Refinement of the structure and composition of the layered pyrochlore-like oxide Cs6+x W11O36

The symmetry, composition, and crystal structure of Cs_6.3W₁₁O₃₆ (a=7.2742, c=110.79 Å, Z=6, $R\bar 3c$ , R=0.057), previously considered monoclinic and stoichiometric, are refined. The tungsten-oxygen octahedral units of the structure, which have an AB₂O₆ defective pyrochlore motif, lie in layers perpendicular to the c axis, with Cs⁺ ions located in the voids of layer units and between them. An additional interlayer position of cesium, occupied by 31(8)%, has been found. The structures of Cs_8.5W₁₁O₄₈ and defective pyrochlore, related to Cs_6+xW₁₁O₃₆, form a homologous series with the general formula A_2nA^′ _1?yM_4n?1X_12n (for the above members, n=3,4 and ∞, respectively); the members in the series differ in the number of storeys in pyrochlore-like layers.     

Crystal structure and some thermodynamic characteristics of cesium silicate Cs6Si10O23

Crystals of cesium silicate Cs₆Si₁₀O₂₃ were prepared upon the crystallization of glass Cs₂O · 4SiO₂. The crystal structure of Cs₆Si₁₀O₂₃ was determined by single-crystal X-ray diffraction (space group P $\bar 6$ 2m, a = 9.578(5) Å, c = 4.155(5) Å, Z = 0.5, 269 F(hkl), R = 0.0424). The three-dimensional tetrahedral silicate framework in Cs₆Si₁₀O₂₃ is similar to that in Rb₆Si₁₀O₂₃ (space group P $\bar 6$ 2m, a = 9.475(5) Å, c = 8.200(5) Å) in which layers formed by 12-membered rings of silicon-oxygen tetrahedra may be distinguished. However, while in the rubidium silicate structure the vertices of the tetrahedra neighboring in a layer point to opposite directions, in cesium silicate these tetrahedra are disordered as regards the arrangement of vertices either upward or downward relative to the layer plane. The random disorder results in a smaller unit cell parameter c in Cs₆Si₁₀O₂₃ compared to Rb₆Si₁₀O₂₃. The compound melts congruently; the melting temperature and the enthalpy of melting of the crystal are 1208 ± 1 K and 156.2 ± 15 kJ/mol, respectively.     

C(methyl)–H ⋅ ⋅ ⋅ π(aryl) Interaction Stabilizing Molecular Conformation. X-Ray Crystal Structure of an Inclusion Compound of a Nonprotic Host with Nitromethane Guest

In the cocrystal formation of a nonprotic polar (host) molecule (1) with nitromethane (guest) several weak, but directional, intermolecular interactions have vital importance. The endo conformation of the (N)-xylene group of the polycyclic succinimide-based host 1 is stabilized by a C_methyl $---$ H ??? π interaction [C ??? π /H ??? π distances are 3.554(7)/2.57 Å, the C $---$ H ??? π angle is 159^○], and the crystal packing is governed by dipole–dipole type interhost (C $ =$ )O ??? C( $ =$ O) connection [C ??? O $ =$ 3.000(5) Å and <C $ =$ O ??? C $ =$ 159.8(3)^○] in conjunction with possible C $---$ H ??? O interactions [with C ??? O distances ranging between 3.20 and 3.50 Å] involving the polar groups of both host and guest. Crystal data: 1 ??? nitromethane (1:1), C₂₆H₂₁O₂ N ? CH₃NO₂, M _w = 440.50, P2 ₁/n, a = 14.143(1), b = 7.973(1), c = 20.291(2) Å, β = 95.183(9)^○, Z = 4, D _c = 1.2840(2) g cm^?3, R = 0.055 for 1709 reflections.     

X-ray diffraction investigation of siloxanes. I. Effects of organic substituents at the silicon atoms on the structure of acyclic trisiloxane-1,5-diols and on formation of different hydrogen bond systems

The molecular and crystal structure of four acyclic trisiloxane compounds, which differ in substituents at the silicon atoms (Ph-phenyl, mPh-methoxyphenyl, 2mPh-dimethoxyphenyl), was investigated by X-ray diffraction analysis. Due to intermolecular hydrogen bonding between the oxygen atoms of the diol fragments, the crystal structure of 1,1,5,5-tetramethyl-3,3-diphenyl-1,3,5-trisiloxane-1,5-diol (C₁₆H₂₄O₄Si₃) (I) is a double chain architecture with hydrogen-bonded dimeric motifs of C(8)R ₄ ⁴ (12) type in graph set representation. In 1,1,5,5-tetramethyl-3,3-(2-methoxybenzo)-1,3,5-trisiloxane-1,5-diol (C₁₈H₂₈O₆Si₃) (II) and 1,1,5,5-tetramethyl-3,3-(2,6-dimethoxybenzo)-1,3,5-trisiloxane-1,5-diol (C₂₀H₃₂O₈Si₃) (III), a double chain structure with a graph set R ₃ ³ (8)D ₃ ³ (10) is formed. In contrast to I–III, 1,1,3,3,5,5-hexaphenyl-1,3,5-trisiloxane-1,5-diol (C₃₆H₃₂O₄Si₃) (IV) has an intramolecular hydrogen bond S(8). The independent molecules are joined by O-H...O intermolecular hydrogen bonds into centrosymmetrical dimers; the system of hydrogen bonds in general may be described as S(8)R ₄ ⁴ (8).     

High-temperature X-ray diffraction studies of compounds in the M 2 I O-Ga2O3-TiO2 system

Compounds that are formed in the M ₂ ^I O-Ga₂O₃-TiO₂ system and crystallize in three structural types were prepared by solid-phase reactions. The M ₂ ^I Ga₂Ti₆O₁₆ (M^I = Na, K, Rb, Cs) compounds were prepared for the first time. The thermal expansion coefficients of LiGaTiO₄, Na₂Ga₂Ti₆O₁₆, K₂Ga₂Ti₆O₁₆, Rb₂Ga₂Ti₆O₁₆, and Cs₂Ga₂Ti₆O₁₆ were determined by high-temperature X-ray diffraction. Some tendencies of thermal distortions in M ₂ ^I A ₂ ^III Ti₆O₁₆ and LiA^IIITiO₄ (M^I = Na, K, Rb, Cs; A^III = Al, Cr, Fe, Ga) were disclosed.     

Crystal structure of (C2H7N4O)2[(UO2)2)(OH)2(C2O4)(CHO2)2]

An X-ray diffraction study of the single crystals of (C₂H₇N₄O)₂[(UO₂)₂(OH)₂(C₂O₄)(CHO₂)₂] was carried out. The compound crystallizes in the triclinic system, space group $P\bar 1$ , Z = 2, a = 5.5621(8) Å, b = 8.1489(10) Å, c = 11.8757(16) Å, α = 88.866(7)°, β = 82.204(6)°, γ = 87.378(6)°, V = 532.7(1) ų, ρ_calcd = 2.988 g/cm³. The main structural units in the crystal are the [(UO₂)₂(OH)₂(C₂O₄)(CHO₂)₂)]^2? chains corresponding to the crystal chemical group A₂M ₂ ² K⁰²M ₂ ¹ (A = UO ₂ ²⁺ , M² = OH^?, K⁰² = C₂O ₄ ^2? , M¹ = CHO ₂ ^? ) of uranyl complexes. The chains are united into a three-dimensional framework through the electrostatic interaction and hydrogen bonds involving uranyl, oxalate, and hydroxyl groups, formate ions, and 1-carbamoylguanidinium cations.     

Synthesis and crystal structure of dibenzo-18-crown-6 oxonium perchlorate trihydrate

A hydrated crystalline ionized adduct of dibenzo-18-crown-6 and perchloric acid DB18C6 · H₃O⁺ · CiO ₄ ^? · 3H₂O (I) is synthesized and characterized by X-ray diffraction. The crystals of I are monoclinic: a = 17.760 Å, b = 12.922 Å, β = 124.27°, Z = 4, space group Cc. The structure of I is solved by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.079 for 3294 independent reflections (CAD4 automated diffractometer, λMoK _α radiation). A DB18C6 molecule has a butterfly conformation with the rough symmetry C _2v . An H₃O⁺ · H₂O dimer is situated on one side of the DB18C6 macrocycle, and the ClO ₄ ^? anion and two other water molecules are on the other side. In the crystal of I, the DB18C6 molecules, H₃O⁺ and ClO ₄ ^? ions, and water molecules are linked through intermolecular (interionic) hydrogen bonds to form broad infinite chains running along the z axis.     

Synthesis and crystal structure of the complex N,N-dimethylanilinium dicitratoborate monohydrate

N,N-Dimethylanilinium dicitratoborate monohydrate [C₆H₅NH(CH₃)₂][(C₆H₆O₇)₂B]·H₂O (I) was synthesized for the first time. Single crystals were obtained in an aqueous solution; the crystal structure was studied by X-ray crystallography. Crystals of I are triclinic, space group $P\bar 1$ , a = 9.7017(2) ?, b = 11.0475(2) ?, c = 12.6282(2) ?, ?? = 106.595(2)°, ?? = 106.931(1)°, ?? = 103.568(1)°, V = 1163.97(4) ?³, Z = 2, ??_calc = 1.516 g/cm³. The structural units of compound 1 are large complex dicitratoborate anions with a spiran structure, N,N-dimethylanilinium cations, and crystal water molecules. The crystal packing is a three-dimensional framework. A hydrogen-bond system is formed by seven independent contacts O(N)-H??O.     

Detection of a ferroelastic phase transition in Csx(NH4)1−xLiSO4 with the use of the DSC method

In this paper the technology of producing solid solutions of Cs_x(NH₄)_1?xLiSO₄ using the slow evaporation method is presented. Appropriate conditions were chosen to grow large samples. The ammonium ion content in the solid solutions was determined using the Kjeldahl method. It was found that the real ammonium ion concentration is twice lower than the one applied in the initial substances. At room temperature, the base crystal, lithium cesium sulfate (CsLiSO₄), is paraelastic, whereas lithium ammonium sulfate (NH₄LiSO₄) is ferroelectric. It is expected that as a result of substituting Cs⁺ ions with $ N{\text{H}}_{4}^{ + } $ N H 4 + ions, instead of the Cs⁺ ions, the modification of the ferroic properties of solid solutions of Cs_x(NH₄)_1?xLiSO₄ will take place. Tests conducted with the use of the differential scanning calorimetry method (DSC) allowed the detection of the ferroelastic phase transition which takes place in these compounds. A gradual increase of temperature transition was observed from 202 K for the pure CsLiSO₄ to 203.8 K for Cs_0.90(NH₄)_0.10LiSO₄ and 230.1 K for Cs_0.85(NH₄)_0.15LiSO₄ with the increase of $ N{\text{H}}_{4}^{ + } $ N H 4 + ions concentration. Using polarized light microscopy, a ferroelastic domain structure was detected in the examined solid solutions, which appeared below the structural phase transition temperature.     

The phase diagrams of the systems MgCl2 + MgB6O10 + H2O and MgSO4 + MgB6O10 + H2O at 323.15 K and Pitzer model

The solubilities and the relevant physicochemical properties of the systems MgCl₂ + MgB₆O₁₀ + H₂O and MgSO₄ + MgB₆O₁₀ + H₂O at 323.15 K were determined by the method of isothermal dissolution, and the phase diagrams and the diagrams of physicochemical properties versus composition were plotted. Both of the systems belong to a simple eutectic type, and neither double salts nor solid solution were found. Based on the extended Harvie-Weare (HW) model and its temperature-dependent equations, the value of the singlesalt Pitzer parameters ??⁽⁰⁾, ??⁽¹⁾, ??⁽²⁾, and C ^? for MgCl₂, MgSO₄, and Mg(B₆O₇)(OH)₆, the mixed ion-interaction parameters $\theta _{Cl, B_6 O_{10} }$ , $\theta _{SO_4 , B_6 O_{10} }$ , $\Psi _{Mg, Cl, B_6 O_{10} }$ , $\Psi _{Mg, SO_4 , B_6 O_{10} }$ , the average equilibrium constants (lnK _aver) of solids in the systems and the Debye-Hückel parameter A ^? were fitted. Using the Pitzer parameters and the average equilibrium constants of solids at equilibrium, the solubilities of the two systems at 323.15 K have been calculated. Comparisons between the calculated and experimental results show that the predicted solubilities agree well with experimental data.     

Equilibria of aqueous solutions of isopolyniobotungstates-6 with c Nb : c W = 1 : 5

Complex formation in the Nb₆O ₁₉ ^8? -WO ₄ ^2? -H⁺-H₂O system with c _Nb : c _W = 1 : 5 and varied c _{Nb + W} ⁰ = 10^?2, 5 × 10^?3, 2.5 × 10^?3, and 10^?3 mol/L) has been studied. Distribution diagrams were simulated for individual niobium(V) and tungsten(VI) isopolyanions and mixed isopolyniobotungstates for $Z = \frac{{c_{H^ + }^0 }}{{c_{Nb + W}^0 }} = 0 - 3.0$ in an NaCl background electrolyte. We have shown that isopolyniobotungstates-6 of composition H _x NbW₅O ₁₉ ^{(3 ? x)?} are formed via H _x Nb _n W_6?n O ₁₉ ^{(2 + n ? x)?} (n=2, 3, 5) ions. The concentration formation constants and thermodynamic formation constants of isopolyniobotungstate anions (IPNTAs) in aqueous solution have been calculated. Salt Tl₃NbW₅O₁₉·9H₂O has been synthesized and identified by chemical analysis and IR spectroscopy.     

Cluster self-organization of intermetallic systems: Nanocluster precursors (i-K8, i-K6, K4) and self-assembly of crystal structures Ir8Mg58(cF396), Ir7Mg44(cF408), and Ir6Mg26 (hR96)

Suprapolyhedral cluster precursors Kn with a hierarchical structure (with the number of polyhedra n = 4, 6, 8) have been derived and their topological representation as bichromatic graphs has been performed. With the use of computer methods (the TOPOS program package), combinatorial-topological analysis of icosahedral monster structures of close compositions Ir₈Mg₅₈ (cF396, F $ \bar 4 $ 3m, V = 8139 ų) and Ir₇Mg₄₄ (cF408, F $ \bar 4 $ 3m, V = 8117 ų) has been performed. Suprapolyhedral nanoclusters consisting of eight and six Ir icosahedra (nanoclusters i-K8 and i-K6 comprising 86 and 50 atoms) have been identified by the method of complete decomposition of the 3D factor graph of crystal structures into cluster substructures in Ir₇Mg₄₄. In Ir₈Mg₅₈, the i-K8 nanocluster is retained, whereas the i-K6 cluster is substituted by the K4 nanocluster composed of four Ir polyhedra with CN = 9 comprising 34 atoms. Complete 3D reconstruction of the self-assembly mechanism of crystal structure has been carried out by the scheme nanocluster precursor-primary chain-microlayer-microframework. It has been demonstrated that the voids in the Ir₈Mg₅₈ and Ir₇Mg₄₄ frameworks accommodate tetrahedral cluster spacers T-Mg(Mg₄) and T-Mg₄, respectively. The Ir₆Mg₂₆ structure (hR96, R $ \bar 3 $ c, V = 1890 ų) is made of the suprapolyhedral cluster K6 formed by six Ir polyhedra with CN = 11 and comprising 50 atoms; in this case, the structure contains no cluster spacers. In all structures, nanoclusters retain their own symmetry ( $ \bar 4 $ 3m for i-K8, i-K6, and K4 and $ \bar 3 $ for K6).     

Synthesis and crystal structure of Cs2[(UO2)2(C2O4)3] and Cs2[UO2(C3H2O4)2] · H2O

Cs₂[(UO₂)₂(C₂O₄)₃] (I) and Cs₂[UO₂(C₃H₂O₄)₂] · H₂O (II) have been synthesized and studied by X-ray diffraction. The crystals of complexes I and II are monoclinic: a = 8.1453(2) Å, b = 8.9831(2) Å, c = 11.3897(4) Å, β = 104.0950(10)°, V = 808.29(4) ų, space group P2₁/n, Z = 2, and R ₁ = 0.0255 for I and a = 9.6998(2) Å, b = 17.8686(3) Å, c = 8.2074(2) Å, β = 97.5780(10)°, V = 1410.10(5) ų, space group P2₁/c, Z = 4, and R ₁ = 0.0287 for II. The uranium-containing structural units of complexes I and II are [(UO₂)₂(C₂O₄)₃]^2? chains and [UO₂(C₃H₂O₄)₂] ₂ ^4? dimers, which belong to the AK _0.5 ⁰² T¹¹ and AT¹¹B⁰¹ crystallochemical groups (A = UO ₂ ²⁺ , K⁰² and T¹¹ = C₂O ₄ ^2? , T¹¹ and B⁰¹ = C₃H₂O ₄ ^2? ) of uranyl complexes.     

Komplexcarbide und-nitride mit aufgefülltem U3Si-Typ

The crystal structure of Cr₃AsN has been determined by single crystal methods: Space group I4/mcm-D _4h ¹⁸ $$a = 5,360 {\AA}, c = 8,066{\AA}; c/a = 1,505$$ The crystal structure can be described by filling of the octahedral voids of the U₃Si-type. The phases Mn₃GeC, Mn₃GeN_1-x, and Fe₃GeN_1-x are isotypic to Cr₃AsN.     

Adsorption studies of the removal of anions from aqueous solutions onto an adsorbent prepared from wheat straw

Modified wheat straw (MWS) was prepared by the grafting of epichlorohydrin, triethylamine and ethylenediamine onto WS. The characteristics of MWS and its adsorption capacity for NO ₃ ^? , PO ₄ ^3? and Cr₂O ₇ ^2? were investigated. The results indicate that amine groups with positive charge have been introduced into the structure of MWS, and significantly increased its anion adsorption property. The functions of MWS dosage, the solution pH, the contact time and temperature have significant influence on the adsorption process, and the adsorption is well fitted with the Langmuir equation and pseudo second-order model. The maximum adsorption capacity of MWS for NO ₃ ^? , PO ₄ ^— (P) and Cr₂O ₇ ^2? (Cr) is 53.5, 62.4 and 386.2 mg g^?1, respectively.     

Numerical modelling of inclusion-type complexes formed by chiral 18-crown-6 ethers bearing sugar moieties with enantiomers of phenylalanine methyl ester cations

The crystal structure of α-d-mannosido-benzo-18-crown-6·KSCN (1) was solved by X-ray single crystal diffractometry. C₂₈H₃₆O₁₀·KSCN is orthorhombic, space groupP2₁2₁2₁ withZ=4,a=8.035(4),b=9.960(2),c=38.83(2) Å,M _r =629.8,V=3103.6 ų,D _x =1.347 g cm^?3, μ(CuKα)=2.53 mm^?1, λ=1.54178 Å,F(000)=1324. FinalR=0.043 for 1139 unique observed reflections measured at room temperature. The potassium ion is surrounded by a nearly planar hexagon of oxygen atoms of the macrocyclic ring and lies on the plane formed by those atoms. Hexagonal pyramidal coordination is completed by the nitrogen atom of the thiocyanate anion. The SCN ion was found on the face of the macrocyclic ring opposite that for the chiral mannopyranoside moiety. The molecular structure of α-d-mannosido-18-crown-6 (2) and the structure of molecular complexes of2 and α-d-glucosido-benzo-18-crown-6 (3) were studied by molecular mechanics methods. The results suggest enthalpy driven selectivity of complexation of the phenylalanine methyl ester (4) by2 and both enthalpy and entropy effects in selective complexation of4 by3.     

Niobium oxochlorides in the gas phase: Quantum chemical calculations of the structure and relative stability of isomers

The gas-phase niobium oxochloride anions that result by the interaction between the finely dispersed stereoselective acetylene cyclotrimerization catalyst NbCl₂(C _n H _n ) (n = 10–12) and atmospheric oxygen and moisture have been characterized by matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry. From the relative intensities of mass spectrometric lines, it has been deduced that, among the various niobium oxochloride species passing into the gas phase under the action of laser radiation, the most abundant monomer ion is NbO₂Cl ₂ ^? , the most abundant dimers are Nb₂O₄Cl ₃ ^? and Nb₂O₃Cl ₅ ^? , the most abundant trimer is Nb₃O₆Cl ₅ ^? , and the most abundant tetramer is Nb₄O₈Cl ₅ ^? . The gas phase also contains low concentrations of fragments corresponding to the pentanuclear anion Nb₃O₁₁Cl ₄ ^? and the hexanuclear anion Nb₆O₁₅Cl ₂ ^? . The geometric parameters and total energy of the stable isomers of the dinuclear and polynuclear niobium oxochloride anions existing in the gas phase has been calculated by quantum chemical methods, and their relative thermodynamic stabilities have been determined for different metal core configurations and different arrangements of oxygen and chlorine ions. The stereochemistry of the niobium oxochlorides is discussed.     

Phytoecdysones ofSilene praemixta. II. Premixisterone

The structure of premixisterone (I) — a new ecdysteroid fromS. praemixta M. Pop. (Caryophyllaceae) — has been established. Compound (I) has the composition C₂₇H₄₄O₅, mp 110–112°C (from C₂H₅OH + H₂O), [α] _D ²⁴ 0 ± 4° (c 0.85; MeOH), \(\lambda _{\max }^{{\text{C}}_{\text{2}} {\text{H}}_{\text{5}} {\text{OH}}}\) 202 nm (log ? 3.35), ν _max ^KBr 3415 cm^?1 (OH), 1710 cm^?1 (C=0), and does not contain the δ⁷-6-keto grouping that is characteristic of natural ecdysteroids. The acetylation of (I) with (CH₃CO)₂ in Py gave the amorphous 3,22-diacetylpremixisterone (II), C₂₁H₄₈O₇. Compound (I) has the structure of 3β,14α,22R,25-tetrahydroxy-5β-cholest-8-en-6-one. The IR, PMR, and mass spectra of (I) and (II) are given.     

Crystal structure of two hydrate phases of ciprofloxacindi-um tetrachloridocobaltate(II)

New (C₁₇H₂₀FN₃O₃)₂[CoCl₄]₂·3H₂O (I) and C₁₇H₂₀FN₃O₃[CoCl₄]·H₂O (II) compounds, where C₁₇H₁₈FN₃O₃ is ciprofloxacin (CfH), are synthesized and their crystal structures are determined. Crystallographic data for I: a = 18.441(5) Å, b = 9.030(3) Å, c = 27.551(8) Å, V = 4588(4) ų, space group Pca2₁, Z = 4; for II: a = 9.305(3) Å, b = 9.885(3) Å, c = 12.999(4) Å, α = 82.782(4)°, β = 72.954(4)°, γ = 89.736(4)°, V = 1133(1) ų, P-1 space group, Z = 2. Both structures contain CfH ₃ ²⁺ ion pairs bonded by the π-π interaction. Additionally, in the crystal of I there is a stacking interaction between the π clouds of aromatic rings and hydrogen atoms of the cyclopropyl group linking the pairs of molecules with each other. The structure of the centrosymmetric crystal of triclinic phase II is also formed from CfH ₃ ²⁺ ion pairs bonded by the π-π interaction, which, in this case, are not independent because they are related by the symmetry center. Hydrogen bonds form a branched three-dimensional network linking the CfH ₃ ²⁺ and CoCl ₄ ^2? ions and water molecules.     

Synthesis and crystal structure of [UO2(L)(OH)], (CN3H6)2[(UO2)2CrO4(L)4 · 2H2O and [UO2(H2O)5][(UO2)2Cr2O7(L)4] (where L is picolinate ion)

[[UO₂(L)(OH)] (I), (CN₃H₆)₂[(UO₂)₂CrO₄(L)₄] · 2H₂O (II), and [UO₂(H₂O)₅][(UO₂)₂Cr₂O₇(L)₄] (III) crystals, where L is picolinate ion C₅H₄NCOO^?, have been synthesized and studied by X-ray diffraction and IR spectroscopy. Complex I crystallizes in triclinic system with the unit cell parameters a = 6.2858(5) Å, b = 7.9522(5) Å, c = 8.3598(6) Å, α = 79.527(6)°, β = 87.760(6)°, γ = 79.126(6)°, space group P $\bar 1$ , Z = 2, R = 0.0306, and complexes II and III crystalize in monoclinic system with a = 8.8630(9) Å, b = 13.4540(13) Å, c = 31.266(3) Å, β = 93.118(3)°, space group C2/c, Z = 4, R = 0.0187 (II), and a = 7.3172(4) Å, b = 15.4719(8) Å, c = 16.6534(10) Å, β = 98.943(4)°, space group P2₁/m, Z = 2, R = 0.0588 (III). The structure of complex I is built of electronegative [UO₂(L)(OH)] chains, which belong to the AT¹¹M² crystallochemical group (A = UO ₂ ²⁺ , T¹¹ = L, M² = OH^?) of uranyl complexes. The structure of complexes II and III contains [(UO₂)₂(L′)(L)₄]^2? dimers (L′ = CrO ₄ ^2? or Cr₂O ₇ ^2? ), which belong to the A₂B²B ₄ ⁰¹ group (A = UO ₂ ²⁺ ,B² = L′, B⁰¹ = L). The specifics of intermolecular interactions in the structures of complexes I–III and some their analogues have been considered using molecular Voronoi-Dirichlet polyhedra.