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abstracts
Lanthanide-Organic frameworks (LnOFs) are currently attracting increasing attention due to their excellent luminescence properties, in which both Ln3+ and organic linkers can be used to give rise to luminescence materials with increased brightness and emission quantum yield [1,2]. Lithium doped MOFs are of particular interest due to the recent studies showing enhanced H2 uptake, as well as promising candidates for replacing the conventional electrode in Li-ion batteries [3,4]. Herein, novel Lithium-lanthanide frameworks based on a rigid dicarboxylic acid, formulated as [LiLn(BDC)2(H2O)·2(H2O)] (Ln = Y, Dy, Ho, Er, Yb, Y1-xEux, Y1-xTbx and H2BDC = Terephthalic acid), have been obtained as single phases under hydrothermal conditions. The crystal structures were solved by single-crystal X-ray diffraction and the bulk characterized by powder X-ray diffraction (PXRD), thermal analyses (TG-MS and DSC), vibrational spectroscopy (FTIR), scanning/transmission electron microscopy (SEM-EDX, TEM, SAED, STEM-EDX), and powder X-ray thermodiffractometry (HT-XRD). All compounds are isostructural (monoclinic P21/c, a = 11.6365(7) Å, b =16.0920(2) Å, c = 13.2243(8) Å and β = 132.23(1)° for Ln = Y [5]) and possess a 3D framework with 1D trigonal channels running along the [101] direction contain water molecules. The structure is built up of unusual four-membered rings formed by edge- and vertex-shared {LnO8} and {LiO4} polyhedra. The four-membered rings are isolated and connected to each other via carboxylate groups. Topologically, the 3D frameworks belongs to a new 2-nodal 3,10-c net with point symbol of {4.5^2}2{4^14.5^10.6^18.7.8^2}. HT-XRD reveals that the compounds undergo phase transformation upon dehydration process which is a reversible process involving a spontaneous rehydration characterized by fast kinetic. The luminescence properties of selected compounds are also studied.
abstracts
The families of thiosemicarbazone compounds have been extensively studied due to their wide range potential in medical applications [1]. Some studies with acetophenone derivatives and their coordination complexes [2] reveal that these compounds could be used as a new class of anti-trypanosomal drug candidate. In view of the importance of these compounds, two new thiosemicarbazones (I) and (II) have been synthesized (compound I substituted with Chloro atom and compound II substituted with Bromine atom), and their crystal structure features are presented here. The crystal structures are isostructural and the molecules crystallize in a P21/c space group. In the crystal packing the molecules are connected through N-H···S hydrogen bonds to form a centrosymmetric synthon. The optimized geometry of the compound (I) was calculated from the DFT-B3LYP gradient calculations employing 6-31G (d,p) basis set and calculated vibrational frequencies are evaluated via comparison with experimental values. Molecular stability has been analyzed using Natural Bond Orbital (NBO) and Natural Localized Molecular Orbital (NLMO) analysis and the limits of the molecular electrostatic potential calculated. The HOMO and LUMO energies shows the charge transfer occurs within the molecule. The results showed no significant geometrical differences (distances and angles), when the solid state crystal structure is compared with the optimized structure in the gas phase. Very good agreements have been found between principal vibrational frequencies calculated from the optimized structure and the experimental spectroscopic data [3]. We thank financial support from Spanish Ministerio de Economía y Competitividad (MAT2010-15094, Factoría de Cristalización- Consolider Ingenio 2010, ERDF funds and German Academic Exchange Service (DAAD).
