Mikhail S. Grigoriev

Solvation of UCl62- anionic complex by MeBu3N+, BuMe2IM+, and BuMeIm(+) cations

The complexes [MeBu 3N] 2[UCl 6] and [BuMe 2Im] 2[UCl 6] were characterized in the solid state and in solution of [MeBu 3N][Tf 2N], [BuMe 2Im][Tf 2N], and [BuMeIm][Tf 2N] room-temperature ionic liquids using single-crystal XRD, EXAFS, electrochemistry, UV-visible absorption spectroscopy, and NMR. In the solid state and in solution, the existence of hydrogen bonding between the UCl 6 (2-) complex and the ionic liquid cations was revealed by these techniques. The MeBu 3N (+) cation interacts with UCl 6 (2-) via the protons on the alpha-carbon atoms of nitrogen. The protons of the imidazolium ring account for the interaction between the BuMe 2Im (+) cation and the UCl 6 (2-) anion. For the BuMeIm (+) cation the major interaction was confirmed between the most acidic proton on C(2) and the chlorides of UCl 6 (2-). The experimental results also show that the intensity of the interaction between the UCl 6 (2-) anion and the cation varies with the ionic liquid cation in the following order: MeBu 3N (+) approximately BuMe 2Im (+) << BuMeIm (+).

Thermodynamics and Structure of Actinide(IV) Complexes with Nitrilotriacetic Acid

Nitrilotriacetic acid, commonly known as NTA (N(CH(2)CO(2)H)(3)), can be considered a representative of the polyaminocarboxylic family. The results presented in this paper describe the thermodynamical complexation and structural investigation of An(IV) complexes with NTA in aqueous solution. In the first part, the stability constants of the An(IV) complexes (An = Pu, Np, U, and Th) have been determined by spectrophotometry. In the second part, the coordination spheres of the actinide cation in these complexes have been described using extended X-ray absorption fine structure spectroscopy and compared to the solid-state structure of (Hpy)(2)[U(NTA)(2)] x (H(2)O). These data are further compared to quantum chemical calculations, and their evolution across the actinide series is discussed. In particular, an interpretation of the role of the nitrogen atom in the coordination mode is proposed. These results are considered to be model behavior of polyaminocarboxylic ligands such as diethylenetriamine pentaacetic acid, which is nowadays the best candidate for a chelating agent in the framework of actinide decorporation for the human body.

Crystal structures of Np(vi) and Pu(VI) phthalates, [NpO2{(OOC)2C6H4}H2O].1/3H2O and [PuO2{(OOC)2C6H4}H2O].H2O

Abstract Single crystals of [NpO2L(H2O)]·1/3H2O (I) and [PuO2L(H2O)]·H2O (II) (H2L — orthophthalic acid) have been synthesized, their structures have been determined by X-ray structural analysis. Actinide atoms in both compounds are seven-coordinated. The interaction between actinide dioxocations and phthalate anions results in formation of infinite tubes in I and layers in II. The structures are compared with those of other phthalate compounds of hexa- and pentavalent actinides, in particular, with the structure of [UO2L(H2O)]·H2O which differs from the structure II.

Novel heptavalent actinide compounds: tetrasodium dihydroxidotetraoxidoneptunate(VII) hydroxide dihydrate and its plutonium analogue

The title compounds, Na(4)[NpO(4)(OH)(2)]OH.2H(2)O and Na(4)[PuO(4)(OH)(2)]OH.2H(2)O, are isostructural and isomorphous, and contain complex [AnO(4)(OH)(2)](3-) anions (Ac is an actinide) in the form of distorted tetragonal bipyramids, Na(+) cations, crystallization water molecules and outer-sphere OH groups. The complex [AnO(4)(OH)(2)](3-) anions occupy general positions and the coordinated OH groups deviate significantly from a centrosymmetric relative orientation. The [AnO(4)(OH)(2)](3-) anions exhibit anisotropic actinide contraction; the shortening of the An-O(hydroxide) bonds on going from Np to Pu is greater than that of the AnO(4) groups.

Phosphorus(V) Porphyrin-Based Molecular Turnstiles

A new cationic molecular turnstile based on a P(V) porphyrin backbone bearing two pyridyl interaction sites, one at the meso position of the porphyrin and the other on the handle connected to the porphyrin through P-O bonds, was designed and synthesized. The dynamic behavior of the turnstile 2, investigated by 1D and 2D 1H NMR techniques, showed that in the absence of an effector, the turnstile is in its open state and undergoes a free rotation of the rotor (the handle) around the stator (the porphyrin backbone). In the presence of an external effector such as Ag+ cation or H+, the turnstile is switched to its closed states 2-Ag+ and 2-H+, respectively. The locking/unlocking process is reversible and may be achieved by precipitation of AgBr upon addition of Et4NBr in the case of the silver-locked turnstile or by addition of Et3N in the case of the proton-locked turnstile.

2,2′:6′,2′′-Terpyridinium dinitrate

The doubly protonated terpyridinium cation in the title compound, C15H13N32+·2NO3−, has a cis–cis conformation. Both H atoms attached to the N atoms of the outer rings form hydrogen bonds with the same O atom of one of the two nitrate anions.

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 (I), Np (II), or Pu (III), are reported. Compounds I-III are isostructural and crystallize in the trigonal crystal system. The structures of I-III are built of hydrated magnesium cations [Mg(H2O)6](2+) and mononuclear [AnO2(C2H5COO)3](-) complexes, which belong to the AB(01)3 crystallochemical group of uranyl complexes (A = AnO2(2+), B(01) = 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 n-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 I-III 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.

Guanidinium dioxidobis(picolinato-κ2N,O)(picolinato-κO)uranate(VI)

In the title compound, (CH6N3)[U(C6H4NO2)3O2], the uranyl group is coordinated by two O and two N atoms from two chelating picolinate ligands, and one O atom from a third picolinate ligand. The coordination environment of the UVI atom (N2O5) is distorted pentagonal–bipyramidal. In the crystal, all amino groups are involved in the formation of N—H⋯O and N—H⋯N hydrogen bonds, which link cations and anions into layers parallel to the ac plane.

Poly[[[diaqua­dioxouranium(VI)]-μ3-nitriliotriacetato-κ3O:O′:O′′] trihydrate]

The basic units in the structure of the title compound, {[UO2(C6H7NO6)(H2O)2]·3H2O}n, are ribbons in which every UO22+ cation is coordinated in a monodentate manner to three tridentate-bridging nitriliotriacetate dianions. Hydrogen bonds bind the ribbons into a three-dimensional structure.

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(I), Np(II), Pu(III), and KR2(H2O)8[UO2(C2H5COO)3]5, where R = Sr(IV), Ba (polymorphs V-a and V-b). FTIR spectra were analyzed for the uranium-containing crystals I, IV, and V-b. Isostructural cubic crystals I-III 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 IV and V two typical complexes [UO2(C2H5COO)3]- bind with a hydrated Sr or Ba cation to form the rare trinuclear neutral complex unit {R(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 IV and V 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 V-a and V-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 I was estimated by its ability for second harmonic generation.