Application of the Method of Molecular Voronoi–Dirichlet Polyhedra for Analysis of Noncovalent Interactions in Crystal Structures of Flufenamic AcidThe Current Record-Holder of the Number of Structurally Studied Polymorphs

Crystal chemical analysis of eight polymorphs of flufenamic acid (FFA, C₁₄H₁₀NO₂F₃)the current record-holder of the number of structurally characterized polymorphic modificationswas carried out using the method of molecular Voronoi–Dirichlet polyhedra. It was proved that every polymorph of FFA, as every polymorph of the previous record-holder ROY (C₁₂H₉N₃O₂S), has a unique set of types of intra- and intermolecular noncovalent interactions

ROY: Using the Method of Molecular Voronoi–Dirichlet Polyhedra to Examine the Fine Features of Conformational Polymorphism

Crystal chemical analysis of 12 polymorphs of 5-methyl-2-[(2-nitrophenyl)­amino]-3-thiophenecarbonitrile (ROY) (C12H9N3O2S)the current record-holder of the number of structurally characterized polymorphic modificationswas carried out using the method of molecular Voronoi–Dirichlet (VD) polyhedra. Based on the k-Φ criterion, it was found that each of the 14 reported to-date independent ROY molecules has a unique conformation. A method for quantifying the significance of noncovalent interactions of various natures together with a new type of graph showing average partial contributions of single contacts of a given type to the values of integral parameters was proposed. The capabilities of the method of molecular VD polyhedra were successfully tested on the example of several forms of ROY with multiple structural solutions. The analysis showed that noncovalent interactions vary more between different forms of ROY than between different structural solutions of the same form. It was calculated that different structural solutions of the same form of ROY may feature up to five varying noncovalent contacts. The k-Φ criterion approved itself as a very sensitive parameter which can easily detect even the subtlest differences in atomic interactions strictly and quantitatively

Quantification and Visualization of the Effect of Pressure and Temperature on Atomic Interactions in Crystal Structures with the Method of Molecular Voronoi–Dirichlet Polyhedra on the Example of ROY Polymorphs

Thirty crystal structures belonging to ROY polymorphs (Y and OP forms) were extracted from the Cambridge Structural Database and analyzed using the method of molecular Voronoi–Dirichlet polyhedra. These structures varied in collection pressure (up to ∼6 GPa) and/or temperature (down to 40 K). The coincidence of the conformations of crystallographically independent molecules of identical composition and structure was established for the first time for three out of 30 crystal structures, which, on the other hand, featured different packing arrangements. It was shown that when external conditions change, quite significant variations can occur in the systems of atomic interactions (including valence ones) while maintaining the symmetry and packing of molecules in the crystal structure (without phase transitions), which, in turn, can lead to changes in the macroscopic properties of compounds. The previously introduced method for visualization of the variation of noncovalent interactions in crystal structures was expanded to cases when environmental parameters, pressure and temperature, are considered instead of geometric characteristics. It was shown that the method of molecular Voronoi–Dirichlet polyhedra makes it possible to objectively and quantitatively describe and visualize variations in atomic interactions with changes in pressure and temperature, providing the possibility of establishing subsequent correlations with the manifested macro properties. Variations in both single interatomic contacts and some of their groups with changes in pressure and temperature were examined in detail for the Y and OP forms of ROY. The most probable reasons for the change in color of the Y form with increasing pressure were suggested

Synthesis and X‑ray Crystallography of [Mg(H₂O)₆][AnO₂(C₂H₅COO)₃]₂ (An = U, Np, or Pu)

Synthesis and X-ray crystallography of single crystals of [Mg­(H₂O)₆]­[AnO₂(C₂H₅COO)₃]₂, where An = U (<b>I</b>), Np (<b>II</b>), or Pu (<b>III</b>), are reported. Compounds <b>I</b>–<b>III</b> are isostructural and crystallize in the trigonal crystal system. The structures of <b>I</b>–<b>III</b> are built of hydrated magnesium cations [Mg­(H₂O)₆]²⁺ and mononuclear [AnO₂(C₂H₅COO)₃]⁻ complexes, which belong to the AB⁰¹₃ crystallochemical group of uranyl complexes (A = AnO₂²⁺, B⁰¹ = C₂H₅COO^–). Peculiarities of intermolecular interactions in the structures of [Mg­(H₂O)₆]­[UO₂(L)₃]₂ complexes depending on the carboxylate ion L (acetate, propionate, or <i>n</i>-butyrate) are investigated using the method of molecular Voronoi–Dirichlet polyhedra. Actinide contraction in the series of U­(VI)–Np­(VI)–Pu­(VI) in compounds <b>I</b>–<b>III</b> is reflected in a decrease in the mean AnO bond lengths and in the volume and sphericity degree of Voronoi–Dirichlet polyhedra of An atoms

New Complexes of Actinides with Monobromoacetate Ions: Synthesis and Structures

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