Synthesis, structures and luminescence properties of metal-organic frameworks based on lithium-lanthanide and terephthalate

Metal-organic frameworks assembled from Ln(III), Li(I) and rigid dicarboxylate ligand, formulated as [LiLn(BDC)2(H2O)·2(H2O)] (MS1-6,7a) and [LiTb(BDC)2] (MS7b) (Ln = Tb, Dy, Ho, Er, Yb, Y0.96Eu0.04, Y0.93Tb0.07, and H2BDC = terephthalic acid), were obtained under hydrothermal conditions. The isostructural MS1-6 crystallize in monoclinic P21/c space group. While, in the case of Tb3+ a mixture of at least two phases was obtained, the former one (MS7a) and a new monoclinic C2/c phase (MS7b). All compounds have been studied by single-crystal and powder X-ray diffraction, thermal analyses (TGA), vibrational spectroscopy (FTIR), and scanning electron microscopy (SEM-EDX). The structures of MS1-6 and MS7a are built up of inorganic-organic hybrid chains. These chains constructed from unusual four-membered rings, are formed by edge- and vertex-shared {LnO8} and {LiO4} polyhedra through oxygen atoms O3 (vertex) and O6-O7 (edge). Each chain is cross-linked to six neighboring chains through six terephthalate bridges. While, the structure of MS7b is constructed from double inorganic chains, and each chain is, in turn, related symmetrically to the adjacent one through the c glide plane. These chains are formed by infinitely alternating {LiO4} and {TbO8} polyhedra through (O2-O3) edges to create Tb–O–Li connectivity along the c-axis. Both MS1-6,7a and MS7b structures possess a 3D framework with 1D trigonal channels running along the a and c axes, containing water molecules and anhydrous, respectively. Topological studies revealed that MS1-6 and MS7a have a new 2-nodal 3,10-c net, while MS7b generates a 3D net with unusual β-Sn topology. The photoluminescence properties Eu- and Tb-doped compounds (MS5-6) are also investigated, exhibiting strong red and green light emissions, respectively, which are attributed to the efficient energy transfer process from the BDC ligand to Eu3+ and Tb3+.Financial support from Spanish Ministerio de Economía y Competitividad (MINECO-13-MAT2013-40950-R, and FPI grant BES-2011-046948 to MSM.A.) and Gobierno del Principado de Asturias (GRUPIN14-060), and El Fondo Europeo de Desarrollo Regional (FEDER) are acknowledged.We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI)

Crystal structures of 4-phenylpiperazin-1-ium 6-chloro-5-ethyl-2,4-dioxopyrimidin-1-ide and 4-phenylpiperazin-1-ium 6-chloro-5-isopropyl-2,4-dioxopyrimidin-1-ide

The title molecular salts, C10H15N2+·C6H6ClN2O2−, (I), and C10H15N2+·C7H8ClN2O2−, (II), consist of 4-phenylpiperazin-1-ium cations with a 6-chloro-5-ethyl-2,4-dioxopyrimidin-1-ide anion in (I) and a 6-chloro-5-isopropyl-2,4-dioxopyrimidin-1-ide anion in (II). Salt (I) crystallizes with two independent cations and anions in the asymmetric unit. In the crystal structures of both salts, the ions are linked via N—H...O and N—H...N hydrogen bonds, forming sheets which are parallel to (100) in (I) and to (001) in (II). In (I), the sheets are linked via C—H...Cl hydrogen bonds, forming a three-dimensional framework

Metastable phase in binary and ternary 12-carat gold alloys at low temperature

Low temperature phase transitions in 12-carat gold alloys have been investigated for binary Au-Cu and ternary Au-Cu-Ag compositions. The thermal analyses investigations using differential scanning calorimetry (DSC) and the dilatometry were performed in the 50-300°C temperature range in order to detect the structural transformations. The thermal analyses were carried out on annealed samples at 700°C for two hour followed by water quenching. They reveal an important new reaction for both used compositions and both thermal techniques confirm each other. This reaction has been assessed as pre-ordering reaction. SEM and STM imaging were performed on annealed samples at 700°C for two hours and water quenched followed by a heating from room temperature up to the temperature of the new peaks obtained in the thermal study. The imaging reveals the relationship between the pre-ordering reaction and the surface aspect presented in the fact of dendrite precipitates. A series of SEM observation have been performed in order to follow the kinetic of the observed precipitates by the way of several series of heating up, from 140 to 220°C for the binary composition and from 100 to 180°C for the ternary composition. Furthermore, this study shows that the silver accelerates the ordering reaction

Crystal structure, phase transitions, dielectric and vibrational studies and photoluminescence properties of a new iron fluoride based on bipyridine

The new iron-fluoride, based on bipyridine formulated as FeF3(2,2′-bpy) (2,2′-bpy = 2,2′-bipyridine), was obtained by hydrothermal synthesis. The crystalline structure was characterized by single crystal X-Ray diffraction data analysis. It crystallizes in monoclinic space group Cc, with a = 14.030(4) Å, b = 9.487(3) Å, c = 7.650(2) Å and β = 103.287(3)º. Moreover, it exhibits three-dimensional organic-inorganic network, resulting from the association of [FeF4N2]∞ chains pertaining to corner sharing FeF4N2 octahedra extending along with the c-axis linked through weak C–H...F hydrogen bonds. The thermal analysis (TG, SDTA and DSC) of the title compound reveals the presence of the phase transitions at high temperature. In order to shed light on the electrical conductivity and dielectric properties of the title compound, we carried out, in the frequency range 200 to 2E5 Hz, impedance spectroscopy technique, in the temperature range 310–380K. The conductivity relaxation parameters of some H+ conducting in the FeF3(2,2′-bpy) material were determined from an analysis pertaining to electric conductivity data. Transport properties in this material appear due to proton hopping mechanism. Finally, the optical properties were evaluated by photoluminescence spectroscopy.We acknowledge financial support from the Ministry of Higher Education and Scientific Research of Tunisia and Spanish Ministerio de Economía y Competitividad (MAT2016–78155-C2-1-R and FPI grant BES-2011–046948 to MSM.A.)

A metal-organic framework assembled from Y(iii), Li(i), and terephthalate: Hydrothermal synthesis, crystal structure, thermal decomposition and topological studies

A novel metal–organic framework assembled from Y(III), Li(I), and terephthalate ligand, formulated as [LiY(BDC)2(H2O)·2(H2O)] (1) (H2BDC = terephthalic acid), has been obtained as single phase under hydrothermal conditions. The crystal structure was solved by single-crystal X-ray diffraction and the bulk was characterized by powder X-ray diffraction (PXRD), thermal analyses (TG-MS and DSC), vibrational spectroscopy (FTIR), scanning/transmission electron microscopy (SEM-EDX, TEM, SAED, and BF-STEM-EDX), and powder X-ray thermodiffractometry (HT-XRD). 1 crystallizes in monoclinic space group (P21/c, with a = 11.6415(7) Å, b = 16.0920(4) Å, c = 13.2243(8) Å and β = 132.23(1)°) and possesses a 3D framework with 1D trigonal channels running along the [101] direction containing water molecules. The structure of 1 is made up of unusual four-membered rings formed by edge- and vertex-shared {YO8} and {LiO4} polyhedra. The four-membered rings are isolated and connected to each other via carboxylate groups. HT-XRD reveals that 1 undergoes phase transformation upon the dehydration process which is a reversible process involving a spontaneous rehydration characterized by fast kinetics. Topological studies were also performed revealing that 1 has a new 2-nodal net.We acknowledge financial support from the Spanish Ministerio de Economía y Competitividad (MAT2010-15094, Factoría de Cristalización – Consolider Ingenio 2010, FPI grant BES-2011-046948 to MSM-A, and Técnicos de Infraestructuras Científico-Tecnológicas grant PTA2011-4903-I to Z-A) and FEDER.Peer Reviewe

Metal-organic frameworks assembled from lanthanide and 2,5-pyridinedicaboxylate with cubane-like [Ln<inf>4</inf>(OH)<inf>4</inf>] building units

Lanthanide–organic frameworks based on 2,5-pyridinedicaboxylate (25p) ligand, formulated as [Yb4(OH)4(25p)4(H2O)3]·H2O (25pYb), [Y4(OH)4(25p)4(H2O)3]·H2O (25pY-1) and [Y6(OH)8(25p)5(H2O)2] (25pY-2), have been obtained as single phases under hydrothermal conditions. 25pYb and 25pY-1 are isostructural, and crystallize in the triclinic space group, P-1, with a=8.6075(5) Å, b=14.8478(7) Å, c=15.9164(9) Å, α=86.277(4)°, β=80.196(5)°, γ=81.785(4)°, and a=8.7166(6) Å, b=14.966(1) Å, c=15.966(1) Å, α=86.260(6)°, β=80.036(6)°, γ=81.599(6)°, respectively. 25pY-2 crystallizes in the monoclinic space group, P21/c, with a=24.9117(17) Å, b=13.7340(8) Å, c=14.3385(10) Å, β=100.551(7)°. 25pYb and 25pY-2 have been structurally characterized by single-crystal X-ray diffraction. The 25pYb structure is based on tetranuclear cubane-like [Yb4(OH)4]8+ clusters, which are interconnected to eight neighbouring clusters through teen surrounding 25p ligands leading to neutral 3D framework, while the structure of 25pY-2 is based on two independent cuban-like [Y4(OH)4]8+ clusters, which are joined together through Y1 cation leading to the formation of hexanuclear [Y6(OH)8]10+ clusters, which in turn are joined via Y2 cation resulting in infinite inorganic chain extending along c-axis, and each chain is interconnected to six adjacent chains through 25p ligands leading finally to 3D framework. The luminescence properties of Eu3+ and Tb3+ doped 25pY-1 and 25pY-2 compounds have also been investigated. All materials has been characterized by powder X-ray diffraction, thermal analyses (TG–SDTA–MS), FTIR spectroscopy, C–H–N elemental analysis, scanning electron microscopy (SEM-EDX), and powder X-ray thermodiffraction.Financial support from Spanish Ministerio de Economía y Competitividad (MAT2013-40950-R, and FPI grant BES-2011-046948 to MSM.A.) and Gobierno del Principado de Asturias (GRUPIN14-060), and FEDER funding are acknowledged.Peer Reviewe

Synthesis, crystal structure, vibrational and optical properties of a new Pb(II) complex (2-hydroxyethyl)piperazine-1,4-diium tetrachloroplombate(II) C6H16N2OPbCl4

A novel hybrid material, C6H16N2OPbCl4, has been successfully synthesized in nitrogen atmosphere by slow evaporation at room temperature. The compound structure was determined by single-crystal X–ray diffraction and crystallizes in the triclinic space group P-1 (a = 5.9926(2) Å, b = 10.3691(5) Å, c = 11.3558(4) Å, α=111.755(4)°,β= 96.080(3)°, γ = 105.948(4)°, Z= 2) at 293 K. The structure is built up from anionic 1-D polymeric chains of PbCl4O octahedral extended along the (b + c)-axis. These chains are interconnected O-H···Cl hydrogen bonds to form inorganic layers parallel to (a, b + c) plane. The organic layers are inserted between the inorganic ones and connect them through N-H···Cl and C-H···Cl hydrogen bonds hydrogen bonds to build a three dimensional network. To gain more information about intermolecular interaction we used Hirshfeld surfaces associated with 2D finger plots. The optical and PL properties of the compound were investigated in the solid state at room temperature and exhibited two bands at 250 and 290 nm and a photoluminescence emission at 529 nm. Raman and infrared spectra were used to gain more information for vibrational modes of the title compound. As for thermal analysis, DSC analysis shows that this compound is stable at temperature below melting point. Finally, XPS analysis is achieved for analyzing the surface chemistry of C6H16N2OPbCl4 crystals