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International audience; The compounds Li3Ba2Ln3(MoO4)8 (Ln = Er, Tm) have been obtained by the high-temperature flux technique using the slow cooling method. Crystals grown spontaneously were used to characterize the materials and investigate their properties using X-ray diffraction (XRD), Raman spectroscopy, and magnetic measurements. Single crystal structures were solved and refined in the monoclinic space group C2/c. Lattice dimensions are a = 5.1935, b = 12.6364, c = 19.1022 Å,  = 91.399 ° for Er-based triple molybdate (pink crystals) and a = 5.1846, b = 12.5766, c = 19.1557 Å,  = 91.525 ° for Tm-molybdate (green crystals). The Ln cations, mainly at general position 8f, are coordinated by eight oxygen atoms and adopt a distorted antiprismatic geometry. The distribution of atoms over the three cationic sites is discussed comparatively to literature reports. Unpolarized Raman characterization supports both the disordered cation distribution, and the distortion of the MoO4 units. From the magnetic susceptibility measurements, it is found that the two triple molybdates follow a Curie-Weiss law in the 10-300 K domain, with a negative paramagnetic temperature θCW. The antiferromagnetic character is highlighted by the field-dependent magnetization curves.

International audience; NaLa(SO4)2,H2O crystalline powder was obtained under hydrothermal conditions at 220°C. A coupled TGA/DTA experiment of NaLa(SO4)2,H2O exhibits a weight loss at 260°C corresponding to the dehydration and an endothermal peak at 774°C. To elucidate the transformation mechanism as a function of temperature, single crystals have been grown at 80°C, 300 and 800°C. For each phase, single crystals have been isolated and structure determination was performed. As already published, NaLa(SO4)2,H2O crystallizes in a P3121 space group. However, the dehydration at 260°C is not a simple loss of the water molecule but a radical change in the structure. The removal of the water molecules inside the tunnels formed by the framework leads to a change in the coordination of the LaO9 Lanthanum-based polyhedrons. The compound obtained after dehydration is a new triple sulfate of the formula Na3La(SO4)3 crystallizing in the R-3 space group (a = 14.0976(1) Å; c = 8.1267(1) Å) with LaO12 icosahedrons. Millimeter size single crystals of this new phase have been grown under hydrothermal conditions (300°C, 157 bars). After the endothermal peak at 774°C, Na3La(SO4)3 decomposes by forming the anhydrous double sulfate NaLa(SO4)2 crystallizing in the P-1 space group with LaO10 polyhedrons. The structure of the three (NaLa)-compounds at RT, 300°C and 800°C is compatible with the expected Raman signatures. Finally, a complete transformation of NaLa(SO4)2,H2O up to 800°C is proposed. After 1000°C, the compound decomposes chemically with a large weight loss.

International audience

The germanate CsSbGe

International audience; Crystals of the rare earth double molybdate KYb(MoO4)2 were grown by spontaneous nucleation from a K2Mo4O13 flux. The typical crystals were colorless and elongated, well-developed plates. The material has been characterized by powder X-ray diffraction (PXRD), energy-dispersive X-ray spectrometry (EDS), and Raman spectroscopy methods. The structural properties have been investigated through single-crystal X-ray diffraction at room temperature. KYb(MoO4)2 crystallizes in the orthorhombic symmetry, space group Pbcn (No. 60), a = 5.0395(2), b = 18.2821(9), c = 7.8635(4) Å, and Z = 4. A complete ordering of the Yb3+ and Mo6+ cations has been found. The Yb3+ ions are located in distorted YbO8 antiprisms which form chains of edge-sharing, aligned along the c-axis while the Mo6+ ions are placed in a slightly deformed tetrahedral environment of oxygen atoms. Double bridge modes of the “Mo2O8 dimers” have been identified in the unpolarized Raman spectra. The temperature-dependent magnetic susceptibility of KYb(MoO4)2 follows a Curie–Weiss law with a Weiss constant of −52 K.

Major-league magnetostriction Magnetoelectric materials polarize in response to either electric or magnetic fields, making them attractive for data-storage applications. Long et al. discovered a ytterbium-based molecular magnetoelectric material with high magnetoelectric coupling (see the Perspective by Zhou and Han). An applied magnetic field strains the material, which changes its electrical properties. The required field is much lower than other magnetoelectric materials, and this work highlights the potential for using molecular materials in devices. Science , this issue p. 671 ; see also p. 627

International audience; Molecular crystals have been prepared from pentafluorophenylphosphonic acid (4). These include 2C6F5PO3H2·H2O (4·4·H2O), [(C6F5PO3H–)(H3O+)]·C6F5PO3H2 (4·4–·H3O+), [(C6F5PO3H–)(NH4+)]·C6F5PO3H2 (4·4–·NH4+), [(C6F5PO3H–)(Me2NH2+)] (4–·DMA+), [(C6F5PO3H–)(Me2NH2+)]·H2O (4–·DMA+·H2O), [(C6F5PO3H–)(Me2NH2+)]·C6F5PO3H2 (4·4–·DMA+), [(C6F5PO3H–)(Me2NH2+)0.5(NH4+)0.5] (4–·DMA+·NH4+), and [(C6F5PO3H–)(+H3NCH2CO2H)] (4–·Gly+), where DMA+ = dimethylammonium and Gly+ = glycinium. All of the assemblies incorporate an ammonium cation, a water molecule, or a hydronium ion in their structure, and these included species act as adhesive agents. They interact via O/N–H···O hydrogen bonds and C–H···O contacts with PO3H2 or PO3H– moieties located in polar sheets, forcing the building blocks to assemble with a 2D layered arrangement. The robustness of this arrangement is reminiscent of that observed in metal arylphosphonates and guanidinium sulfonates, yet the architectures described herein differ significantly from the second family of compounds in two aspects: the lack of puckering of the layers and the absence of void spaces to accommodate solvent molecules. Interestingly, however, just as in guanidinium sulfonates, two structural types have been recognized depending on the size of the included species: a single-layer stacking motif and a bilayer stacking motif. Even though hydrogen bonding is the prevailing interaction in these systems, the use of perfluoroaryl groups is also central, as these moieties bring about weak C–F···π, π···π, C–F···F–C, C–F···H–C, and O/N–H···F–C interactions that help to increase the cohesion of the nonpolar regions. As a result, new architectures are created that significantly differ in some cases from those prepared from phenylphosphonic acid. However, the weakness of perfluoroaryl-based interactions is also their strength, as these interactions are sufficiently flexible to allow changes in the organization of the aromatic groups in response to changes (ionization) occurring in the polar regions, as observed in the structures of 4·4·H2O and 4·4–·H3O+. This situation is quite unusual and may be regarded as some kind of acidity-modulated polymorphism. The work presented here broadens the knowledge on molecular crystal formation with arylphosphonic acids, a research area largely dominated by carboxylic and sulfonic acids. Also, the computational evaluation of 4·4·H2O and 4·4–·H3O+ described in this report suggests that this family of fluorinated compounds may show interesting prospects as molecular semiconductors, a research area that is currently receiving increased attention.

International audience; Crystals of the Yb-containing double tungstate and double molybdate LiYbX2O8 (X = W, Mo) have been spontaneously grown by a high-temperature flux technique. Their structure has been determined from single-crystal X-ray diffraction at room temperature. LiYbW2O8 crystallizes in the monoclinic P2/n space group (No. 13), with unit cell parameters a = 4.9910(2), b = 5.7964(2), c = 9.8886(4) Å, β = 93.353(1) °. LiYbMo2O8 displays the tetragonal symmetry and is described in the noncentrosymmetric I4̅ space group (No. 82) with a = b = 5.1149(1), c = 11.0919(4) Å. Structural features such as coordination numbers around the atoms and ordered/disordered arrangement of the Yb3+ and Li+ cations explain the differences between these compounds whose vibrational and magnetic properties have also been studied.

Mercury porosimetry and in situ high pressure single crystal X-ray diffraction revealed the wine-rack CUK-1 MOF as a unique crystalline material capable of a fully reversible mechanical pressure-triggered structural contraction. The near-absence of hysteresis upon cycling exhibited by this robust MOF, akin to an ideal molecular spring, is associated with a constant work energy storage capacity of 40 J g−1. Molecular simulations were further deployed to uncover the free-energy landscape behind this unprecedented pressure-responsive phenomenon in the area of compliant hybrid porous materials. This discovery is of utmost importance from the perspective of instant energy storage and delivery., Mercury porosimetry and in situ high pressure single crystal X-ray diffraction revealed the wine-rack CUK-1 MOF as a unique crystalline material capable of a fully reversible mechanical pressure-triggered structural contraction.

Alkali hydrazinidoboranes MN2H3BH3 (M = Li, Na, K, Rb) have been developed for hydrogen storage. To complete the family of MN2H3BH3, we focused on cesium hydrazinidoborane CsN2H3BH3 (CsHB). It has been synthesized by reaction of cesium with hydrazine borane (N2H4BH3) at −20 °C under inert atmosphere, and it has been characterized. A crystalline solid (monoclinic, s.g. P21 (No. 4)) has been obtained. Its potential for hydrogen storage has been studied by combining different techniques. It was found that, under heating at constant heating rate (5 °C min−1) or at constant temperature (e.g. 120 °C), CsHB decomposes rather than it dehydrogenates. It releases several unwanted gaseous products (e.g. NH3, B2H6) together with H2, and transforms into a residue that poses safety issues because of shock-sensitivity and reactivity towards O2/H2O. Though the destabilization brought by Cs+ onto the anion [N2H3BH3]− has been confirmed, the effect is not efficient enough to avoid the aforementioned drawbacks. All of our results are presented herein and discussed within the context of solid-state hydrogen storage.

In this work we aim to study the effect of temperature on the mechanical properties of a solid. For this, we have introduced a new first-principles based methodology to obtain the thermal variation of the elastic constants of NiTiSn, a multifunctional Heusler compound. In parallel using X-ray diffraction, we have measured the isothermal bulk modulus at 300 K. The agreement between the calculations and the experiments is within the experimental error bars showing the accuracy of the calculations. Using two other numerical methods, which give all coherent results, we have shown that NiTiSn conserves its very good mechanical properties up to 1500 K. In particular at 700 K (the best working temperature for thermoelectric applications), NiTiSn remains a ductile and robust material making it a compound of choice for applications in which large temperature fluctuations are present.

Ammonia borane NH3BH3 is able to generate H2 by catalytic hydrolysis at ambient conditions. Such a potential has been much studied but the hydrolysis by-products, i.e. ammonium borates, have been little studied. As such we undertook a systematic work aiming at getting a sound understanding of the borates forming by hydrolysis. Contrary to what is commonly believed, NH3BH3 (10 M) in aqueous alkaline (pH = 8) solution is not completely stable. Spontaneous hydrolysis takes place, resulting in the formation of by-products and precipitation of borate crystals. This means that long-term storage of concentrated AB solution is not possible. The borate crystals were analyzed with the help of various techniques and was identified as being diammonium tetraborate dihydrate (NH4)2B4O5(OH)4⋅2H2O (263.39 g mol−1). The crystal structure was solved and found to be monoclinic with a space group P21. The borate is an analog of borax Na2B4O5(OH)4⋅8H2O. These results, among others, are reported in details hereafter and they are discussed in order to bring elements of response to the questions concerning storage of aqueous NH3BH3 and recyclability of such a borate.

The potential of the decahydro-closo-decaborate anion B10H102− in alkaline aqueous solution as anodic fuel was investigated by using cyclic voltammetry and three different bulk metal electrodes (platinum, gold and silver). The sodium salt NaB10H10 was first synthesized, fully characterized and assessed for its relative stability in alkaline medium for 25 days. Then, oxidation of B10H102− in alkaline aqueous solution was studied. With platinum, the electrochemical activity is nil. With gold and silver, oxidation takes place at >0 V vs. SCE, suggesting direct oxidation of B10H102−. A current density of e.g. 15.1 mA cm−2 at 0.51 V vs. SCE is produced, supporting an electrocatalytically activity for both electrodes. There is even some reversibility of the process (i.e. reduction of intermediate species) with silver. The most important oxidation products were identified as being B7-based anions for both silver and gold. Such results suggest the occurrence of partial oxidative degradation of B10H102− at positive potential and may open new application prospects to polyborate anions.

In this work we present rubidium hydrazinidoborane RbN2H3BH3 (RbHB), the newest and last member of the alkali metal derivatives of hydrazine borane N2H4BH3 (HB). It is shown that HB readily reacts with metallic rubidium in THF at room temperature to form RbHB under argon atmosphere. The molecular and crystal structures of this new compound are discussed on the basis of FTIR spectroscopy, 11B MAS NMR spectroscopy, and powder X-ray diffraction analyses. RbHB crystallizes in a monoclinic P21 (No. 4) unit cell where each Rb+ cation adopts octahedral coordination surrounded by six [N2H3BH3]− anions, which are two more than for e.g. LiN2H3BH3 (with tetrahedral coordination) in accordance with the larger size of Rb+. RbHB is isostructural to potassium hydrazinidoborane KN2H3BH3. Its dehydrogenation properties, evaluated by using thermogravimetric analysis, differential scanning calorimetry, and isothermal analysis, are compared to those of the parent HB as well as to analogous compounds in order to evaluate the potential of RbHB as hydrogen storage material. According to the presented data, the dehydrogenation properties of RbHB are much better than those of HB and are comparable to those of the lithium derivative. Our main results are reported therein.

International audience; We report on the preparation and the X-ray crystal structure of colorless KSbGe 3 O 9 , its vibrational properties (Raman and infrared studies), and density functional theory (DFT) calculations. KSbGe 3 O 9 , grown by the hightemperature flux method from K 2 Mo 4 O 13 flux, is thermally stable at least up to 1200 C and is isostructural to the benitoite BaTiSi 3 O 9 (space group P6c2 (n o. 188)). The hexagonal unit cell contains two formula units and the structure was refined to R1 ¼ 0.0324 from single-crystal X-ray diffraction data. KSbGe 3 O 9 is characterized with only one crystallographically independent Ge atom involved in three-member units [Ge 3 O 9 ] 6of regular germanate tetrahedra. The K þ ions are located in channels and, like Sb V , are octahedrally surrounded by oxygen atoms. The KSbGe 3 O 9 local structure and the planarity of Ge 3 O 3 rings are also studied by a room-temperature vibrational investigation using non-polarized infrared and Raman spectroscopy. Both the infrared and Raman phonon modes have been assigned from the agreement observed between our experimental data and the corresponding DFT ones. In particular, two E' (TO) modes (both IR and Raman active) characterize the planarity of the Ge 3 O 3 ring in the ab plane.

International audience; Boron-and nitrogen-based materials have shown to be attractive for solid-state chemical hydrogen storage owing to gravimetric hydrogen densities higher than 10 wt% H. Herein, we report a new derivative of hydrazine borane N 2 H 4 BH 3 , namely lithium hydrazinidoborane ammoniate LiN 2 H 3 BH 3 ·0.25NH 3. It is easily obtained in ambient conditions by ball-milling N 2 H 4 BH 3 and lithium amide LiNH 2 taken in equimolar amounts. Both compounds react without loss of any H atoms. The molecular and crystallographic structures of our new compound have been confirmed by NMR/FTIR spectroscopy and powder X-ray diffraction. The complexation of the entity LiN 2 H 3 BH 3 by some NH 3 has been also established by thermogravimetric and calorimetric analyses. In our conditions, LiN 2 H 3 BH 3 ·0.25NH 3 has been shown to be able to release H 2 at temperatures lower than the parent N 2 H 4 BH 3 or the counterpart LiN 2 H 3 BH 3. It also liberates non-negligible amounts of NH 3 at temperatures lower than 100 • C. This is actually quite detrimental for chemical H storage, but alternatively LiN 2 H 3 BH 3 ·0.25NH 3 might be seen as a potential NH 3 carrier.

The spontaneous nucleation by the high-temperature flux method of GeO2and SiO2-substituted GeO2(Ge1−xSixO2) compounds was improved to give single crystals free of hydroxy groups. The crystal structure and quality of these α-quartz-like piezoelectric materials were studied by single-crystal X-ray diffraction at room temperature. The refinements gave excellent final reliability factors, which are an indication of single crystals with a low level of defects. A good correlation was found between the silicon content in Ge1−xSixO2crystals determined through extrapolation from the inter-tetrahedral bridging angle and that found from energy-dispersive X-ray spectroscopy. The effect of germanium replacement by silicon on the distortion of the α-quartz-type GeO2structure was followed by the evolution of the intra-tetrahedral angle and other structural parameters. TheTO4(T= Si, Ge) distortion was found to be larger in α-GeO2than in α-SiO2and, as expected, the irregularity of theTO4tetrahedra decreased linearly as the substitution of Si for Ge increased.

International audience; The structure and electronic structure of a series of thiogermanate glasses has been investigated by means of X-ray photoelectron spectroscopy (XPS) and ab initio calculations with optimisation of geometrical parameters. The study has been focused on the influence of the content and nature of the modifier. On the whole it was shown that the modifier cation induces important electronic redistribution in the glassy matrix which extends to all sulfide atoms, either bridging or non-bridging, the evolution being all the more important that the modifier content is high. The present results evidence an important influence of the nature of the modifier cation; for silver glasses more covalent M–S bonds, less negative sulfur atoms and a more homogeneous electronic distribution on sulfur atoms are observed as compared to sodium glasses.

The mechanical energy absorption ability of the highly flexible; MIL-53(Al) MOF material was explored using a combination of; experiments and molecular simulations. A pressure-induced transition; between the large pore and the closed pore forms of this solid; was revealed to be irreversible and associated with a relatively large; energy absorption capacity. Both features make MIL-53(Al) the first; potential MOF candidate for further use as a shock absorber.

International audience; Benzoxaboroles are organoboron molecules which are gaining growing interest in different fields, notably for the development of new drugs. However, extensive characterization of these molecules in the solid state is still lacking. Here, questions related to the structure and spectroscopic signatures of crystalline benzoxaborole phases are thus addressed, using a combined experimental-computational approach. Two simple benzoxaboroles were studied: 1,3-dihydro-1-hydroxy-2,1-benzoxaborole (denoted as BBzx) and 5-fluoro-1,3-dihydro-1-hydroxy-2,1-benzoxaborole (also referred to as AN2690, a newly developed antifungal drug). First, the crystal structures of AN2690 and BBzx at room temperature are discussed, emphasizing the intermolecular interactions which play an important role in their formation. Then, results of IR and multinuclear (H-1, B-11, C-13 and F-19) solid state NMR characterization are presented, together with density functional theory (DFT) calculations which were carried out to assist in the interpretation of the spectra. Finally, the influence of polymorphism and anisotropic thermal expansion properties of the crystal structures on the NMR parameters of BBzx and AN2690 is discussed

In this paper, the syntheses of two styrene-based monomers bearing either an optical active group, Dispersed Red 1, or a photocrosslinkable cinnamate group are described. The study of their copolymerizations with maleic anhydride and the characterizations of the copolymers are given. Polymer materials with exposure to UV curing light, 254 nm, exhibit a photobleaching process. This feature can be used in the preparation of channelized wave-guide using photomask methods.

Freezing of water in hydrophilic nanopores ($D=1.2\text{ }\text{ }\mathrm{nm}$) is probed at the microscopic scale using x-ray diffraction, Raman spectroscopy, and molecular simulation. A freezing scenario, which has not been observed previously, is reported; while the pore surface induces orientational order of water in contact with it, water does not crystallize at temperatures as low as 173 K. Crystallization at the surface is suppressed as the number of hydrogen bonds formed is insufficient (even when including hydrogen bonds with the surface), while crystallization in the pore center is hindered as the curvature prevents the formation of a network of tetrahedrally coordinated molecules. This sheds light on the concept of an ubiquitous unfreezable water layer by showing that the latter has a rigid (i.e., glassy) liquidlike structure, but can exhibit orientational order.

We describe the preparation of the first crystalline compounds based on arylboronate ligands PhB(OH)(3)(-) coordinated to metal cations: [Ca(PhB(OH)(3))(2)], [Sr(PhB(OH)(3))(2)]·H(2)O, and [Ba(PhB(OH)(3))(2)]. The calcium and strontium structures were solved using powder and single-crystal X-ray diffraction, respectively. In both cases, the structures are composed of chains of cations connected through phenylboronate ligands, which interact one with each other to form a 2D lamellar structure. The temperature and pH conditions necessary for the formation of phase-pure compounds were investigated: changes in temperature were found to mainly affect the morphology of the crystallites, whereas strong variations in pH were found to affect the formation of pure phases. All three compounds were characterized using a wide range of analytical techniques (TGA, IR, Raman, XRD, and high resolution (1)H, (11)B, and (13)C solid-state NMR), and the different coordination modes of phenylboronate ligands were analyzed. Two different kinds of hydroxyl groups were identified in the structures: those involved in hydrogen bonds, and those that are effectively "free" and not involved in hydrogen bonds of any significant strength. To position precisely the OH protons within the structures, an NMR-crystallography approach was used: the comparison of experimental and calculated NMR parameters (determined using the Gauge Including Projector Augmented Wave method, GIPAW) allowed the most accurate positions to be identified. In the case of the calcium compound, it was found that it is the (43)Ca NMR data that are critical to help identify the best model of the structure.

Herein, we report the sonochemical reactions with MSU-X mesoporous alumina (m-Al 2 O 3 ) in aqueous solutions. Sonication ( f = 20 kHz, I = 30 W cm −2 , W aq = 0.67 W mL −1 , T = 36–38 °C, Ar) causes significant acceleration of m-Al 2 O 3 dissolution in the pH range of 4–11. Moreover, power ultrasound has a dramatic effect on the textural properties and phase composition of m-Al 2 O 3 . Short-time sonication at pH = 4 leads to the formation of nanorods and nanofibers of boehmite, AlO(OH). Prolonged ultrasonic treatment causes high aspect morphology transformation to aggregated nanosheets in weakly acid solutions or plated nanocrystals in alkaline solutions. Sonochemical products in alkaline medium are composed principally from boehmite and small amounts of bayerite, Al(OH) 3 . Silent hydrolysis of m-Al 2 O 3 yields boehmite at pH = 4 and bayerite at pH = 11. The effect of ultrasound on the textural properties of mesoporous alumina as well as on the transformation of nanosized bayerite to boehmite can be consistently attributed to the transient strong heating of the liquid shell surrounding the cavitation bubble which caused the chemical processes similar to those occurred during hydrothermal treatment.

cited By 9; International audience; The paper reports on structural investigation and electronic structure of thiogermanate and thioarseniate glasses by means of X-ray photoelectron spectroscopy (XPS) and ab initio calculation. Besides an increase of nonbridging sulfur (nbS) when increasing the amount of modifier (Ag2S), a limit in the breakdown between nbS and bridging sulfur (bS) atoms was observed for the intermediate Ag concentrations in the two families for the silver containing glasses. The influence of the modifier cation has been studied for the M2GeS3 glass family (M = Ag, Li, Na). Compared to alkali glasses, a more homogeneous electronic distribution on sulfur atoms was observed for Ag2GeS3. Furthermore, the electronic redistribution along Ge-S bonds is the most important in the case of Na2GeS3. In agreement with XPS results, Mulliken population analysis showed only a small difference (more important for Na than for Ag) between the charges on bS and nbS. According to XPS data (valence band), ab initio calculations on cluster models showed important changes - compared to GeS2 - in both Ge-S and Ge-Ge interactions, and support the concept of a nonlocalized effect of alkali-metal atoms.

Chalcogenide glasses with composition 0.5@(12x)Rb2S-xAg2S#-0.5GeS2 ,0

The cubic structure of trirubidium molybdophosphate, Rb3[PMo12O40], contains α-type Keggin [PMo12O40]3− anions and Rb+ counter-ions located in orthogonally intersecting channels. The P and Rb atoms are located on special positions with site symmetries \overline{4}3m and \overline{4}2.m, respectively. The three-dimensional arrangement is isostructural with that found in, for example, X 3[PMo12O40], with X = K, NH4 and H3O, or X 3[PW12O40] and X 4[SiW12O40], with X = Ag and Tl. The compound was crystallized using a typical high-temperature solid-state reaction with GaPO4 and X 3Mo3O10 (X = Rb or Li) as starting materials.