A. Ayi

Transformations of low-dimensional zinc phosphates to complex open-framework structures. Part 1: zero-dimensional to one-, two- and three-dimensional structures

Zero-dimensional 4-membered zinc phosphate monomers, [C6N2H18][Zn(HPO4)(H2PO4)2], I, and [C6N4H21][Zn(HPO4)2(H2PO4)], II, transform under simple reaction conditions to one-, two- and three-dimensional structures. Monomer II, on heating with zinc acetate dihydrate (Zn(OAc)2) in aqueous solution, gives a layered phosphate [C6N4H21][NH4][Zn6(PO4)4(HPO4)2]H2O, III. A novel three-dimensional structure [C6N4H21]4[Zn7(PO4)6]3, IV, with channels comprising Zn7O6 clusters is obtained on heating II in water under hydrothermal conditions. The monomer I transforms to a one-dimensional ladder, [C3N2H5][Zn(HPO4)], V, on heating with imidazole and to a three-dimensional structure, [C4N2H12][Zn2(H2O)(PO4)(HPO4)]2, VI, on heating with piperazine under ordinary conditions. I also transforms to a layered zinc phosphate, [C6N2H18][Zn3(H2O)4(HPO4)4], VII, on heating in water. In addition to the monomer, II, compounds III–VI have been obtained for the first time. The structures formed by the transformations of the monomers also exhibit unique structural features. Thus, in the ladder structure, V, the imidazole molecule is linked to the Zn center similar to the phosphate unit in a typical ladder structure, while in the layered phosphate, III, one-dimensional tubules are linked via ZnO4 tetrahedra and the three-dimensional structure, IV, possesses Zn7O6 clusters. Isolation of several related solids encompassing a variety of architectures through the transformations of zero-dimensional monomeric phosphates demonstrates not only that the 4-membered ring is a basic structural building unit in these open-framework materials, but also sheds light on the building-up process involved in their formation.

Synthesis, spectral and cytotoxicity studies of palladium(II) and platinum(II) amino acid Schiff base complexes

Novel PdII and PtII complexes of substituted o-hydroxyacetophenone-glycine have been synthesized, and characterized by conductivity measurements, i.r., electronic and 1H-n.m.r. spectra. The spectral data indicate that the ligands are monobasic bidentate, coordinating through imino nitrogen and the carboxylate group. A four coordinate square planar configuration has been proposed for all the complexes. The ligands, as well as their PdII and PtII complexes, exhibit potent cytotoxic activity against Ehrlich ascites tumour cells in vitro, but appear to be more active in vivo.

One-dimensional zinc phosphates with linear chain structure

Three one-dimensional zinc phosphates, [C5N2H14][Zn(HPO4)2], I, [C10N4H26][Zn(HPO4)2].2H2O II, and [C4N2H6]2[Zn(HPO4)], III, have been prepared employing hydro/solvothermal methods in the presence of organic amines. While I and II consist of linear chains of corner-shared four-membered rings, III is a polymeric wire where the amine molecule is directly bonded to the metal center. The wire, as well as the chain in these structures, are held together by hydrogen bond interactions involving the amine and the framework oxygens. The polymeric zinc phosphate with wire-like architecture, III, is only the second example of such architecture. Crystal data: I, monoclinic, P21/c (no. 14), a=8.603(2), b=13.529(2), c=10.880(1) A, β=94.9(1)°, V=1261.6(1) A3, Z=4, ρcalc.=1.893 gcm−3, μ(MoKα)=2.234 mm−1, R1=0.032, wR2=0.086, [1532 observed reflections with I>2σ(I)], II, orthorhombic, Pbca (no. 61), a=8.393(1), b=15.286(1), c=22.659(1) A, V=2906.9(2) A3, Z=8, ρcalc.=1.794 gcm−3, μ(MoKα)=1.957 mm−1, R1=0.055, wR2=0.11, [1565 observed reflections with I>2σ(I) and III, monoclinic, P21/c (no. 14), a=8.241(1), b=13.750(2), c=10.572(1) A, β=90.9(1)°, V=1197.7(2) A3, Z=4, ρcalc.=1.805 gcm−3, μ(MoKα)=2.197 mm−1, R1=0.036, wR2=0.10, [1423 observed reflections with I>2σ(I)].

The first organically templated open-framework metal selenate with a three-dimensional architecture

A three-dimensional metal selenate of the formula [C2N2H10][La2(SeO4)4(H2O)3].H2O, comprising La2Se4 building units and possessing 12-membered channels, has been prepared in an acidic medium under hydrothermal conditions.

Cyclic acetate dimers formed by C–H···O hydrogen bonds in an open-framework zinc phosphate-acetate

A novel three-dimensional zinc phosphate-acetate, formed by acetate dimers with C–H···O bonds, has been synthesized for the first time under mild conditions.

On the Synthesis of Molybdenum Nanoparticles under Reducing Conditions in Ionic Liquids

We report on attempts to synthesize Mo nanoparticles under reducing conditions in ionic liquids (ILs). Ionic liquids were based on the 1-ethyl-3-methylimidazolium or 1-butyl-3-methylimidazolium (Emim and Bmim, resp.) cations and the dicyanamide N(CN)2, triflate (OTf), bis(trifluoromethylsulfonyl)imide-(NTf2), tetrafluoroborate (BF4), ethyl sulfate (ES), and methylsulfonate (MS) anions. (NH4)6Mo7O24∗4H2O and NaBH4 were reacted in a set of imidazolium ionic liquids (ILs) at 180°C to evaluate the potential of the ILs for stabilization of metallic Mo nanoparticles. XRD and TEM reveal a strong influence of the IL anion on the particle sizes, shapes, and crystal structures. The influence of the IL cation and the reaction temperature is much less pronounced.

Hydrothermal synthesis and structural characterization of an organically-templated open-framework trimolybdates

A new one-dimensional coordination polymer formulated as [C2H10N2] [Mo3O10], 1, has been synthesized under hydrothermal conditions in the presence of ethylenediamine. The surface morphology of the assynthesized product reveals colorless rod-like single crystals of 1. The compound crystallizes in monoclinic space group P21/n with a = 8.08 Å, b =14.39 Å, c = 8.89 Å; β = 97.76°, V = 1033.65(12) Å3, Z = 4. The structure is a one-dimensional chain consisting of [Mo3O10] 2clusters of Mo (VI) octahedral interspersed by the amine molecules. In the infrared spectrum of the compound, the symmetric stretching vibrational mode of the -NH2 group is observed at 3278 cm -1 , while the band at 1604 cm -1 is assigned to scissoring mode of the –NH2 group. The peaks in the spectral range 1913 -2492 and 2962 cm -1 are attributed to -CH2 symmetric and asymmetric stretching vibrations respectively. The absorption bands at 1404 cm -1 is due to scissoring, while the one at 1149 cm -1 is attributable to twisting modes of CH2 group . The characteristic band of the stretching vibrational modes of the Mo=O double bonds is observed at 1018 cm -1 , while the vibrational stretching frequency involving single MoO bonds is observed at 846 cm -1 and the scissoring mode of this bond is at 542 cm -1 .

Hydrothermal synthesis and structural characterization of ammonium ion-templated lanthanide(III) carboxylate-phosphonates.

Using N-(phosphonomethyl) iminodiacetic acid (H4PMIDA), as a complexing agent, two new complexes, (NH4)La(PMIDA)(H2O)•H2O, 1 and (NH4)Yb(PMIDA), 2 have been synthesized hydrothermally. In both compounds, the metal ions are trapped by a three five-membered chelate rings by the chelating PMIDA anions giving a tricapped trigonal prismatic LaO8N and monocapped trigonal prismatic YbO6N geometries for 1 and 2, respectively. The structure of 1 consists of La(PMIDA)(H2O) chelating units, linked together by the phosphonate oxygen atoms O1 and O3 to form a chain along the c-axis. The chains are then connected together by the bridging phosphonate oxygen O2 to form a 2D layered structure with alternating 4- and 8-membered apertures. The structure of 2 consists Yb(PMIDA) chelating units, which are connected by alternating bridging carboxylate and phosphonate groups along the [010] direction forming chains with a corrugated pattern. The third phosphonate oxygen bridges the chains together along the [001] direction to build the two-dimensional layer with 4- and 6-membered apertures in the bc-plane. Under excitation of 330 nm, compound 2 shows a broad emission band at λmax = 460 nm. This emission is essentially in the blue luminescent region, which corresponds to ligand centered fluorescence.

Use of Nanostructured Layered Double Hydroxides as Nanofilters in the Removal of Fe2+ and Ca2+ Ions from Oil Wells

Four new metal-aluminum layered double hydroxides (LDHs), Mg-Al(OH)2PO4 (1), Mg-Al(OH)2PO4PF6 (2), Ca-Al(OH)2SO4 (3), and Ca-Al(OH)2PO4PF6 (4), were prepared by the coprecipitation method followed by mild hydrothermal processing at 60°C. Mg2+ and Ca2+ in solution with Al3+ were titrated with NaOH over 3–5 h to yield Mg-Al and Ca-Al layered double hydroxides, respectively, incorporating PO43−, PO43−PF6−, and SO42− anions in the interlamellar spaces. The isolated compounds were characterized with the help of XRD, IR, and SEM/EDAX, and their ability to remove scale-forming ions from the aqueous system was studied with the help of atomic absorption spectroscopy (AAS). The SEM micrographs of Mg-O-Al-OH and Ca-O-Al-OH layers intercalated with PO43− and/or [PO4PF6]4− anions are similar consisting of uniform nanospheres with an average size of 100 nm, while the M-O-Al-OH layer of compound 3, intercalated with SO42− anions, consists of hexagonal nanoplate crystals. In the infrared spectra, the characteristic absorption band for water molecules was observed in all the compounds. The XRD pattern showed that d012 and d104 peaks of M-Al-PO4 LDHs corresponding to interplanar spacing of 3.4804 and 2.5504 A, respectively, shifted to higher 2θ values for the M-Al-PO4PF6 system, which indicates a decrease in the interlamellar spacing as PF6− was incorporated along with PO43− anion. The XRD pattern for Ca-Al-SO4 LDHs was quite different, showing the presence of low-angle peaks at 2θ = 11.68 and 14.72°. The results of the column adsorption studies showed that there was a significant removal of Ca2+ by all the compounds under investigation with an efficiency of 84–99%. However, compounds 1 and 2 remove Fe2+ effectively with the efficiency of 98.73 and 99.77%, respectively; compounds 3 and 4 were shown to have little or no effect.

Solvent-Mediated Synthesis of M(II)-Coordination Polymer Part 1: Crystal Structure of Poly(1,2-di(4-pyridyl)ethylene-k2N,N')-bis(1,4-benzenediacetato-k4O,O′,O′′,O′′')zinc(II)], C22H18ZnN2O4

An interaction of water-methanol solution of sodium1,4-benzenediacetate (bda) and 4,4′-bipyridylethelene (bpee) with aqueous solution of Zn(NO3)2·6H2O at room temperature yielded colourless crystals of 1 after three weeks in a sealed glass tube. The compound with composition C22H18ZnN2O4 crystallizes in monoclinic space group P21/c, with the following cell dimensions: a = 10.4566(2), b = 13.3085(2), c = 13.7189(2) A, β = 101.491(1)°. In the structure of 1, two Zn(II) neighbours are connected by two bda ligands adopting chelating and bidentate-bridging coordination modes to form a dimeric unit (Zn2O8N4) with the Zn–Zn distance of 4.0432(6) A. The carboxyl-bridged dimeric units are extended along the [001] direction by bpee co-ligands and further linked by bda ligand to form a three-dimensional network structure. The IR shows the characteristic bands of the carboxylates at 1611/1507 cm−1 and 1424/1373 cm−1, respectively, for asymmetric and symmetric stretching −CO2− vibrations. The separation ∆[νasym(CO2−) − νsym(CO2−)] values of 187 and 134 cm−1 are indicative of chelating and bidentate bridging coordination modes of the carboxylate to the metal centre.