Methylenephosphonic Groups Research Articles

Functionalization of Magnetic-Chitosan Nanocomposite for Enhancing Th(IV) Ions Sorption.

Designing new chelating sorbents for the sorption of thorium as (Th4+) has become an impending challenge. This study describes a simple one-pot in situ co-precipitation method was used to synthesize a multifunctional magnetic-chitosan nanocomposite core-shell for enhanced Th4+ ions sorption from aqueous solutions. The synthesized biosorbent was well characterized by various techniques such as FTIR, XRD, pHzpc, TEM, VSM and elemental analysis. The sorption behavior of magnetic-chitosan nanocomposite (R-I) is systematically compared to the performance of functionalized magnetic-chitosan nanocomposite (R-II). The magnetic nanocomposites sizes around 25.0 nm. The grafting of methylene phosphonic groups on chitosan increased Th4+ sorption efficiency. Maximum sorption capacities reach 89.7 and 142.3 mg Th g−1 for R-I, and R-II sorbents, respectively at pH 3.5. Kinetics, isotherms, and thermodynamic behaviors of Th4+ ions sorption into the synthesized nanocomposite from an aqueous solution were studied in detail. The studies showed that the Langmuir isotherm and pseudo-second order model gave a better description for the sorption process. The sorption is spontaneous, endothermic and controlled by entropic change. EDTA solutions (0.25 M) can be efficiently used for metal recovery and sorbent can be recycled for at least 5 cycles without significant loss in sorption/desorption performances.

Synthesis of polyaminophosphonic acid-functionalized poly(glycidyl methacrylate) for the efficient sorption of La(III) and Y(III)

After synthesis of parent PGMA micro-particles by dispersion polymerization method, diethylenetriamine (DETA) is grafted on the polymer (DETA-PGMA). In the last step, methylene phosphonic groups are grafted on DETA-PGMA by reaction of phosphonic acid groups onto amine functions in the presence of formaldehyde to produce polyaminophosphonic acid sorbent (PPA-PGMA). The sorbent is characterized by elemental analysis, FTIR spectrometry, XPS, XRD, TG-TDA and SEM-EDX analyses. The sorption properties of the material are tested for the sorption of La(III) and Y(III): the effect of pH on sorption performance is investigated before studying uptake kinetics, sorption isotherms (and thermodynamics), metal desorption and sorbent recycling. Maximum sorption capacities reach up to 0.79 mmol La g−1 and 0.73 mmol Y g−1 at pH 5 (optimum initial pH value). Sorption isotherms are characterized by a saturation plateau: the Langmuir equation fits well data. The sorption on micron-sized particles is fast and equilibrium is reached within 3–4 h: the kinetic profiles are modelled by the Crank equation (resistance to intraparticle diffusion) though the pseudo-first order rate equation fits well experimental data. Nitric acid (0.5 M) solutions can be used for metal recovery and the sorbent is re-used for at least 6 cycles of sorption and desorption with limited decrease in performance (less than 7%). The sorbent has a preference at pH 5 for La(III) vs. Y(III) but the selectivity coefficient is not high enough for potentiating the selective separation of the two metals.

Study of two chitosan derivatives phosphorylated at hydroxyl or amino groups for application as flocculants

AbstractTwo phosphorylated chitosan derivatives with a similar degree of substitution of about 0.5 were synthesized via either the esterification of chitosan's hydroxyl groups by P2O5 in methanesulfonic acid or the selective incorporation of methylene phosphonic groups on chitosan's amino groups by formaldehyde/H3PO3 in water. The performances of the resulting O‐phosphorylated chitosan (OPC) and N‐methylene phosphonic chitosan (NMPC) as amphoteric flocculants were assessed in comparison with that of unmodified chitosan. In turbidity removal experiments using kaolin suspensions in water, OPC removed about 90% turbidity, but NMPC only removed 60%. The lower flocculation efficiency of NMPC was attributed to the decreased acid strength of the N‐methylene phosphate groups in NMPC. These results revealed that the acidity of the phosphate groups introduced in the modified chitosans is an important factor with regard to the flocculation efficiency, and consequently that O‐phosphorylation is more suitable than N‐phosphorylation for preparing chitosan‐based amphoteric flocculants. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Synthesis of new polyhalogenoalkyl-containing phosphonates with an enaminone core and their use in the preparation of fluorinated heterocycles

A number of polyhalogenoalkyl-containing phosphonates with an enaminone core were synthesized from readily available β-alkoxyvinyl polyhalogenoalkyl ketones by successive bromination, amination, and Arbuzov reaction. The new phosphonates were used for the syntheses of five- and six-membered heterocycles bearing both trifluoromethyl and methylenephosphonate groups.

1H and 17O NMR relaxometric study in aqueous solution of Gd(III) complexes of EGTA-like derivatives bearing methylenephosphonic groups

The Gd(III) complexes of three new octadentate chelators, prepared by substitution of four, two, and one carboxylate groups of EGTA with phosphonate groups, have been investigated by 1H and 17O NMR relaxometric techniques in aqueous solutions. The analysis of the solvent proton relaxivity data as a function of pH, temperature, and magnetic field strength (nuclear magnetic relaxation dispersion (NMRD) profiles) in combination with the 17O transverse relaxation rate data at variable temperature allowed assessing the hydration state of the complexes, the occurrence of pH-dependent oligomerization processes for the tetraphosphonate derivative, the presence of a well-defined second sphere of hydration that markedly contributes to the relaxivity, and the values of the structural and dynamic relaxation parameters. In addition, in the case of the monophosphonate derivative the presence of a coordinated water molecule has allowed evaluation of the kinetic parameters of the exchange process, highly relevant for the possible use of this Gd(III) complex as an MRI probe. The rate of exchange of the water molecule, (298)k(ex) = 4.2 x 10(8)s(-1), is one of the highest measured so far for a nonacoordinate Gd(III) chelate and optimal for developing contrast-enhancing probes of high efficacy at high magnetic fields.

Rapid characterization of alkylpolyphosphonates by CZE with indirect photometric and mass spectrometric detection

Methods for the rapid characterization of industrial alkylpolyphosphonates (APPs) by infusion MS and CZE with indirect photometric (IPD) and MS detection are described. Technical-grade APPs, including alkylaminepolyphosphonates with 3-5 phosphonate groups and different hydrocarbon skeletons, hydroxyethyl-amino-bis(methylenephosphonic acid), hydroxyethylidene-diphosphonic acid, and 2-phosphonobutane-1,2,4-tricarboxylic acid, were examined. A 10 mM solution of adenosine triphosphate disodium salt at pH 2.2 was used as BGE. The nominal compounds of the industrial APPs and their impurities were well resolved in less than 15 min. The peaks were identified by using extracted ion electropherograms, which were obtained at the m/z values indicated by the peaks of the infusion spectra. Low concentrations of esters, anhydrides, and APPs having different hydrocarbon skeletons compared to nominal compounds, and lacking phosphonate and methylene-phosphonate groups with respect to them, were found. Also, hydroxyethyl-aminobis(methylenephosphonic acid) contained an intramolecular ester at a concentration close to that of the nominal compound. Application of CZE-IPD and CZE-MS to the quality control of industrial APPs, and of CZE-MS to the identification and characterization of APPs in cleaning products, was demonstrated.

CR(III) removal by macroreticular chelating ion exchange resins

The poly(styrene-co-divinylbenzene) beads were synthesized by suspension polymerization using benzoylperoxide as an initiator and i -octane as a diluent. The copolymer beads with a particle size range of 32-60 mesh were selected. Chloromethylation was performed with chloromethylether at 0°C using tetrachloroethane as swelling agent and AlCl 3 as catalyst. The phosphorylation of copolymer beads (RS) and its chloromethylated derivative (RCS) was carried out using a mixture of PCl 3 and AlCl 3 under the reflux. The phosphorylated resins (RSP) were further oxidized using concentrated HNO 3 to obtain the oxidized form of RSP resins (RSPO). The removal of Cr(III) by the resins RSP, RSPO, and RCSP containing phosphinic, phosphonic, and methylenephosphonic groups, respectively, was investigated by batch and column methods. The results were compared with that of Diaion CRP-200 resin having methylenephosphonic functional groups. These resins exhibited a high affinity for Cr(III). The percent removal of Cr(III) reached a plateau with almost a 100% of removal at pH range between 2 and 2.5. The breakthrough capacity decreased in the order RCSP>RSPO>Diaion CRP-200>RSP.

A thermodynamic approach, using speciation studies, towards the evaluation and design of bone-seeking radiopharmaceuticals as illustrated for 117mSn(II)-PEI-MP

Blood plasma modeling has proved effective in the evaluation of clinical observations recorded for baboon and rat tests with 153Sm- ethylenediaminetetraphosphonic acid (EDTMP) as well as for 166Ho-EDTMP. In the search for a cure for metastatic bone cancer, 117mSn with its conversion electrons of discrete energies shows low bone marrow toxicity, providing the opportunity to increase the administered dose. Selective accumulation in lesions would capitalize on this advantage. The 10-30 kDa fraction of the water-soluble polymer polyethyleneimine, functionalized with methylene phosphonate groups (PEI-MP) and labeled with 99mTc, has shown selective uptake into bone tumours. This paper relates the speciation of Sn(II)-PEI-MP and other known 117mSn(II) containing bone-seeking radiopharmaceuticals in blood plasma. Apparent formation constants for the complexation of SnII with PEI-MP, DTPA, HEDP and other important blood plasma ligands were measured potentiometrically or estimated by linear free energy relationships (LFER). These data were added to the ECCLES database in order to construct a blood plasma model for SnII. From this model it is predicted that SnII will remain bound to the polymer (PEI-MP) in blood plasma and therefore, have only slight reticuloendothelial uptake. Preliminary primate studies indeed proved that the complex between SnII and PEI-MP remains intact in blood plasma, which is consistent with the observation for PEI-MP labeled with 99mTc. From these data, it was also possible to explain in retrospect the lower bone uptake, the slow blood clearance and the liver uptake of the agents 117mSn(II) DTPA and 117mSn(II) HEDP agents as reported in the literature.

Metal-ion speciation in blood plasma incorporating the water-soluble polymer, polyethyleneimine functionalised with methylenephosphonate groups, in therapeutic radiopharmaceuticals

Summary A water-soluble polymer, polyethyleneimine functionalised with methylene phosphonate groups (PEI-MP) and labelled with 99mTc, has shown selective uptake into bone tumours. Apparent formation constants for the complexation of important blood plasma metal-ions and metal-ions of radionuclides used in therapeutic radiopharmaceuticals (excluding Tc) with PEI-MP were measured potentiometrically. These were added to the ECCLES data base in order to construct a blood plasma model for PEI-MP. From this model it could be predicted that the polymer would not deliver the therapeutic radionuclides 153Sm, 166Ho, 212Pb, 213Pb and 89Sr to bone. This was clinically verified for 153Sm. However good uptake of 99mTc-PEI-MP could be demonstrated in dogs. Due to the similar chemistry of Re as compared to Tc, it can be expected that PEI-MP labelled with 186Re or 188Re could result in effective therapeutic radiopharmaceuticals for bone cancer.

Towards MRI contrast agents of improved efficacy. NMR relaxometric investigations of the binding interaction to HSA of a novel heptadentate macrocyclic triphosphonate Gd(III)-complex

A novel heptacoordinating ligand consisting of a thirteen-membered tetraazamacrocycle containing the pyridine ring and bearing three methylenephosphonate groups (PCTP-[13]) has been synthesized. Its Gd(III) complex displays a remarkably high longitudinal water proton relaxivity (7.7 mM–1 s–1 at 25 °C, 20 MHz and pH 7.5) which has been accounted for in terms of contributions arising from (1) one water molecule bound to the metal ion, (2) hydrogen-bonded water molecules in the second coordination sphere, or (3) water molecules diffusing near the paramagnetic chelate. Variable-temperature 17O-NMR transverse relaxation data indicate that the residence lifetime of the metal-bound water molecule is very short (8.0 ns at 25 °C) with respect to the Gd(III) complexes currently considered as contrast agents for magnetic resonance imaging. Furthermore, GdPCTP-[13] interacts with human serum albumin (HSA), likely through electrostatic forces. By comparing water proton relaxivity data for the GdPCTP-[13]-HSA adduct, measured as a function of temperature and magnetic field strength, with those for the analogous adduct with GdDOTP (a twelve-membered tetraaza macrocyclic tetramethylenephosphonate complex lacking a metal-bound water molecule), it has been possible to propose a general picture accounting for the main determinants of the relaxation enhancement observed when a paramagnetic Gd(III) complex is bound to HSA. Basically, the relaxation enhancement in these systems arises from (1) water molecules in the hydration shell of the macromolecule and protein exchangeable protons which lie close to the interaction site of the paramagnetic complex and (2) the metal bound water molecule(s). As far as the latter contribution is concerned, the interaction with the protein causes an elongation of the residence lifetime of the metal-bound water molecule, which limits, to some extent, the potential relaxivity enhancement expected upon the binding of the paramagnetic complex to HSA.

Protonation Behavior and Intramolecular Interactions of α,ω-Alkanediaminepolymethylenepolyphosphonates

Abstract The protonation equilibria of two types of aminopolyphosphonates ((CH3)2−p(CH2PO3)pN(CH2)mN(CH2PO3)p′(CH3)2−p′) in aqueous solution were investigated by means of potentiometry and 31P NMR spectroscopy. The protonation behavior of diaminotetramethylenetetraphosphonate (p = p′ = 2) is significantly altered by a change in the number of methylene chains (m = 2, 3, 6). The protonations of the imino fragments of hdtmp, which is connected with a six methylene chain (m = 6), are essentially independent of each other, whereas edtmp, which is connected with a two methylene chain (m = 2), forms a hydrogen bond between both nitrogen atoms (NH+···N) in the mono protonated species. The ethylenediaminepolyphosphonates (m = 2), having an iminodiphosphonate group (p = 2, p′ = 0—2), show a peculiar 31P NMR behavior in which the signal shows a downfield shift at higher protonated species. However, eddmp (N,N′), having one methylenephosphonate group at each imino fragment (p = p′ = 1), does not show such an anomaly. These results indicate the existence of an intramolecular interaction between both fragments, such as a hydrogen bond of a protonated nitrogen atom with unprotonated phosphonates of another imino fragment, where two methylenephosphonate groups in one imino fragment are required to operate such an interaction.

Formation and protonation of aminopolyphosphonate complexes of alkaline-earth and divalent transition-metal ions in aqueous solution

The formation and protonation of N-methyliminobis(methylenephosphonic acid)(midmp, H4L) and N,N-dimethylaminomethylphosphonic acid (dmamp, H2L) complexes with alkaline-earth (M = Mg2+, Ca2+, Sr2+ or Ba2+) and divalent transition metals (M = Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, or Cd2+) have been investigated at 25.0 °C and at an ionic strength of 0.1 mol dm–3(KNO3) by means of potentiometry and 31P NMR spectroscopy. The complex-formation constants, KML, for the alkaline-earth metals decrease with increasing ion size. The order of KML for the transition-metal complexes agrees with the Irving–Williams series for each ligand. The first protonation constants, KMHL, of the alkaline earth–midmp and transition metal–dmamp complexes are quite large compared with the first protonation constants of the phosphonate group of the free ligand (the second protonation constants of the ligand KH2L), and decrease with increasing complex-formation constant. The values of KMHL for the transition metal–midmp complexes are of the same order of magnitude as the value of KH2L for the ligand. The second protonation constants KMH2L of all complexes are smaller than KH2L and there is no significant difference among the complexes. The 31P NMR spectra of the metal–ligand solutions have been measured at 25 °C as a function of pH and the chemical shift of each species was evaluated. The results of the potentiometric and NMR studies suggest that the M–N bond of the ML complex is weakened by a decrease in the number of methylenephosphonate groups of the ligand, i.e. protonation of midmp complexes of alkaline-earth and some transition metals and of all the dmamp complexes occurs at the nitrogen atom of the ligand, rupturing the M–N bond.

Effect of a single 3′-methylene phosphonate linkage on the conformation of an A-DNA octamer double helix

The three-dimensional structure of the self-complementary DNA octamer d(GCCCGpGGC) has been determined in the crystalline state using X-ray diffraction data to a nominal resolutoin of 2.12 measured from a very small crystal at DESY, Hamburg. The structure was refined with stereochemical restraints to an R value of 17.1%. d(GCCCGpGGC), containing one single 3'-methylene phosphonate linkage (denoted p), forms an A-DNA double helix with strict dyad symmetry, that is distinct from canonical A-DNA by a wide open major groove and a small average base-pair inclination against the helix axis. The conformation of the unmodified control d(GCCCGGGC) is known from an X-ray analysis of isomorphous crystals (Heinemann et al. (1987) Nucleic Acids Res. 15, 9531-9550). Comparison of the two structures reveals only minor conformational differences, most notably in the pucker of the reduced deoxyribose. It is suggested that oligonucleotides with charged 3'-methylene phosphonate groups may form stable duplexes with complementary DNA or RNA strands rendering them candidates for use as gene-regulatory antisense probes.