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

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