Walid Rekik

Inorganic layered structures in hybrid double sulfates: related phases and thermal reactivity

The use of benzimidazole as an aromatic diamine template in the synthesis of a series of hybrid double sulfate salts containing transition metals provided a new structure topology that gathers between the supramolecular aspect and the lamellar aspect, which is not very much encountered in the literature. The obtained materials with the general formula (C7H7N2)2[MII(H2O)6](SO4)2·4H2O (MII = Zn, Cu, Ni, Co) and (C7H7N2)2[Fe(H2O)6](SO4)2·3H2O crystallize according to the triclinic symmetry (S.G. P) and to the monoclinic symmetry (S.G. P21/n), respectively. The mineral layer is built from sulfate (SO4), hexaaquametal-complex[MII(H2O)6] and free H2O molecules, linked together by hydrogen bonds only. The aromatic amines are intercalated between the inorganic layers and form chains through π⋯π interactions. The orientation of the amine molecule in two different directions can modify the interlayer space, which is able to vary from 12.3 to 13.2 A depending upon on the nature of the metal. The thermal behaviour of the five metal compounds, studied by TDXD and TG, shows a good stability of precursors and indicates that the dehydration proceeds differently according to the metal incorporated into the structure leading to the formation of crystalline phases during heating. In particular, the Fe-related compound becomes amorphous when subjected to temperature increase.

Bis[tris(propane-1,3-diamine-κ2N,N′)­nickel(II)] di­aqua­bis(propane-1,3-di­amine-κ2N,N′)nickel(II) hexa­bromide dihydrate

In the title compound, [Ni(C3H10N2)3]2[Ni(C3H10N2)2(H2O)2]Br6·2H2O, one Ni2+ cation, located on an inversion centre, is coordinated by four N atoms from two ligands and by two water O atoms. The other Ni2+ cation, located in a general position, is coordinated by six N atoms from three ligands. In both cases, the Ni2+ cation has an octahedral coordination environment. The overall structural cohesion is ensured by three types of hydrogen bonds, N—H⋯Br, O—H⋯Br and O—H⋯O, which connect the two types of complex cations, the bromide counter-anions and the lattice water molecules into a three-dimensional network.

Thermal decomposition and biological activity of two supramolecular hybrid nitrates templated by piperazine

The combination between piperazine, nitrate anions and nickel/zinc metals provided two new hybrid compounds with the general formula (C4H12N2)2[MII(H2O)6](NO3)6 [MII: Ni (1) and Zn (2)]. Their characterization is performed through FTIR spectroscopy and single-crystal X-ray diffraction which gives, as a result, isotype crystal structures, according to the triclinic system (space group Pī), built from: isolated metallic cations coordinated by six water molecules in a distorted octahedral environment [MII(H2O)6]2+, free nitrate anions and protonated piperazine related together through a hydrogen bond network. These bonds together with other attractive forces, being responsible for the crystal formation, were examined using density-functional theory electron density and the non-covalent interaction plot technique. The thermal behavior of the two materials, studied by thermogravimetric analysis and thermal-dependent X-ray diffraction analysis, starts with the dehydration step proceeding differently according to the used metal. The total decomposition leads to the formation of metal oxides: NiO and ZnO. In order to evaluate their biological activity, the two hybrids have been screened against bacteria and fungi and the findings have been reported and explained.Graphical Abstract

A new organically templated magnesium sulfate: structure, spectroscopic analysis, and thermal behaviour

A new magnesium sulfate templated by 2-methylpiperazine, (C5H14N2)[Mg(H2O)6](SO4)2, was prepared by the slow evaporation method. The obtained crystals were investigated by the Raman and FTIR spectroscopy and crystallographically characterised by single-crystal X-ray diffraction. The compound crystallises in the monoclinic system, space group P21/n. Supramolecular network of this hybrid material consists of Mg2+ cations octahedrally coordinated by six water molecules, sulfate tetrahedra and protonated and disordered diamine linked together by two types of hydrogen bonds: OW—H…O and N—H…O. Dehydration of the title compound takes place in three steps. Thermal decomposition of the anhydrous phase consists in the loss of the organic moiety and one sulfate group leading to the formation of magnesium sulfate.

Ethyl-enediammonium tetra-aqua-disulfato-cadmate.

The crystal structure of the title compound, [NH3(CH2)2NH3][Cd(SO4)2(H2O)4], consists of [Cd(SO4)2(H2O)4]2− anions that are built from octahedral Cd(H2O)4O2 and SO4 tetrahedral units linked by corner sharing. The ethylenediamminium cations are linked to the anions via N—H⋯O hydrogen bonds. The asymmetric unit contains one-half of the compound, the other half being related to the first by an inversion centre. The crystal structure presents alternate stacking of the inorganic and organic layers along the crystallographic b axis. The structure cohesion and stability is further assured by O(water)—H⋯O hydrogen bonds.

Crystal architecture and thermal decomposition of two new organically templated cadmium sulfates

Two organic-inorganic hybrid compounds (C5H14N2)[Cd(H2O)6](SO4)2 (I) and R-(C5H14N2)×[Cd(H2O)6](SO4)2 (II) are synthesized by the slow evaporation method and characterized by single crystal X-ray diffraction, thermogravimetry, temperature-dependent X-ray diffraction, and infrared spectroscopy. The first compound crystallizes in the centrosymmetric space group P21/n with the following unit cell parameters: a = 6.6208(2) Å, b = 10.6963(3) Å, c = 12.9318(4) Å, V = 893.05(6) Å3, and Z = 2. Its structure is solved by direct methods and refined by the least-squares analysis [R1 = 0.0389 and wR2 = 0.0821]. This compound shows a crystallographic disorder II destroys the inversion symmetry and leads to a fully ordered structure. Indeed, compound II crystallizes in the non-centrosymmetric space group P21 with the following unit cell parameters: a = 6.6306(1) Å, b = 10.7059(2) Å, c = 12.9186(1) Å, V = 894.67(2) Å3, and Z = 2. The crystal structure of both compounds is built from isolated SO42− anions, disordered 2-methylpiperazinediium, (C5H14N2)2+ in compound I or R-2-methylpiperazinediium R-(C5H14N2)2+ in compound II, and divalent metal cations surrounded by six water molecules. These different entities are connected together only by a 3D hydrogen bond network. The thermodiffractometry and the thermogravimetric analyses indicate that the decomposition of the supramolecular precursors proceeds through several stages leading to cadmuim oxide.