Independent Cations Research Articles

Li4Ba[BN2]2 – Structure and Vibrational Spectra

The nitridoborate Li4Ba[BN2]2 was synthesized from a 4:1 molar ratio of Li3[BN]2 and Ba3[BN2]2 in an arc‐welded niobium ampoule at a maximum annealing temperature of 1173 K. The structure was refined from single‐crystal X‐ray diffractometer data: new type, P1, a = 533.9(2), b = 585.0(3), c = 860.6(4) pm, α = 80.72(3), β = 73.84(6), γ = 89.87(4)°, wR2 = 0.1196, 1429 F2 values, 50 variables. The Li4Ba[BN2]2 structure contains two crystallographically independent [BN2]3– units with 134 pm B–N distance, which are slightly bent: 178° for N2–B1–N1 and 175° for N4–B2–N3. Due to the high lithium content both [BN2]3– units have a strongly distorted coordination by 8Li+ + 3Ba2+. The four crystallographically independent lithium cations show distorted tetrahedral coordination by [BN2]3– units with Li–N distances ranging from 195 to 247 pm. IR and Raman spectra show the typical vibrations of the [BN2] unit along with a well‐resolved splitting of the ν(10Β) and ν(11B) frequencies.

Zero- and mono-coordinate transition metals in crystal structures: A box full of surprises

In crystal structural databases one finds here and there structures in which a transition metal atom is encoded as mono- or zero-coordinated, a situation that one might expect only in the gas phase, but not in solution or in the solid state. In some instances such an assignment is unavoidable due, e.g., to the presence of disorder in the metal coordination sphere that makes the determination of a coordination number impossible. In other cases, the lack of attribution of a coordination number (in practice encoded as zero-coordination) may result from the complexity of the crystal structure, or from the consideration of the transition metal atom as an independent cation, as usually done for highly ionic species such as the alkaline and alkaline-earth metal compounds. Here, a closer structural analysis is carried out on such low-coordinated metals, and some interesting geometrical and bonding features are found, such as the first chemical structure recognized to have the shape of the elongated square cupola, a 20 vertices Johnson polyhedron.

Tricaesium citrate monohydrate, Cs3C6H5O7·H2O: crystal structure and DFT comparison.

The crystal structure of tricaesium citrate monohydrate, 3Cs+·C6H5O73-·H2O, has been solved and refined using laboratory X-ray single-crystal diffraction data, and optimized using density functional techniques. This compound is isostructural to the K+ and Rb+ compounds with the same formula. The three independent Cs cations are eight-, eight-, and seven-coordinate, with bond-valence sums of 0.91, 1.22, and 1.12 valence units. The coordination polyhedra link into a three-dimensional framework. The hy-droxy group forms the usual S(5) hydrogen bond with the central carboxyl-ate group, and the water mol-ecule acts as a donor in two strong hydrogen bonds.

Gradual Thermal Spin-Crossover Mediated by a Reentrant Z' = 1 → Z' = 6 → Z' = 1 Phase Transition.

The Fe[BF4]2 complex of the Schiff base podand tris[4-(thiazol-4-yl)-3-aza-3-butenyl]amine exhibits gradual thermal spin-crossover with T1/2 ≈ 208 K in the solid state. A weak discontinuity in the magnetic susceptibility curve at 190 K is associated with a reentrant symmetry-breaking transition involving a trebling of the unit cell volume (from P21/c, Z = 4, to P21, Z = 12). The intermediate phase contains six independent cations in puckered layers of low-spin, and high-spin or mixed-spin, molecules with an overall 30% high-spin population at 175 K.

Crystal structure of trirubidium citrate monohydrate from laboratory X-ray powder diffraction data and DFT comparison.

The crystal structure of the title compound, 3Rb+·C6H5O73-·H2O, has been solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. The hy-droxy group participates in an intra-molecular hydrogen bond to the deprotonated central carboxyl-ate group with graph-set motif S(5). The water mol-ecule acts as a hydrogen-bond donor to both terminal and central carboxyl-ate O atoms. The three independent rubidium cations are seven-, six- and six-coordinate, with bond-valence sums of 0.84, 1.02, and 0.95, respectively. In the extended structure, their polyhedra share edges and corners to form a three-dimensional network. The hydro-phobic methyl-ene groups occupy channels along the b axis.

A three-dimensional ZnII coordination polymer constructed from 1,1'-biphenyl-2,2',4,4'-tetracarboxylate and 1,4-bis(1H-imidazol-1-yl)benzene ligands exhibiting photoluminescence.

Ligands based on polycarboxylic acids are excellent building blocks for the construction of coordination polymers; they may bind to a variety of metal ions and form clusters, as well as extended chain or network structures. Among these building blocks, biphenyltetracarboxylic acids (H4bpta) with C2 symmetry have recently attracted attention because of their variable bridging and multidentate chelating modes. The new luminescent three-dimensional coordination polymer poly[(μ5-1,1'-biphenyl-2,2',4,4'-tetracarboxylato)bis[μ2-1,4-bis(1H-imidazol-1-yl)benzene]dizinc(II)], [Zn2(C16H6O8)(C12H10N4)]n, was synthesized solvothermally and characterized by single-crystal X-ray diffraction, elemental analysis and IR spectroscopy. The crystal structure contains two crystallographically independent ZnII cations. Both metal cations are located on twofold axes and display distorted tetrahedral coordination geometries. Neighbouring ZnII centres are bridged by carboxylate groups in the syn-anti mode to form one-dimensional chains. Adjacent chains are linked through 1,1'-biphenyl-2,2',4,4'-tetracarboxylate and 1,4-bis(1H-imidazol-1-yl)benzene ligands to form a three-dimensional network. In the solid state, the compound exhibits blue photoluminescence and represents a promising candidate for a thermally stable and solvent-resistant blue fluorescent material.

Синтез и строение комплекса родия [trans-Na∙18-crown-6∙(dmso-O)2]+ [trans-RhBr4(dmso-S)2

Шарутин Владимир Викторович – доктор химических наук, профессор, старший научный сотрудник УНИД, Южно-Уральский государственный университет. 454080, г. Челябинск, пр. им. В.И. Ленина, 76. E-mail: vvsharutin@rambler.ru. Шарутина Ольга Константиновна – доктор химических наук, профессор, кафедра теоретической и прикладной химии, Южно-Уральский государственный университет. 454080, г. Челябинск, пр. им. В.И. Ленина, 76. E-mail: sharutinao@mail.ru. Сенчурин Владислав Станиславович – кандидат химических наук, доцент, кафедра теоретической и прикладной химии, Южно-Уральский государственный университет. 454080, г. Челябинск, пр. им. В.И. Ленина, 76. E-mail: senvl@rambler.ru Сонникова Екатерина Сергеевна – студент, химический факультет, Южно-Уральский государственный университет. 454080, г. Челябинск, пр. им. В.И. Ленина, 76. E-mail: katerina_sonnikova@mail.ru V.V. Sharutin, vvsharutin@rambler.ru O.K. Sharutina, sharutinao@mail.ru V.S. Senchurin, senvl@rambler.ru E.S. Sonnikova, katerina_sonnikova@mail.ru South Ural State University, Chelyabinsk, Russian Federation

Crystal structure, Hirshfeld surface and spectroscopic studies of the noncentrosymmetric Bi(III) halide complex: [C8H12N]3BiCl6

A new organic–inorganic hybrid material with the formula [C8H12N]3BiCl6 has been synthesized and characterized by spectroscopic techniques and single crystal X-ray structure determination. This compound crystallizes in the non-centrosymmetric space group Pna21 of the orthorhombic system with crystallographic parameters a=25.5620(2), b=16.7170(5), c=7.8840(4)Å, V=3369.0(2)Å3 and Z=4. Its structure consists of discrete [BiCl6]3− anions, showing the distorted octahedral geometry, surrounded by three crystallographically independent 2-phenylethylammonium cations. The crystal packing is governed by the formation of a number of N–H⋯Cl hydrogen bonds arranged in a three-dimensional network. Crystal structure analysis supported with the Hirshfeld surface and fingerprint plots enabled the identification of the significant intermolecular interactions. The 13C and 15N CP-MAS NMR spectra are in agreement with the X-ray structure. The optical properties of [C8H12N]3BiCl6 were investigated by UV–Vis and luminescence spectroscopy. The differential scanning calorimetry (DSC) revealed that the title compound is stable up to 210°C.

Si44– in Solution – First Solvate Crystal Structure of the Ligand‐free Tetrasilicide Tetraanion in Rb1.2K2.8Si4·7NH3

We report the first solvate structure of the silicide anion Si44–, which provides circumstantial evidence of the stability of the highly charged anion in liquid ammonia solutions. The solvate Rb1.2K2.8Si4·7NH3 crystallized from a mixture of the ternary compound K6Rb6Si17 with the transition metal complex [(C6H5)3P]2Ni(CO)2 [bis(triphenylphosphine)dicarbonylnickel] in the presence of the chelating agents 18‐crown‐6 (1,4,7,10,13,16‐hexaoxacyclooctadecane) and [2.2.2]cryptand (4,7,13,16,21,24‐hexaoxa‐1,10‐diazabicyclo[8.8.8]hexacosane) in liquid ammonia. Single X‐ray diffraction analysis confirms the presence of the Si44– anion in the crystal structure of Rb1.2K2.8Si4·7NH3, which represents the first solvate compound of the naked tetrasilicide tetraanion. All five crystallographically independent cation positions show mixed occupancy by Rb+ and K+.

Crystal structure, Raman spectroscopy and crystal chemistry of K7Ca9[Si2O7]4F, a new potassium-calcium silicate-fluoride

In the course of a series of KF-flux synthesis experiments aiming at the preparation of new compounds in the ternary system K 2 O–CaO–SiO 2 , of interest to e.g . the glass and fertiliser industries and to recycling of ashes of biomass combustion, a novel potassium-calcium silicate-fluoride was obtained whose composition was determined as K 7 Ca 9 [Si 2 O 7 ] 4 F using electron-microprobe analysis. Polycrystalline material of the same compound could be also prepared by solid-state reactions. Applying direct methods it was possible to solve the crystal structure of this compound from single-crystal diffraction data. Structure solution was complicated due to complex pseudo-merohedral twinning. K 7 Ca 9 [Si 2 O 7 ] 4 F crystallises in the monoclinic space group P 2 1 / m , with a = 5.6122(2) A, b = 13.8143(5) A, c = 9.8016(4) A, β = 90.255(4)°, V = 759.90(5) A 3 , Z = 1. Additional characterisation has been performed by Raman spectroscopy. The compound belongs to the group of sorosilicates and is built up from Si 2 O 7 groups. Potassium and calcium cations are distributed among five crystallographically independent cation positions, which are coordinated in form of distorted octahedra, trigonal prisms or more irregular polyhedra. By sharing common faces, octahedra and trigonal prisms form infinite columns running parallel to [010]. These columns are connected to the Si 2 O 7 groups through common corners. Additional fluorine positions are located in voids between the Si 2 O 7 groups and the columns. A detailed comparison with structurally related compounds is given, including a group-theoretical discussion of the symmetry relationships.

Structures of new triple phosphates Ca9CoМ(PO4)7 (M - Li, Na, K).

New triple phosphates Ca9CoM(PO4)7 (M=Li, Na, K) were synthesized by solid state method. Their crystal structures were determined by Rietveld analysis. They are related to tricalcium phosphate and crystallize into trigonal system (space group R3c) with unit-cell parameters a=10.327(1) Å, с=37.10(1) Å, M=Li; a=10.351(1) Å, с=37.073(1) Å, M =Na; a=10.401(1) Å, с=37.009(1) Å, M=K. Five independent cation sites are filled in Ca9CoM(PO4)7 (M=Li, Na, K). Cobalt occupies the octahedral site M(5), alkali metal cations occupy the M(4).

Progress in SO<sub>2</sub> capture by ionic liquids

Minimizing the emissions of SO2 is highly important, because it is a significant source of atmospheric pollution that threatens environment and human health. SO2 can be absorbed by ionic liquids (ILs) due to their unique properties, such as ultra low vapor pressure, wide liquid temperature range, non-flammability, chemical stability, and tunable structure and properties. As a new sorption technology, ILs with useful functional groups are attracting the attention of a growing number of scientists and engineers in recent years. In this article, the recent advances on the studies of ILs in the capture of SO2 were reviewed, where traditional ILs and functionalized ILs were included. Traditional ILs with the anions such as BF4 - , PF6 - , Tf2N - , F - , Cl - , Br - and I - could uptake SO2 at ambient temperature and pressure through physical interaction between IL and SO2, but they could not be used under industrial conditions because of the weak interactions. Industrial condition means high temperature and low SO2 partial pressure, which needs strong interaction between IL and SO2. Functional ILs, including organic acid salt ILs, phenolate ILs, azolate ILs, ether-based ILs, amine-based ILs and multi-functional ILs, showed highly efficient SO2 absorption under ambient conditions. 1,1,3,3-Tetramethylguanidine lactate ([TMG][L]) was the first functional IL used to achieve about equal mole SO2 capacity under 40°C and 8% SO2 through chemical interaction. [SCN]-based ILs were proved to be highly efficient and reversible ILs for SO2 capture under low partial pressure by the single-site interaction mechanism. Although ether-based ILs could achieve much higher SO2 capacity due to their multiple ether groups, they could not be used to capture SO2 under industrial conditions because of the weak physical interaction. Among the functional ILs investigated, novel azolate ILs were found to have the two mole of chemical absorption capacity through two-site cooperative interactions under low partial pressure. Very recently, other kinds of multiple-site based ILs were developed, including sites on the independent cation and anion as well as those on the same anion. [Et2NEmim][Tetz] was found to be a kind of multi-functional IL that could absorb two mole of SO2 under low partial pressure through independent anion···SO2 and amine···SO2 interactions. Among the above mentioned functional ILs, the ILs based on [Tetz] and [SCN] anions were proved to be more efficient and highly reversible for the capture of SO2 under low SO2 partial pressure. The perspective for further researches on the design of functionalized ILs was also provided. Finally, some challenges in the absorption of SO2 from flue gas were indicated, which includes the high cost of ILs, the deep mechanism study of SO2 absorption, the investigations under high temperature and low SO2 partial pressure, as well as the effect of other species (such as CO2, NO x , O2, dust, and moisture) in flue gas. The development of alternative ILs that are able to achieve rapid and reversible SO2 capture in high capacity is always highly desired.

Study of the Effect of Electrolyte Concentration on Li-Air Battery Performance

Rechargeable Li-air (Li-O2) batteries have recently attracted enormous attention due to their prospective high energy density. To realize reversible and stable operation of Li-air batteries, however, many serious problems, such as volatilization of electrolyte, high charge overpotential and electrolyte decomposition by O2 - radical, have to be solved [1]. We previously reported that equimolar mixtures of glymes and Li salts behave as ionic liquids (ILs) rather than as ordinary concentrated electrolyte solutions [2]. For instance, triglyme (G3) can coordinate to a Li+ ion, forming a 1:1 solvate cation of [Li(G3)]+, which behaves as an independent cation similar to the cation of typical ionic liquids. Thus, the glyme-Li salt complex has been categorized as a new subclass of ionic liquids called “solvate ILs” [3]. Solvate ILs show negligible volatility and high oxidative stability which are important for stable operation of the Li-air battery system [4]. The concentration of Li salt in glyme-Li salt solvate ionic liquids are extremely high ~ 3 mol dm−3. In this extremely concentrated electrolyte, almost all the solvents (glyme) coordinate to Li+ cation and almost no free (uncoordinated) solvent exists, which is an unique nature of the “concentrated electrolyte” [5]. These days, highly concentrated electrolytes, including solvate ionic liquids, have been attracted much attention owing to their unique properties [6]. In this study, we investigated the relationship between solubility of the intermediate and reversibility of Li-air battery performance as a function of Li+ concentration by RRDE method. Although it has been already reported that solubility of the intermediate depends on donor number of the solvent species and affects morphology of the discharge compounds [7], our results revealed that high Li+ concentration suppresses the intermediate solubility even in high donor number solvents such as DMSO (Figure). This low intermediate solubility originates from the absence of free solvent molecules. For the dissolution of LiO2, LiO2 should be solvated. The absence of free solvent in the highly concentrated electrolytes results in insolubility of LiO2. Interestingly, reversibility of the disk electrode reaction in highly intermediate soluble electrolyte (0.1 mol dm-3 Li[TFSA]/DMSO) is much lower than that of the intermediate insoluble electrolyte (3 mol dm-3 Li[TFSA]/DMSO) (Figure) because of dissolution of the intermediate species into the electrolyte solution. Further discussion such as relationship between solubility of LiO2 and battery performance will also be discussed. Acknowledgement This study was partly supported by RISING program from the New Energy and Industrial Technology Development Organization (NEDO) of Japan.

Structural, Hirshfeld surface and spectroscopic studies of the noncentrosymmetric 1-ethylpiperazinediium pentachloroantimonate (III) monohydrate

1-Ethylpiperazinediium pentachloroantimonate (III) monohydrate, C6H16N2SbCl5·H2O, has been synthesized by the reaction of antimony trioxide (Sb2O3) and 1-ethylpiperazine in an aqueous solution of hydrochloric acid. The structure crystallizes in orthorhombic system, in the non-centrosymmetric space group Pca21 and consists of isolated [C6H16N2]2+ cations, square pyramidal [SbCl5]2− anions and lattice water molecules. OH⋯Cl hydrogen bonds link the [SbCl5]2− anions and water molecules to form double chains stretching along the [101] direction. The chains in turn are linked to the organic cations via NH⋯Cl, CH⋯Cl, CH⋯O and NH⋯O hydrogen bonds to form a three-dimensional network. This structure presents an example of a general square pyramidal complex ion containing a stereo-chemically active lone pair of electrons. Solid state 13C and 15N CP-MAS NMR spectra are in agreement with the X-ray structure, and vibrational absorption bands were identified by infrared spectroscopy. DFT calculations allowed the attribution of the NMR peaks and IR absorption bands. The interactions variability of the two independent cations and ten chloride atoms is analyzed via Hirshfeld surface analysis.

Solvent Activity in Highly Concentrated Electrolyte and Reversible Li Intercalation into Graphite Electrode

We reported that the equimolar mixtures of glymes and Li salts behave like ionic liquids.[1] As shown in Figure 1, triglyme (G3) can coordinate to a Li+, forming a 1:1 solvate cation of [Li(G3)]+, which acts as an independent cation. Therefore, the glyme-Li salt complexes have been categorized as “solvate” ionic liquids consisting of the solvate cations and the counter anions.[2] The concentration of Li salt in glyme-Li salt solvate ionic liquids are extremely high ~ 3 mol dm−3. In this extremely concentrated electrolyte, almost all the solvents (glyme) coordinate to Li+ cation and almost no free (uncoordinated) solvent exists, which is an unique nature of the concentrated electrolyte.[3] In this study, we estimated the activity of free solvent species in concentrated electrolyte by measuring the electrode potential of Li/Li+. As shown in Figure 2, the electrode potential in the G3-Li[TFSA] mixtures increase drastically in the highly concentrated region (> 1 mol dm-3). To interpret this remarkable increment of the potential, we assumed equilibrium reaction of Li/Li+ as following, which takes the solvation/de-solvation processes into account: [Li(G3)1]+ + e- = Li + G3. Nernst equation of above reaction can be written as: E = E0 + 2.303RT/F log a [Li(G3)]/a G3. In this equation, the term of logarithm diverges infinitely if activity of free G3 is zero. The remarkably high electrode potential in the concentrated electrolyte proved that the amount of free glyme approaches zero at high concentrations > 3 mol dm−3. The amount of free solvents was also evaluated using Raman spectroscopy and will also be reported. It is well known that ethylene carbonate is compatible with graphite anode because a good SEI layer, which prevents the cointercalation of solvents into the graphite, is formed. In contrast, the cointercalation of solvents with Li+ into graphite takes place in other common solvents such as propylene carbonate (PC) and ethers, causing destruction of the graphite crystalline structure. However, it was reported that cointercalation of these solvents, namely, PC, dimethoxy ethane, and other solvents into graphite anode can be inhibited by increasing the Li salt concentration and intercalation of Li+ into graphite anode occurs reversibly.[4] We also observed the reversible Li+ intercalation/de-intercalation reaction in extremely concentrated G3-Li[TFSA] solution, although the cointercalation takes place in the solution containing excess G3 (Figure 3).[5] The electrode potential for the formation of Li+ intercalated graphite (including desolvation process of [Li(G3)]+) is expected to increase greatly against the Li salt concentration as well as the aforementioned potential of Li/Li+, because the potential depends on the activity of not only solvate cation but also free solvent. On the other hand, the electrode potential for cointercalation depends on only the activity of solvate cation, since the reaction does not include desolvation process. Thus, in the highly concentrated region, the activity of free solvent is very small, and the electrode potential for Li-intercalated graphite formation is higher than that for cointercalation, leading to the suppression of cointercalation. In this study, it was revealed that the activity of the solvent in an electrolyte should be a key factor in controlling electrochemical reaction. Detail discussion of the relationship between the activity of free solvent and electrochemical reaction will be reported. Acknowledgement This study was supported in part by the ALCA program of the Japan Science and Technology Agency, and by the Technology Research Grant Program of NEDO, for which the authors are grateful.

Crystal structure of [tris-(pyridin-2-ylmeth-yl)amine-κ(4) N]copper(II) bromide.

In the asymmetric unit of the title compound, [CuBr(C18H18N4)]Br, there are three crystallographically independent cations. One of the cations exhibits positional disorder of the pyridin-2-yl-methyl groups over two sets of sites with refined occupancies of 0.672 (8) and 0.328 (8). The outer-sphere bromine counter-ion is severely disordered over multiple sites. In each cation, the Cu(II) ion is coordinated by the four N atoms of the tris-(pyridin-2-ylmeth-yl)amine ligand and one bromine and adopts a slightly distorted trigonal-bipyramidal geometry.

Complexes of Eu(III), Tb(III) and Cu(II) with proton transfer compound between 2,6-pyridinedicarboxylic acid and 2-aminobenzothiazole: characterization of the structures and physical properties

A proton transfer compound, (ABTH)+(PydcH)− (1), obtained from 2-aminobenzothiazole (ABT) and 2,6-pyridinedicarboxylic acid (Pydc) as well as its Eu(III), Tb(III), and Cu(II) complexes (ABT)3[Eu(Pydc)3]·5H2O (2), (ABT)3[Tb(Pydc)3]·5H2O (3), and (ABT)[Cu(Pydc)(PydcH)]·3H2O (4) were obtained under ambient conditions and structurally verified by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, powder X-ray diffraction (PXRD), infrared spectroscopy (IR), thermogravimetric analysis (TGA), and magnetic measurements. Compounds 2–4 are the first known solids containing complex anions with Pydc ligands, 2-aminobenzothiazole cations (ABT), and solvate water molecules. During the synthesis of 3, a secondary phase with the formula ABTCl∙H2O was obtained and characterized by elemental analysis and single-crystal X-ray diffraction. The asymmetric unit of 5 consists of six symmetry independent ABT cations, six chlorides, and six water molecules. The two lanthanide complexes showed characteristic emissions of Eu3+ and Tb3+ ions. The good solubilities of these complexes in water and their luminescence properties make them attractive luminescent labels of biological molecules.

Crystal structure of 3-benzamido-1-(4-nitro-benz-yl)quinolinium tri-fluoro-methane-sulfonate.

In the title compound, C23H18N3O3 (+)·CF3SO3 (-), the asymmetric unit contains two crystallographically independent organic cations with similar conformations. Each cation shows a moderate distortion between the planes of the amide groups and the quinolinium rings with dihedral angles of 14.90 (2) and 31.66 (2)°. The quinolinium and phenyl rings are slightly twisted with respect to each other at dihedral angles of 6.99 (4) and 8.54 (4)°. The tri-fluoro-methane-sulfonate anions are linked to the organic cations via N-H⋯O hydrogen-bonding inter-actions involving the NH amide groups. In the crystal, the organic cations are linked by weak C-H⋯O(nitro group) inter-actions into supramol-ecular chains propagating along the b-axis direction.

Polysomatism and structural complexity: structure model for murataite-8C, a complex crystalline matrix for the immobilization of high-level radioactive waste

Murataite-8 C , a prospective synthetic material for the long-term immobilization of high-level radioactive waste and a member of the pyrochlore–murataite polysomatic series, was investigated by means of single-crystal X-ray diffraction. The crystal structure (cubic, F -43 m , a = 39.105(12) A, V = 59799(32) A3, Z = 4) is of outstanding complexity and contains forty symmetrically independent cation sites. Its crystal-chemical formula determined on the basis of the crystal-structure refinement, Al25.44Ca55.96Ti282.20Mn53.72Fe17.24Zr15.00Ho36.64O823, is in good agreement with the empirical formula calculated from electron-microprobe data, Al23.02Ca52.85Ti284.10Mn54.31Fe17.59Zr14.83Ho38.04O823. The crystal structure is based upon a three-dimensional octahedral framework that can be described as an alternation of murataite and pyrochlore modules immersed into a transitional substructure that combine elements of the crystal structures of murataite-3 C and pyrochlore. The obtained structural model confirms the polysomatic nature of the pyrochlore–murataite series and illuminates the chemical and structural peculiarities of crystallization of the murataite-type titanate ceramic matrices. The high chemical and structural complexity of the members of the pyrochlore–murataite series is unparalleled in the world of crystalline materials proposed for the high-level radioactive waste immobilization, which makes it unique and promising for further technological and scientific exploration.

Glide planes symmetry in the organization of some sulfide structures

The role of glide planes in the organization of structures is shown based on a crystallographic analysis of the monoclinic structures of TlAs3S5 and Tl2(As,Sb)3S13 sulfides. In the first structure, cations and anions form systems (with identical geometries) of two face-centered sublattices, linked by the c plane, with the effect of unified “two-dimensional” (2D) ordering. The second structure, exhibiting signs of order–disorder (OD) type, is interpreted as a superposition of two noncentrosymmetric components with independent cation and anion sublattices, which, however, also form a regular 2D order due to the n plane. The stabilizing role of Tl cations in the geometry of cation matrices is indicated.