonds than in the control sample, most likely between PEG and the silica species. The presence of PEG in these precipitates is unequivocally proven by (13)C CP MAS NMR spectroscopy. The (13)C signal of PEG significantly shifts and is much narrower in the precipitates as compared to the pristine PEG, indicating that PEG is embedded into the silica or at least bound to its surface (or both), and not phase separated. FT-IR spectra corroborate the above arguments. The H-bonding between silanol and ethereal O perturbs the band positions attributed to vibrations involving the O atom. This work may invoke an alternative way to envision silica species stabilization (prior to biosilica formation) in diatoms by investigating possible scenarios of uncharged biomacromolecules playing a role in biosilica synthesis.

The outcome of a synthesis involving a metal ion and a (poly)phosphonic acid depends on a plethora of variables such as solution pH, reactant molar ratios, nature of the metal ion, number of phosphonate groups, and other “functional” moieties present on the ligand backbone. Products are usually coordination polymers of diverse dimensionality. Here we report that the use of a chelating auxiliary ligand (2,2′-bpy) can “disrupt” the polymeric architecture of the copper phosphonate, causing the isolation of a series of molecular complexes (mononuclear or binuclear) that incorporate both the phosphonate and the 2,2′-bpy ligands. Synthetic details, crystal structures, and intermolecular interactions (π–π stacking and hydrogen bonding) are discussed. The structures of the obtained Cu complexes are extended into 2D or 3D networks via multiple hydrogen bonds involving the molecular units and crystallization water molecules. These H-bonded networks have been classified from the topological viewpoint, revealing dive...

Two new families of divalent metal hybrid derivatives from the aromatic tetraphosphonic acids 1,4- and 1,3-bis(aminomethyl)benzene-N,N′-bis(methylenephosphonic acid), (H2O3PCH2)2−N−CH2C6H4CH2−N(CH2PO3H2)2 (designated herein as p-H8L and m-H8L) have been synthesized by crystallization at room temperature and hydrothermal conditions. The crystal structures of M[(HO3PCH2)2N(H)-CH2C6H4CH2N(H)(CH2PO3H)2(H2O)2]·2H2O (M = Mg, Co, and Zn), M−(p-H6L), and M[(HO3 PCH2)2N(H)-CH2C6H4CH2N(H)(CH2PO3H)2]·nH2O (M = Ca, Mg, Co, and Zn and n = 1−1.5), M−(m-H6L), were solved ab initio by synchrotron powder diffraction data using the direct methods and subsequently refined using the Rietveld method. The crystal structure of the isostructural M−(p-H6L) is constituted by organic−inorganic monodimensional chains where the phosphonate moiety acts as a bidentate chelating ligand bridging two metal octahedra. M−(m-H6L) compounds exhibit a 3D pillared open-framework with small 1D channels filled with water molecules. These channels are formed by the pillaring action of the organic ligand connecting adjacent layers through the phosphonate oxygens. Thermogravimetric and X-ray thermodiffraction analyses of M−(p-H6L) showed that the integrity of their crystalline structures is maintained up to 470 K, without significant reduction of water content, while thermal decomposition takes place above 580 K. The utility of M−(p-H6L) (M = Mg and Zn) hybrid materials in corrosion protection was investigated in acidic aqueous solutions. In addition, the impedance data indicate both families of compounds display similar proton conductivities (σ ∼ 9.4 × 10−5 S·cm−1, at 98% RH and 297 K), although different proton transfer mechanisms are involved. Proyecto nacional MAT2010-15175

Easy-to-prepare drug delivery systems, based on smart, silica gels have been synthesized, characterized, and studied as hosts in the controlled release of bisphosphonates. They exhibit variable release rates and final % release, depending on the nature of bisphosphonate (side-chain length, hydro-philicity/-phobicity, water-solubility), cations present, pH and temperature. These gels are robust, injectable, re-loadable and re-usable., published version, peerReviewed

The (31)P chemical shift tensor of the phosphonate group [RC-PO(2)(OH)](-) is investigated with respect to its principal axis values and its orientation in a local coordinate system (LCS) defined from the P atom and the directly coordinated atoms. For this purpose, six crystalline metal aminotris(methylenephosphonates), MAMP·xH(2)O with M = Zn, Mg, Ca, Sr, Ba, and (2Na) and x = 3, 3, 4.5, 0, 0, and 1.5, respectively, were synthesized and identified by diffraction methods. The crystal structure of water-free BaAMP is described here for the first time. The principal components of the (31)P shift tensor were determined from powders by magic-angle-spinning NMR. Peak assignments and orientations of the chemical shift tensors were established by quantum-chemical calculations from first principles using the extended embedded ion method. Structure optimizations of the H-atom positions were necessary to obtain the chemical shift tensors reliably. We show that the (31)P tensor orientation can be predicted within certain error limits from a well-chosen LCS, which reflects the pseudosymmetry of the phosphonate environment.

[EN] The chemistry of metal phosphonates has been progressing fast with the addition of new materials that possess novel structural features and new properties, occasionally in a cooperative manner. In this paper, we report a new family of functional lanthanide-carboxyphosphonate materials. Specifically, the lanthanide is La, Ce, Pr, Sm, Eu, Gd, Tb, or Dy and the carboxyphosphonate ligand is 2-hydroxyphosphonoacetic acid (H(3)HPA). All reported LnHPA compounds, Ln(3)(H0.73O3PCHOHCOO)(4)center dot xH(2)O (x = 15-16), crystallize in the orthorhombic system. Two types of structures were isolated: series I and II polymorphs. For both series, the three-dimensional (3D) open frameworks result from the linkage of similar organo-inorganic layers, in the ac-plane, by central lanthanide cations, which yield trimeric units also found in other metal-HPA hybrids. Large oval-shaped 1D channels are formed by the spatial separation of the layers along the b-axis and filled with lattice water molecules. LnHPA materials undergo remarkable crystalline-to-amorphous-to crystalline transformations upon dehydration and rehydration cycles, as confirmed by thermodiffraction and NMR spectroscopy. The highest proton conductivity was observed for GdHPA (series II), 3.2 X 10(-4) S cm(-1) at 98% RH and T = 21 degrees C. The dehydration-rehydration chemistry was also followed by photoluminescence spectroscopy. It was shown that loss and reuptake of water molecules are accompanied by clear changes in the photoluminescence spectra and lifetimes of the Eu analog (series II). Our present results reveal a wide family of well-characterized, multifunctional lanthanide-based phosphonate 3D-structured metal-organic frameworks (MOFs) that show reversible crystalline-to-amorphous-to-crystalline transformations and, at the same time, exhibit high proton conductivity., The work at UMA was funded by MAT2010-15175 research grant (Spain), which is cofunded by FEDER. The work at the UoC was supported by a grant from the Research Committee of the University of Crete, ELKE, (KA 3517). The project "Factoria de Crystalizacion, CONSOLIDER INGENIO-2010" provided X-ray structural facilities for this work.

Multifunctional materials, especially those combining two or more properties of interest, are attracting immense attention due to their potential applications. MOFs, metal organic frameworks, can be regarded as multifunctional materials if they show another useful property in addition to the adsorption behavior. Here, we report a new multifunctional light hybrid, MgH6ODTMP·2H2O(DMF)0.5 (1), which has been synthesized using the tetraphosphonic acid H8ODTMP, octamethylenediamine-N,N,N′,N′-tetrakis(methylenephosphonic acid), by highthroughput methodology. Its crystal structure, solved by Patterson-function direct methods from synchrotron powder Xray diffraction, was characterized by a 3D pillared open framework containing cross-linked 1D channels filled with water and DMF. Upon H2O and DMF removal and subsequent rehydration, MgH6ODTMP·2H2O (2) and MgH6ODTMP·6H2O (3) can be formed. These processes take place through crystalline−quasi-amorphous−crystalline transformations, during which the integrity of the framework is maintained. A water adsorption study, at constant temperature, showed that this magnesium tetraphosphonate hybrid reversibly equilibrates its lattice water content as a function of the water partial pressure. Combination of the structural study and gas adsorption characterization (N2, CO2, and CH4) indicates an ultramicroporous framework. High-pressure CO2 adsorption data are also reported. Finally, impedance data indicates that 3 has high proton conductivity σ = 1.6 × 10−3 S cm−1 at T = 292 K at ∼100% relative humidity with an activation energy of 0.31 eV. Proyecto nacional MAT2010-15175 (MICINN, España)

In this paper we report the synthesis and structural characterization of the 2D layered coordination polymer Mg(BPMGLY)(H2O)2 (BPMGLY = bis-phosphonomethylglycine, (HO3PCH2)2N(H)COO2−). The Mg ion is found in a slightly distorted octahedral environment formed by four phosphonate oxygens and two water molecules. The carboxylate group is deprotonated but noncoordinated. This compound is a useful starting material for a number of topotactic transformations. Upon heating at 140 °C one (of the two) Mg-coordinated water molecule is lost, with the archetype 2D structure maintaining itself. However, the octahedral Mg in Mg(BPMGLY)(H2O)2 is now converted to trigonal bipyramidal in Mg(BPMGLY)(H2O). Upon exposure of the monohydrate Mg(BPMGLY)(H2O) compound to ammonia, one molecule of ammonia is inserted into the interlayer space and stabilized by hydrogen bonding. The 2D layered structure of the product Mg(BPMGLY)(H2O)(NH3) is still maintained, with Mg now acquiring a pseudo-octahedral environment. All of these topotactic transformations are also accompanied by changes in hydrogen bonding between the layers. Proyecto nacional MAT2010-15175

The catalytic role of Mg2+ ions in the polycondensation of silicic acid to form amorphous silica has been investigated in detail. This behavior is pH-dependent. As pH increases (herein, the three p...

The effect of various fluorine-containing chemical additives on the dissolution of colloidal silica is systematically studied. These silica scale dissolvers are ammonium bifluoride (NH4·HF2), ammonium fluoride (NH4F), sodium tetrafluoroborate (NaBF4), and disodium fluorophosphate (Na2PO3F). The most effective dissolver was NH4·HF2, which was extensively studied at the pH range 2–7. The highest dissolution efficiency was demonstrated in the pH range 2–4. The dissolution capability of Na2PO3F was monitored not by the silicomolybdate method, but on the basis of a weight-loss approach. It showed substantial dissolution ability at pH’s 7 and 9.

Phosphonium-based bolaamphiphiles have been found to stabilise silicic acid beyond its solubility limit (∼150 ppm). Three bolaamphiphiles have been tested having a quaternary phosphonium group on each end, linked by a number of ethylene oxide (EO) units (5, 21, and 91, resulting in PEGP+-200, PEGP+-1000, and PEGP+-4000 dicationic bolaamphiphiles, respectively). Specifically, the ability of PEGP+-200, PEGP+-1000, and PEGP+-4000 to retard silicic acid condensation at circumneutral pH in aqueous supersaturated solutions was explored. The goal was to investigate the effect of P-based cationic molecules, EO chain length (and by inference the P-to-P spatial separation) on silicic acid stabilisation performance. PEGP+-200 showed no stabilisation ability in “long term” tests (i.e. 24, 48, 72 h). For PEGP+-1000, and PEGP+-4000, it was discovered that in “short-term” (0–8 h) and “long term” (> 24 h) studies the inhibitory activity is additive dosage-dependent, demonstrating that there is a clear increase in stabilisation ability upon phosphonium PEG dosage increase. Specifically, soluble silicic acid levels reach 420 ppm and 400 ppm after 24 h in the presence of 150 ppm PEGP+-1000, or PEGP+-4000, respectively. PEG additives (PEG-200, PEG-1000, and PEG-4000) containing no phosphonium cations were also tested. Although PEG-200 and PEG-1000 showed no silicic acid stabilisation effects, PEG-4000, surprisingly, was a strong stabiliser. In fact, the inhibitory efficiencies of PEGP+-4000 and PEG-4000 were virtually identical. These results present strong proof that the polyethylene chain beyond a certain length strongly contributes to silicic acid stabilisation. Lastly, the effects of these boloamphiphiles on silica particle morphology were investigated by SEM. Spherical particles and their aggregates, irregularly shaped particles and porous structures, are obtained depending on the additive.

Five compounds based on the versatile pyrazole-4-sulfonate anion (4-SO3-pzH = L−) were synthesized by the reaction of ligand HL with ZnO, CdCO3, Ag2O, NaOH and NH3, respectively. Crystals of Zn(4-SO3-pzH)2(H2O)2, Cd(4-SO3-pzH)2(H2O)2, Ag(4-SO3-pzH), Na(4-SO3-pzH)(H2O) and NH4(4-SO3-pzH) were obtained from aqueous solutions upon evaporation, and were characterized by single-crystal X-ray diffraction, IR and NMR spectroscopy, thermogravimetric analysis and copper corrosion inhibition experiments. We found that the non-isomorphous, 3-dimensional inorganic–organic layered solid state structure of these compounds is determined by an intricate interplay between the size, charge and coordination preference of the cation, and an extended lattice of hydrogen bonds and aromatic interactions. Ligand L− incorporates a host of different binding capabilities (metal coordination through the pyrazole N-atom and/or the sulfonate O-atom, hydrogen-bonding both as donor and acceptor, π–π and C–H⋯π interactions). Thin films formed by these complexes on copper metal surfaces were studied by optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. ZnL2, CdL2, AgL and NH4L, in addition to the free ligand HL, were tested as corrosion inhibitors on copper metal surfaces at three different pH values (2, 3 and 4), and the corrosion rates were quantified. Significant corrosion protection was observed with all compounds at pH 4 and 3.

The effect of various environmentally friendly chemical additives and natural products on the dissolution of amorphous silica (Aerosil 200 and laboratory-synthesized, SSD) is studied. The silica scale dissolvers tested include the following: ascorbic acid (vitamin C, ASC), citric acid (CITR), carboxymethyl inulin (CMI), 3,4-dihydroxybenzoic acid (catechuic acid, DHBA), 3,4,5-trihydroxybenzoic acid (gallic acid, GA), dopamine hydrochloride (DOPA), iminodiacetic acid (IDA), histidine (HIST), phenylalanine (PHALA), and malic acid (MAL). The chemical structures of these chemical additives contain potentially dissolution-active moieties, such as 1,2-dihydroxyethylene (ASC), α-hydroxycarboxylate (MAL and CITR), catecholate (DHBA, GA, and DOPA), α-aminocarboxylate (HIST and PHALA, both aminoacids), and finally carboxy-modified fructofuranose units (CMI). It was found that all studied molecules showed variable dissolution efficiency, with MAL, CMI, HIST, and PHALA being the slowest/least effective dissolvers, and...

The effect of various chemical additives (small molecules and polymers) on the dissolution of two kinds of colloidal silica (Aerosil 200 and laboratory-synthesized, SSD) is systematically studied at pH 10. The silica scale dissolvers tested are 5-carboxybenzotriazole (CBZT), amino-tris(methylene phosphonic acid) (AMP), a phosphino-polycarboxylic acid (PPCA), diethylenetriamine pentacarboxylic acid (DETPA), a proprietary polymer (Genesol 40), poly(acrylic acid) (PAA), ethylenediamine-tetrakis(methylenephosphonic acid) (EDTMP), phosphonobutane-1,2,4-tricarboxylic acid (PBTC), sodium metaborate, and N-phosphonomethylimino-diacetic acid (PMIDA). Of the polymeric additives only Genesol 40 shows some dissolution activity, dissolving ∼280 ppm silica at 10 000 ppm dosage after 72 h. PBTC and DETPA are the best-performing additives of all those tested. PBTC is effective even at the 2500 ppm dosage, as it solubilizes ∼290 ppm silica after 72 h. Its efficiency is dosage-dependent. DETPA is also an effective silica d...

The influence of a number of N-containing macromolecules on the polycondensation of silicic acid to form amorphous silica is studied by the combined use of 29Si NMR spectroscopy and the silicomolybdate test. Polymeric additives include poly(allylamine hydrochloride) (PAH), the poly(aminoamide) dendrimer of generation 1 (PAMAM-1), poly(ethyleneimine) (PEI), and poly(vinylpyrrolidone) (PVP). These studies were performed under biologically relevant conditions (pH 5.4 and 7.0) using aqueous solutions of isotope-labeled sodium [29Si]metasilicate as the precursor compound. It was found at pH 5.4 that all additives accelerate silicic acid polycondensation, except for PVP, which exerts a minor silicic acid stabilizing effect. At pH 7.0, polycondensation is much faster in the presence of PAMAM-1, PEI, and PAH. However, PVP significantly stabilizes mono- and disilicic acid. Silica precipitates were also studied by 29Si NMR spectroscopy. The effect observed for PVP is striking and indicates that the silicic acid pol...

A family of M-VP (M = Ni, Co, Cd, Mn, Zn, Fe, Cu, Pb; VP = vinylphosphonate) and M-PVP (M = Co, Cd; PVP = phenylvinylphosphonate) materials have been synthesized by hydrothermal methods and characterized by FTIR, elemental analysis, and thermogravimetric analysis (TGA). Their structures were determined either by single crystal X-ray crystallography or from laboratory X-ray powder diffraction data. The crystal structure of some M-VP and M-PVP materials is two-dimensional (2D) layered, with the organic groups (vinyl or phenylvinyl) protruding into the interlamellar space. However, the Pb-VP and Cu-VP materials show dramatically different structural features. The porous, three-dimensional (3D) structure of Pb-VP contains the Pb center in a pentagonal pyramid. A Cu-VP variant of the common 2D layered structure shows a very peculiar structure. The structure of the material is 2D with the layers based upon three crystallographically distinct Cu atoms; an octahedrally coordinated Cu2+ atom, a square planar Cu2+ atom and a Cu+ atom. The latter has an unusual co-ordination environment as it is 3-coordinated to two oxygen atoms with the third bond across the double bond of the vinyl group. Metal-coordinated water loss was studied by TGA and thermodiffractometry. The rehydration of the anhydrous phases to give the initial phase takes place rapidly for Cd-PVP but it takes several days for Co-PVP. The M-VP materials exhibit variable dehydration-rehydration behavior, with most of them losing crystallinity during the process. Proyecto nacional MAT2010-15175 (MICINN, España)

Herein, the controlled release of etidronic acid (hydroxyethylidene-bis(phosphonic) acid), an important drug for osteoporotic conditions, immobilized onto cationic polymeric matrices, such as polyethyleneimine (PEI) or cationic inulin (CATIN) is reported. Several CATIN- and PEI-etidronate composites have been synthesized at various pH regions and characterized. Tablets with starch as the excipient containing the active ingredient (polymer-etidronate composite) were prepared, and the controlled release of etidronate was studied at aqueous solutions of pH 3 (to mimick the pH of the stomach) for 8 h. All studied composites showed a delayed etidronate release in the first 4 h, compared to the "control" (a tablet containing only starch and etidronic acid, without the polymer).

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.

In this study, the effect of phosphonate additives oil the crystallization of calcium sulfite dihydrate (CaSO4 center dot 2H(2)O, gypsum) has been investigated in aqueous solutions. Ethylenediamine-tetrakis(methylenephosphonic acid) (EDTMP), hexamethylenediamine-tetrakis(methylenephosphonic acid) (HDTMP), octamethylenediamine-tetrakis-(methylenephosphonic acid) (ODTMP), and dodecamethylenediamine-tetrakis(methylenephosphonic acid) (DDTMP) have been used as additives. It Was found that they are very effective retardants for the crystallization of calcium sulfate dihydrate. The inhibition efficiency is directly proportional to the number of methylene groups in the organic chain that connects the amino-bis-(methylenephosphonate) moieties. The degree of inhibition of crystallization was measured as an increase in induction time and reduction in crystallization rate. Particle size and crystal morphology were determined with a particle-sizer and scanning electron microscopy. According to experimental results, phosphonate additives tested in this study are very effective retardants for the formation of calcium sulfate dihydrate scale. The crystal structure of [Ca(EDTMP)(H2O)(2)]center dot H2O is also reported. This is a one-dimensional coordination polymer in which EDTMP acts as both a bidentate chelate and a bridge for Ca2+ centers.

A biomimetic approach toward type A polyprenylated acylphloroglucinols (PPAPs) is described. The method is based on a C-alkylation-cation cyclization reaction sequence, leading to a convenient buildup of molecular complexity, employing the simple and readily available deoxycohumulone and an appropriately functionalized hydroxy halide. Thus, a versatile construction of the fully functionalized bicyclic framework of type A PPAPs (5) was achieved.

The constant growth in the area of metal phosphonate materials is exemplified with rich chemistry and a variety of applications. From the multitude of subjects related to metal phosphonates, we have decided to focus on metal phosphonate coordination polymers as corrosion inhibitors in the present Comment. A plethora of metal phosphonate organic-inorganic polymeric hybrid materials have been synthesized, structurally characterized, and evaluated for their anticorrosion properties for the protection of carbon steels. These materials are composed of a metal ion (usually Zn2+, Ca2+, Sr2+, Ba2+, etc.) and polyphosphonate ligands such as AMP (amino-tris(methylenephosphonate) and HDTMP (hexamethylenediamine-tetrakis(methylenephosphonate), or carboxyphosphonate ligands, such as PBTC (2-phosphonobutane-1,2,4-tricarboxylate) and HPAA (hydroxyphosphonoacetate). Their corrosion inhibition performance has been evaluated and some interesting conclusions are drawn relating molecular structure to inhibitory activity.

The structures of various layered calcium tetraphosphonates (CaH6DTMP; H8DTMP=hexamethyl- tetrakis(methylenephosphonic acid)), have been determined. Starting from CaH6DTMP·2H2O, thermal treatment and subsequent exposure to NH3 and/or H2O vapors led to four new compounds that showed high storage capacity of guest species between the layers (up to ten H2O/NH3 molecules) and a maximum volume increase of 55%. The basic building block for these phosphonates consists of an eight-membered ring chelating Ca2+ through two phoshonate groups, and the organic ligand is located within the layers, which are held together by hydrogen bonds. The structural analysis revealed that the uptake/removal of guest species (H2O and NH3) induces significant changes in the framework not only by changing the interlayer distances but also through important conformational changes of the organic ligand. An anisotropic breathing motion could be quantified by the changes of the unit-cell dimensions and ligand arrangements in four crystalline derivatives. Complete characterization revealed the existence of interconversion reactions between the different phases upon gas uptake and release. The observed behavior represents, to the best of our knowledge, the first example of a breathing-like mechanism in metal phosphonates that possess a 2D topology.

Syntheses and structures of alkaline earth metal ions and EDTMP, ethylenediamine-tetrakis(methylenephosphonate), are reported. The isostructural Ca2+ and Sr2+ analogs have 1D topologies, with EDTMP acting as both chelating and bridging ligand. The M-EDTMP compounds act as Fe-oxide removers from corroded surfaces.

The syntheses and structural characterization of 1D, 2D, and 3D materials based on copper phosphonocarboxylate backbones are described. More specifically, the synthesis of materials from diethylphosphonoacetic acid (DEPAA) or the close variant hydroxyphosphonoacetic acid (HPAA) and water-soluble Cu2+ salts has been studied. The initial synthesis involving copper acetate and DEPAA was carried out at 160 °C under hydrothermal conditions and a Cu:P ratio of 1:1 resulted in the formation of a mixture of products with the same composition, Cu1.5(O3PCH2CO2)·H2O. Compound 1, which is blue in color and crystallizes in the triclinic space group P1, has a layered structure. Compound 2, which is green in color and crystallizes in the monoclinic space group P21/c, has a three-dimensional structure. Reduction of the reaction temperature to 140 °C results in the exclusive formation of the α-phase (1), while an increase in the reaction temperature to 180 °C yields a pure sample of 2. A Cu:P ratio of 2:3 in a reaction a...

In contrast to biomineralization phenomena, that are among the most widely studied topics in modern material and earth science and biomedicine, much less is systematized on modern view of demineralization. Biomineralized structures and tissues are composites, containing a biologically produced organic matrix and nano- or microscale amorphous or crystalline minerals. Demineralization is the process of removing the inorganic part, or the biominerals, that takes place in nature via either physiological or pathological pathways in organisms. In vitro demineralization processes, used to obtain mechanistic information, consist in the isolation of the mineral phase of the composite biomaterials from the organic matrix. Physiological and pathological demineralization include, for example, bone resorption mediated by osteoclasts. Bioerosion, a more general term for the process of deterioration of the composite biomaterials represents chemical deterioration of the organic and mineral phase followed by biological attack of the composite by microorganisms and enzymes. Bioerosional organisms are represented by endolithic cyanobacteria, fungi, algae, plants, sponges, phoronids and polychaetes, mollusks, fish and echinoids. In the history of demineralization studies, the driving force was based on problems of human health, mostly dental caries. In this paper we summarize and integrate a number of events, discoveries, milestone papers and books on different aspect of demineralization during the last 400 years. Overall, demineralization is a rapidly growing and challenging aspect of various scientific disciplines such as astrobiology, paleoclimatology, geomedicine, archaeology, geobiology, dentistry, histology, biotechnology, and others to mention just a few.

Dissolution of biologically important sparingly soluble salts, such as calcium carbonate and calcium oxalate, is possible by use of carboxyl- and carboxyl/phosphonate-bearing, anionic additives, citrate, malate, carboxyphosphonate, and butane tetracarboxylate. Calcium-containing dissolution products have been identified, characterized, and independently synthesized. These are polymeric materials composed of calcium and the additive as the ligand. Their full characterization was carried out by single-crystal X-ray crystallography and other techniques.

Reactions of M2+ (M = Mg2+ (1), Ca2+ (2), Sr2+ (3), or Ba2+ (4)) salts with R,S-hydroxyphosphonoacetic acid (HPAA) in aqueous solutions of pH 2.0−2.7 at a 1:1 ratio yield hydrated M−HPAA layered or three-dimensional coordination polymers with varying degrees of hydration (metal-coordinated water or lattice water). The crystal structures of 3 (two different phases, 3a and 3b, formed at slightly different pH) and 4 have been determined by single-crystal X-ray crystallography. Both enantiomers (R and S) of HPAA are incorporated in these metal−HPAA materials. Compounds were also characterized by a plethora of other techniques (ATR-IR, SEM, TGA, elemental analyses, powder XRD). Corrosion experiments were carried out at pH 2.0 and 7.3 to study the effect of combinations of externally added Sr2+ or Ba2+ and HPAA (1:1 ratio) on corrosion rates of carbon steel. It was found that at pH 2.0 Sr/HPAA or Ba/HPAA 1:1 combinations are not able to inhibit corrosion. However, at pH 7.3 quantitative corrosion inhibition is ...

In this work, the effect of a biodegradable, environmentally friendly polysaccharide-based polycarboxylate, carboxymethyl inulin (CMI), on the crystal growth kinetics of calcium oxalate was studied...

The inhibition performance of three synthetic amine/ammonium-containing cationic polymers in colloidal silica particle growth is reported. The three additives are compared to control (no additives present during silicate polymerization). The three polymers, polyethyleneimine (PEI), polyallylamine hydrochloride (PALAM) and poly(acrylamide-co-diallyl-dimethylammonium chloride) (PAMALAM), were screened in two sets of experiments: long term (24–72 h) and short term (0–8 h). Silica inhibition performance is profoundly dependent on the polymeric additive dosage. The most effective dosages were found to be 10 ppm for PEI, 20 ppm for PALAM and 80–100 ppm for PAMALAM. The inhibitory efficiency of PEI (at 10 ppm dosage) reaches 55% at 24 h (inhibitory efficiency is defined as reactive silica in ppm at the time of measurement divided by 500 ppm, times 100). PALAM reches 65% inhibitory activity at 20 ppm, after 24 h. PAMALAM at 80 ppm dosage shows 60% inhibition. Inhibitory activity drops on longer silicate polymerization times (48 and 72 h). All three inhibitors show activity higher than the control during the first 8 h, exhibiting small variations in performance.

Mineral scale deposits in industrial waters supporting a number of process industries are a major problem that causes unexpected shutdowns and costly chemical or mechanical cleaning operations. Some deposits, although less common, are exceptionally troublesome. These include silica and magnesium silicate. Accumulation of these deposits greatly diminishes system performance. Scale prevention can be achieved by use of scale inhibitors that are added to any given treatment in minute (parts per million) quantities. Use of environmentally friendly water additives for colloidal silica scale control is a topic of great interest and intense research efforts in our laboratory. Inhibition and dispersion are two generic approaches for preventing silica scale and fouling. Inhibition stops scaleforming precipitates from forming, whereas dispersion keeps scale particles from being attached onto critical surfaces. We have pursued silicate polymerization inhibition by use of “green”, environmentally-friendly cationic macromolecules. These utilize inulin as the backbone, which has been chemically modified to introduce quaternary ammonium moieties. Three CATIN polymers (CATIN = cationic inulin) were tested: CATIN-1 (DS = 0.22), CATIN-2 (DS = 0.86), CATIN-3 (DS = 1.28), DS = degree of substitution at dosages 40, 80 and 100 ppm in supersaturated silicate solutions (500 ppm) adjusted to pH 7 for 8 h. Measurements for soluble silicate were performed every hour. After 8 h polymerization time, CATIN-1 achieves stabilization of 275 ppm silicate (~90 ppm above the control), whereas CATIN-2 and CATIN-3 exhibit virtually identical performance, stabilizing ~340 ppm silicate (~150 ppm above the control). Inhibitor dosage increase to 80 ppm does not induce any additional inhibitory performance. Further inhibitor dosage increase to 100 ppm appears to have additional detrimental effects on inhibitory activity. CATIN-1 maintains 247 ppm soluble silicate (only ~50 ppm above the control), CATIN-2 keeps ~300 ppm soluble

Reactions of Mg2+ (1), Ca2+ (2), Sr2+ (3), or Ba2+ (4) salts with hydroxyphosphonoacetic acid (HPAA) at a 1:1 ratio yield M-HPAA layered coordination polymers. The crystal structures of 3 (two phases) and 4 have been determined by single crystal X-ray crystallography. Both stereoisomers (R and S) of HPAA are incorporated in the metal-HPAA materials. Synergistic combinations of Sr2+ or Ba2+ and HPAA at pH 7.3 are effective corrosion inhibitors for carbon steel, but are ineffective at pH 2.0.

In this paper the preparation and characterization of some chelating resins, phosphonate grafted on polystyrene divinylbenzene supports, are reported. The resins were prepared by an Arbuzov-type reaction between chloromethyl polystyrene-divinylbenzene copolymers and triethylphosphite, yielding the phosphonate ester copolymer (resin A). This can be hydrolyzed by HCl to yield the phosphonate/phosphonic acid copolymer (resin B). The phosphonate resins A and B were characterized by determination of the phosphorus content, infrared spectrometry, and thermal analysis. The total sorption capacity of the phosphonate ester functionalized resin (A) and phosphonate/phosphonic acid functionalized resin (B) for divalent metal ions such as Ca 2+ , Cu 2+ , and Ni 2+ was studied in aqueous solutions. Resin A retains 3.25 mg of Ca 2+ /g of copolymer and 2.75 mg of Cu 2+ /g of copolymer, but retains no Ni 2+ at pH 1. On the other hand, resin B retains 8.46 mg of Ca 2+ /g of copolymer, 7.17 mg of Cu 2+ /g of copolymer, and no Ni 2+ at pH 1. Efficient Ni 2+ retention was observed at pH 7 only for the phosphonate/phosphonic acid functionalized resin (B) at the level of 19 mg of Ni 2+ /g of polymer B. Polymer A was incapable of retaining Ni 2+ at pH 7.

The synthesis, structural characterization, luminescence properties, and proton conduction performance of a new family of isostructural cationic 2D layered compounds are reported. These have the general formula [Ln(H4NMP)- (H2O)2]Cl·2H2O [Ln = La3+, Pr3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, H6NMP = nitrilotris(methylphosphonic acid)], and contain Cl− as the counterion. In the case of Ce3+, a 1D derivative, [Ce2(H3NMP)2(H2O)4]·4.5H2O, isostructural with the known lanthanum compound has been isolated by simply crystallization at room temperature. The octa-coordinated environment of Ln3+ in 2D compounds is composed by six oxygen atoms from three different ligands and two oxygens from each bound water. Two of the three phosphonate groups act as both chelating and bridging linkers, while the third phosphonate group acts solely as a bridging moiety. The materials are stable at low relative humidity at less at 170 °C. However, at high relative humidity transform to other chloride-free phases, including the 1D structure. The proton conductivity of the 1D materials varies in a wide range, the highest values corresponding to the La derivative (σ ≈ 2 × 10−3 S·cm−1 at RH 95% and 80 °C). A lower proton conductivity, 3 × 10−4 S·cm−1, was measured for [Gd(H4NMP)(H2O)2]Cl·2H2O at 80 °C, which remains stable under the work conditions used. Absorption and luminescence spectra were recorded for selected [Ln(H4NMP)(H2O)2]Cl·2H2O compounds. In all of them, the observed transitions are attributed solely to f−f transitions of the lanthanide ions present, as the H4NMP2− organic group has no measurable absorption or luminescence properties. Proyecto nacional MAT2013-41836-R (MINECO) y Proyecto de la Junta de Andalucía P12-FQM-1656

The effect of citrate and phosphocitrate ions on the spontaneous precipitation of magnesium ammonium phosphate hexahydrate (MgNH4PO4·6H2O, struvite) at pH 8.50 and 25 °C was investigated at conditions of constant solution supersaturation. The supersaturated solutions were prepared in synthetic wastewater. The presence of citrate and phosphocitrate in the working solutions showed reduction of the initial rates of struvite precipitation when compared with solutions in their absence. The parabolic dependence of the rates of precipitation on the relative solution supersaturation suggested a surface-diffusion-controlled mechanism. Presence of citrate and phosphocitrate in the supersaturated solutions at concentration levels from 1 to 10 µM resulted in a drastic increase in induction times. The presence of citrate and phosphocitrate inhibited struvite precipitation up to 75–80%. The reduction of precipitation rates was related to additive concentration following an expression suggested by the kinetic Langmuir-t...

Mineral scale deposits such as calcium carbonate and phosphate, calcium oxalate, barium and strontium sulfate, magnesium silicate and others and colloidal inorganic species such as silica present important challenges for process water applications. When silica is left uncontrolled it forms hard and tenacious deposits that are difficult and hazardous to remove. Conventional phosphonate mineral scale inhibitors do not inhibit silica formation and deposition. Chemical cleaning is not free from hazards and requires operational shut-downs. Another challenge is corrosion of critical metal surfaces of industrial equipment. Last but not least, biofouling due to the development of microorganisms. This paper is focused on the presentation of the general scope of these problems and their solutions. More specifically, it concentrates on (a) inhibition of colloidal silica formation, (b) colloidal silica dissolution, and (c) metallic corrosion, in water applications by use of designed chemical approaches. The additives used for silica inhibition were polyaminoamide dendrimers, polyethyloxazoline and polyethyleneimine polymers. For silica dissolution the dissolvers tested were carboxymethyl inulin (CMI), Genesol 40 (a proprietary blend of additives), polyacrylic acid. In principle, silica inhibition is a function of time and inhibitor dosage. Silica dissolution is dependent in a rather unpredictable fashion on the structure of the dissolver, time and dosage. Mild steel corrosion inhibition has been achieved by synergistic use of zinc ions and polyphosphonate anions that create protective films.

Supersaturated process waters high in silicates frequently result in deposition of colloidal silica or metal silicate salts. Silica cannot be inhibited by conventional phosphonate mineral scale inhibitors. Chemical cleaning poses hazards and requires operational shut-downs. This paper is focused on a dual approach for silica scale control, inhibition of colloidal silica formation and colloidal silica dissolution in water technology applications by use of designed chemical approaches. The additives used for silica inhibition were polyaminoamide dendrimers (PAMAM) and polyethyleneimine (PEI), in combination with carboxymethyl inulin (CMI) and polyacrylate (PAA) polymers. In principle, silica inhibition is a function of time and inhibitor dosage. Amine-terminated PAMAM-1 and 2 dendrimers as well as PEI combined with anionic polymers, such as CMI and PAA, seem to have a significant inhibitory effect on silica formation, most likely at its earlier stages where the reaction products are oligomeric silicates. CMI and PAA assist the inhibitory action of PAMAM-1 and 2 and PEI by alleviating formation of insoluble SiO2-PAMAM precipitates. This most likely occurs by partial neutralization of the positive charge that exists in –NH+3 surface groups. Increase of anionic polymer dosage above a certain threshold has a detrimental effect on the activity of the cationic inhibitors. In that case the polymer’s negative charge “overwhelms” the cationic charge of the inhibitor and poisons its inhibition ability. For silica dissolution, acetic, oxalic, citric acids, histidine and phenylalanine were used as potential replacements of ammonium bifluoride (NH4F·HF). Silica dissolution is dependent in a rather unpredictable fashion on the structure of the dissolver, time and dosage. This paper continues our research efforts in the discovery, design and application of antiscalant additives that have mild environmental impact. These chemicals are also known as “green additives”.