L. B. Serezhkina

Causes of uranyl ion nonlinearity in crystal structures

The stereochemical features of U(VI) in the structure of crystals containing UOa or UObNc coordination polyhedra (a or b + c = 5, 6, 7, 8, or 9) were examined using Voronoi-Dirichlet polyhedra (VDPs). The volume of VDP of U atoms in UOa complexes is independent of the coordination number of U atoms. An increase in the number of N atoms in UObNc complexes is accompanied by a regular increase in the volume of VDP of the U atom. The nonlinearity of uranyl ions in the crystal structures correlates with the displacement of the nuclei of the U(VI) atoms from the center of gravity of their VDP.

New Criterion for Conformational Polymorphism

An analysis of nonvalent interactions in 29 crystal structures of compounds that have the CaHbNcOd composition (salicylaldoxime, glycine, and 2,4,6,8,10,12-hexaazaisowurzitane) and form polymorphic modifications is performed using molecular Voronoi-Dirichlet polyhedra. It is found that each conformational polymorph is characterized by a unique combination of the types of intramolecular and intermolecular nonvalent interactions. It is shown that a criterion which takes into account the total number of intramolecular nonvalent contacts and their distribution depending on the nature of neighboring atoms and the rank of faces of molecular Voronoi-Dirichlet polyhedra can be used to reveal conformational polymorphs.

Voronoi-Dirichlet tesselation as a tool for investigation of polymorphism in molecular crystals with CwHxNyOz composition and photochromic properties.

The non-bonded interactions in five sets of polymorph substances with photochromic properties have been investigated within the Voronoi-Dirichlet approach. Twenty compounds with the general formula C(w)H(x)N(y)O(z) were analyzed. Among ten possible types of non-bonded interactions at least five types are observed in the crystal structures of compounds under discussion. For all the structures the majority of interactions involve H atoms, namely London forces (H...H and H...C) and hydrogen bonds (H...O and H...N). A conformational polymorph was stated to be characterized by a unique set of inter- and intramolecular non-bonded interactions. It was quantitatively demonstrated that molecules in the same conformation can pack in a different way, and, vice versa, the change in conformation of a molecule does not prevent a substance from realising the same set of intermolecular contacts. In accordance with the data obtained for 2,4-dinitrobenzylpyridine derivatives, only conformational polymorphs with an intramolecular N...N interaction between a nitro group and a pyridine are photochromic.

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.

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.

Synthesis and crystal structures of [UO2(C6H4NO2)2(C6H5NO2)] and [UO2SO4(C6H5NO2)(H2O)] · H2O

AbstractThe complexes [UO2(C6H4NO2)2(C6H5NO2) (I) and [UO2SO4(C6H5NO2)(H2O)] · H2O (II) were synthesized and studied by X-ray diffraction analysis. Crystals I are monoclinic: a = 7.0081(3), b = 14.9624(7), c = 9.1837(5) Å, β = 96.594(2)°, Z = 2, space group P21/m. Crystals II are triclinic: a = 6.8097(6), b = 9.3837(8), c = 10.4556(10) Å, α = 85.279(3), β = 75.434(3), γ = 69.180(3)°, Z = 2, space group

Crystal structure of R[UO2(CH3COO)3] (R = NH4+, K+, or Cs+)

P\bar 1