UO22+-polycarboxylate heterometallic complexes: structure,spectra, and photocatalytic properties

[Cu₂(UO₂)₄(suc)₄(pac)₄] (1), [(Cu(H₂O)₂)(4,4′-bipy)₂][(UO₂)₂(H₂O)₂(Hca)₂]·3H₂O (2), and [(Cu(H₂O)₂)(UO₂)(bta)]·4H₂O (3) were synthesized by the reaction of succinic acid and 3-pyridinecarboxylic acid, citric acid and 4,4′-bipyridine, or 1,2,4,5-benzenetetracarboxylic acid ligands with Cu(NO₃)₂·3H₂O and UO₂(CH₃COO)₂·2H₂O. The complexes were characterized by IR and UV–vis spectroscopy, powder X-ray diffraction, single-crystal X-ray diffraction, and photoluminescence spectroscopy. Photocatalytic activities of the complexes were also investigated.     

Crystal structure of two new molecular adducts of uranyl nitrate with 2,2′-6,2″-terpyridine

The crystal structures of two uranyl nitrate complexes with 2,2′-6,2″-terpyridine (Trpy), [(UO (Trpy)-[(UO₂)₂(Trpy)₂(OH)₂][UO₂(NO₃)₂(OH)₂] · 2CH₃OH (I) and [(UO₂)₂(Trpy)₂(OH)₂]₂[UO₂(NO₃)₃(H₂O)](NO₃)₃ · 3H₂O (II), were studied. Compound I consists of the centrosymmetric dimeric cations [(UO₂)₂(Trpy)₂(OH)₂]²⁺, the anions [UO₂(NO₃)₂(OH)₂]^2?, and solvation methanol molecules. Complex II consists of dimeric cations [(UO₂)₂(Trpy)₂(OH)₂]²⁺, the complex anions [UO₂(NO₃)₃(H₂O)]^?, nitrate anions, and water molecules of crystallization. The uranium atom in the [UO₂(NO₃)₃(H₂O)]^? anion in II has an unusual coordination polyhedron representing a hexagonal bipyramid in which one oxygen atom in the equatorial plane is replaced by two atoms equidistant from this plane.     

Structural topology and dimensional reduction in uranyl oxysalts: eight novel phases in the methylamine–(UO2)(NO3)2–H2SeO4–H2O system

Single crystals of eight novel uranyl selenates, (CH₃NH₃)₂[(UO₂)(SeO₄)₂(H₂O)](H₂O) (I) and (CH₃NH₃)₂[(UO₂)(SeO₄)₂(H₂O)] (II), (CH₃NH₃)₂[(UO₂)₂(SeO₄)₃] (III) and (CH₃NH₃)(H₃O)[(UO₂)₂(SeO₄)₃(H₂O)](H₂O) (IV), (CH₃NH₃)₄[(UO₂)₃(SeO₄)₅](H₂O)₄ (V) and (CH₃NH₃)(H₅O₂)(H₃O)₂[(UO₂)₃(SeO₄)₅](H₂O)₄ (VI), (CH₃NH₃)₄(H₃O)₂[(UO₂)₅(SeO₄)₈(H₂O)](H₂O)₄ (VII), and (CH₃NH₃)_1.5(H₅O₂)_1.5(H₃O)₃[(UO₂)₅(SeO₄)₈(H₂O)](H₂SeO₄)_2.6(H₂O)₃ (VIII), have been prepared by isothermal evaporation from aqueous solutions and structurally characterized. The observed structural topologies of uranyl selenate units have been investigated using graph theory. The principle of dimensional reduction has been used for analysis of the uranyl oxysalts with general chemical formula A _n (UO₂) _p (TO₄) _q (H₂O) _r (A = monovalent cation, and T = S, Se, Cr, Mo), which allowed to construct three-component composition-structure diagram with separate dimensionality fields for different chemical compositions.     

Crystal structures of the dicyclohexyl-(18-crown-6) uranyl perchlorate complex and of its hydrolysis product

The structures of dicyclohexyl-(18-crown-6) uranyl perchlorate, [(C₂₀H₃₆O₆)UO₂] (ClO₄)₂ (complex I) and of dicyclohexyl-(18-crown-6) uranyl hydroxyperchlorate [C₂₀H₃₆O₆]₃ [(UO₂)₂(H₂O)₆] · (ClO₄)₂, CH₃CN, (complex II) have been determined from three dimension X-ray diffraction data.The uranyl group is directly coordinated to the oxygen atoms of the polyether ring in complex I; its hydrolysis (complex II) leads to a dimerization of the uranyl ions by sharing two OH groups with an U-U distance of only 3.827(8) Å. The polyether molecules are connected by hydrogen bonds with the dimeric ion [(UO₂)₂ (OH)₂ (H₂O)₆]²⁺.     

Synthesis,structure, and catalytic bromination of supramolecular oxovanadium complexes containing oxalate

Three supramolecular complexes, [VO(phen)(C₂O₄)(H₂O)]·CH₃OH (1) [(VO)₂(u₂-C₂O₄)(C₂O₄)₂(H₂O)₂]·L·H₂O (2), and [(4,4′-bipyH₂)_0.5]⁺[VO₂(2,6-dipic)]^?·2H₂O (3) (phen?=?1,10-phenanthroline 4,4′-bipy?=?4,4′-bipyridine, 2,6-dipic?=?2,6-pyridinedicarboxylic, L?=?1,4-bis((3,5-dimethyl-1H-pyrazol-1-yl)methyl)benzene), have been prepared and characterized by elemental analysis, IR, and UV–vis spectroscopy and single-crystal diffraction analysis. Structural analysis shows that the three complexes all contain carboxylate and V=O moiety; vanadium of 1 and 2 are six coordinate with distorted octahedral geometry with N₂O₄ and O₆ donor sets, respectively, while 3 is five coordinate with distorted trigonal bipyramidal geometry with a NO₄ donor set. The complexes exhibit catalytic bromination activity in the single-pot reaction for the conversion of phenol red to bromophenol blue in H₂O–DMF at 30?±?0.5?C with pH 5.8, indicating that they can be considered as functional model vanadium-dependent haloperoxidases. In addition, electrochemical behaviors are also studied.     

Mononuclear and binuclear lanthanide(III) complexes: syntheses,structural, photophysical and thermal properties

Six new Ln(III) complexes viz., [Gd(tptz)(SCN)₃(CH₃OH)₂OH₂]·CH₃OH (1), [Eu(tptz)(SCN)₃(CH₃OH)₂OH₂]·CH₃OH (2), [Tb(tptz)(SCN)₃(OH₂)₃]₄ (3), [Gd(tptz)(OBz)₂(μ-OBz)OH₂]₂·2H₂O (4), [OH₂(OBz)₂(tptz)Eu₁(μ-OBz)₂Eu₂(tptz)(OBz)₂OH₂]·CH₃OH·7H₂O (5), and {[Tb₁(tptz)(OBz)₂(μ-OBz)]₂·[Tb₂(tptz)(OBz)₃CH₃OH]₂}·2CH₃OH·4H₂O (6) (Ln = Gd, Eu, Tb; tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine; BzONa = sodium benzoate), have been synthesized and characterized by physicochemical methods including single-crystal X-ray crystallography. The X-ray studies demonstrate that 1–3 are mononuclear, whereas 4–6 are binuclear. The photophysical properties of 1–6 have been studied with ultraviolet absorption and emission spectral studies. Their thermal properties have been studied by thermogravimetric (TG) and derivative thermogravimetric analysis (DTG), demonstrating that the final product after decomposition was Ln₂O₃ for all these complexes.     

A DFT study of uranyl hydroxyl complexes: structure and stability of trimers and tetramers

A DFT study of U(VI) hydroxy complexes was performed with special attention paid to the [(UO₂)₃(OH)₅(H₂O)_4–7]⁺ and [(UO₂)₄(OH)₇(H₂O)_5–8]⁺ species. It was established that the ionicity of the U=O bond increased when moving from [(UO₂)(H₂O)₅]²⁺, [(UO₂)₂(OH)(H₂O)₈]³⁺, [(UO₂)₂(OH)₂(H₂O)₆]²⁺, [(UO₂)₃(OH)₅(H₂O)_4–6]⁺ to [(UO₂)₄(OH)₇(H₂O)_5–8]⁺ species. In both [(UO₂)₃(OH)₅(H₂O)_4–6]⁺ and [(UO₂)₄(OH)₇(H₂O)_5–8]⁺ complexes, the U=O bond was observed to have a range of different lengths which depended on the composition of the first coordination sphere of UO₂ ²⁺. The cyclic structures of trimeric complexes were somewhat more stable than their linear structures, which was probably due to the steric effect.

     

[Ni(H2O)4]3[U(OH,H2O)(UO2)8O12(OH)3], crystal structure and comparison with uranium minerals with U3O8-type sheets

The new U(VI) compound, [Ni(H₂O)₄]₃[U(OH,H₂O)(UO₂)₈O₁₂(OH)₃], was synthesized by mild hydrothermal reaction of uranyl and nickel nitrates. The crystal-structure was solved in the P-1 space group, a=8.627(2), b=10.566(2), c=12.091(4) Å and α=110.59(1), β=102.96(2), γ=105.50(1)°, R=0.0539 and wR=0.0464 from 3441 unique observed reflections and 151 parameters. The structure of the title compound is built from sheets of uranium polyhedra closely related to that in β-U₃O₈. Within the sheets [(UO₂)(OH)O₄] pentagonal bipyramids share equatorial edges to form chains, which are cross-linked by [(UO₂)O₄] and [UO₄(H₂O)(OH)] square bipyramids and through hydroxyl groups shared between [(UO₂)(OH)O₄] pentagonal bipyramids. The sheets are pillared by sharing the apical oxygen atoms of the [(UO₂)(OH)O₄] pentagonal bipyramids with the oxygen atoms of [NiO₂(H₂O)₄] octahedral units. That builds a three-dimensional framework with water molecules pointing towards the channels. On heating [Ni(H₂O)₄]₃[U(OH,H₂O)(UO₂)₈O₁₂(OH)₃] decomposes into NiU₃O₁₀.     

Isopropylammonium Layered Uranyl Chromates: Syntheses and Crystal Structures of [(CH3)2CHNH3]3[(UO2)3(CrO4)2O(OH)3] and[(CH3)2CHNH3]2[(UO2)2(CrO4)3(H2O)]

Two novel isopropylamine‐templated uranyl chromates, [(CH₃)₂CHNH₃]₃[(UO₂)₃(CrO₄)₂O(OH)₃] ( 1 ) and [(CH₃)₂CHNH₃]₂[(UO₂)₂(CrO₄)₃(H₂O)] ( 2 ) were prepared by hydrothermal method at 100 °C. The compounds were characterized by electron microprobe analysis and X‐ray diffraction crystal structure analysis [ 1 : trigonal, P31m, a = 9.646(4), c = 8.469(4) Å, V = 682.4(5) ų; 2 : monoclinic, P2₁/c, a = 11.309(3), b = 11.465(3), c = 17.055(5) Å, β = 99.150(6)°, V = 2183.2(11) ų]. The structure of 1 is based upon trimers of uranyl bipyramids interlinked by CrO₄ tetrahedra to form [(UO₂)₃(CrO₄)₂O(OH)₃]^3– layers, whereas, in the structure of 2 , UO₇ and UO₆(H₂O) pentagonal bipyramids are linked through CrO₄ tetrahedra into the [(UO₂)₂(CrO₄)₃(H₂O)]^2– layers. The structures show many similarities to related uranyl selenate compounds, thus providing additional data on similarities and differences between uranyl sulfates, chromates, selenates, and molybdates.     

Synthesis and structure of uranyl complexes with malonic acid dianions

The uranyl complexes with malonic acid dianions [UO₂(C₃H₂O₄)(CO(NH₂)₂)]·H₂O (1), [UO₂(C₃H₂O₄)(CONH₂NMe₂)]·H₂O (2), and [UO₂(C₃H₂O₄)(MeCONMe₂)] (3) were synthesized and characterized by X-ray crystallography. The structural units [UO₂(C₃H₂O₄)L] in the crystals of 1–3 refer to the AK²¹M¹ crystal chemical group (A = UO₂ ²⁺, K²¹ = C₃H₂O₄ ^2?, M¹ = L) of uranyl complexes; the crystals of 1 have a framework structure and 2 and 3 have a chain structure. Some structural features of the [UO₂(C₃H₂O₄)L] complex groups are discussed.     

Novel platinum(II) and (IV) complexes of naphthaldimine schiff bases

Naphthaldimines containing N₂O₂ donor centers react with platinum(II) and (IV) chlorides to give two types of complexes depending on the valence of the platinum ion. For [Pt(II)], the ligand is neutral, [(H₂L¹)PtCl₂]·3H₂O (1) and [(H₂L³)₂Pt₂Cl₄]·5H₂O (3), or monobasic [(HL²)₂Pt₂Cl₂]·2H₂O (2) and [(HL⁴)₂Pt]·2H₂O (4). These complexes are all diamagnetic having square-planar geometry. For [Pt(IV)], the ligand is dibasic, [(L¹)Pt₂Cl₄(OH)₂]·2H₂O (5), [(L²)Pt₃Cl₁₀]·3H₂O (6), [(L³)Pt₂Cl₄(OH)₂]·C₂H₅OH (7) and [(L⁴)Pt₂Cl₆]·H₂O (8). The Pt(IV) complexes are diamagnetic and exhibit octahedral configuration around the platinum ion. The complexes were characterized by elemental analysis, UV-Vis and IR spectra, electrical conductivity and thermal analyses (DTA and TGA). The molar conductances in DMF solutions indicate that the complexes are non-ionic. The complexes were tested for their catalytic activities towards cathodic reduction of oxygen.     

Uranyl complexes with methyl derivatives of alicyclic dioximes

A reaction of uranyl dioxalate complexes with methyl derivatives of alicyclic ??-dioximes, 3-methyl-1,2-cyclohexanedione dioxime and 3-methyl-1,2-cyclopentanedione dioxime, was studied. The structure of (CN₃H₆)₄[(UO₂)₂(C₆H₈N₂O₂)(CO₃)(C₂O₄)₂] · (C₆H₁₀N₂O₂) · 2H₂O and NH₄(CN₃H₆)₃[(UO₂)₂(C₇H₁₀N₂O₂)(CO₃)(C₂O₄)₂] · 2H₂O based on binuclear complex anions with carbonate-dioximate fragment was studied by X-ray diffraction.     

Coumarin-naphthohydrazone ligand with a rare coordination mode to form Mn(II) and Co(II) 1-D coordination polymers: synthesis,characterization, and crystal structure

The hydrazone (E)-3-hydroxy-N’-(1-(2-oxo-2H-chromen-3-yl)ethylidene)-2-naphthohydrazide (H₂L) was synthesized from the reaction of 3-acetylcoumarin and 3-hydroxy-2-naphthoic hydrazide in methanol. Compounds [Mn(H₂L)(NO₃)₂(CH₃OH)]·CH₃OH (1a), [Mn(HL)(NO₃)(CH₃OH)]_n (1b), [Co(HL)(NO₃)(CH₃OH)]_n (2), and [Cu(HL)(NO₃)] (3) were obtained by reaction of an equimolar amount of H₂L with nitrate salts of Mn(II), Co(II), or Cu(II) in methanol. The reaction of ligand and Mn(NO₃)₂·4H₂O was also carried out in the presence of sodium azide which led to the 1-D coordination polymer, [Mn(HL)(N₃)(CH₃OH)]_n (4). All of the synthesized compounds were characterized by elemental analyses and spectroscopic methods. Single-crystal X-ray analysis of 1–4 indicated that H₂L is neutral (in 1a) or mononegative ligand (in 1b, 2, 3 and 4). In 1b, 2 and 4 the 1-D polymeric chain is found by a rare coordination mode of this kind of hydrazone ligand since the naphtholic oxygen is coordinated to the neighboring metal ions while the NH moiety of hydrazone remains intact, also confirmed by FT-IR spectroscopic studies. The thermal stability of 2 and 4 were also studied from 30–1000 °C.     

Three 1-D molybdenum(V) phosphates with copper/nickel coordination cations

Three 1-D reduced molybdenum(V) phosphates, [Ni(OH)₂][Na₂(H₂O)₃]₂{Ni[(MoO₂)₆(OH)₃(HPO₄)₃(PO₄)]₂}?·?2C₆H₁₄N₂?·?2H₃O?·?5H₂O (1), [Ni(H₂O)₂][K(H₂O)₅]₂{Ni[(MoO₂)₆(OH)₃(HPO₄)₃(PO₄)]₂}?·?2C₆H₁₄N₂?·?2H₃O?·?4H₂O (2), and [Cu(H₂O)₂][Na(H₂O)₅]₂{Cu[(MoO₂)₆(OH)₃(HPO₄)₃(PO₄)]₂}?·?2C₆H₁₄N₂?·?2H₃O?·?4H₂O (3), have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. The crystallographic analysis reveals that 1 is based on {Ni[Mo₆O₁₂(OH)₃(HPO₄)₃(PO₄)]₂} clusters connected through {[Ni(OH)₂][Na₂(H₂O)₃]₂} pentanuclear mixed-metal cluster units to yield unusual 1-D chains along the c-axis, which further form 3-D supramolecular networks via hydrogen-bonding. Compounds 2 and 3 are heterogeneous isostructural compounds. Both are built from M[Mo₆P₄]₂ (M?=?Ni or Cu) blocks as the structural motif combined with [MO₄(H₂O)₂] (M?=?Ni or Cu) octahedra to form 1-D chains, where M[Mo₆P₄]₂ (M?=?Ni or Cu) is bonded by [M′(H₂O)₅] (M′?=?K or Na). Furthermore, bulk carbon paste electrode modified with 1 (1-CPE) displays good electrocatalytic activity toward reduction of nitrite or bromate.     

Two Chain Like B-Type-Anderson-Based Hybrids Synthesized in Choline Chloride/Urea Eutectic Mixture

Two new chain like B-Anderson type polyoxomolybdates based hybrids {Na[(CH₃)₃N(CH₂)₂OH]₂}[Al(OH)₆Mo₆O₁₈]·2(NH₂CONH₂)·6H₂O (1) and {Na[(CH₃)₃N(CH₂)₂OH]₂}[Cr(OH)₆Mo₆O₁₈]·2(NH₂CONH₂)·6H₂O (2) were synthesized in choline chloride/urea eutectic mixture and characterized by element analysis, IR, UV–vis, TG, single-crystal X-ray analysis, and power X-ray diffraction. Through the linkage [Na(H₂O)₂(NH₂CONH₂)₂]⁺, the [X(OH)₆Mo₆O₁₈]³⁻ (X = Al, Cr) units are arranged into a chain. Considering hydrogen bonding interactions between the chains, compound 1 and 2 are all well-arranged into 3-D supermolecular assembly. The structure is first obtained in the choline chloride/urea eutectic mixture.     

“Forced” coordination modes of 1,2-cyclohexanedione dioxime in uranyl complexes

Unusual coordination modes of 1,2-cyclohexane dionedioxime in uranyl complexes, i.e., tridentate chelating/bridging and (E, Z)-pentadentate chelating/bridging ones, were established by X-ray crystallography of single crystals of (CN₃H₆)₃[(UO₂)₂(C₆H₉N₂O₂)(C₆H₈N₂O₂)(C₂O₄)₂] · 2H₂O and [(UO₂)₂(C₆H₈N₂O₂)₂(H₂O)₃] · 2H₂O. The conditions of the emergence of such coordination modes were determined. The possibility of (E/Z) izomerization of α-dioximes in reactions of uranyl complexes.     

Hydrothermal syntheses,crystal structures and thermal stability of two divalent metal phosphonates with a layered and a 3D structure

Two new divalent metal phosphonates, [Cu₂{CH₃C(OH)(PO₃)₂}(H₂O)₂]?·?0.5H₂O (1) and [NH₃CH₂CH₂NH₃][Zn₃{CH₃C(OH)(PO₃)₂}₂(H₂O)]?·?H₂O (2), have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction as well as with infrared spectroscopy, elemental analysis and thermogravimetric analysis. The structure of 1 comprises [Cu₃(hedp)₂]^2? layers connected by [CuO₄] units to form a 3D open-framework structure with a one-dimensional channel system along the b axis. In 2, the connections of alternately arranged [ZnO₄] tetrahedra, [ZnO₆] octahedra and [CPO₃] tetrahedra via vertex-sharing result in a 2D layered structure. The protonated ethylenediamine cations and water molecules are located between adjacent layers.     

Ab Initio Calculations of Hydroxoplatinum Compounds: II. Binuclear Platinum(IV) Superoxo Complexes

The structural and spectral data have been obtained by ab initio methods for the [(OH)₄Pt(μ-O₂)(μ- OH)Pt(OH)₄]^2?, [(OH)₄Pt(μ-O₂)(μ-OH)Pt(OH)₄(OH)]^3?, [(OH)₅Pt(μ-O₂)Pt(OH)₅]^3?, and [(H₂O)(OH)₄Pt(μ- O₂)Pt(OH)₄(H₂O)]- clusters, corresponding to binuclear platinum(IV) superoxo complexes with one and two bridges. The data obtained are in good agreement with experimental data and make it possible to judge the structure of available complexes.     

Filling the equatorial garland of uranyl ion: its content and limitations

Crystal structure determinations on the uranyl ion complexes [H₂N(CH₃)₂]₂[UO₂(bpdc)₂], (1), (bpdc?=?2,2′-bipyridine-3,3′-dicarboxylate), [pyH]₂[UO₂(btfac)(NO₃)₂](NO₃), (2), (btfac?=?1-phenyl-4,4,4-trifluorobutane-1,3-dionate), [H₂dabco][UO₂(nta)]₂·3H₂O, (3), (dabco?=?1,4-diazabicyclo[2.2.2]octane; nta?=?nitrilotriacetate) and [Ni(cyclam)UO₂(edta)]^.2H₂O, (4), (cyclam?=?1,4,8,11-tetrazacyclotetradecane; edta?=?ethylenediaminetetraacetate) have provided further examples of U(VI) in tetragonal-, pentagonal and hexagonal-bipyramidal coordination environments. Consideration of each structure within the context of those of known relatives has been used to assess the influence of factors in addition to repulsions within the primary coordination sphere on the equatorial coordination number of U(VI).

     

Two 2D uranyl coordination complexes showing effective photocatalytic degradation of Rhodamine B and mechanism study

Two new hydrostable two-dimensional(2 D) uranyl coordination complexes [(UO_2)_5(μ_3-O)_2(nbca)_2].7 H_2O(1) and [(UO_2)_3(nbca)_2(H_2O)_3]·2 H_2O(2)(H_3 nbca=5-nitro-1,2,3-benzenetricarboxylic acid) were hydrothermal synthesized.Single-crystal structural refinements reveal that both of the two complexes were formed by the packing of 2D uranyl coordination sheets via the hydrogen bonds.The nbca ligand coordinating to the uranyl polyhedron centers constructed the 2D sheets.There are UO_8 hexagonal bipyramids and UO_7 pentagonal bipyramids in 1 while only U07 pentagonal bipyramids in 2.Photocatalytic degradation of rhodamine B(RhB) in aqueous solution was studied.Complex 2 possesses better performance than 1 with 96.2 % of the RhB was degraded in only 60 min.Mechanism studies reveal that the dissolved oxygens are essential to the RhB degradation.The photocurrent density of 2 is more stable than that of 1,which indicating the stronger ability to separate photoexcited electrons and hole pairs of 2.