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The iron(III) spin-crossover compounds [Fe(Hthsa)(thsa)]⋅H2O (1), [Fe(Hth5Clsa)(th5Clsa)2]⋅H2O (2), and [Fe(Hth5Brsa)(th5Brsa)2]⋅H2O (3) (H2thsa=salicylaldehyde thiosemicarbazone, H2th5Clsa=5-chlorosalicylaldehyde thiosemicarbazone, and H2th5Brsa=5-bromosalicylaldehyde thiosemicarbazone) have been synthesized and their spin-transition properties investigated by magnetic susceptibility, Mossbauer spectroscopy, and differential scanning calorimetry measurements. The three compounds exhibit an abrupt spin transition with a thermal hysteresis effect. The more polarizable the substituent on the salicylaldehyde moiety, the more complete is the transition at room temperature with an increased degree of cooperativity. The molecular structures of 1 and 2 in the high-spin state are revealed. The occurrence of the light-induced excited-spin-state trapping phenomenon appears to be dependent on the substituent incorporated into the 5-position of the salicylaldehyde subunit. Whereas the compounds with an electron-withdrawing group (-Br or ‒Cl) exhibit light-induced trapped excited high-spin states with great longevity of metastability, the halogen-free compound does not, even though strong intermolecular interactions (such as hydrogen-bonding networks and π stacking) operate in the system. For compound 2, the surface level of photoconversion is less than 35 %. In contrast, compound 3 displays full photoexcitation.

Single crystals of CaCr0.84Fe3.16As3, a Cr substituted analog of CaFe4As3, were grown from Sn flux and characterized with single crystal neutron diffraction. CaCr0.84Fe3.16As3 crystallizes in the orthorhombic space group Pnma with a three-dimensional framework, where Fe, Cr, and As form a covalent channel-like network with Ca2+ cations residing in the channels. CaCr0.84Fe3.16As3 has a unit cell of a = 12.057(4) A, b = 3.7374(13) A, and c = 11.694(3) A, as determined by room temperature single crystal neutron diffraction (R1 = 0.0747, wR2 = 0.1825). Structural data was also collected at 10 K. The single crystal neutron data showed that Cr selectively occupies a particular metal site, Fe(4). The antiferromagnetic transition associated with spin density wave (SDW) in the parent compound is preserved and shifts from 96 to 103 K with the selective Cr doping. Mossbauer, magnetic, and electrical resistivity measurements are reported.

A trinuclear iron(III) oxo-centered complex [Fe3(μ3-O)(3-OCH3-salnec)3]OH·5H2O was synthesized and characterized as cluster containing the semi-cubane [Fe3(μ3-O)]7+ core. The central oxygen atom is bridging the three iron(III) ions, which form an equilateral triangle with an average edge of –3.00 A as it was deduced from X-ray diffraction studies. The new tetradentate ligand 3-OCH3-salnecH2 = 1-[1-hydroxy-2-(9′-methyl-1,10′-phenanthrolin-2-yl)ethyl]-3-methoxyphenol-2, was generated “in situ” during the synthesis process as a product of the addition reaction between the starting ligands 2,9-dimethyl-phenanthroline(neoc) and 3-methoxy-salicylaldehyde(3-OCH3-saloH2), in the presence of sodium methoxide and Fe3+. Variable-temperature magnetic measurements indicate antiferromagnetic exchange interactions between the iron(III) ions in the cluster. Additionally, spectroscopic (IR, UV/Vis, Mossbauer, EPR) and electrochemical studies (CV) are presented and discussed.

Experimental interactions of Slovak bentonites with metallic ironThe experimental stability of four bentonites and one K-bentonite from Slovak deposits in the presence of iron was studied to simulate the possible reactions of clays (bentonite barrier) in the contact with Fe containers in a nuclear waste repository. The batch experiments were performed at 60 °C for 30 and 120 days in aerobic conditions. The reaction products were examined by XRD, FTIR, and Mössbauer spectroscopies and CEC (cation exchange capacities) were determined. Reaction solutions were analysed for selected elements using AAS (atomic absorption spectrometry). The results show that bentonites do not interact equally with metallic iron. Bentonites from the Jelšový Potok, Kopernica and Lieskovec deposits reacted similarly whereas the interaction between the bentonite from Lastovce and the iron was less intensive. The lower reactivity of the bentonite from Lastovce can be explained by its low content of smectite. During iron-clay interactions the iron was consumed and Fe oxides (magnetite, lepidocrocite) were formed. Decrease of the smectite diffraction peaks intensity and CEC values during the experiments show rather the rearrangement of the original smectite crystals than dissolution of smectite. In the K-bentonite from the Dolná Ves deposit where the mixed-layer illite-smectite is present instead of smectite, the dissolution of illite-smectite was observed along with the neoformation of smectite. The structure of illite-smectite deteriorated more than the structure of smectites which suggests that this mixed-layer illite-smectite is much less stable in the presence of iron than smectites.

Synthesis and structural investigation of trimethyl and triphenyltin esters of the 3-, 4-amino and 3,5-diaminobenzoic acids are reported as a reinvestigation of their local and overall molecular structure based on crystal structure determinations and on correlation of solid state vibrational and -emission spectroscopic evidence. Evidence is provided for the existence of more than one tin environment and therefore different carboxylate coordination modes in the compounds. Journal of Coordination Chemistry

Two rare earth iron aluminum silicides, REFe4Al9Si6 (RE = Tb, Er), were synthesized in liquid Al at temperatures below 850 °C. They crystallize in the tetragonal space group P42/nmc (no. 137) with cell dimensions of a = 8.718(1) A and c = 15.171(3) A for the Tb analogue. The structure, which is highly intricate and represents a rare structural arrangement, is based on that of NdRh4Al15.4. It can be understood in terms of highly corrugated layers of merged Al6 rings stacking to form a three-dimensional framework. The Fe and Si atoms are situated in various sites in the framework. The RE atoms have a very high coordination number (20) and sit in remaining pockets formed by the bonding arrangements in the structure. Magnetic measurements show that the rare earth ions are in a 3+ state, whereas Mossbauer measurements show that the Fe atoms do not exhibit a magnetic moment and are more reduced than in elemental Fe. The possible insights gained from these results into the metallurgical processing of advanced al...

The magnetic critical behavior of the manganese perovskite series La0.67−y (Sr, Ba, Ca)0.33+y Mn1−x SnxO3 (x=0.0l, 0.02, y=0, 0.07) is studied by means of de magnetic measurements and 119Sn Mossbauer spectroscopy. The structure can be described by a rhombohedral unit cell (space group R-3C) for the samples where the A-site is occupied by La and Sr or La and Ba ions and orthorhombic unit cell (space group Pnma) for the samples where the A-site is occupied by La and Ca ions. Arrott and scaling plots show that the samples, where the A-site is occupied by La and Sr or La and Ba ions, follow the behavior of a conventional second-order ferromagnetic transition. In contrast, the samples that contain La and Ca ions in the A-site show anomalous behavior around Curie point. Mossbauer measurements show two magnetic phases below T c . One of them exhibits stronger exchange interactions with more rapid electron transfer between Mn3+/Mn4+, compared to the other.

Substituted perovskite-type mixed oxides of the general formula La 1− x Sr x (Fe 3+ /Fe 4+ )O 3± δ were prepared for x =0.00, 0.15, 0.30, 0.40, 0.60, 0.70, 0.80, and 0.90 by the ceramic method and heating at 1000 °C. The prepared solids were examined by X-ray diffractogram (XRD) for their crystal structure and by Mossbauer spectroscopy at RT for the kind and the exact amount of iron containing crystal phases. The gradual substitution of La 3+ by Sr 2+ results in a quantitative development of the crystal phase SrFe 4+ O 3 and the corresponding diminution of the rest phases containing iron, i.e. LaFeO 3 and Fe 2 O 3 (traces). Detailed thermogravimetric O 2 /temperature-programmed desorption (TPD) experiments showed that the solids release oxygen when heated in a He atmosphere which is strictly proportional to the amount of Fe 4+ in the samples. Quantitative calculations showed that exactly one atom of oxygen is released per unit cell of Sr–Fe–O perovskite, which contains four Sr(Fe 4+ /Fe 3+ )O 3± δ units. The phenomenon is reversible and the solids re-adsorb fast and quantitatively the lost lattice oxygen when gaseous oxygen is admitted back to the system.

The title compounds are characterized by synchrotron powder XRD, neutron powder diffraction, 57Fe and 119Sn Moessbauer spectroscopy, UV/VIS/NIR diffuse reflectance spectroscopy, and magnetic measurements.

Li2FeGeS4 (LIGS) and Li2FeSnS4 (LITS), which are among the first magnetic semiconductors with the wurtz-kesterite structure, exhibit antiferromagnetism with TN ≈ 6 and 4 K, respectively. Both compounds undergo a conventional metamagnetic transition that is accompanied by a hysteresis; a reversible spin-flop transition is dominant. On the basis of constant-wavelength neutron powder diffraction data, we propose that LIGS and LITS exhibit collinear magnetic structures that are commensurate and incommensurate with propagation vectors km = [1/2, 1/2, 1/2] and [0, 0, 0.546(1)], respectively. The two compounds exhibit similar magnetic phase diagrams, as the critical fields are temperature-dependent. The nuclear structures of the bulk powder samples were verified using time-of-flight neutron powder diffraction along with synchrotron X-ray powder diffraction. (57)Fe and (119)Sn Mössbauer spectroscopy confirmed the presence of Fe(2+) and Sn(4+) as well as the number of crystallographically unique positions. LIGS and LITS are semiconductors with indirect and direct bandgaps of 1.42 and 1.86 eV, respectively, according to optical diffuse-reflectance UV-vis-NIR spectroscopy.

Polycrystalline Fe2BO4 was prepared by solid state reactions and its electronic and magnetic properties were investigated by Mossbauer spectroscopy and magnetization measurements. The Mossbauer spectra of Fe2BO4 below 270 K indicate the presence of Fe2+ and Fe3+ sites in the structure, in a ratio 1 : 1. Above this temperature electron delocalization sets in between the divalent and trivalent iron ions and Fe2.5+ states are observed. The temperature dependence of the Mossbauer spectra and magnetization measurements clearly show the onset of magnetic order below 155 K.

Polycrystalline Fe2 BO4 prepared by solid-state reaction was investigated over a wide temperature range using Mossbauer spectroscopy and magnetization and resistivity measurements. The Mossbauer data below 270 K reveal four iron sites (two Fe2+ and two Fe3+ ) in a 1:1:1:1 ratio. Above this temperature, electron delocalization sets in between the divalent-trivalent iron ions and up to 400 K both delocalized and localized iron states are observed. The magnetization and Mossbauer data indicate that this oxoborate mixed-valence system is an L-type ferrimagnet below Tc = 155 K, with the iron atoms in each sublattice having different point symmetries and different magnetic interactions. The resistivity data show the first-order nature of the charge-ordering transition (Tco = 316 K).

Five adducts of general formula Me2SnCl2L2 [L = IQNO(isoquinoline-N-oxide), 4-C1QNO, 4-MeQNO, 6-MeOQNO (6-methoxyquinoline-N-oxide) and 4-PhPyNO (4-Phenylpyridine-Af-oxide)] have been prepared by the addition of L to chloroform solutions of Me2SnCl2. The adducts have been characterized by analysis and spectroscopic (1R, 1H, 13C and Mossbauer) data. Structural predictions were derived from 119Sn NMR parameters such as 1 J(119Sn-13C) and 2 J(119Sn-1H). The single crystal diffraction study of the adduct Me2SnCl2(4-PhPyNO)2 shows the metal to be six-coordinate inan all trans-octahedral configuration; Sn-O and Sn-CI distances are 2.227(2) and 2.5774(9)A, respectively, and the CH3-Sn-CH3 bond angle is 180.0°.

Divale nt tin has been intercalated into montmorillonite by reacting partially hydrolyzed so- lutions of SnC12 under aerobic conditions at pH = 2.8 with aqueous dispersions of the smectite mineral. The precursor tin solution contains mainly the cationic trimeric ion Sn3(On)4 2§ which is shown to take part in the exchange reactions with the surface cations of the mineral. Variable temperature Mrssbauer spectroscopy was used in order to: 1) directly probe changes in the oxidation state and coordination environment of Sn 2§ in the process of intercalation; 2) examine the nature of tin atoms on the external surfaces and in the interlayer space of the clay platelets; and 3) study the dynamics of motion of tin atoms on the clay surfaces. The main conclusion from these studies is that about 75% of the Sn 2§ ions undergo extensive oxidation to the +4 state with concomitant hydrolysis and condensation that lead to the precipitation of SnO2 on the external surfaces of the clay. The rest of the Sn 2§ ions are introduced into the lamellar zone, as evidenced by the detailed Mrssbauer analysis of the dynamics of motion of tin atoms on the clay surfaces.

SmFe and SmFe(Nb or Zr) alloys, with stoichiometry RE:TM = 2:17 were prepared in ribbon form, using the melt spinning technique. The samples then were annealed and nitrated. X-ray diffraction and Mossbauer spectroscopy were used to study the samples. The presence of Nb(Zr) atoms stabilize the TbCu 7 structure, while the samples without substitutions crystallize in the Th 2 Zn 17 -type structure. The hyperfine parameters for the corresponding phases are deduced from analysis of Mossbauer spectra in the temperature range 15–300 K. At 300 K the mean hyperfine fields are 241 and 219 kOe for the Nb and Zr phases, respectively. The Curie temperature of Sm 2 Fe 17 is higher than that of the intermetallic compound Sm 2 Fe 17 prepared by the arc melting technique, and the Curie temperatures of the TbCu 7 -type phases are in the range 200–230°C. Remarkable enhancements in the coercive fields of the 1:7 nitride products are observed.

57 Fe Mossbauer spectra at 85, 200 and 293 K of magnetically aligned powders of Nd 3 (Fe 1− x Co x ) 27.7 Ti 1.3 (0⩽ x ⩽0.4) have been obtained. The fitting procedure has been done taking into account the occupancy of the Fe sites by Co and Ti. From the intensity ratio of the Mossbauer lines it has been concluded that the x =0 compound presents easy-cone-type anisotropy and the x =0.3, 0.4 axial anisotropy over the whole temperature range 85–293 K. For x =0.1, 0.2 a spin reorientation transition has been observed from axial anisotropy at 293 K to an easy-cone-type anisotropy at low temperatures.

Pillared structures with an interlayer opening of approximately 0.3 nm were obtained after successive heat treatments of the PILC precursor in reducing and oxidizing conditions. This precursor was prepared by reacting a Na+-montmorillonite with an intercalant containing Al and Fe oxo-hydroxides (Al/Fe = 1). Powder X-ray diffraction, elemental analysis, Fe-57 Mossbauer spectroscopy, catalytic activity measurements and surface area data were used to characterize the samples. On the basis of Mossbauer spectra taken at temperatures between 4.2 and 300 K, it is deduced that oxidizing steps produce Al substituted maghemite which converts into Al substituted magnetite upon reducing heat treatment. Firing the precursor in oxidizing atmosphere forms pillars of few nm in diameter. However, heating under reducing conditions yields pillars of smaller diameter. This later behaviour is maintained even after reheating the material in oxidizing atmosphere. From the temperature dependence of Mossbauer spectra it is deduced that the diameter of the Fe oxide particles in the pillars is smaller than 10 nm. Clays and Clay Minerals

Single crystals of CaCr0.84Fe3.16As3 are prepared from the elements using Sn as a flux (1000 °C, 6 h) and characterized by single crystal neutron diffraction, Moessbauer spectroscopy, electrical resistivity, and magnetic measurements.

The redox chemistry and transformations of NaFeAs in water and air are characterized by single crystal and powder XRD, magnetization measurements, TEM, and Moessbauer spectroscopy.

The synthesis and the structural investigation of triorganostannyl esters of the 3- and 4-[1-pyridin-2-yl-methylidene]- and 3,5-bis-[1-pyridin-2-yl-methylidene]-benzoic acids are reported with methyl, n-butyl, cyclohexyl, phenyl and benzyl substituents on tin. The organic carboxylates may be considered as iminopyridines emerging from the condensation of the corresponding aminobenzoic acid with pyridine-2-carboxaldehyde. In this respect it is interesting to investigate their physicochemical properties since their coordination to metal centers will affect both the photophysical properties of the metal and the conformation and intermolecular interactions of the ligands. Therefore, the structure of the above triorganotin compounds is studied and discussed in relation to those of the unsubstituted benzoates as well as of the free ligands. X-ray crystallography and a coalescence of spectroscopic methods applied both in the solid state and in Solution have been used in this effort. (C) 2009 Elsevier B.V. All rights reserved. Journal of Molecular Structure

Spinel iron oxide nanoparticles capped with organic molecules have been successfully prepared and used to produce iron oxide nanoparticles-single wall carbon nanotubes hybrid materials, which were characterized by a number of experimental techniques. The nanoparticles in both samples have an average particle size of about 10 nm and acquire a chemical composition of the type Fe3-xO4, with 0

A detailed comparative M\"ossbauer study of ${\mathrm{La}}_{0.67}{\mathrm{Ca}}_{0.33}\mathrm{Mn}{\mathrm{O}}_{3}$ and ${\mathrm{La}}_{0.67}{\mathrm{Sr}}_{0.33}\mathrm{Mn}{\mathrm{O}}_{3}$ samples doped with 1% Sn is presented. The spectra at $5\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ can be analyzed by a single ferromagnetic component. However, at higher temperatures two separate ferromagnetic components and a paramagnetic one are required to fit the spectra. The ferromagnetic component with the lower hyperfine field is attributed to clusters of weakened double-exchange interactions due to competition by localization mechanisms. Clear differences between the two samples in regard to the critical behavior arise: (i) The hyperfine field of ${\mathrm{La}}_{0.67}{\mathrm{Ca}}_{0.33}{\mathrm{Mn}}_{0.99}{\mathrm{Sn}}_{0.01}{\mathrm{O}}_{3}$ disappears abruptly at ${T}_{c}$ in contrast to that of ${\mathrm{La}}_{0.67}{\mathrm{Sr}}_{0.33}{\mathrm{Mn}}_{0.99}{\mathrm{Sn}}_{0.01}{\mathrm{O}}_{3}$ which varies continuously and goes to zero smoothly at the critical temperature. (ii) The second ferromagnetic phase appears above $0.35{T}_{c}$ in the Ca sample but only above $0.83{T}_{c}$ in the Sr sample. The paramagnetic component appears for $Tg0.67{T}_{c}$ in the former compared to $Tg0.9{T}_{c}$ in the latter. The results support recent studies that show differences in the polaronic character, and critical behavior thereof, between the two materials.

Organotin(IV) complexes with the formulas [(C(6)H(5))(3)Sn(mbzt)] (1), [(C(6)H(5))(3)Sn(cmbzt)] (3), and [(C(6)H(5))(2)Sn(cmbzt)(2)] (4) (Hmbzt = 2-mercaptobenzothiazole and Hcmbzt = 5-chloro-2-mercaptobenzothiazole) have been synthesized and characterized by elemental analysis; FT-IR, Raman, (1)H, (13)C, and (119)Sn NMR, and Mossbauer spectroscopic techniques; and X-ray crystallography at various temperatures. The crystal structures of complexes 1, 3, and 4 were determined by X-ray diffraction at room temperature [295(1) or 293(2) K]. The complexes [(C(6)H(5))(3)Sn(mbzo)] (2) and [(n-C(4)H(9))(2)Sn(cmbzt)(2)] (5) (Hmbzo = 2-mercaptobenzoxazole) were synthesized by new improved methods, and their structures were determined at low temperature [100(1) K] and compared to those solved at room temperature. Comparison with {(CH(3))(2)Sn(cmbzt)(2)]} (6), already reported, was also attempted. The influence of temperature on the geometry of the complexes is discussed. In the cases of complexes 1-3, three carbon atoms from phenyl groups and one sulfur atom and one nitrogen atom from thione ligands form a tetrahedrally distorted trigonal-bipyramidal geometry around the five-coordinate tin(IV) ion. In complexes 4-6, two carbon atoms from aryl groups and two sulfur atoms and two nitrogen atoms from thione ligands form a distorted tetrahedral geometry, tending toward octahedral, around the six-coordinate tin(IV) ions, with trans-C(2), cis-N(2), and cis-S(2) configurations. Although the C-Sn and S-Sn bond distances are found to be constant in compounds 1-6, their N-Sn bond lengths vary significantly (from 2.635 to 3.078 angstrom), with the longer distances found in the cases of five-coordinate complexes 1-3. Inorg Chem

The synthesis and detailed characterization of a few samples of the compound RbxMn[Fe(CN)(6)](y)center dot zH(2)O are described. The composition of the materials significantly depends on the applied preparative conditions. Analysis of spectroscopic results (FTIR, Raman, Fe-57 Mossbauer, XPS) and X-ray powder-diffraction data yielded a further assessment of the difference in structural features in terms of the amount of Fe(CN)6 vacancies and the associated number of water molecules. The characteristic individual magnetic behavior, as well as the metal-to-metal charge-transfer capabilities of the various samples, could be related to significant changes within the structures that appear to be associated with the synthetic method used.

Room temperature ferromagnetism is found in (Sn1−xMx)O2 (M=Mn, Fe, Co, x=0.05) ceramics where x-ray diffraction confirms the formation of a rutile-structure phase. Room temperature saturation magnetization of 0.2 and 1.8 Am2 kg−1 for (Sn0.95Mn0.05)O2 and (Sn0.95Fe0.05)O2, respectively, corresponds to a moment of 0.11 or 0.95 μB per Mn or Fe atom. The Curie temperatures are 340 and 360 K, respectively. The magnetization cannot be attributed to any identified impurity phase. 57Fe Mossbauer spectra of the Fe-doped SnO2 samples, recorded at room temperature and 16 K, show that about 85% of the iron is in a magnetically ordered high spin Fe3+ state, the remainder being paramagnetic.

Novel clay-carbon tube composites were synthesized by catalytic decomposition of acetylene over iron-catalyst centers supported on montmorillonite surfaces by ion-exchange. TEM and SEM micrographs show the growth of carbon tubes rooted to the clay surfaces, while the iron-nanoparticles (which catalyze the formation of carbon-nanotubes) are detected and characterized by Mossbauer spectroscopy, mainly as ferromagnetic cementite (Fe3C). In the hybrid materials the clay retains its exchange properties making possible the preparation of clay-carbon nanotube derivatives that are valuable for various technological applications. (C) 2002 Elsevier Science Ltd. All rights reserved. Carbon

R3(Fe1−xCox)29−yTy (R=Nd, Tb, Dy; T=Ti, V) intermetallic compounds have been studied by 57Fe Mossbauer spectroscopy at 85 and 293 K. The hyperfine interaction parameters depend on the amount of Co atoms. It is shown that Co atoms are equally distributed in all Fe sites but strongly avoid the Fe2, Fe3 and Fe6 sites which are the dumb-bell sites.

The interactions of Et2SnCl2 with 5'-IMP and 5'-GMP have been studied in aqueous solutions by 1H- and 31P-NMR spectroscopy as a function of pH. At low pH values (4.0) Sn(IV) interacts with the pyrophosphate oxygens of these nucleotides. At intermediate pH values (4-9.5) no interaction of the metal with the nucleotides take place, while at pH9.5 the sugar O'2 and O'3 atoms are the preferred coordination sites. In addition, the solid adducts obtained from aqueous solutions at pH = 3-4 of the above interactions correspond to formulae; (Et2Sn)2(5'-IMP)2(H2O) and (Et2Sn)3(5'-GMP)2(OH)2(H2O)2 as their elemental analysis show. IR spectra and solid state 13C, 31P-NMR spectra 119Sn Mössbauer and solution 119Sn-NMR spectra once more confirm the pyrophosphate involvement in bonding with Sn(IV) in oligomeric or polymeric structures and trigonal bipyramidal or octahedral geometries.

The origin of ferromagnetism observed in 2 at.% 57Fe-doped NiO samples is investigated. A precursor was produced from the co-precipitation of stoichiometric 57Fe and Ni nitrate solutions, and the 2% 57Fe-doped NiO samples were prepared by heating this precursor in air at temperatures between 673 and 873 K, for 1–25 h. X-ray diffraction, scanning electron microscopy, magnetization measurements and 57Fe Mossbauer spectroscopy were used to study the properties of the prepared compounds. The samples are composed of crystalline nanoparticles with average sizes between 9 and 29 nm, depending on the heating conditions. Magnetization measurements show the appearance of room-temperature ferromagnetism for samples heated both at 673 and 873 K. The 57Fe Mossbauer spectroscopy results indicate that this ferromagnetism is related to Ni57Fe2O4 ferrimagnetic impurities for the samples heated at 873 K and to finite-size effects for the samples heated at 673 K. The Ni57Fe2O4 impurities interact magnetically with the antiferromagnetic 57Fe-doped NiO matrix and it is proposed that they result from a diffusion-type process of 57Fe3+ ions during the heat treatment of the precursor.

Mesoporous solids of the general formula Al100PxFe5-y[x= 0, 15, 60, and y(the final firing temperature in °C)= 400 or 600] have been prepared and characterised by surface area and porosity measurements, X-ray diffraction (XRD), Mossbauer spectroscopy and solid-state NMR (27Al and 31P). The surface acidities of the solids were also determined by ammonia adsorption, and the ζ-potential of the particles was measured. The gradual incorporation of phosphate groups into the alumina results in an increase of the surface area. The materials possess a pore-size distribution approximated by a mixed Gaussian and Lorentzian component which varies in a controllable manner according to the elemental composition. The material Al100P15Fe5 corresponds to that with the maximum surface area and pore volume. The XRD analysis showed that the materials without phosphorus possess the γ-Al2O3 structure, but they become amorphous upon addition of 15% P. A further increase in the amount of phosphorous to 60% initiates the transformation of the solids to AlPO4. The Mossbauer spectra suggest that, in the samples without phosphorus, the iron species are segregated, but the addition of phosphorus results in a dispersion of the iron into the aluminium phosphate matrix. The 27Al MAS NMR spectra indicate that the aluminium atoms are predominately in octahedral environments in the samples Al100P0Fe5-600 and Al100P15Fe5-600 but they become equally distributed between octahedral and tetrahedral sites in Al100P60Fe5-600. The ζ-potential of the particles in aquatic suspension indicates that this parameter is sensitive to the temperature of thermal treatment. The surfaces of the solids showed increased acidity which is linearly related to the phosphorus content.

Treatment of Fe(NO3)3·9H2O with 1-methylbenzotriazole in EtOH–CH(OEt)3 gave the unique, oxo-bridged complex [Fe2O(NO3)4(C7H7N3)4]; crystal structure and Mossbauer studies showed that the molecule has both bidentate and monodentate nitrates and possesses an S= 0 ground state, respectively.

The intercalation of dimethyltin(IV) cationic clusters in montmorillonite leads to an organotin-clay complex exhibiting a basal spacing of 1.66 ± 0.02 nm. The maximum cluster loading is larger than expected on the basis of the cation-exchange capacity of the clay and the formal charge of monomeric tin complexes, indicating intercalation of organotin oligomers. The thermal transformation of the intercalated montmorillonite to pillared clay was studied via XRD, 119 Sn Mossbauer, and IR spectroscopies

In this short communication we present preliminary results from our current investigation by 57Fe Moessbauer Spectroscopy of the effects of pillaring dioctahedral smectites with aluminium polyoxo cations. In particular we report here the marked effect found on the magnetic ordering of iron in Nontronite after pillaring it with the above cations.