D. V. Pushkin

Crystal-chemical role of malonate ions in the structure of coordination polymers

In the crystal structures of the malonate-containing compounds of d- or f-metals, the C3H2O42− anions were found to exhibit 17 topologically different types of coordination to the metal atoms A, playing the role of mono-, bi-, tri-, or tetradentate ligands and forming one to seven O-A bonds. The C-C-C bond angle in the malonate ions changed from 103° to 126° and depended linearly on the dihedral angle (φCOO) between the planes of the two carboxyl groups of the anion. At φCOO < 60°, the malonate ions in the crystal structures always form six-membered metallocycles with d- or f-metal atoms, while at φCOO > 67°, they can form only four-membered metallocycles. The factors that influence the conformation of malonate ions in the structures of coordination polymers were discussed.

Maximum Filling Principle and Sublattices of Actinide Atoms in Crystal Structures

The most important characteristics of the Voronoi-Dirichlet polyhedra (VDP) of A atoms (A is actinide) in chemically homogeneous sublattices in the crystal structures of 3479 inorganic, coordination, and organometallic compounds are determined. The effect of the actinide nature on the A-A interatomic distances in the crystal structures is considered. In the Th, U, Np, or Pu sublattices, VDP have most often 14 faces and the Fedorov cuboctahedron is the most abundant type of VDP, whereas in Ac, Pa, Am, Cm, Bk, or Cf sublattices, the VDP have mainly 12 faces and are shaped like rhomobododecahedra. In A sublattices that typically form VDP with 14 faces, the actinide atoms occupy, most often, sites with C1 symmetry (47 to 59% of the sample size). In the case of actinides whose A sublattices tend to form VDP with 12 faces, the C1 site symmetry is found either very rarely (Pa, Am, Cf) or not at all (Ac, Cm, Bk).

Analysis of the Conformational Polymorph Crystal Structures by Means of Molecular Voronoi-Dirichlet Polyhedra

The nonvalent interactions in the crystal structures of 16 conformational polymorphs of the CaHbNcOdSe composition (a, b, c, d, and e are stoichiometric indices), including 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile (“ROY”) (which has seven different modifications), have been analyzed using the characteristics of molecular Voronoi-Dirichlet polyhedra. It is established that a unique combination of implementable types of intra- and intermolecular nonvalent contacts corresponds to each conformational polymorph.

Coordination polyhedra TeOn in crystal structures

The Voronoi-Dirichlet (VD) polyhedra and the intersecting spheres method have been used to analyze the coordination of Te(IV) and Te(VI) atoms by oxygen atoms in the crystal structures of 317 compounds. The quantitative estimation of the steric effect of the Te(IV) lone electron pair, giving rise to the asymmetry of the coordination sphere and manifesting itself as a substantial (on average, by 0.5(1) Å) displacement of Te(IV) atoms from the centroids of their VD polyhedra, is presented.

Trinuclear {Sr[UO2L3]2(H2O)4} and pentanuclear {Sr[UO2L3]4}2− uranyl monocarboxylate complexes (L-acetate or n-butyrate ion)

Crystals of two acetate complexes, Cs2{Sr[UO2L3]4} (1) and [Sr(H2O)6][UO2L3]2{Sr(H2O)4[UO2L3]2}2 (2), and one n-butyrate complex, {Sr(H2O)4[UO2L3]2}·2H2O (3), of uranium(VI), where L is a corresponding monocarboxylate ion, were studied by means of FTIR spectroscopy and single crystal X-ray analysis. The structure of 1 contains pentanuclear anionic complexes, {Sr[UO2L3]4}2−, bonded in a three dimensional framework by electrostatic interactions with Cs+ cations. The structure of 2, in addition to ‘typical’ uranyl triacetate complexes of [UO2L3]− and [Sr(H2O)6]2+ cations, contains neutral trinuclear complexes, {Sr(H2O)4[UO2L3]2}. The structure of 3 with n-butyrate ions consists of neutral complexes of {Sr(H2O)4[UO2L3]2} and molecules of crystallized water. Analysis of intermolecular interactions in 2 and 3 by means of two independent approaches (molecular Voronoi–Dirichlet polyhedra and molecular Hirshfeld surfaces) revealed that discrete complex groups are connected with one another mostly due to H/O hydrogen bonds and H/H dispersion interactions. A dynamic balance among mono- and poly-nuclear complexes in aqueous solutions containing R2+ and [UO2L3]− ions is proposed. The effect of the alkyl chain and the nature of the R2+ cation on the balance is discussed.

Cation-cation interactions between uranyl(VI) ions

Data on crystalline U(VI) compounds with mutual coordination of uranyl ions in their structure (cation-cation interactions, CCIs) are summarized. The topology and geometry of CCIs, including the characteristics of Voronoi-Dirichlet polyhedra of uranium atoms, are analyzed. 15 types of complexes [UO22+]n formed by CCIs are revealed. The influence of CCIs on the stereochemical features of U(VI) are considered, and common and distinctive features of CCIs in uranyl(VI) and neptunyl(V) compounds are discussed. Factors favoring the occurrence of CCIs in uranyl compounds are analyzed. The spectroscopic manifestations of CCIs are considered. Data on CCIs in some noncrystalline media are presented. The strength of cation-cation bonds in uranyl complexes is analyzed.

X-Ray diffraction and IR-spectroscopic studies of UO2(n-C3H7COO)2(H2O)2 and Mg(H2O)6[UO2(n-C3H7COO)3]2

Single crystals of UO2(n-C3H7COO)2(H2O)2 (I) and Mg(H2O)6[UO2(n-C3H7COO)3]2 (II) are synthesized. Their IR-spectroscopic and X-ray diffraction studies are performed. Crystals I are monoclinic, a = 9.8124(7) Å, b = 19.2394(14) Å, c = 12.9251(11) Å, β = 122.423(1)°, space group P21/c, Z = 6, and R = 0.0268. Crystals II are cubic, a = 15.6935(6) Å, space group

Synthesis, crystal structure, and IR spectral study of Na[(UO2)(C3H7COO)3] · 0.25H2O and K[(UO2)(C3H7COO)3]

Pa\bar 3

Electronic structure of cesium butyratouranylate(VI) as derived from DFT-assisted powder X-ray diffraction data.

, Z = 4, and R = 0.0173. The main structural units of I and II are [UO2(C3H7COO)2(H2O)2] molecules and [UO2(C3H7COO)3]− anionic complexes, respectively, which belong to AB201M21 (I) and AB301 (II) crystal chemical groups of uranyl complexes (A = UO22+, B01 = C3H7COO−, and M1 = H2O). A crystal chemical analysis of UO2L2 · nH2O compounds, where L is a carboxylate ion, is performed.

Neutron diffraction study of UO2SeO4 · 2D2O

Synthesis, IR spectral study and X-ray diffraction analysis of single crystals of Na[(UO2)(C3H7COO)3] · 0.25H2O (I) and K[(UO2)(C3H7COO)3] (II) were carried out. Compound I is monoclinic, unit cell parameters are: a = 13.5671(15) Å, b = 20.070(2) Å, c = 13.6139(15) Å, β = 106.839(2)°, space group P21, Z = 8, R = 0.0493. Compound II is orthorhombic, unit cell parameters are: a = 17.1325(9) Å, b = 19.6966(11) Å, c = 21.9686(11) Å, space group P212121, Z = 16, R = 0.0563. Mononuclear groups [UO2(C3H7COO)3]− related to the A301 crystal-chemical group (A = UO22+, B01 = C3H7COO−) of uranyl complexes are the uranium-containing structural units of crystals I and II. The data of IR spectral study agree well with X-ray diffraction data.