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ABSTRACT: Three novel europium platinum borides have been synthesized by arc melting of constituent elements and subsequent annealing. They were characterized by X-ray powder and single-crystal diffraction: EuPt4B, CeCo4B type, P6/mmm, a = 0.56167(2) nm, c = 0.74399(3) nm; Eu3Pt7B2, Ca3Al7Cu2 type as an ordered variant of PuNi3, R3̅m, a = 0.55477(2) nm, c = 2.2896(1) nm; and Eu5Pt18B6-x, a new unique structure type, Fmmm, a = 0.55813(3) nm, b = 0.95476(5) nm, c = 3.51578(2) nm. These compounds belong to the CaCu5 family of structures, revealing a stacking sequence of CaCu5-type slabs with different structural units: CaCu5 and CeCo3B2 type in EuPt4B; CeCo3B2 and Laves MgCu2 type in Eu3Pt7B2; and CaCu5-, CeCo3B2-, and site-exchange ThCr2Si2-type slabs in Eu5Pt18B6-x. The striking motif in the Eu5Pt18B6-x structure is the boron-centered Pt tetrahedron [BPt4], which build chains running along the a axis and plays a decisive role in the structure arrangement by linking the terminal fragments of repeating blocks of fused Eu polyhedra. Physical properties of two compounds, EuPt4B and Eu3Pt7B2, were studied. Both compounds were found to order magnetically at 36 and 57 K, respectively. For EuPt4B a mixed-valence state of the Eu atom was confirmed via magnetic and specific heat measurements. Moreover, the Sommerfeld value of the specific heat of Eu3Pt7B2 was found to be extraordinarily large, on the order of 0.2 J/mol K(2).
Inorganic Chemistry 03/2013; · 4.60 Impact Factor
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ABSTRACT: Three novel copper(II) complexes with the second-generation quinolone antibacterial agents norfloxacin (nfH) and ofloxacin (ofloH) have been synthesized resulting in the complexes [Cu(nfH)(phen)Cl]Cl·5H(2)O (1·5H(2)O), [Cu(nfH)(2)]Cl(2)·6H(2)O (2·6H(2)O) and [Cu(II)(ofloH)(2)][(Cu(I)Cl(2))(2)] (3), respectively. The crystal structures of the complexes have been determined by X-ray crystallography revealing that the quinolones act as bidentate ligands coordinated to Cu(II) atom through the pyridone oxygen and a carboxylato oxygen. UV study of the interaction of the quinolones and the complexes with calf-thymus DNA (CT DNA) has shown that they can bind to CT DNA with [Cu(II)(ofloxacin)(2)][(Cu(I)Cl(2))(2)] exhibiting the highest binding constant to CT DNA. The cyclic voltammograms of the complexes in the presence of CT DNA solution have shown that the interaction of the complexes with CT DNA is mainly through electrostatic binding. DNA solution viscosity measurements have shown that the interaction of the compounds with CT DNA by classical intercalation may be ruled out. Competitive studies with ethidium bromide (EB) indicate that the complexes can partially displace the DNA-bound EB suggesting low to moderate competition with EB. Norfloxacin, ofloxacin and their copper complexes exhibit good binding propensity to human or bovine serum albumin protein having relatively high binding constant values.
Journal of inorganic biochemistry 08/2012; 117C:35-47. · 3.25 Impact Factor
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ABSTRACT: The crystal structures of three ternary Ni-Zn borides have been elucidated by means of X-ray single-crystal diffraction (XSC) and X-ray powder diffraction techniques (XPD) in combination with electron microprobe analyses (EMPA) defining the Ni/Zn ratio. Ni(21)Zn(2)B(24) crystallizes in a unique structure type (space group I4/mmm; a = 0.72103(1) nm and c = 1.42842(5) nm; R(F)(2) = 0.017), which contains characteristic isolated cages of B(20) units composed of two corrugated octogonal boron rings, which are linked at four positions via boron atoms. The B(20) units appear to have eight-membered rings on all six faces like the faces of a cube. Each face is centered by a nickel atom. The six nickel atoms are arranged in the form of an octahedron nested within the B(20) unit. Such a boron aggregation is unique and has never been encountered before in metal-boron chemistry. The crystal structure of Ni(12)ZnB(8-x) (x = 0.43; space group Cmca, a = 1.05270(2) nm, b = 1.45236(3) nm, c = 1.45537(3) nm; R(F)(2) = 0.028) adopts the structure type of Ni(12)AlB(8) with finite zigzag chains of five boron atoms. The compound Ni(3)ZnB(2) crystallizes in a unique structure type (space group C2/m, a = 0.95101(4) nm, b = 0.28921(4) nm, c = 0.84366(3) nm, β = 101.097(3)°, and R(F)(2) = 0.020) characterized by B(4) zigzag chain fragments with B-B bond lengths of 0.183-0.185 nm. The Ni(3)ZnB(2) structure is related to the Dy(3)Ni(2) type.
Inorganic Chemistry 08/2011; 50(16):7669-75. · 4.60 Impact Factor
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ABSTRACT: Phase relations have been established in the ternary system Ce–Rh–Si for the isothermal section at 800°C based on X-ray powder diffraction and EPMA on about 80 alloys, which were prepared by arc melting under argon or by powder reaction sintering. From the 25 ternary compounds observed at 800°C 13 phases have been reported earlier. Based on XPD Rietveld refinements the crystal structures for 9 new ternary phases were assigned to known structure types. Structural chemistry of these compounds follows the characteristics already outlined for their prototype structures: τ7—Ce3RhSi3, (Ba3Al2Ge2-type), τ8—Ce2Rh3−xSi3+x (Ce2Rh1.35Ge4.65-type), τ10—Ce3Rh4−xSi4+x (U3Ni4Si4-type), τ11—CeRh6Si4 (LiCo6P4-type), τ13—Ce6Rh30Si19.3 (U6Co30Si19-type), τ18—Ce4Rh4Si3 (Sm4Pd4Si3-type), τ21—CeRh2Si (CeIr2Si-type), τ22—Ce2Rh3+xSi1−x (Y2Rh3Ge-type) and τ24—Ce8(Rh1−xSix)24Si (Ce8Pd24Sb-type). For τ25—Ce4(Rh1−xSix)12Si a novel bcc structure was proposed from Rietveld analysis. Detailed crystal structure data were derived for τ3—CeRhSi2 (CeNiSi2-type) and τ6—Ce2Rh3Si5 (U2Co3Si5-type) by X-ray single crystal experiments, confirming the structure types. The crystal structures of τ4—Ce22Rh22Si56, τ5—Ce20Rh27Si53 and τ23—Ce33.3Rh58.2−55.2Si8.5−11.5 are unknown. High temperature compounds with compositions Ce10Rh51Si33 (U10Co51Si33-type) and CeRhSi (LaIrSi-type) have been observed in as-cast alloys but these phases do not participate in the phase equilibria at 800°C.
Journal of Solid State Chemistry - J SOLID STATE CHEM. 01/2010; 183(4):829-843.
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ABSTRACT: New ternary compounds La3Pd25-xB8-y (x=1.75, y=0.07) and Ce3Pd25-xB8-y (x=1.25, y=2.00) have been synthesized by arc melting. Their crystal structures were determined from X-ray single crystal diffraction data. Both compounds crystallize with a new monoclinic structure type, space group P21/c with a=1.17567(2) nm, b=1.05757(2) nm, c=1.60664(3) nm, β = 102.1788(10) deg, RF2=0.030 for 7427 structure factors and 289 variable parameters for La3Pd25-xB8-y and a=1.17453(3) nm, b=1.04571(3) nm, c=1.59759(5) nm, β=102.132(2) deg, RF2=0.035 for 2805 structure factors and 283 variable parameters for Ce3Pd25-xB8-y. Rietveld refinement for the X-ray powder diffraction patterns for both compounds confirmed the structure models determined from X-ray single crystal diffraction data.
Journal of Physics Conference Series 07/2009; 176(1):012007.
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ABSTRACT: Single crystals and microcrystalline samples of the calcium tellurate(IV) phases alpha-, beta-, beta'- and gamma-CaTeO3 as well as of two solid solutions Ca(x)Sr(1-x)TeO3 (x = 0.55 and 0.77) have been synthesized and characterized by X-ray diffraction and thermal analysis. A comparative description of the structures and the relations between the polymorphs is given. The main building units of the hitherto unknown structures are isolated [Te(IV)O3]2- units and [(Ca,Sr)O(x)] (x = 6-8) polyhedra. All structures exhibit channels in which the Te(IV) electron lone pairs protrude. The low-temperature phase alpha-CaTeO3 is stable up to 1168 K. It exhibits nearly cylindrical channels (diameter approximately 4 A) and differs structurally from the other phases, whereas the metastable high-temperature phases are closely related to each other. They feature oval channels (shortest and longest diameter approximately 2 and 8 A). Gamma-CaTeO3 can be described as an order-disorder (OD) structure of two non-polar layers with layer groups p12(1)/m1 and p12(1)1. The gamma-CaTeO3 crystal under investigation consists of two polytypes with a maximum degree of order. The two phases Ca(x)Sr(1-x)TeO3 (x = 0.55 and 0.77) are isostructural to the MDO1 polytype of gamma-CaTeO3. Beta-CaTeO3 shows a distinct reversible phase transition at approximately 293 K. The low-temperature modification beta'-CaTeO3 as well as its high-temperature modification beta-CaTeO3 can be considered as threefold superstructures along [100] based on the MDO1 polytype of gamma-CaTeO3.
Acta crystallographica. Section B, Structural science 05/2009; 65(Pt 2):167-81. · 1.80 Impact Factor
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ABSTRACT: 9-Bromo-7,12-dihydroindolo[3,2-d][1]benzazepin-6-ylhydrazine was reacted with 2-acetylpyridine to give a Schiff base as a potential tridentate ligand. The
reaction of this ligand with gallium chloride afforded complexes of 1:1 and 2:1 stoichiometry. The results of X-ray diffraction
studies of the ligand and both gallium complexes are reported and compared with the data for a related gallium complex with
a Schiff base obtained from 9-bromo-7,12-dihydroindolo[3,2-d][1]benzazepin-6-ylhydrazine and 2-hydroxybenzaldehyde.
Central European Journal of Chemistry 08/2008; 6(3):340-346. · 1.07 Impact Factor
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ABSTRACT: Solvatomorphism has been found between two series of complexes of the composition [M(bpy)3]2[NbO(C2O4)3]Cl.nH2O [M = Fe2+ (1, 2), Co2+ (3, 4), Ni2+ (5, 6), Cu2+ (7) and Zn2+ (8, 9); bpy = 2,2'-bipyridine)], crystallizing in the monoclinic space group P2 1/c [3, 5, 8 (n = 11)] or in the orthorhombic space group P21 21 21 [2, 4, 6, 7 (n = 12)]. All the structures contain two symmetry independent [M(bpy)3]2+ cations, one [NbO(C2O4)3]3- anion, one Cl(-) anion, and crystal water molecules. The cations possess a trigonally distorted octahedral geometry, with an additional tetragonal distortion in 7. Analysis of crystal packing reveals a specific type of supramolecular contact comprising four bipyridine ligands from two neighbouring [M(bpy)3]2+ cations--quadruple aryl embrace (QAE) contact. The contact is realized by the alignment of two molecular two-fold rotation axes, preserving the parallel orientation of the molecular three-fold rotation axes. The resulting two-dimensional honeycomb lattices of [M(bpy)3]2+ cations are placed between the hydrogen bonding layers made of [NbO(C2O4)3]3- and Cl(-) anions and the majority of the crystal water molecules. The temperature-dependent magnetic susceptibility measurements (1.8-300 K) show a significant orbital angular momentum contribution for 3 and 4 (high-spin Co2+), the influence of zero-field splitting for 5 and 6(Ni2+) and a substantially paramagnetic Curie behaviour for the Cu2+ compound (7).
Dalton Transactions 03/2008; · 3.84 Impact Factor
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ABSTRACT: The crystal structure of the title basic copper(II) sulfate, {(C(5)H(7)N(2))[Cu2(OH)(SO4)2(H2O)2]}n, shows an unprecedented structural arrangement of two distinct copper centres. CuO6 and CuO5 polyhedra are linked through bridging hydroxide and sulfate anions to form negatively charged infinite chains propagated along the a axis. The negative charge is balanced by 3-aminopyridinium cations that are held in the structure by extensive hydrogen bonding to the inorganic chains. Additionally, the cationic arrangement features pi-pi stacking.
Acta Crystallographica Section C Crystal Structure Communications 06/2007; 63(Pt 5):m222-4. · 0.52 Impact Factor
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ABSTRACT: The magnesium complexes of racemic ofloxacin (oflo) and its pure S-form levofloxacin (S-oflo) have been studied by X-ray crystallography and NMR spectroscopy. Two compounds, [Mg(R-oflo)(S-oflo)(H(2)O)(2)].2H(2)O (1) and [Mg(S-oflo)(2)(H(2)O)(2)].2H(2)O (2), respectively, have been prepared by hydrothermal reactions and their crystal structures have been determined. In both structures the anionic fluoroquinolone ligands are coordinated through the keto and carboxylate oxygens forming 1:2 Mg:oflo complexes. The two structures are practically identical except for the orientation of one of the oxazine methyl groups at the chiral center of 2 which was found in equatorial position, the other oxazine methyl groups in 1 and 2 being axial. This difference affects the stacking pattern of quinolone molecules in the cell. (1)H NMR chemical shift data and Mn(II) paramagnetic line broadening measurements on the free ofloxacin suggest that the coordination of the ligands in solution involves the keto and carboxylate oxygens. However, it is not possible to decide whether the complexes in aqueous solution have 1:1 or 1:2 stoichiometry. The methylated piperazine nitrogen does not interact with the metal ion. Magnesium-quinolone interaction is discussed in relation to the biological activity of quinolones. The antimicrobial activity of the complexes against various microorganisms was tested and it was established that their activity is similar to that of free quinolone drugs.
Journal of Inorganic Biochemistry 12/2006; 100(11):1755-63. · 3.35 Impact Factor
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ABSTRACT: A series of mixed chloro-azole ruthenium complexes with potential antitumor activity, viz., mer-[RuIIICl3(azole)3] (B), trans-[RuIIICl2(azole)4]Cl (C), trans-[RuIICl2(azole)4] (D), and [RuII(azole)6](SO3CF3)2 (E), where azole = 1-butylimidazole (1), imidazole (2), benzimidazole (3), 1-methyl-1,2,4-triazole (4), 4-methylpyrazole (5), 1,2,4-triazole (6), pyrazole (7), and indazole (8), have been prepared as a further development of anticancer drugs with the general formula [RuCl4(azole)2]- (A). These compounds were characterized by elemental analysis, IR spectroscopy, electronic spectra, electrospray mass spectrometry, and X-ray crystallography. The electrochemical behavior has been studied in detail in DMF, DMSO, and aqueous media using cyclic voltammetry, square wave voltammetry, and controlled potential electrolysis. Compounds B and a number of C complexes exhibit one RuIII/RuII reduction, followed, at a sufficiently long time scale, by metal dechlorination on solvolysis. The redox potential values in organic media agree with those predicted by Lever's parametrization method, and the yet unknown EL parameters were estimated for 1 (EL = 0.06 V), 3 (EL = 0.10 V), 4 (EL = 0.17 V), and 5 (EL = 0.18 V). The EL values for the azole ligands 1-8 correlate linearly with their basicity (pK(a) value of the corresponding azolium acid H2L+). In addition, a logarithmic dependence between the homogeneous rate constants for the reductively induced stepwise replacement of chloro ligands by solvent molecules and the RuIII/RuII redox potentials was observed. Lower E(1/2) values (higher net electron donor character of the ligands) result in enhanced kinetic rate constants of solvolysis upon reduction. The effect of the net charge on the RuIII/RuII redox potentials in water is tentatively explained by the application of the Born equation. In addition, the pH-dependent electrochemical behavior of trans-[RuCl2(1,2,4-triazole)4]Cl is discussed.
Inorganic Chemistry 10/2005; 44(19):6704-16. · 4.60 Impact Factor
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ABSTRACT: The compound Rb3[NbO(C2O4)3]⋅2H2O (1) has been synthesized by two different methods and its exact chemical composition established. The niobium atom is heptacoordinated by oxygen atoms forming a distorted pentagonal bipyramid. Inspite of some similarities, the structure of 1 is not isotypic with the structure of (NH4)3[NbO(C2O4)3]⋅H2O.
Structural Chemistry 07/2005; 16(4):409-414. · 1.85 Impact Factor
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ABSTRACT: The synthesis and crystal structure of the mononuclear title compound, [Co(C(2)O(4))(C(10)H(8)N(2))(2)].5H(2)O, is reported. The Co atom is six-coordinated by two O atoms of a bidentate oxalate group and by four N atoms of two bipyridine ligands. The neutral [Co(C(2)O(4))(C(10)H(8)N(2))(2)] entities are connected by pi-pi stacking interactions of the aromatic systems into a two-dimensional layer, interconnected through a ladder-like hydrogen-bonding pattern of solvate water molecules.
Acta Crystallographica Section C Crystal Structure Communications 12/2004; 60(Pt 11):m595-7. · 0.52 Impact Factor
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ABSTRACT: [structure: see text] Inclusion of achiral carbene precursor endo-8-azibicyclo[3.2.1]octan-3-ol (1) in chiral beta-cyclodextrin (7-Cy) and tri-O-methyl-beta-cyclodextrin (TRIMEB) leads to 1:1 complexes 1@7-Cy and 1@TRIMEB, respectively. The combined methods of induced circular dichroism, NMR spectroscopy, and X-ray structure determination were employed for the first time for structural elucidation of the complexes in solution and the solid state. Significantly different orientations of 1 were observed. Compared with 1@7-Cy, 1@TRIMEB exhibits a different guest orientation and an association constant one-twentieth lower.
Organic Letters 07/2004; 6(12):1967-70. · 5.86 Impact Factor
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Synthesis-stuttgart. 01/2004; 2004(16):2704-2710.
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ABSTRACT: The X-ray structure analysis of the title compound, chloro[1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-(piperazin-4-ium-1-yl)-3-quinolinecarboxylate-kappa(2)O(3),O(4)](1,10-phenanthroline-kappa(2)N,N')copper chloride dihydrate, [CuCl(C(17)H(18)FN(3)O(3))(C(12)H(8)N(2))]Cl x 2H(2)O or [CuCl(cfH)(phen)]Cl x 2H(2)O, where cfH is 1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-(piperazin-4-ium-1-yl)-3-quinolinecarboxylate and phen is 1,10-phenanthroline, shows that the geometry around the Cu ion is a slightly distorted square pyramid. Two O atoms of the carbonyl and carboxyl groups of ciprofloxacin and two N atoms of 1,10-phenanthroline are coordinated to the metal centre in the equatorial plane, and a Cl(-) ion is coordinated at the apical position. Extensive intermolecular hydrogen bonding produces a supramolecular structure that consists of alternating six- and 12-membered rings.
Acta Crystallographica Section C Crystal Structure Communications 10/2003; 59(Pt 9):m376-8. · 0.52 Impact Factor
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ABSTRACT: For the unsymmetrical title compound, 1-bromo-1′-[(2S)-N-(1-hydroxy-3-methylbutane-2-yl)]-ferroceneamide, two independent molecules were found in the asymmetric unit. Copyright © 2003 John Wiley & Sons, Ltd.
Applied Organometallic Chemistry 07/2003; 17(9):723 - 724. · 2.06 Impact Factor
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ABSTRACT: The two title ethoxycarbonylmethoxy derivatives of calix[4]arene, namely diethyl 2,4-dihydroxycalix[4]arene-1,3-diyldi(oxyacetate), C(36)H(36)O(8), (I), and tetraethyl calix[4]arene-1,2,3,4-tetrayltetra(oxyacetate), C(44)H(48)O(12), (II), form two different conformations, viz. a cone in (I), where intramolecular hydrogen bonds are formed through OH groups in a partially substituted calix[4]arene, and a 1,3-alternate form of a completely substituted calix[4]arene in (II). A unique three-dimensional array of molecules exists in (II), with the channels extended along the entire crystal.
Acta Crystallographica Section C Crystal Structure Communications 05/2003; 59(Pt 4):O221-4. · 0.52 Impact Factor
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ABSTRACT: The first single-crystal X-ray diffraction study of 2,6-diaziadamantane (2), a compound containing two diazirine functionalities, and B3LYP/6-311+G* and MP2/6-311+G* calculations relating to the interaction between carbon-nitrogen and nitrogen-nitrogen covalent bonds and electron density within the diazirine rings have been performed. In addition, the protonation of 2-aziadamantane (1) has been investigated. The single-crystal X-ray diffraction study of 2, including UV/vis titrations of 1, corroborate the theoretical conclusion that the low basicity can be attributed to a rehybridization of the nitrogen lone pairs. Moreover, the strain in diazirine is unusually small.
The Journal of Organic Chemistry 04/2003; 68(6):2129-34. · 4.45 Impact Factor
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ABSTRACT: The title compound, [Ta(6)Br(12)(H(2)O)(6)](Br(0.4)Cl(1.6)) x 8H(2)O, crystallizes in space group P 1 macro. The structure contains two crystallographically independent [Ta(6)Br(12)(H(2)O)(6)](2+) cluster cations forming distinct layers parallel to the ab plane. The compound is isoconfigurational with the double salts [Ta(6)Br(12)(H(2)O)(6)]X(2) x trans-[Ta(6)Br(12)(OH)(4)(H(2)O)(2)] x 18H(2)O (X = Cl, Br).
Acta Crystallographica Section C Crystal Structure Communications 07/2002; 58(Pt 6):i71-3. · 0.52 Impact Factor
