Mongi Debbabi

X-ray Powder Diffraction and Solid-State NMR Investigations in Cadmium−Lead Hydroxyapatites

In the proposed experiment, the maximum amount of cadmium substitution in lead hydroxyapatite accounts for about 30 atom-%. The crystal structures of PbHA at different degrees of cadmium substitution for lead (4.9, 10.0, 22.4 and 29.0% Cd atoms) have been investigated by X-ray powder pattern fitting and 31P MAS NMR. The site-occupancy factors of metal atoms clearly indicate a preference of cadmium for site 1 of the apatite structure, which is more selective at low cadmium content. A progressive shift of the OH group towards the center of the triangles formed by the site 2 metals has been observed with increasing cadmium content. The different environments of the phosphate group demonstrated by 31P NMR spectroscopic data are discussed in relation to structural data.

Sorption of tartrate ions to lanthanum (III)-modified calcium fluor- and hydroxyapatite

The present article details the formation of lanthanum-modified apatites and the binding process of tartrate ions with these obtained apatites. Chemical analyses, FT-IR and (31)P NMR spectroscopies, XRD powder, TGA, and TEM analyses were employed for studying the reaction between Ca(10)(PO(4))(6)(OH)(2) (HAp) or Ca(10)(PO(4))(6)(F)(2) (FAp) and LaCl(3). The reaction was found to take place mainly through partial dissolution of the apatite followed by precipitation of a new phase containing lanthanum phosphate. When La(3+) was introduced in the presence of L(+)-tartaric acid (TAH(2)), no fundamental changes were observed in the HAp or FAp structures. However, there did occur a formation of a new phase of Ca or/and La tartrate salt.

SYNTHESIS, SPECTROSCOPIC AND STRUCTURAL CHARACTERIZATION OF THE PENTACOORDINATE HIGH-SPIN FE(III) ISOTHIOCYANATE PICKET FENCE PORPHYRIN COMPLEX

Abstract The preparation and the characterization of the (isothiocyanato) (α,α,α,α-tetrakis (o-pivalamidophenyl) porphinato) iron (III) complex is described. The synthesis procedure utilizes the crown ether 18-C-6 to solubilize potassium thiocyanate. 1H NMR and EPR data of the isolated product are in accordance with a high-spin (S=5\2) ferric porphyrin species. The X-ray molecular structure confirms the above deductions. The iron atom is pentacoordinated by the four nitrogen atoms of the pyrrole rings of the porphyrin and the nitrogen atom of the NCS− group. It lies at 0.504 A out of the porphinato plane and 0.462 A out of the four nitrogen plane. The Fe–N (NCS) bond length is 1.956 (5) A and the Fe–N–C (NCS) bond angle is 176.1 (5) °.

Preparation and characterization of functionalized hybrid hydroxyapatite from phosphorite and its potential application to Pb2+ remediation

AbstractCalcium hydroxyapatite–aspartate (CaHAp–Asp) and calcium hydroxyapatite–glutamate (CaHAp–Glu) hybrid materials were prepared by the dissolution of Tunisian Phosphate Rocks in concentrated nitric acid and re-precipitation in basic solution in the presence of aspartic and glutamic acids . Chemical analyses, X-ray powder diffraction, infrared spectroscopy, 13C MAS-NMR spectroscopy, thermogravimetry and scanning electron microscopy were used to characterize the materials and also the organic–inorganic interfaces. All techniques converge to the formation of hybrid organic–inorganic compounds composed of hydroxyapatite solids with organic anions incorporated at the surface. XRPD and SEM observations showed that not only the crystallinity significantly was affected by the presence of organic anions, but also the structural and morphological properties. The presence of organic anions has been confirmed by IR and 13C MS-NMR spectroscopies, and their amount has been evaluated by TG and chemical analyses. The three CaHAp, CaHAp–Asp and CaHAp–Glu materials were evaluated for Pb2+ sorption from aqueous solutions. Sorption isotherms have been analyzed using Langmuir and Freundlich models showing that the Pb2+ sorption capacity is increased for CaHAp–Asp and CaHAp–Glu. The comparison of the two models indicates a single active site corresponding to a homogeneous interface between Pb2+ aqueous adsorbate and the solid adsorbent surface.Graphical Abstract

Surface modification of calcium-nickel hydroxyapatite by grafting organic moieties

Investigated compounds represent a novel group of αsubstituted-β-aminophosphonic acids which show similarity to phosphorus herbicides commonly used in agriculture. On the contrary to α-aminophosphonic acids, structural information on their β-analogs is limited to eight compounds only [1]. An X-ray analysis based on a low temperature data accompanied by the ab initio MP2 and B3LYP [2] calculations revealed that strong electron density delocalizations exist in all structures. In particular, the phosphorus – oxygen double bond has a strongly pronounced dipolar character. This situation prompts electron density back-donation from the oxygen lone-pairs towards the phosphorus atom bearing the large positive charge. Investigated compounds adopt anti conformation with the central P-C-C-N torsion angles close to 180°. This arrangement prompts mutual σ(C-N)-σ*(C-P) interactions. All oxygen and nitrogen atoms are involved in hydrogen bonding. In particular, the strongest symmetrical hydrogen bonds link oxygen atoms of the neighbouring phosphoryl groups. Additionally, several intraand intermolecular interactions exist in the crystals. All those interactions are analysed using the Natural Bond Orbital [3] and Atoms in Molecules [4] approach at the ab initio level of theory. Wavefunctions are calculated either for the isolated molecules or within the periodic boundary conditions framework.

Surface modification of hydroxyapatite by grafting alkyl phosphonic dichloride

The inorganic-organic hybrids have interesting applications resulting from the combination of some characteristic properties of the inorganic substrate (mechanical and chemical properties, exchange capacity, bioreactivity, optical properties...) with those of the organic grafting (polymerizability, superficial tension...). Such modified materials are used in catalysis, chromatography, biomedical domain... A suspension of calcium hydroxyapatite Ca10(PO4)(OH)2 was treated by the different alkylphosphonates (R-POCl2, R= methyl or octyl) in organic solvent using a molar ratio x=2 or 4, x=n(organic)/ n(apatite). The surface of the modified CaHAp was characterized using X-ray diffraction, IR and 31P MAS-NMR spectroscopies, chemical analysis and Atomic Force Microscopy (AFM). No remarkable change in XRD patterns was observed after grafting. FTIR results indicated that new vibration modes related to phosphonate groups appear essentially at 2930, 1315, 945, 764 and 514 cm-1. The 31P MAS-NMR spectra of treated hydroxyatite show new signals due to the formation of organic –inorganic bonds in the surface between the superficial hydroxyl groups of the apatite (≡CaOH and ≡POH) and alkyl phosphonic dichloride. AFM proved that the texture surface was changed and roughness decreased. The number of phosphonate groups grafted, in the modified materials, was calculated from chemical analysis results.

Synthesis and structural characterization of new organic-inorganic hybrids based on polyoxometalates

MS25 P04 Cobalt cations distribution in fully dehydrated CoX zeolite studied by XRD and XAS Elena Borissenko, Florence Porcher, Mohamed Souhassou, I-Jui Hsu, Yu Wang, Claude Lecomte, Laboratoire de Cristallographie et Modélisation des Matériaux Minéraux et Biologiques, LCM3B UMR 7036, CNRS Université Henri Poincaré, BP 239, 54506 Vandœuvre-lès-Nancy, France. Department of Chemistry, National Taiwan University, Taipei, Taiwan. E-mail: elena.borissenko@lcm3b.uhp-nancy.fr