A crystal chemical analysis based on the stereoatomic model of crystal structures and Voronoi–Dirichlet polyhedra is performed to study non-covalent interactions in imidazole crystal structures determined for a wide range of pressures. It is established that the formation of various non-covalent contacts in imidazole crystal structures is determined by external pressure. It is shown that the area of Voronoi–Dirichlet molecular polyhedra depends on the external pressure. The topology of H-bonding between imidazole molecules and the influence of external pressure on the characteristics of N–H⋯N hydrogen bonds in the structures of imidazole crystals are analyzed.

С использованием стереоатомной модели строения кристаллов и полиэдров Вороного-Дирихле осуществлен кристаллохимический анализ невалентных взаимодействий в структурах кристаллов имидазола, расшифрованных в широком диапазоне давлений. Показано, что в зависимости от величины внешнего давления в кристаллических структурах имидазола реализуются различные невалентные контакты. Установлена линейная зависимость значений площади молекулярных полиэдров Вороного-Дирихле от величины внешнего давления. Проанализирована топология связывания молекул имидазола друг с другом посредством водородных связей, а также влияние величины внешнего давления на характеристики водородных связей N–H···N в структурах кристаллов имидазола.

New iodoacetate complexes of uranyl with imidazoles have been synthesized: (C3H5N2)[UO2(mia)3] (I) and (C4H7N2)[UO2(mia)3] (II), where mia is the iodoacetate ion CH2ICOOˉ, C3H5N _2^ + is the imidazolium cation, and C4H7N _2^ + is the 2-methylimidazolium cation. The complexes were studied by IR spectroscopy, thermography, and X-ray diffractometry. In crystals I and II, each uranium(VI) atom coordinates three cyclic bidentate mia anions, forming a hexagonal bipyramidal complex [UO2(mia)3]ˉ with the crystal chemical formula A(B01)3, where A = UO _2^2 + and B01 = mia. The nonvalence interactions in the structures of crystals I and II were analyzed by the Voronoi–Dirichlet polyhedra method. It was established that, in addition to hydrogen bonds, the U=O⋅⋅⋅I−C halogen bonds also contribute to the formation of the supramolecular structure of crystals II.

Проведены синтез, ИК-спектроскопическое, термографическое и рентгеноструктурное исследование новых иодоацетатных комплексов уранила с имидазолами: (C3H5N2)[UO2(mia)3] (I) и (C4H7N2)[UO2(mia)3] (II), где mia — иодоацетат-ион CH2ICOOˉ, C3H5N2+ – катион имидазолия, C4H7N2+ – катион 2-метилимидазолия. В кристаллах I и II каждый атом урана(VI) координирует три бидентатно-циклических аниона mia, образуя гексагонально-бипирамидальный комплекс [UO2(mia)3]ˉ с кристаллохимической формулой А(В01)3, где A = UO22+, B01 = mia. С помощью метода молекулярных полиэдров Вороного-Дирихле проведен анализ невалентных взаимодействий в структурах кристаллов I и II. Установлено, что в формирование супрамолекулярной структуры кристаллов II, помимо водородных связей, вносят вклад галогенные связи U = O∙∙∙I−C.

Using X-ray diffraction analysis, the structure of the crystals of Li(UO2)2(C5H6O4)2F⋅6H2O (I), NaUO2(C5H6O4)F⋅4H2O (II) and Sr(UO2)2(C5H6O4)2F2⋅8H2O (III) was studied for the first time. The uranium-containing structural units in crystals of I are 1D complexes [UO2(C5H6O4)F0.5(H2O)]0.5– with the crystal chemical formula AQ02M20.5M1, where A = UO22+, Q02 = C5H6O42–, M2= F–, M1 = H2O, and in II and III, 1D complexes of the same composition and structure [UO2(C5H6O4)F]– with the crystal chemical formula AQ02M2. In all compounds, the U(VI) atoms implement hexagonal-bipyramidal coordination, forming coordination polyhedra UO2FO5 (I) and UO2F2O4 (II and III). It was found that the long-characterized uranyl fluoroglutarate {UJUBEG}, for which the composition [UO2(С5H6O4)F]⋅2H2O was erroneously indicated, contradicting the principle of electrical neutrality, should be considered as (Н3O)[UO2(С5H6O4)F]⋅H2O.

Crystal-chemical analysis of 1124 silicon compounds with the general formula CaHbSic (a, b, and c are the stoichiometric coefficients) whose structure contained SiCn and SiCnSim coordination polyhedra (CPs) has been performed by the intersecting spheres method using Voronoi–Dirichlet polyhedra. In the structure of the compounds, the silicon atoms have coordination numbers (c.n.) of 1–4 and 10. The effects of the coordination number, oxidation state, and chemical nature of the surrounding (C and Si) atoms on the main characteristics of the Voronoi–Dirichlet polyhedra (VDP) of silicon atoms were considered. A single linear dependence of the solid angles of the VDP faces corresponding to the Si–C and Si–Si valence and nonvalence contacts on the corresponding internuclear distances was established. A stereo effect of the lone electron pair of Si(II) atoms in the Si(II)Cn complexes (n = 2 or 10) was revealed, which manifests itself in the displacement of the nuclei of Si(II) atoms from the centers of gravity of their VDP (0.35–0.39 Å) and in the asymmetry of the coordination sphere.

A crystal chemical analysis of the 3 d -metal benzoate- and phenylacetate-containing compounds is carried out in terms of the stereoatomic crystal structure model using characteristics of the Voronoi–Dirichlet polyhedra. Coordination types of benzoate and phenylacetate anions toward the transition metals from Ti to Zn are considered. The influence of the coordination type on the characteristics of M–O bonds in the crystal structures is revealed. The electron-donating ability of benzoate and phenylacetate anions toward 3 d metals is quantitatively estimated using the 18-electron rule.

Crystal chemical analysis was carried out of compounds containing UO22+ ions in the structure, which coordinate fluorine and oxygen atoms. It was found that in 193 complexes of the composition UObFc at b ≥ 2 and c ≠ 0, the U(VI) atoms exhibit coordination numbers of 7 and 8. The volume of the Voronoi–Dirichlet polyhedra of U(VI) atoms in the UObFc complexes was found to regularly reduce with increasing parameter λ = c/(b + c). The data on the most important topological features of structural groups arising from the mutual binding of UObFc complexes are systematized. It was established that formed by UO2F5 pentagonal bipyramids, which are connected to each other only by common equatorial vertices or edges, can have an identical topology even at different F : U ratios.

The structures of the single crystals of compounds K2UO2(tca)4(tcaH)2 (I), K4NpO2(tca)6(tcaH)(H2O)3 (II), Rb4UO2(tca)6(tcaH)(H2O)3 (III), and Cs3UO2(tca)5(tcaH)2·H2O (IV), where tca is the trichloroacetate ion, were established by X-ray diffraction analysis. The crystals of II-IV have a framework structure, whereas in the layered crystals of I, neighboring layers are connected to each other via halogen bonds. In this regard, the crystals of I possess perfect cleavage along the (001) plane: the crystals are easily cut into stacks of very thin layers. Halogen bonds in the structures of all title compounds were characterized using the method of molecular Voronoi-Dirichlet polyhedra. The donor-acceptor halogen bond synthon, where the same halogen atom is both the donor towards one halogen atom and the acceptor from the second halogen atom, is recognized for its usefulness in the crystal design. The description of the ligand coordination modes and crystal chemical formulae of complexes is adapted for cases when ligands have chemically non-equivalent and unobvious donor atoms (for example, oxygen and halogen atoms in halogen-substituted carboxylate anions).

Synthesis, FTIR spectral study, and X-ray diffraction analysis of single crystals of (CH3)4N[UO2(mba)3] (I), (CH3)4N[NpO2(mba)2(NO3)] (II), (CH3)4N[PuO2(mba)2(NO3)] (III), and (CH3)4N[NpO2(mba)(NO3)2] (IV), where mba is a monobromoacetate ion (CH2BrCOO–), were conducted. The main structural units of crystals I–IV are mononuclear anionic complexes of the [AnO2(mba)3]−, [AnO2(mba)2(NO3)]−, or [AnO2(mba)(NO3)2]− composition. All these complex units are characterized with the same crystal-chemical formula AB013 (A = AnO22+ and B01 = CH2BrCOO– or NO3–). Using the method of molecular Voronoi–Dirichlet polyhedra, the contributions of various types of noncovalent interactions into the formation of supramolecular structures of the obtained complexes were characterized. The analysis of coordination modes of all monobromoacetate-containing compounds from the Cambridge Structural Database was accomplished. Actinide contraction in the studied compounds is discussed.

Crystallochemical analysis with the use of Voronoi–Dirichlet polyhedra (VDPs) has been performed for 711 sulfides, whose structures contain 1199 coordination polyhedra LnSn, where Ln is a lanthanide from La to Lu. It has been established that the sulfides incorporate Ln(II), Ln(III), and Ce(IV) atoms bonding from 6 to 10 sulfur atoms, which exist in the form of S2– or S– ions. The VDP parameters provide the possibility to determine the valence state of Ln atoms in the structures of sulfides and distinguish S2– or S– ions. The VDPs of 2913 sulfur atoms have been characterized to establish the dependence between the multiplicity of S–S bonds and their length. A quantitative estimate of lanthanide contraction in LnIIIXn polyhedra is given depending on the nature of chalcogen Х (O, S, Se, or Te).

We performed the synthesis. Fin spectral study. and X-ray diffraction (XRD) analysis of single crystals of [UO2(C5H4O4)(Dma] (I). where C5H4O42- and Dma are the itaconate ion and N,N-dimethylacetamide (C4H9NO). respectively. The crystal structure of I consists of [UO2(C5H4O4)(Dma] layers, which have the crystal chemical formula AQ(21) M-1 (A = UO22+, Q(21) = C5H4O42-, M-1 = Dma). The method of molecular Voronoi-Dirichlet polyhedra was employed to characterize intermolecular noncovalent interactions in the structure of I. A comparative analysis of noncovalent interactions in the structures of the title compound and the isomeric complex of uranyl citraconate with Dma was performed. An analysis of coordination modes of all itaconate-containing compounds from the CSD was performed.

Using the parameters of Voronoi-Dirichlet (VD) polyhedra the authors have verified the maximum space-filling principle in substructures constructed of actinide atoms (from thorium to einsteinium) in all crystal structures from the Inorganic Crystal Structure Database (ICSD) and Cambridge Structural Database (CSD). It is shown that most of the actinide atoms in such substructures are surrounded by 14 or 12 neighboring atoms. It was discovered that U substructures with greater than or equal to 20 crystallographically independent U atoms in the unit cell feature 15-faceted VD polyhedra as the most common type. Analogous unimodal distributions of VD polyhedra with maxima at 15 faces are observed for F and H substructures and the model system `ideal gas', which has no order in the arrangement of atoms. This similarity allows one to assume that substructures of crystal structures with greater than or equal to 20 crystallographically independent atoms in the unit cell do not possess short-range (local) order in the mutual arrangement of atoms, but feature long-range order (translational symmetry). Thus, crystalline compounds with such substructures can formally be regarded as `antiliquid', that is the antipode of a liquid, whose structure possesses short-range order but lacks translational symmetry.

Abstract A series of uranyl acrylate complexes with s-, p-, and d- monovalent cations (Li, Na, Tl, and Ag) was synthesized and characterized by single crystal X-ray diffraction and IR spectroscopy. We demonstrated that the nature of the monovalent cation strongly affects the composition and crystal structure of an uranyl acrylate. Li[UO2(acr)3]·H2O (1, acr=CH2CHCOO−) crystallizes in the tetragonal crystal system and is built of chains which are connected through hydrogen bonding. The presence of an acrylic acid dimer in the reaction results in the monoclinic compound Na3[UO2(acr)3][UO2(acr)2.5(CH2CHCOOCH2CH2COO)0.5]2·5H2O (2), in which the acrylic dimer shares a position with both the acrylate anion and a water molecule. Tl[UO2(acr)3] (3) exists as two polymorphs and crystallizes in either P1̅ (3a) or P2 1 3 (3b) space groups. The polymorphs differ in the dimensionality, 2D for 3a and 3D for 3b, and density. Ag2[UO2(NO3)2(acr)2]·2Hacr (4) is the first example of the Ag atom coordination to the acrylate anion through the vinyl group. In 4, the Ag–C bonds enhances the connectivity of the trinuclear [Ag2UO2(acr)2(Hacr)2(NO3)2] clusters into a layered coordination polymer. A detailed structural study of the obtained compounds was performed using Voronoi-Dirichlet tessellation.