(CN3H6)[FeIIFeIII(SO4)3(H2O)3]: A Framework Iron Sulfate with a Mixed S = 2 and S = 5/2 Honeycomb Lattice.

A new guanidinium-templated hydrated iron sulfate, [CN3H6][FeIIFeIII(SO4)3(H2O)3] (1), was prepared from strongly acidic aqueous solutions. Its crystal structure is comprised from FeIIIO6 and FeIIO3(H2O)3 octahedra linked by sulfate bridges forming a [FeIIFeII(SO4)3(H2O)3]- 3D framework with a layer-by-layer ordering of ferric and ferrous cations. The structural topology of the framework is related to the anhydrous rhombohedral mikasaite Fe2(SO4)3. The removal of part of the sulfate tetrahedra and the partial replacement of the Fe3+ cations in the [Fe3+2(SO4)3]0 framework by Fe2+ provide a negative charge and allow the incorporation of the protonated organic species in the voids. The compound 1 has been characterized by single-crystal X-ray diffraction, TG and DSC analyses, UV-vis-NIR spectroscopy, magnetic susceptibility, Mössbauer spectroscopy, IR and Raman spectroscopy, and density functional band-structure calculations. The magnetic behavior of 1 shows an interplay of FeII (S = 2) and FeIII (S = 5/2) sublattices that exhibit different types of antiferromagnetic couplings, one FeIII-FeIII (J1 ∼ 6.1 K) and two FeII-FeIII couplings (J2 ∼ 1 K, J3 ∼ 5.9 K) within corrugated honeycomb layers. These ferrimagnetic layers are coupled antiparallel to each other, resulting in an overall antiferromagnetic order below TN = 31 K.

Protonated Organic Diamines as Templates for Layered and Microporous Structures: Synthesis, Crystal Chemistry, and Structural Trends among the Compounds Formed in Aqueous Systems Transition Metal Halide or Nitrate-Diamine-Selenious Acid.

Systematic studies of crystalline compounds formed in aqueous systems containing aliphatic diamines, divalent transition metal halides, and selenious acid resulted in the discovery of a large family of new complex species corresponding to several new structure types. With ethylenediamine (en), layered (enH2)[M(HSeO3)2X2] compounds are the most commonly formed species which constitute a significant contribution to the family of layered hydrogen selenites containing neutral [M(HSeO3)2] (M = Mg, Mn, Co, Ni, Cu, Zn, Cd) 2D building blocks. In contrast to some previous suggestions, piperazine (pip), as well as its homologue N-methylpiperazine, mostly give rise to quite different, sometimes more complex, structures of varied dimensionality while the (pipH2)[M(HSeO3)2X2] compounds are formed only with M = Cu and Cd. In addition, metal-, halide-, or selenium-free by-product species are observed. The SeIV can be present in a multitude of forms, including H2SeO3, HSeO3-, SeO32-, and Se2O52-, reflecting amazing adaptability to the shape of the templating cations.

Framework Uranyl Silicates: Crystal Chemistry and a New Route for the Synthesis.

To date, uranyl silicates are mostly represented by minerals in nature. However, their synthetic counterparts can be used as ion exchange materials. A new approach for the synthesis of framework uranyl silicates is reported. The new compounds Rb2[(UO2)2(Si8O19)](H2O)2.5 (1), (K,Rb)2[(UO2)(Si10O22)] (2), [Rb3Cl][(UO2)(Si4O10)] (3) and [Cs3Cl][(UO2)(Si4O10)] (4) were prepared at harsh conditions in "activated" silica tubes at 900 °C. The activation of silica was performed using 40% hydrofluoric acid and lead oxide. Crystal structures of new uranyl silicates were solved by direct methods and refined: 1 is orthorhombic, Cmce, a = 14.5795(2) Å, b = 14.2083(2) Å, c = 23.1412(4) Å, V = 4793.70(13) Å3, R1 = 0.023; 2 is monoclinic, C2/m, a = 23.0027(8) Å, b = 8.0983(3) Å, c = 11.9736(4) Å, ß = 90.372(3) °, V = 2230.43(14) Å3, R1 = 0.034; 3 is orthorhombic, Imma, a = 15.2712(12) Å, b = 7.9647(8) Å, c = 12.4607(9) Å, V = 1515.6(2) Å3, R1 = 0.035, 4 is orthorhombic, Imma, a = 15.4148(8) Å, b = 7.9229(4) Å, c = 13.0214(7) Å, V = 1590.30(14) Å3, R1 = 0.020. Their framework crystal structures contain channels up to 11.62 × 10.54 Å filled by various alkali metals.

The Chemistry, Recrystallization and Thermal Expansion of Brannerite from Akchatau, Kazakhstan.

Numerous studies expose the potential of brannerite to become a good matrix, concentrating fission products and actinides. Minerals can complement the data collected from the synthetic materials and offer an advantage of a long-time exposure to radiation. Natural metamict brannerite from Akchatau, Kazakhstan, and its annealed sample were studied by EPMA, Raman spectroscopy, TGA, DSC, XRD and HTXRD. The radioactivity of pristine and annealed samples of brannerite was measured. Brannerite from Akchatau is characterized by the absence of significant amounts of REE and yttrium. The studied brannerite regains its structure at a temperature ~650 °C, revealed by the HTXRD and DSC. HTXRD was also performed on the annealed recrystallized brannerite. The thermal expansion for brannerite has been determined for the first time. The brannerite structure expands anisotropically with temperature increase. All the thermal expansion coefficients are positive except for αß. The decreasing beta parameter indicates a "shear structural deformation". The angle between the 1st axis of the tensor and the crystallographic a axis decreases with the increase of the temperature. The structure expands mostly in the α11 direction, approaching the bisector of the ß angle. Brannerite has a low CTE at room temperature-αv = 16 × 10-6 °C-1, which increases up to 39.4 × 10-6 °C-1 at 1100 °C. In general, the thermal stability of brannerite is comparable to that of the other perspective oxide radioactive waste-immobilizing matrices (e.g., Ln2Zr2O7, CePO4, CaTiO3, CaZrTi2O7). The calculated thermal expansion of brannerite and the understanding of its underlying crystal chemical mechanisms may contribute to the behavior prediction of the material (both metamict and crystalline) at high temperatures.

Chemical Vapor Transport Synthesis of Cu(VO)2(AsO4)2 With Two Distinct Spin-1/2 Magnetic Ions.

A new copper vanadyl arsenate, Cu(VO)2(AsO4)2, was synthesized via the chemical vapor transport method. Cu(VO)2(AsO4)2 adopts an original structure type. It is characterized by layers formed by edge-sharing and corner-sharing V-centered octahedra resulting in a unique topology that was hitherto not reported for vanadates. Single CuO6 octahedra connect vanadate layers into a rigid framework. The thermal expansion of the framework studied by the single-crystal HT X-ray diffraction is reported. The magnetic behavior of Cu(VO)2(AsO4)2 shows an interplay of ferromagnetic V4+-V4+ and antiferromagnetic Cu2+-V4+ interactions that result in a ferrimagnetic long-range order below TC = 66 K.

Exploring new belousovite-related zinc and cadmium alkali sulfate halides: synthesis and structural variability.

Fourteen new belousovite-related compounds, AZn(TO4)X (A = K, Rb, Cs, Tl, NH4; T = S, Se; X = Cl, Br, I) have been prepared via melt and evaporation techniques by reacting AX and ZnTO4 either at high temperatures or in hot aqueous solutions. They adopt the layered structure of the belousovite archetype, and constitute a morphotropic series. The apophyllite-type layers in these structures undergo different corrugations, most pronounced in the case of CsZn(SO4)I. In addition, during the study two species unrelated to belousovite, namely Na4Zn(SO4)2Cl2 and Cs2Cd3(SO4)4, were found with framework crystal structures having different topology and belonging to new structure types.

Multiple dimensionalities in A2M3(SO4)4 (A = Rb, Cs; M = Co, Ni) analogues.

New representatives of the A2M3(SO4)4 (A = Rb and Cs, M = Co, Ni) family were found, inspired by the discovery and characterization of itelmenite, a mineral of composition Na2CuMg2(SO4)4. Four new compounds were obtained by high-temperature solid-state reactions in air. All new compounds were structurally characterized by single-crystal and powder X-ray diffraction. Rb2Ni3(SO4)4 and Rb2Co3(SO4)4 crystallize in the monoclinic space group P21/c, Cs2Ni3(SO4)4 in P21/n whereas Rb2Co3(SO4)4 crystallizes in the orthorhombic space group P212121. In order to determine the temperature of crystallization of the new phases DTA and TG were performed for the mixtures of the precursors. Several synthesis strategies were tested and discussed. The investigation of the reactivity upon heating highlights the stability of the precursors before they collapse, explaining the difficulties to get pure powder samples.

Morphotropism in fumarolic mineral-related anhydrous sulfates: novel representatives in A+2M2+(SO4)2 and A+2M2+2(SO4)3 series.

The discovery of numerous endemic anhydrous sulfate minerals in fumaroles of the Tolbachik volcano (Kamchatka, Russia) has revived interest in the whole family of anhydrous sulfates. Herein is reported the crystal structure of Cs2Cu(SO4)2 which adds important data on the `final' contributor with the largest A+ cation to the A2[Cu(SO4)2] morphotropic series (A = Na, K, Rb, Cs), the `initial' structurally characterized representative of this family being saranchinaite Na2Cu(SO4)2. With increasing ionic radius of the alkali metal cation(s), embedded in the [Cu(SO4)2]2- framework, symmetry-breaking transformations occur. Cs2Cu(SO4)2, which is here designated as the ϵ-phase, has a layered structure. Cs2Co2(SO4)3 is a new representative of another morphotropic series of the orthorhombic A2[M2+2(SO4)3] family, being also the first anhydrous Cs-Co sulfate. Structural relationships in A+2M2+(SO4)2 and A+2M2+2(SO4)3 morphotropic series are discussed in detail.

From (S = 1) Spin Hexamer to Spin Tetradecamer by CuO Interstitials in A2Cu3O(CuO)x(SO4)3 (A = alkali).

(Na,K)2Cu3O(SO4)3 compounds form structural chains of Cu6 hexameric units with nominal S = 1 spins due to the interplay between inner strong antiferromagnetic and ferromagnetic exchanges. We show here that the lattice relaxation after the replacement of alkali by larger Rb and Cs ones is accompanied by the insertion of neutral CuO species into (Rb,Cs)2Cu3O(CuO)x(SO4)3 phases. Structurally, interstitial CuO links the next two Cu6 units in longer Cu14 tetradecameric ones. For A = Cs (x = 0.5), the cationic ordering is perfect inside a double-cell superstructure. Magnetically, the original Cu14 units consist of frustrated fragments of an S = 1/2 spin ladder, with ferromagnetic rung-like but antiferromagnetic leg-like and next-nearest neighbor couplings. It returns S = 1 Cu14 spin clusters, effective around 100 K. Our density functional theory calculations and susceptibility fits also show that at low temperatures they interact in two-dimensional lattices, despite the existence of short inter-Cu-Cu distances between the next two clusters along pseudo-one-dimensional chains.

Expanding the Averievite Family, (MX)Cu5O2(T5+O4)2 (T5+ = P, V; M = K, Rb, Cs, Cu; X = Cl, Br): Synthesis and Single-Crystal X-ray Diffraction Study.

Averievite-type compounds with the general formula (MX)[Cu5O2(TO4)], where M = alkali metal, X = halogen and T = P, V, have been synthesized by crystallization from gases and structurally characterized for six different compositions: 1 (M = Cs; X = Cl; T = P), 2 (M = Cs; X = Cl; T = V), 3 (M = Rb; X = Cl; T = P), 4 (M = K; X = Br; T = P), 5 (M = K; X = Cl; T = P) and 6 (M = Cu; X = Cl; T = V). The crystal structures of the compounds are based upon the same structural unit, the layer consisting of a kagome lattice of Cu2+ ions and are composed from corner-sharing (OCu4) anion-centered tetrahedra. Each tetrahedron shares common corners with three neighboring tetrahedra, forming hexagonal rings, linked into the two-dimensional [O2Cu5]6+ sheets parallel to (001). The layers are interlinked by (T5+O4) tetrahedra (T5+ = V, P) attached to the bases of the oxocentered tetrahedra in a "face-to-face" manner. The resulting electroneutral 3D framework {[O2Cu5](T5+O4)2}0 possesses channels occupied by monovalent metal cations M+ and halide ions X-. The halide ions are located at the centers of the hexagonal rings of the kagome nets, whereas the metal cations are in the interlayer space. There are at least four different structure types of the averievite-type compounds: the P-3m1 archetype, the 2 × 2 × 1 superstructure with the P-3 space group, the monoclinically distorted 1 × 1 × 2 superstructure with the C2/c symmetry and the low-temperature P21/c superstructure with a doubled unit cell relative to the high-temperature archetype. The formation of a particular structure type is controlled by the interplay of the chemical composition and temperature. Changing the chemical composition may lead to modification of the structure type, which opens up the possibility to tune the geometrical parameters of the kagome net of Cu2+ ions.

Li2(Se2O5)(H2O)1.5·CuCl2, a salt-inclusion diselenite structurally based on tetranuclear Li4 complexes.

A new lithium copper diselenite chloride hydrate, Li2Se2O5(H2O)1.5·CuCl2, was prepared from aqueous solution. Its unique 2D structure can be interpreted as Li2Se2O5(H2O)1.5 layers with CuCl2 hosts embedded in the interlayer space, and be considered halfway between the salt-inclusion and host-guest structures. The CuO2Cl4 octahedra form chains similar to those in CuCl2·2H2O, yet water molecules are coordinated exclusively to Li+ while Se2O52- and Cl- bridge Li+ and Cu2+. The complexity of the structure is likely responsible for both very long pre-crystallization time and non-existence of the corresponding bromide analogue. Despite the relatively long CuCu separations, the compound exhibits weak ferromagnetic interactions along the chains of CuO2Cl4 octahedra.

Pb6O5(NO3)2: A Nonlinear Optical Oxynitrate Structurally Based on Lead Oxide Framework.

A high second harmonic generation response is demonstrated by a Pb6O5(NO3)2 lead oxynitrate whose identity was verified upon reinvestigation of the PbO-Pb(NO3)2 system. Its crystal structure exhibits a unique cationic [Pb6O5]2+ framework hosting orientationally ordered NO3- triangles in the channels. Easy preparation and high thermal stability (until ∼500 °C in air) suggest it to be a new promising NLO material.

Cu9O2(VO4)4Cl2, the First Copper Oxychloride Vanadate: Mineralogically Inspired Synthesis and Magnetic Behavior.

A new spin-1/2 frustrated antiferromagnet, Cu9O2(VO4)4Cl2, was synthesized via chemical vapor transport method that emulates mineral formation in volcanic fumaroles. Cu9O2(VO4)4Cl2 is the first copper oxychloride vanadate obtained in the ternary CuO-V2O5-CuCl2 anhydrous system. Copper ions constitute a three-dimensional complex framework with a topological structure novel for synthetic compounds but similar to that in the fumarolic mineral yaroshevskite. All of the oxygen atoms except for the O7 site are strongly bonded in the VO4 tetrahedra. The O7 site belongs to an additional oxygen atom (Oa) being tetrahedrally coordinated by four Cu atoms, thus forming the OCu4 tetrahedra. The structural formula can be represented as Cu3[Cu6O2](VO4)4Cl2 highlighting oxocentered units in the structure. IR spectra reveal several absorption bands at 526, 578, and 601 cm-1 interpreted as a characteristic feature of the OCu4 tetrahedra. Cu9O2(VO4)4Cl2 reveals ferrimagnetic behavior with the Curie temperature TC = 24 K and the uncompensated moment of Mr ∼ 1.9 µB/f.u.

Uranyl Sulfate Nanotubules Templated by N-phenylglycine.

The synthesis, structure, and infrared spectroscopy properties of the new organically templated uranyl sulfate Na(phgH⁺)7[(UO2)6(SO4)10](H2O)3.5 (1), obtained at room temperature by evaporation from aqueous solution, are reported. Its structure contains unique uranyl sulfate [(UO2)6(SO4)10]8- nanotubules templated by protonated N-phenylglycine (C6H5NH2CH2COOH)⁺. Their internal diameter is 1.4 nm. Each of the nanotubules is built from uranyl sulfate rings sharing common SO4 tetrahedra. The template plays an important role in the formation of the complex structure of 1. The aromatic rings are stacked parallel to each other due to the effect of π-π interaction with their side chains extending into the gaps between the nanotubules.

The first lead cobalt phosphite, PbCo2(HPO3)3.

Single crystals of a new lead cobalt phosphite, PbCo2(HPO3)3, have been synthesized using mild hydrothermal techniques and characterized by X-ray diffraction analysis, SQUID magnetic measurements, IR spectroscopy, UV/vis spectroscopy, thermogravimetric analysis, and scanning electron microscopy. PbCo2(HPO3)3 crystallizes in the non-centrosymmetric (NCS) R3m space group, a = 5.3145(15) Å, c = 25.494(7) Å, V = 623.6(4) Å3. The crystal structure of PbCo2(HPO3)3 is based upon 2D heteropolyhedral blocks built up from Co2O9 octahedral dimers and HPO3 pseudo-tetrahedra. Lead cations reside in the interlayer space of the structure. Here, the NCS character results reasonably from the cooperative Pb2+ lone electron pair arrangements, by analogy to the centrosymmetric compound (NH4)2Co2(HPO3)3 with similar but disordered blocks. A local twisting of specific HPO3 groups arises due to unreasonably short HH contacts between two phosphite oxoanions. In terms of the magnetic behavior, the new PbCo2(HPO3)3 phase demonstrates weak antiferromagnetic interactions inside the Co2O9 dimers between cobalt ions as expected from the phosphite µ-O bridges.

Lead Oxychloride Borates Obtained under Extreme Conditions.

[Pb10O4]Pb2(B2O5)Cl12 (1) and [Pb18O12]Pb(BO2OH)2Cl10 (2) were obtained via high-temperature high-pressure experiments. [O12Pb18](12+) and [O4Pb10](12+) oxocentered structural units of different dimensionality are excised from the ideal [OPb] layer in tetragonal α-PbO. 2 is formed with an excess of lead oxide component, and 1 is formed with an excess of borate and halide reagents. The structure of 2 can be visualized as the incorporation of {Pb(10)Cl4(BO2OH)2} clusters into alternating PbO and chloride layers, with the existence of square vacancies in both. However, the structure of 1 is described as the intrusion of [O4Pb10](12+) tetramers linked by disordered Pb(B2O5) groups into a halogen three-dimensional matrix. The structure of 2 contains 10 symmetrically independent Pb positions. The 6s(2) lone electron pair is stereochemically active on Pb(1)-Pb(9) atoms, whereas it is inert on Pb(10). All of the Pb coordinations in the structure of 2, in accordance with ECCv (volume eccentricity) parameters and the density of states (DOS), can be subdivided into three groups. The current study is the first attempt to analyze this unusual behavior in structurally complex oxyhalide material with the rare case of Pb(2+) cations, demonstrating both stereochemically active and inactive behavior of the lone pair via charge and first-principle calculations.

Structural Evolution from 0D Units to 3D Frameworks in Pb Oxyhalides: Unexpected Strongly Corrugated Layers in Pb7O6Br2.

Novel Pb7O6Br2 (1) lead oxybromide was prepared from Pb oxybromide melt by the "rapid quenching" route. Bonding scheme, thermal expansion, and structural properties were studied. The structural features of this unexpectedly complex phase are described on the basis of lone electron pair stereochemical activity and Pb-Br versus Pb-O bonding scheme. The structure of 1 contains a number of cavities, which can be assigned to the self-containments of the lone electron pairs on Pb(2+) cations. "Empty" □Pb4 chains are observed in between of the folding sides of the adjacent strongly corrugated oxocentered [Pb7O6](2+) layers. Highly isotropic thermal expansion of 1 appeared to be unexpected. The possible explanations of such a behavior in 1 are given. The structure of 1 is an interesting example of tetrahedral framework with mixed chemical bonding and is the densest known among Pb oxyhalides with the density of 18.4 tetrahedra/1000 Å(3). Current study shows that oxocentered layers derivatives from α-PbO can be very flexible and form rather dense three-dimensional structural topologies. The properties and structure are compared to other phases crystallizing in the anhydrous PbO-PbX2 (X = F, Cl, Br, I) systems, illustrate the complexity of lead oxyhalides, and reveal new and general pathways for the targeted synthesis of new phases with the Pb-O units of desired dimensionality. The indirect gap value of ∼ 2.04 eV obtained from generalized gradient approximation calculations demonstrates potentially good photocatalytic properties of 1.

Oxocentered Cu(II) lead selenite honeycomb lattices hosting Cu(I)Cl2 groups obtained by chemical vapor transport reactions.

Chemical vapor transport (CVT) reactions were used to prepare three modular mixed-valent Cu(I)-Cu(II) compounds, (Pb2Cu(2+)9O4)(SeO3)4(Cu(+)Cl(2))Cl5 (1), (PbCu(2+)5O2)(SeO3)2(Cu(+)Cl2)Cl3 (2), and (Pb(x)Cu(2+)(6-x)O2)(SeO3)2(Cu(+)Cl2)K(1-x)Cl(4-x) (x = 0.20) (3). In their crystal structures chains of anion-centered (OCu(2+)4) and (OCu(2+)3Pb) tetrahedra form honeycomb-like double layers with cavities occupied by linear [Cu(+)Cl2](-) groups.

pH controlled pathway and systematic hydrothermal phase diagram for elaboration of synthetic lead nickel selenites.

The PbO-NiO-SeO2 ternary system was fully studied using constant hydrothermal conditions at 473 K. It yields the establishment of the corresponding phase diagram using a systematic assignment of reaction products by both powder and single-crystal X-ray diffraction. It leads to the preparation of three novel lead nickel selenites, α-PbNi(SeO3)2 (I), ß-PbNi(SeO3)2 (II), and PbNi2(SeO2OH)2(SeO3)2 (III), and one novel lead cobalt selenite, α-PbCo(SeO3)2 (IV), which have been structurally characterized. The crystal structures of the α-forms I, IV, and III are based on a 3D complex nickel selenite frameworks, whereas the ß-PbNi(SeO3)2 modification (II) consists of nickel selenite sheets stacked in a noncentrosymmetric structure, second-harmonic generation active. The pH value of the starting solution was shown to play an essential role in the reactive processes. Magnetic measurements of I, III, and IV are discussed.

Synthesis and modular structural architectures of mineralogically inspired novel complex Pb oxyhalides.

Three novel Pb oxyhalides, Pb3[O10Pb20](GeO4)4Cl10 (1), [O16Pb22][OPb](OH)I10(I,Br)(H2O) (2), and Pb5.5Si0.5O6Cl (3), have been prepared by high-temperature solid-state reactions (1 and 3) and hydrothermal method (2). The structure of 1 is based upon novel [O10Pb20](20+) layers of edge- and corner-sharing oxocentered OPb4 tetrahedra with cavities occupied by the GeO4 tetrahedral anions. The interlayer space contains low-occupied Pb sites and Cl(-) anions. The structure of 2 contains unique [O16Pb22][12+] layers of edge-sharing OPb4 tetrahedra with X(-) ions (X = I, Br) in and in between the layers. The structure of 3 is the first example of the Pb oxyhalide with the 3:1 ratio between the O-Pb and X sheets (X = halide). The unprecedented structure topologies and architectures observed in the title compounds are closely related to those observed in rare natural Pb oxyhalides that have no synthetic analogues to date.