Crystal structures and magnetic interactions in nickel(II) dibridged complexes formed by both phenolate oxygen-azide,or methanlate groups

Abstract  

Tridentate Schiff base ligands L¹ and L², derived from the condensation of 2-hydroxy-3-methoxybenzaldehyde (L) with 2-aminoethanol or 2-aminobutan-1-ol, react with nickel chloride, azide, or thiocyanate to give rise to two dinuclear complexes of formulas [Ni₂(L)(L¹)₂N₃]·H₂O (1), [Ni₂(L²)₃(μ_1,1-N₃)]·2H₂O (2), and one tretranuclear complex [Ni₂(L²)₂(NCS)]₂(C₂H₅OH)₂ (3), where L¹ = HOCH₂CH(C₂H₅)NCHC₆H₃(O⁻)(OCH₃) and L² = HO(CH₂)₂NCHC₆H₃(O⁻)(OCH₃). We have characterized these complexes by analytical, crystal structures, and variable temperature magnetic susceptibility measurements. The magnetic properties of the complexes are studied by magnetic susceptibility (χ_M) vs. temperature measurements. The χ_M T vs. T plots reveal that compounds 1, 2 and 3 are ferromagnetically coupled.     

Sulfanilamide copper(II) chelates with 2-[(2-hydroxyphenyl-imino)methyl]phenolom and 1-[(2-hydroxyphenylimino)-methyl]naphthalen-2-ol

2-[(2-Hydroxyphenylimino)methyl]phenol (H²L¹) and 1-[(2-hydroxyphenylimino)methyl]naphthalen-2-ol (H²L²) reacted with copper(II) acetate hydrate and sulfanilamide (Sf¹), sulfathiazole (Sf²), sulfaethidole (Sf³), sulfadiazine (Sf⁴), and sulfadimidine (Sf⁵) in ethanol to give mixed-ligand copper chelates with the composition Cu(Sf^1–5)(L^1–2) · n H₂O (n = 1, 2). All these complexes are monomeric. Salicylaldehyde imines (H₂L¹ and H₂L²) behave as doubly deprotonated tridentate O,N,O ligands, whereas sulfanilamides (Sf^1–5) are unidentate ligands. Thermolysis of the synthesized complexes includes dehydration at 70–90°C, followed by complete thermal decomposition (290–380°C). The complexes [Cu(Sf¹)(L¹)] · 2H₂O and [Cu(Sf³)(L¹)] · H₂O at a concentration of 10⁻⁴ M inhibited growth and reproduction of 100% of human myeloid leukemia cells (HL-60). The inhibitory effect was 90 and 75%, respectively, at a concentration of 10⁻⁵ M, whereas no antitumor activity was observed at a concentration of 10⁻⁶ M.     

Extraction of pertechnetate anion as a ligand in metal complexes with tributylphosphate

The extraction of the pertechnetate anion has been investigated in the systems tributylphosphate (TBP)—solvent (carbon tetrachloride, n-heptane, chloroform)—metal salt (uranyl nitrate and chloride, thorium nitrate)—ammonium salt. In the absence of a metal, the solvates HTeO₄. iTBP (i=4) are extracted, while in the presence of uranium and thorium, the distribution of technetium corresponds to the formation of the mixed complexes: UO₂(NO₃)(TeO₄)·2TBP, UO₂Cl(TcO₄)·2TBP and Th(NO₃)₃ (TcO₁)·2TBP. The effective constants of the reactions H⁺+TcO ₄ ⁻ +i(TBP)_org←(HTcO₁·iTBP)_org, and (ML_n·2TBP)_org+TcO ₄ ⁻ ←(ML_n−1TcO₄·2TBP)_org+L were established in the above systems. The extraction of pertechnetate ion is more effective when it is coordinated to a cation solvated by TBP than the extraction in the form of pertechnetate acid solvated by TBP.     

Dioxouranium Complexes with Acetylpyridine Benzoylhydrazones and Related Ligands

Acetylpyridine benzoylhydrazone and related ligands react with common dioxouranium(VI) compounds such as uranyl nitrate or [NBu₄]₂[UO₂Cl₄] to form air‐stable complexes. Reactions with 2, 6‐diacetylpyridinebis(benzoylhydrazone) (H₂L^1a) or 2, 6‐diacetylpyridinebis(salicylhydrazone) (H₂L^1b) give yellow products of the composition [UO₂(L¹)]. The neutral compounds contain doubly deprotonated ligands and possess a distorted pentagonal‐bipyramidal structure. The hydroxo groups of the salicylhydrazonato ligand do not contribute to the complexation of the metal. The equatorial coordination spheres of the complexes can be extended by the addition of a monodentate ligand such as pyridine or DMSO. The uranium atoms in the resulting deep‐red complexes have hexagonal‐bipyramidal coordination environments with the oxo ligands in axial positions. The sterical strains inside the hexagonal plane can be reduced when two tridentate benzoylhydrazonato ligands are used instead of the pentadentate 2, 6‐diacetylpyridine derivatives. Acetylpyridine benzoylhydrazone (HL²) and bis(2‐pyridyl)ketone benzoylhydrazone (HL³) deprotonate and form neutral, red [UO₂(L)₂] complexes. The equatorial coordination spheres of these complexes are puckered hexagons. X‐ray diffraction studies on [UO₂(L^1a)(pyridine)], [UO₂(L^1b)(DMSO)], [UO₂(L²)₂] and [UO₂(L³)₂] show relatively short U—O bonds to the benzoylic oxygen atoms between 2.328(6) and 2.389(8) Å. This suggests a preference of these donor sites of the ligands over their imino and amine functionalities (U—N bond lengths: 2.588(7)—2.701(6) Å ).     

Radiation reduction of binuclear Rh(II) complexes in aqueous-methanol solutions

Radiation reduction of binuclear [Rh₂(OAc)₂(phen)₂(H₂O)₂](OAc)₂, [Rh₂(OAc)(tpy)₂Cl₂]Cl·2H₂O and [Rh₂Cl₂(HCOO)₂(bpy)₂]·4H₂O complexes in aqueous-methanol solution have been studied. The reduction yields as equal to ca. 6 equiv/100eV and the rate constants of reactions: complex+e _solv ⁻ as equal to 2.9·10¹⁰, 3.2·10¹⁰ and 3.7·10¹⁰ M⁻¹·s⁻¹, respectively, have been determined. On the basis of electronic spectra it has been shown that Rh(II) compounds were reduced giving several Rh(I) complexes being in equilibrium. The mechanism of the processes has been discussed.     

Synthesis,spectroscopic, thermal and biological aspect of mixed ligand copper(II) complexes

Derivative of 8-hydroxyquinoline i.e. Clioquinol is well known for its antibiotic properties, drug design and coordinating ability towards metal ion such as Copper(II). The structure of mixed ligand complexes has been investigated using spectral, elemental and thermal analysis. In vitro anti microbial activity against four bacterial species were performed i.e. Escherichia coli, Pseudomonas aeruginosa, Serratia marcescens, Bacillus substilis and found that synthesized complexes (15–37 mm) were found to be significant potent compared to standard drugs (clioquinol i.e. 10–26 mm), parental ligands and metal salts employed for complexation. The kinetic parameters such as order of reaction (n = 0.96–1.49), and the energy of activation (E _a = 3.065–142.9 kJ mol⁻¹), have been calculated using Freeman–Carroll method. The range found for the pre-exponential factor (A), the activation entropy (S* = −91.03 to−102.6 JK⁻¹ mol⁻¹), the activation enthalpy (H* = 0.380–135.15 kJ mol⁻¹), and the free energy (G* = 33.52–222.4 kJ mol⁻¹) of activation reveals that the complexes are more stable. Order of stability of complexes were found to be [Cu(A⁴)(CQ)OH] · 4H₂O > [Cu(A³)(CQ)OH] · 5H₂O > [Cu(A¹)(CQ)OH] · H₂O > [Cu(A²)(CQ)OH] · 3H₂O     

Ten complexes constructed by two reduced Schiff base tetraazamacrocycle ligands: syntheses,structures, magnetic and luminescent properties

Ten new complexes, [Cu₂(L¹)(NO₃)₂]·2H₂O (1), [Cu₄(L¹)₂]·4ClO₄·H₂O (2), [Cu₂(L¹)(H₂O)₂]·(adipate) (3), [Cu₆(L¹)₂(m-bdc)₄]·2DMF·5H₂O (4), [Cu₂(L¹)(Hbtc)]·5H₂O (5), [Cu₂(L¹)(H₂O)₂]·(ntc)·3H₂O (6), [Co₂(L²)]·[Co(MeOH)₄(H₂O)₂] (7), [Co₃(L²)(EtOH)(H₂O)] (8), [Ni₆(L²)₂(H₂O)₄]·H₂O (9) and [Zn₄(L²)(OAc)₂]·0.5H₂O (10), have been synthesized. 1 displays a [Cu₂(L¹)(NO₃)₂] monomolecular structure. 2 shows a supramolecular chain including [Cu₂L¹]²⁺. In 3, two Cu(II) ions are connected by L¹ to form a [Cu₂(L¹)(H₂O)₂]²⁺ cation. In 4, the m-bdc anions bridge Cu(II) ions and L¹ anions to form a layer. Both 5 and 6 display 3-D supramolecular structures. 7 consists of both [Co₂L²]^2? and [Co(MeOH)₄(H₂O)₂]²⁺ units. 8 and 9 show infinite chain structures. In 10, Zn(II) dimers are linked by L² to generate a 3-D framework. The magnetic properties for 4 and 8 and the luminescent property for 10 have been studied.     

Copper complexes of 1-[(2-carboxyethyl)benzene]-3-[2-pyridine]triazene

The triazenide, 1-[(2-carboxyethyl)benzene]-3-[2-pyridine]triazene (HL), has been synthesized. In the presence of Et₃N, the reaction of HL with Cu(OAc)₂·H₂O or CuCl₂·2H₂O gives the tetranuclear copper(II) complexes {Cu₄(L)₂(μ₂-OH)₂(OAc)₄} 1 and {Cu₄L₄(μ₄-O)Cl₂} 2, respectively. The X-ray crystal structures of both complexes have been obtained. Magnetic studies indicate significant antiferromagnetic coupling between the copper(II) centers for both complexes, with coupling constants (J) of −493.4 cm⁻¹ for 1 and −165 cm⁻¹ for 2.     

Macrocyclic effects upon isomeric CuIIMII and MIICuII cores. Formation with unsymmetric phenol-based macrocyclic ligands

This paper discusses coordination-position isomeric M^IICu^II and Cu^IIM^II complexes, using unsymmetric dinucleating macrocycles (L^m;n)²⁻ ((L^2;2)²⁻, (L^2;3)²⁻ and (L^2;4)²⁻) that comprise two 2-(N-methyl)-aminomethyl-6-iminomethyl-4-bromo-phenonate entities, combined through the ethylene chain (m = 2) between the two amine nitrogens and through the ethylene, trimethylene or tetramethylene chain(n = 2, 3 or 4) between the two imine nitrogens. The macrocycles have dissimilar N(amine)₂O₂ and N(imine)₂O₂ metal-binding sites sharing the phenolic oxygens. The reaction of the mononuclear Cu^II precursors, [Cu(L^2;2)], [Cu(L^2;2)] and [Cu(L^2;2)], with a M^II perchlorate and a M^II acetate salt formed (acetato)M^IICu^II complexes: [CoCu(L^2;2)(AcO)]ClO⁴·0.5H₂O] (1), [NiCu(L^2;2) (AcO)]ClO₄ (2), [ZnCu(L^2;2) (AcO)]ClO₄ (3), [CoCu(L^2;3)(AcO)]ClO₄·0.5H₂O (4), [NiCu(L^2;3)(AcO)]ClO₄ (5), [ZnCu(L^2;3)(AcO)]ClO₄·0.5H₂O (6), [CoCu(L^2;4)(AcO)(DMF)]ClO₄ (7), [NiCu(L^2;4) (AcO)]ClO₄·2DMF (8) and [ZnCu(L^2;4)(AcO)]ClO₄ (9) (the formulation [M_aM_b (L^m;n)]²⁺ means that M_a resides in the aminic site and M_b in the iminic site). The site selectivity of the metal ions is demonstrated by X-ray crystallographic studies for 2·MeOH,3,5,7, and9. An (acetato)Cu^IIZn^II complex, [CuZn(L^2;3)(AcO)]ClO₄ (10), was obtained by the reaction of [PbCu(L^2;3)]-(ClO₄)₂ with ZnSO₄·4H₂O, in the presence of sodium acetate. Other complexes of the Cu^IIM^II type were thermodynamically unstable to cause a scrambling of metal ions. The Cu migration from the iminic site to the aminic site in the synthesis of10 is explained by the ‘kinetic macrocyclic effect’. The coordination-position isomers,6 and10, are differentiated by physicochemical properties.     

Thermal behaviour of new Cu(II) complexes with Schiff bases functionalised with 1,3,5-triazine moieties as potential antibacterial agents

New complexes of type [Cu(L¹)₂(OH₂)]·4H₂O (1), [Cu(L²)(OH₂)]·0.5H₂O (2) and [Cu₃(L³)₂(OH₂)₃]·0.5H₂O (3) were synthesized by [1 + 1], [1 + 2] and [1 + 3], respectively, template condensation of 2,4,6-triamino-1,3,5-triazine and salicylic aldehyde in the presence of copper(II). The features of complexes have been established from microanalytical, IR and UV–Vis data. The thermal analyses have evidenced the thermal intervals of stability and also the accompanying thermodynamic effects. Processes as water elimination and oxidative degradation of the organic ligands were observed. After water elimination, complexes revealed a similar thermal behaviour. The final product of decomposition was copper(II) oxide as powder X-ray diffraction indicated.     

Syntheses and Structures of Coordination Polymers Constructed by Semi‐Rigid Bicarboxylic Acid Ligands

The complexes [Co(L¹)(mpy)] ( 1 ), [Ni(L¹)(mpy)] ( 2 ), [Co(L¹)(tbpy)] · 2H₂O ( 3 ), [Ni₂(L¹)₂(tbpy)₂] · 5H₂O ( 4 ), [Mn₂(L¹)₂(tbpy)₂] · 3H₂O ( 5 ), [Mn(L¹)(biim‐3)] ( 6 ), [Ni₂(L¹)₂(btb)₂(H₂O)] · 2H₂O ( 7 ), [Cu(L²)(mpy)] · 7H₂O ( 8 ), [Co(L²)(tbpy)(H₂O)] ( 9 ), [Ni(L²)(tbpy)(H₂O)] · H₂O ( 10 ), [Cu(L²)(bib)] · 2H₂O ( 11 ), and [Cu(L²)(btb)] · 2H₂O ( 12 ) [H₂L¹ = (3‐carboxyl‐phenyl)‐(4‐(2′‐carboxyl‐phenyl)‐benzyl)ether, H₂L² = 3‐carboxy‐1‐(4′‐carboxybenzyl)‐2‐oxidopyridinium, mpy = 2‐(4‐(4′‐methylphenyl)‐6‐(pyrindin‐2‐yl)pyridin‐2‐yl)pyridine), tbpy = 2‐(4‐(4′‐tert‐butylphenyl)‐6‐(pyrindin‐2‐yl)pyridin‐2‐yl)pyridine), biim‐3 = 1,3‐bis(imidazol‐1′‐yl)propane, btb = 1,4‐bis(1,2,4‐triazol‐1‐ylmethyl)benzene, bib = 1,4‐bis(imidazol‐1′‐ylmethyl)benzene] were synthesized. Compounds 1 – 6 have similar 1D chain structures, which are further linked by π–π interactions to generate supramolecular double chains for 1 and 2 , and supramolecular layers for 3 – 6 . Compound 7 displays a 3D 6‐connected framework with (4⁴ · 6¹¹) topology. Compound 8 features a monomolecular structure, which is further linked by hydrogen bonds between the lattice water molecules and carboxylate oxygen atoms of L² anions to form a 2D supramolecular layer. The monomolecular structures of 9 and 10 are connected by hydrogen bonds and π–π interactions simultaneously to generate supramolecular layers. Compounds 11 and 12 show layer structures.     

Studies on mono- and dinuclear bisoxime copper complexes with different coordination geometries

Two new mono- and dinuclear Cu(II) complexes, namely [CuL¹]·0.5H₂O (1) and [(Cu₂(L²)₂)(DMF)]·0.5DMF (2) (H₂L¹ = 1,2-bis{[(Z)-(3-methyl-5-oxo-1-phenyl-1H-pyrazolidin-4(4H)-yl)(phenyl)]methylene-aminooxy}ethane; H₂L² = 1,3-bis{[(Z)-(3-methyl-5-oxo-1-phenyl-1H-pyrazolidin-4(4H)-yl)(phenyl)] methyleneaminooxy}propane), have been synthesized and characterized by X-ray crystallography. The unit cell of complex 1 contains two crystallographically independent but chemically identical [CuL¹] molecules and one crystalline water molecule, showing a slightly distorted square-planar coordination geometry and forming a wave-like pattern running along the a-axis via hydrogen bonding and π···π stacking interactions. Complex 2 has a dinuclear structure, comprising two Cu(II) atoms, two completely deprotonated phenolate bisoxime (L²)²⁻ moieties (in the form of enol), and both coordinated and hemi-crystalline DMF molecules. Complex 2 has square-planar and square-pyramidal geometries around the two copper centers, whose basic coordination planes are almost perpendicular and form an infinite three-dimensional supramolecular network structure involving intermolecular C–H···N, C–H···O, and C–H···π(Ph) hydrogen bonding and π···π stacking interactions of neighboring pyrazole rings.     

Hemoglobin-stabilized tetranitrosyl binuclear iron complex with pyridine-2-yl in aqueous solutions

The tetranitrosyl iron complex with pyridine-2-yl [Fe₂(SC₅H₄N)₂(NO)₄] (1) has higher NO-donating activity in 3% aqueous solutions of DMSO (pH 7.0, 25 °C) than the organic NO donor, viz., adduct of NO with diethylenetriamine (NO-adduct). The NO concentration was determined by the spectrophotometric method based on the formation of an NO complex with hemoglobin (Hb). The apparent first-order rate constants of the studied reactions are (6.15±0.6)·10⁻¹ s⁻¹ and (0.8±0.08)·10⁻¹ s⁻¹ for complex 1 and the NO-adduct, respectively, at an Hb concentration of 2·10⁻¹ mol L⁻¹ and the ratio [NO donor]/[Hb] = 10. The effect of Hb and [NO donor]/[Hb] ratio on the rate of NO generation from a solution of complex 1 was studied. For a fourfold decrease in the concentration of complex 1 the reaction rate constant decreases to 0.5·10⁻⁴ s⁻¹, whereas the fourfold increase in the Hb concentration results in the stabilization of complex 1. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 732–736, April, 2007.     

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.     

Fluorescent UO2(II) and ZrO(II) complexes: Synthesis,structural characterization,fluorescence, DNA binding studies and biological applications in cell probing

A new series of UO2(II) and ZrO(II) azo‐complexes based on 5‐nitro‐8‐hydroxyquinoline; [UO₂(H₂L¹)(NO₃)EtOH] (1), [ZrO(H₂L¹)(NO₃)H₂O] (2), [UO₂(HL²)(NO₃)EtOH]3H₂O (3), [ZrO(HL²)(NO₃)EtOH] (4), [UO₂(HL³)(NO₃)(H₂O)₃]2H₂O (5) and [ZrO(HL³)(NO₃)EtOH] (6); have been synthesized. The structure of these complexes has been characterized using elemental analysis, thermal analysis, molar conductance, UV–vis, IR, electron impact mass, X‐ray powder diffraction and NMR spectra. The results revealed the formation of non‐electrolyte mononuclear complexes via the N atom of the azo group or of the quinoline ring and the oxygen atom of the deprotonated OH. Fluorescence properties of the synthesized complexes have been examined and the fluorescence quantum yield (Φ_f) has been determined. The complexes have been tested as cell staining and imaging under the fluorescent microscope. The data showed that complexes 1 and 2 efficiently stain the nuclei in addition to some focal cytoplasmic areas. Other than complexes 3 and 4 exclusively stained the nuclei. On the other hand, complexes 5 and 6 stained the cytoplasm exclusively. It has been demonstrated that complex 4 was the most effective in cell staining. The binding constant (Kb) with DNA was calculated using UV–vis absorption titration and fluorescence spectral methods. It was concluded that complex 4 can be used effectively as fluorescent probes in studying cell biology.     

Synthesis and characterization of nickel(II) complexes with three potentially hexadentate Schiff-base ligands and polyamines: X-ray crystal structure determination of one nickel(II) complex

Three new potentially hexadentate N₄O₂ Schiff-base ligands (H₂L¹, H₂L² and H₂L³) were prepared from the reaction of the polyamines N,N′-bis(2-aminophenyl)-1,2-ethanediamine (L¹), N,N′-bis(2-aminophenyl)-1,3-propanediamine (L²) and N,N′-bis(2-aminophenyl)-1,4-butanediamine (L³), respectively with salicylaldehyde. Reaction of the Schiff bases with Ni(II) salts in the presence of N(Et)₃ gave the neutral complexes [NiL⁴], [NiL⁵] and [NiL⁶]. Ni(II) complexes of the polyamines were also prepared. One of complexes [Ni(L¹)(MeCN)₂](ClO₄)₂·MeCN has been characterized through X-ray diffraction methods.     

Structure of uranyl complexes with acetylenedicarboxylic acid, K(H5O2)[UO2(OOCC≡CCOO)2 · H2O] · 2H2O and Cs2[UO2(OOCC≡CCOO)2 · H2O] · 2H2O

Uranyl complexes with acetylenedicarboxylic acid, K(H₅O₂)[UO₂L₂H₂O] · 2H₂O (I) and Cs₂[UO₂L₂H₂O] · 2H₂O (II), L²⁻ = C₄O ₄ ²⁻ were prepared for the first time. The composition and structure of the complexes were determined by X-ray diffraction. The crystal data are as follows: a = 16.254(12) ?, b = 13.508(8) ?, c = 7.683(6) ?, β = 90.91(7)°, space group C2/c, V = 1687(2) ?³ (I); a = 7.0745(10), b = 18.4246(10), c = 13.1383(10) ?, space group Abm2, V = 1712.5(3) ?³ (II). The structures of I and II are based on [UO₂L₂H₂O] _n ²⁻ anionic chains stretched along the [101] direction (I) or [010] direction (II). In I and II, the uranium coordination polyhedron is a pentagonal bipyramid in which the equatorial environment of the uranyl ions is formed by the oxygen atoms of the four L²⁻ anions and the water molecule. The L²⁻ anions in I and II are bidentate bridging ligands connecting two uranium atoms that are next to each other in the anionic chain; their coordination capacity is equal to 2. In I, the K⁺ and H₅O ₂ ⁺ cations are outer-sphere species. The latter form hydrogen bonds combining the anionic chains shifted by translation b with respect to each other. The [UO₂L₂H₂O] _n ²⁻ chains in I are surrounded by the potassium and oxonium cations; in II, these are combined by hydrogen bonds into anionic layers between which Cs⁺ cations are arranged. The IR spectrum of compound II was measured and interpreted. Original Russian Text ? I.A. Charushnikova, A.M. Fedoseev, N.A. Budantseva, I.N. Polyakova, Ph. Moisy, 2007, published in Koordinatsionnaya Khimiya, 2007, Vol. 33, No. 1, pp. 63–69.     

Interaction of <Emphasis Type="Italic">E. coli</Emphasis> DNA with diazine-bridged late first row transition metal complexes derived from hexadentate compartmental ligands: an approach to DNA cleavage/binding studies

A series of binuclear Co^II, Ni^II, Cu^II and Zn^II complexes having μ-1,2 diazine bridging have been prepared and characterized by various physico-chemical methods. The hexadentate ligands were synthesized by condensing 3,5-dichloroformyl-1H-pyrazole with 2-hydrazinobenzothiazole (L¹H) or 4-aminoantipyrine (L²H) in 1:2 ratio. Gel electrophoresis data indicate cleavage of E. coli DNA to a minute extent by both [Co₂L²(μ-Cl)Cl₂(H₂O)₂]·H₂O and [Ni₂L²(μ-Cl)Cl₂(H₂O)₂]. Conversely, the data for the remaining complexes indicated binding but not cleavage. These results were confirmed by viscosity measurements and absorption spectral studies. An intercalative binding mode is predicted when the title complexes interact with DNA.     

Structure of Dibenzocrown Ethers and their H-bonded Adducts. 3. Isolation of Oxonium Ions by Biphenyl-20-crown-6 and [1.5]Dibenzo-18-Crown-6 in Complexes with [NbF6]− and [TaF6]−

The reaction of Nb₂O₅ and Ta₂O₅ with an aqueous solution of hydrofluoric acid, HF in the presence of biphenyl-20-crown-6 (BP20C6, L¹) or [1.5]dibenzo-18-crown-6 ([1.5]DB18C6, L²) results in the complexes [L¹·(H₃O)][NbF₆] (1), [L¹ (H₃O)][TaF₆] (2), [2L²·(H₇O₃)][NbF₆] (3) and [2L²·(H₇O₃)][TaF₆] (4). Complexes 1–4 were identified by the elemental and X-ray structural analysis and IR spectroscopy. Complexes 1 and 2 are isostructural, with the H₃O⁺ oxonium ion embedded in one crown molecule via OH···O hydrogen bonds. Complexes 3 and 4 represent the supramolecular isomers distinctive by the crown conformations and crystal packing, with the (H₇O₃)⁺ cation enclosed in the cage of two crown molecules. Being poor H-bond acceptors, NbF₆⁻ and TaF₆⁻ anions do not compete with the crown oxygen atoms for the oxonium hydrogen atoms, but are involved in the numerous C–H···F short contacts responsible for the extended supramolecular architectures in all cases. A change of crown ethers’ conformation in complexes 1–4 and a correlation between the degree of proton hydration and an accessibility of the crown ether oxygen atoms is observed. Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

Synthesis and structures of Cs4[(UO2)2(C2O4)(SO4)2(NCS)2] · 4H2O and (NH4)4[(UO2)2(C2O4)(SO4)2(NCS)2] · 6H2O

Single crystals of Cs₄[(UO₂)₂(C₂O₄)(SO₄)₂(NCS)₂] · 4H₂O (I) and (NH₄)₄[(UO₂)₂(C₂O₄)(SO₄)₂(NCS)₂] · 6H₂O (II) have been synthesized and studied by X-ray diffraction. The crystals of both compounds are orthorhombic with the space group Pbam, Z = 2, and unit cell parameters a = 12.0177(3) ?, b = 18.6182(5) ?, c = 6.7573(10) ?, R = 0.0376 (I); a = 11.6539(9) ?, b = 18.3791(13) ?, c = 6.7216(5) ?, R = 0.0179 (II). The main structural units of crystals I and II are [(UO₂)₂(C₂O₄)(SO₄)₂(NCS)₂]⁴⁻ chains belonging to the crystal-chemical group A₂K⁰²B₂²M₂¹ (A = UO₂²⁺, K⁰² = C₂O₄²⁻, B² = SO₄²⁻, M¹ = NCS⁻) of the uranyl complexes. The uranium-containing chains are joined into a three-dimensional framework due to a system of electrostatic interactions with the cesium or ammonium ions in the structure of I. In the structure of II, this framework is additionally stabilized by hydrogen bonds involving the outer-sphere water molecules and ammonium ions. Original Russian Text ? I.V. Medrish, A.V. Virovets, E.V. Peresypkina, L.B. Serezhkina, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 7, pp. 1115–1120.