Tamara Đorđević

Zn1.86Cd0.14(OH)VO4

The title compound, dizinc cadmium hydroxide tetraoxidovanadate, Zn1.86Cd0.14(OH)VO4, was prepared under low-temperature hydrothermal conditions. It is isostructural with Zn2(OH)VO4 and Cu2(OH)VO4. In the crystal structure, chains of edge-sharing [ZnO6] octahedra are interconnected by VO4 tetrahedra (site symmetries of both V atoms and their coordination polyhedra are .m.) to form a three-dimensional [Zn(OH)VO4]2− framework with channels occupied by Zn and Zn/Cd cations adopting trigonal–bipyramidal and distorted octahedral coordinations, respectively. Zn1.86Cd0.14(OH)VO4 is topologically related to adamite-type phases, and descloizite- and tsumcorite-type structures.

Hydrothermal synthesis of single crystal CoAs2O4 and NiAs2O4 compounds and their magnetic properties

The crystal structures of the hydrothermally synthesised trippkeite-related materials, CoAs2O4 and NiAs2O4 were investigated by means of single-crystal X-ray diffraction, Raman and infrared spectroscopy. The obtained compounds crystallise in the tetragonal crystal system (P42/mbc), with unit cell parameters at 293 K of a = 8.34530(10)/8.2277(12) A, c = 5.62010(10)/5.6120(11) A, V = 391.406(12)/379.90(13) A3, Z = 4, for CoAs2O4 and NiAs2O4 respectively. Magnetic measurements show that the resulting single crystal of NiAs2O4 exhibits an antiferromagnetic transition at TN = 53 K in a high magnetic field of 10 kOe, as already reported in the literature. The single crystal of CoAs2O4 reveals an interplay between ferromagnetic and a canted antiferromagnetic interactions resulting in a canted antiferromagnetic state which occurs at 105 K – the highest critical temperature among all similar structures.

A single-crystal X-ray and Raman spectroscopic study of hydrothermally synthesized arsenates and vanadates with the descloizite and adelite structure types

Abstract Studying the reason for the formation of two structural sub-types, seven arsenate and vanadate compounds of descloizite and adelite groups [specifically (1) CdCo(OH)(AsO4), (2) CdCu(OH) (AsO4), (3) SrCo(OH)(AsO4), (4) SrZn(OH)(AsO4), (5) SrCu(OH)(VO4), (6) CdCo(OH)(VO4), and (7) CdCu(OH)(VO4) (bold numbers throughout paper refer to these compounds)] were synthesized under low-temperature hydrothermal conditions. 1–2 and 6–7 are isostructural with descloizite, and 3–5 are with adelite-group minerals and several synthetic compounds. Together with a sample of conichalcite, (8) CaCu(OH)(AsO4), they were investigated using single-crystal X-ray diffraction [R(F) = 0.0153–0.0283 for 1–5 and 8; for 6 and 7, R(F) = 0.0603 and 0.0444, respectively] and Raman spectroscopy. Although crystallizing in different orthorhombic space groups, the atomic arrangements of descloizite-(Pnam) and adelite-(P212121) type compounds adopt the same topology: the atomic arrangement is characterized by M2O6 octahedrons (M2 = Mg2+, Al3+, Mn2+,3+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+) edge-linked into chains. These chains are interconnected by XO4 tetrahedrons (X = Si4+, P5+, V5+, As5+, Mo6+) into a three-dimensional framework. Cavities host M1 atoms (M1 = Na+, Ca2+, Cd2+, Hg2+, Pb2+); their coordination varies from 7 for descloizite-type representatives to 8 for adelite-type structures. The OH stretching frequencies in the Raman spectra are in good agreement with the observed O–H…O donor-acceptor distances. A detailed discussion of the crystal chemistry of these compounds and their influence on the space-group symmetry indicate a distinct dependence of the structural changes on the average ionic radii (rM1 + rX)/2.

An investigation of polyhedral deformation in two mixed‐metal diarsenates: SrZnAs2O7 and BaCuAs2O7

Two isostructural diarsenates, SrZnAs2O7 (strontium zinc diarsenate), (I), and BaCuAs2O7 [barium copper(II) diarsenate], (II), have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction. The three-dimensional open-framework crystal structure consists of corner-sharing M2O5 (M2 = Zn or Cu) square pyramids and diarsenate (As2O7) groups. Each As2O7 group shares its five corners with five different M2O5 square pyramids. The resulting framework delimits two types of tunnels aligned parallel to the [010] and [100] directions where the large divalent nine-coordinated M1 (M1 = Sr or Ba) cations are located. The geometrical characteristics of the M1O9, M2O5 and As2O7 groups of known isostructural diarsenates, adopting the general formula M1(II)M2(II)As2O7 (M1(II) = Sr, Ba, Pb; M2(II) = Mg, Co, Cu, Zn) and crystallizing in the space group P2₁/n, are presented and discussed.

Zn3(PO4)2(H2O)0.8(NH3)1.2

The structure of the title compound, ammineaquadi-mu(5)-phosphato-trizinc(II), [Zn(3)(PO(4))(2)(H(2)O)(0.8)(NH(3))(1.2)], consists of two parts: (i) PO(4) and ZnO(4) vertex-sharing tetrahedra arranged in layers parallel to (100) and (ii) ZnO(2)(N/O)(2) tetrahedra located between the layers. Elemental analysis establishes the ammine-to-water ratio as 3:2. ZnO(2)(N/O)(2) tetrahedra are located at special position 4e (site symmetry 2) in C2/c. The two O atoms of ZnO(2)(N/O)(2) are bonded to neighbouring P atoms, forming two Zn-O-P linkages and connecting ZnO(2)(N/O)(2) tetrahedra with two adjacent bc plane layers. A noteworthy feature of the structure is the presence of NH(3) and H(2)O at the same crystallographic position and, consequently, qualitative changes in the pattern of hydrogen bonding and weaker N/O-H...O electrostatic interactions, as compared to two closely related structures.

Cd2Cu(PO4)2.

During an investigation of the insufficiently known system M1O-M2O-X(2)O(5)-H(2)O (M1 = Cd(2+), Sr(2+) and Ba(2+); M2 = Cu(2+), Ni(2+), Co(2+), Zn(2+) and Mg(2+); X = P(5+), As(5+) and V(5+)), single crystals of the novel compound dicadmium copper(II) bis[phosphate(V)], Cd(2)Cu(PO(4))(2), were obtained. This compound belongs to a small group of compounds adopting a Cu(3)(PO(4))(2)-type structure and having the general formula M1(2)M2(XO(4))(2) (M1/M2 = Cd(2+), Cu(2+), Mg(2+) and Zn(2+); X = As(5+), P(5+) and V(5+)). The crystal structure is characterized by the interconnection of infinite [Cu(PO(4))(2)](n) chains and [Cd(2)O(10)](n) double chains, both extending along the a axis. Exceptional characteristics of this structure are its novel chemical composition and the occurrence of double chains of CdO(6) polyhedra that were not found in related structures. In contrast to the isomorphous compounds, where the M1 cations are coordinated by five O atoms, the Cd atom is coordinated by six. The dissimilarity in the geometry of M1 coordination between Cd(2)Cu(PO(4))(2) and the isomorphous compounds is mostly due to the larger ionic radius of the Cd cation in comparison with the Cu, Mg and Zn cations. Sharing a common edge, two CdO(6) polyhedra form Cd(2)O(10) dimers. Each such dimer is bonded to another dimer sharing common vertices, forming [Cd(2)O(10)](n) double chains in the [100] direction. The Cu atoms, located on an inversion centre (site symmetry \overline{1}), form isolated CuO(4) squares interconnected by PO(4) tetrahedra, forming [Cu(PO(4))(2)](n) chains similar to those found in related structures. Conversely, the [Cd(2)O(10)](n) double chains, which were not found in related structures, are an exclusive feature of this structure.

Crystal structure of the tetra-gonal polymorph of bis-(1-ethyl-3-methyl-imidazolium) tetra-bromido-cadmate.

The title structure represents the tetragonal polymorph (the other known structure being monoclinic) and is isotypic with its [MBr4] analogues (M = Co, Ni, Zn).

Ionothermal synthesis and crystal structure of a new organic–inorganic hybrid compound: catena‐poly[bis(1‐ethyl‐3‐methylimidazolium) [hepta‐μ‐bromido‐pentacuprate(I)]]

A new organic-inorganic hybrid compound, catena-poly[bis(1-ethyl-3-methylimidazolium) [μ5-bromido-tri-μ3-bromido-tri-μ2-bromido-pentacuprate(I)]], {(C6H11N2)2[Cu5Br7]}n, has been obtained under ionothermal conditions from a reaction mixture containing Ba(OH)2·8H2O, Cu(OH)2·2H2O, As2O5, 1-ethyl-3-methylimidazolium bromide and distilled water. The crystal structure consists of complex [Cu5Br7](2-) anions arranged in sinusoidal {[Cu5Br7](2-)}n chains running along the a axis, which are surrounded by 1-ethyl-3-methylimidazolium cations. Three of the five unique Br atoms and one of the three Cu(I) atoms occupy special positions with half-occupancy (a mirror plane perpendicular to the b axis, site symmetry m). The Cu(I) ions are in a distorted tetrahedral coordination environment, with four Br atoms at distances ranging from 2.3667 (10) to 2.6197 (13) Å, and an outlier at 3.0283 (12) Å, exceptionally elongated and with a small contribution to the bond-valence sum of only 6.7%. Short C-H···Br contacts build up a three-dimensional network. The Cu···Cu distances within the chain range from 2.8390 (12) to 3.0805 (17) Å, indicating the existence of weak Cu(I)···Cu(I) cuprophilic interactions.