Dicaesium tetramagnesium pentakis(carbonate) decahydrate, Cs2Mg4(CO3)5·10H2O

The title carbonate hydrate, Cs2Mg4(CO3)5·10H2O, was crystallized at room temperature out of aqueous solutions containing caesium bicarbonate and magnesium nitrate. Its monoclinic crystal structure (P21/n) consists of double chains of composition 1 ∞[Mg(H2O)2/1(CO3)3/3], isolated [Mg(H2O)(CO3)2]2– units, two crystallographically distinct Cs+ ions and a free water molecule. The crystal under investigation was twinned by reticular pseudomerohedry.

A new lanthanum coordination polymer built from a semi-rigid tripodal carboxylic acid ligand: synthesis, crystal structure and properties

By employing the semi-rigid multidentate carboxylic acid ligand 4,4′,4′′-{[(2,4,6-trimethylbenzene-1,3,5-triyl)tris(methylene)]tris(oxy)}tribenzoic acid (denoted H3 L), a new lanthanum coordination polymer, namely poly[[bis(dimethylformamide)(μ6-4,4′,4′′-{[(2,4,6-trimethylbenzene-1,3,5-triyl)tris(methylene)]tris(oxy)}tribenzoato)lanthanum(III)] dimethylformamide tetrasolvate 0.25-hydrate], {[La(C33H27O9)(C3H7NO)2]·4C3H7NO·0.25H2O} n or {[La(L)(DMF)2]·4(DMF)·0.25(H2O)} n (DMF is dimethylformamide) (1), was prepared and characterized by single-crystal X-ray diffraction, elemental analysis, thermogravimetric analysis, IR spectroscopy and photoluminescence studies. The asymmetric unit contains one LaIII cation, one anionic L 3− ligand, two coordinated DMF molecules, four free DMF molecules and one-quarter of a free water molecule. Compound 1 possesses (3,6)-connected two-dimensional kgd topology sheets consisting of secondary building units of La2 clusters and L 3− ligands, which further stack into three-dimensional supramolecular networks through π–π interactions. Compound 1 exhibits a photoluminescence emission at room temperature, with a peak at 410 nm, owing to a ligand-centred excited state.

Crystal structures of two mononuclear complexes of terbium(III) nitrate with the tripodal alcohol 1,1,1-tris(hydroxymethyl)propane

Two new mononuclear cationic complexes in which the TbIIIion is bis-chelated by the tripodal alcohol 1,1,1-tris(hydroxymethyl)propane (H3LEt, C6H14O3) were prepared from Tb(NO3)3·5H2O and had their crystal and molecular structures solved by single-crystal X-ray diffraction analysis after data collection at 100 K. Both products were isolated in reasonable yields from the same reaction mixture by using different crystallization conditions. The higher-symmetry complex dinitratobis[1,1,1-tris(hydroxymethyl)propane]terbium(III) nitrate dimethoxyethane hemisolvate, [Tb(NO3)2(H3LEt)2]NO3·0.5C4H10O2,1, in which the lanthanide ion is 10-coordinate and adopts ans-bicapped square-antiprismatic coordination geometry, contains two bidentate nitrate ions bound to the metal atom; another nitrate ion functions as a counter-ion and a half-molecule of dimethoxyethane (completed by a crystallographic twofold rotation axis) is also present. In product aquanitratobis[1,1,1-tris(hydroxymethyl)propane]terbium(III) dinitrate, [Tb(NO3)(H3LEt)2(H2O)](NO3)2,2, one bidentate nitrate ion and one water molecule are bound to the nine-coordinate terbium(III) centre, while two free nitrate ions contribute to charge balance outside the tricapped trigonal-prismatic coordination polyhedron. No free water molecule was found in either of the crystal structures and, only in the case of1, dimethoxyethane acts as a crystallizing solvent. In both molecular structures, the two tripodal ligands are bent to one side of the coordination sphere, leaving room for the anionic and water ligands. In complex2, the methyl group of one of the H3LEtligands is disordered over two alternative orientations. Strong hydrogen bonds, both intra- and intermolecular, are found in the crystal structures due to the number of different donor and acceptor groups present.

Poly[[diaquabis[μ4-5-nitroisophthalato-κ4O1:O1:O3:O3′]bis[μ3-pyridine-4-carboxylato-κ3O:O′:N]tricobalt(II)] tetrahydrate]

The title compound, {[Co3(C6H4NO2)2(C8H3NO6)2(H2O)2]·4H2O}n, exhibits a two-dimensional layer-like structure in which the CoIIions exhibit two kinds of coordination geometries. One nearly octahedral CoIIion with crystallographic inversion symmetry is coordinated to six carboxylate O atoms from four bridging 5-nitroisophthalate (NIPH) ligands and two isonicotinate (IN) anions, while the other type of CoIIion binds with one N atom and one carboxylate O atom from two IN anions, two carboxylate O atoms from two different NIPH anions and one ligated water molecule, displaying a distorted square-pyramidal coordination geometry. Three adjacent CoIIions are bridged by six carboxylate groups from four NIPH ligands and two IN anions to form a linear trinuclear secondary building unit (SBU). Every trinuclear SBU is linked to its nearest neighbours in theabplane, resulting in a two-dimensional layer-like structure perpendicular to thecaxis. Along thea-axis direction neighbouring molecules are connected through carboxylate and pyridyl units of the IN anions, along thebaxis through carboxylate groups of the NIPH ligands. The H atoms of one free water molecule are disordered in the crystal in a 1:1 ratio. Typical O—H...O hydrogen bonds are observed in the lattice, which include the following contacts: (a) between coordinated water molecules and carboxylate O atoms of the NIPH anions, (b) between lattice water molecules and carboxylate O atoms of the NIPH anions, and (c) between coordinated and lattice water molecules. These intermolecular hydrogen bonds connect the two-dimensional layers to form a three-dimensional supramolecular structure.

Calculations of the Oxygen Isotope Fractionation between Hydration Water of Cations and Free Water

The oxygen isotope fractionation factors between the hydration complex of the alkali ions in the gas phase and a free water molecule have been computed on the basis of the energy surfaces calculated by Kistenmacher, Popkie and Clementi for a water molecule in the field of an alkali ion. For comparison with recently measured oxygen isotope fractionation factors in aqueous alkali halide solutions, the gas phase values are multiplied with the corresponding separation factors between water vapor and liquid water thus relating the hydration complex in the gas phase with pure water. Qualitative agreement between computed and observed fractionation factors has been found for H2O and D2O even neglecting the isotope effect connected with the transfer of the hydration complex from the gas phase to the solution. This transfer effect is estimated for H2O by a quantitative comparison of computed and observed oxygen isotope fractionation factors.