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

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

Syntheses, Crystal Structures, and Nonlinear Optical Activity of Cs₂Ba[AnO₂(C₂H₅COO)₃]₄ (An = U, Np, Pu) and Unprecedented Octanuclear Complex Units in KR₂(H₂O)₈[UO₂(C₂H₅COO)₃]₅ (R = Sr, Ba)

X-ray diffraction was applied to the elucidation of crystal structures of single crystals of Cs₂Ba­[AnO₂(C₂H₅COO)₃]₄, where An = U­(<b>I</b>), Np­(<b>II</b>), Pu­(<b>III</b>), and KR₂(H₂O)₈[UO₂(C₂H₅COO)₃]₅, where R = Sr­(<b>IV</b>), Ba (polymorphs <b>V-a</b> and <b>V</b><b>-</b><b>b</b>). FTIR spectra were analyzed for the uranium-containing crystals <b>I</b>, <b>I</b><b>V</b>, and <b>V</b><b>-</b><b>b</b>. Isostructural cubic crystals <b>I</b>–<b>I</b><b>I</b><b>I</b> are constructed of typical mononuclear anionic complex units [AnO₂(C₂H₅COO)₃]⁻ and charge-balancing Cs and Ba cations. Features of actinide contraction in the six U–Np–Pu isostructural series known to date are analyzed. In crystal structures of <b>IV</b> and <b>V</b> two typical complexes [UO₂(C₂H₅COO)₃]⁻ bind with a hydrated Sr or Ba cation to form the rare trinuclear neutral complex unit {<i>R</i>(H₂O)₄[UO₂(C₂H₅COO)₃]₂}, where R = Sr, Ba. Two such trinuclear units and one typical mononuclear unit further bind with a K cation to form the unprecedented octanuclear neutral complex unit K­[UO₂(C₂H₅COO)₃]­{R­(H₂O)₄[UO₂(C₂H₅COO)₃]₂}₂. As the derived polynuclear complexes of uranyl ion with carboxylate ligands in the crystal structures of <b>IV</b> and <b>V</b> are not the first but are rare examples, the equilibrium between mono and polynuclear complex units in aqueous solutions is discussed. The two polymorphic modifications <b>V-a</b> and <b>V-b</b> were studied at 100 K and at room temperature, respectively. Peculiarities of noncovalent interactions in crystal structures of the two polymorphs are revealed using Voronoi–Dirichlet tessellation. The nonlinear optical activity of noncentrosymmetric crystals <b>I</b> was estimated by its ability for second harmonic generation