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

Structural features of uranyl acrylate complexes with s-, p-, and d-monovalent metals

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 P-1 (3a) or P213 (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

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