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1.
Fluorine substitutions on the furanose ring of nucleosides are known to strongly influence the conformational properties of oligonucleotides. In order to assess the effect of fluorine on the conformation of 3′‐deoxy‐3′‐fluoro‐5‐methyluridine (RTF), C10H13FN2O5, we studied its stereochemistry in the crystalline state using X‐ray crystallography. The compound crystallizes in the chiral orthorhombic space group P212121 and contains two symmetry‐independent molecules (A and B) in the asymmetric unit. The furanose ring in molecules A and B adopts conformations between envelope (2E, 2′‐endo, P = 162°) and twisted (2T3, 2′‐endo and 3′exo, P = 180°), with pseudorotation phase angles (P) of 164.3 and 170.2°, respectively. The maximum puckering amplitudes, νmax, for molecules A and B are 38.8 and 36.1°, respectively. In contrast, for 5‐methyluridine (RTOH), the value of P is 21.2°, which is between the 3E (3′‐endo, P = 18.0°) and 3T4 (3′‐endo and 4′‐exo, P = 36°) conformations. The value of νmax for RTOH is 41.29°. Molecules A and B of RTF generate respective helical assemblies across the crystallographic 21‐screw axis through classical N—H…O aand O—H…O hydrogen bonds supplemented by C—H…O contacts. Adjacent parallel helices of both molecules are linked to each other via O—H…O and O…π interactions.  相似文献   

2.
Summary Copper(II), nickel(II) and cobalt(II) perchlorate complexes of 5,5-dimethylcyclohexane-1,2,3-trione-2-(p-nitrophenyl-hydrazone) (HL1), 5,5-dimethyl-cyclohexane-1,2,3-trione-2-(p-chlorophenylhydrazone) (HL2), 5,5-dimethylcyclohexane-1,2,3-trione-2-(o-chlorophenylhydrazone) (HL4), 5,5-dimethylcyclohexane-1,2,3-trione-2-(o-methylphenyl-hydrazone) (HL5) and 5,5-dimethylcyclohexane-1,2,3-trione-2-(m-methylphenylhydrazone) (HL6) have been prepared, and characterized using analytical, spectral and magnetic measurements. The data reveal that the reaction of Cu(ClO4)2 (1 mol) in EtOH, with all ligands, produces complexes of the type CuL(ClO4)(H2O).nH2O. Nickel(II) and cobalt(II) perchlorates react only with HL1 and HL2 to produce the complexes ML(ClO4)(H2O)3 (where M = NiII, L = L and L2, M = CoII, L = L1) and Co(HL2)2-(ClO4)2.2H2O. The spectral data show that the ligands behave as monobasic bidentate in their azo forms, except HL2 which reacts with cobalt(II) as a neutral bidentate ligand in its hydrazone form.  相似文献   

3.
A new series of complexes is synthesized by template condensation of glyoxal and oxalyldihydrazide in methanolic medium in the presence of divalent cobalt, nickel, copper, zinc and cadmium salts forming complexes of the type: [M(C8H8N8O4)X2] where M = Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and X = Cl−1, Br−1, NO 3 −1 , OAc−1. The complexes have been characterized with the help of elemental analyses, conductance measurements, magnetic susceptibility measurements, electronic, n.m.r., infrared and far infrared spectral studies. On the basis of these studies, a six coordinate octahedral geometry for these complexes has been proposed. The biological activities of the metal complexes have been tested in vitro against a number of pathogenic bacteria to assess their inhibiting potential. Most of the compounds have been found to exhibit remarkable antibacterial activities.  相似文献   

4.
The infrared and Raman spectra were recorded in the range 4000–160 cm–1 forM(BF4)2·6 H2O whereM=Fe2+, Co2+, Ni2+. The spectroscopic data support the X-ray structural data in showing that in the crystal hydrates studied two kinds of hydrogen bonds are present: H2O...H2O and OH2... F4B. The energies and molecular force constants (f OH and fH2O) andr OH for OH2...F4B were calculated for the three crystal hydrates. It was found that the bond OH2... F4B is comparatively weak, with mean energy 3.7–3.3 kcal/mol. Two types of water molecule with different structures are existing as the first are participating in H2O...H–O–H...F4B and the second in BF4 ...H–O–H...F4B.  相似文献   

5.
5(2′-Hydroxyphenyl)-3-(4-substituted-phenyl)pyrazolinates of cobalt(II) of the type (C15H12N2OX)2Co [here substituted group X is–H,–Cl,–CH3 or–OCH3] have been synthesized by reaction of anhydrous cobalt(II)chloride with the sodium salt of the pyrazolines in 1 : 2 molar ratio. Their addition complexes with N and P donor ligands [2, 2′-bipyridine, 1, 10-phenanthroline and triphenylphosphine] were prepared in 1 : 1 molar ratio. The newly synthesized complexes were characterized by elemental analyses, molecular weight measurement, magnetic susceptibility, IR, electronic, 31P NMR and FAB mass spectra. All complexes are amorphous as determined by XRD. Tetrahedral geometry around cobalt(II) has been suggested, confirming the presence of two pyrazoline bidentate ligands, cobalt(II)5- (2′-hydroxyphenyl)-3-(4-substituted-phenyl)pyrazolinates. Upon ligand addition, pyrazoline changes to monodentate. The bidentate and monodentate behavior of pyrazoline ligands was confirmed by IR spectral data. The metal complexes and their adducts exhibit good antibacterial and antifungal activity, better than the pyrazolines.  相似文献   

6.
Helium atoms were excited by hydrogen-ion impact, and electric dipole transitions between Stark substates of the 1s 4f multiplet of HeI were induced. Resonance signals were investigated at various frequencies 200 MHz<ν<800 MHz by scanning a static electric fieldF 0?1 kV/cm and observing the intensity of the impact radiation for the singlet or triplet 1s 3d?1s 2p spectral line. From these measurements the following zero-field transition frequencies of the 1s 4f fine structure were deduced: ν(1 F 3?3 F 2)=232.2(1.0) MHz; ν(3 F 3?3 F 4)=214.0(1.3) MHz; ν(1 F 3?3 F 4)=490.6(0.4) MHz. Using calculated parameters of the magnetic fine-structure coupling, the exchange integral 2K=158.0(0.6) MHz of the 1s 4f configuration was evaluated.  相似文献   

7.
Three new oxo‐centered trinuclear mixed‐bridged carboxylate complexes with terminal unsaturated ligands ([M2M′(μ3‐O)(μ‐O2C3H3)5(μ‐O4C6H7)(O2C3H3) (H2O)2]·2H2O [M = Fe, M′ = Fe ( 1 ); M = Fe, M′ = Cr ( 2 ); M = Cr, M′ = Fe ( 3 )]) have been synthesized and characterized by means of elemental analyses, IR spectra and crystal structure analyses. The compounds crystallize isotypically in the orthorhombic space group type Pbcn with a = 24.622(3) Å, b = 16.304(2) Å, c = 17.491(2) Å, V = 7021.5(15) Å3 ( 1 ), a = 24.708(5) Å, b = 16.290(2) Å, c = 17.394(2) Å, V = 7001.0(18) Å3 ( 2 ), a = 24.611(4) Å, b = 16.300(3) Å, c = 17.359(3) Å, V = 6964(2) Å3 ( 3 ), and Z = 8. The infrared spectra show resolved bands arising from νasym(OCO) and νsym(OCO) vibrations of monodentate and bridging carboxylate ligands along with those of νasym(M2M′O) vibrations in the complexes.  相似文献   

8.
Displacement of η6-arene in (C6F5)2Co(η6-toluene), (Cl3Si)2Ni(η6-toluene), and (F3Si)2Ni(η6-toluene) by CO yielded very labile (C6F5)2Co(CO)3, (Cl3Si)2Ni(CO)3, and (F3Si)2Ni(CO)3, which are rare examples of isolated, characterized, simple carbonyl complexes of cobalt(II) and nickel(II). According to infrared ν(CO) studies the cobalt(II) tricarbonyl and the nickel(II) tricarbonyl derivatives are trigonal bipyramidal with the CO ligands in the axial positions. These η6-arene substitutions with CO are reversible under mild conditions. However, the cobalt system slowly degrades to cobalt(I) while the nickel system degrades to nickel(0) carbonyl compounds.  相似文献   

9.
In the cobalt(II) coordination polymer poly[[(μ2‐benzene‐1,3‐dicarboxylato){μ2‐1,1′‐[2,2′‐oxybis(ethane‐2,1‐diyl)]di‐1H‐imidazole}cobalt(II)] monohydrate], {[Co(C10H14N4O)(C8H4O4)]·H2O}n, two crystallographically distinct CoII cations are four‐coordinated by N2O2 donor sets in distorted tetrahedral geometries. The CoII centers are connected by benzene‐1,3‐dicarboxylate (m‐BDC) anions, giving two types of linear chains, which are further joined via meso‐helical 1,1′‐[2,2′‐oxybis(ethane‐2,1‐diyl)]di‐1H‐imidazole ligands to yield a thick two‐dimensional slab. The compound displays a two‐dimensional four‐connected 42.63.8 topology, which is unprecedented in coordination polymers.  相似文献   

10.
Palladium(II) and platinum(II) complexes of the types PdLX2, PdL2X2, PtL2X2 and the Pt(IV) complexes PtLX2Y2, PtL2X2Y′2 (where L = mono- or bidentate organic ligand containing nitrogen donor atoms; X = Cl or Br; Y = Br and Y′ = OH) have been synthesized and characterized by elemental analysis, IR and X-ray photoelectron spectral data. The Pd 3d5/2 binding energies indicate that the 8-aminoquinoline ligand is a better electron donor to the metal than other ligands studied. The Cl 2p3/2 binding energies in the square planar pd(II) complexes are observed in the range 198.0–199.56 eV. The ν(PdCl) vibrations (ca 340 and 320 cm?1) corresponding to two cis-Cl ligands were observed in the IR spectra. Binding through probably N-7 of the guanine residue and the phosphate oxygen in a chelate form is implied from UV difference spectral data.  相似文献   

11.
A new series of antibacterial and antifungal amino acid derived Schiff bases and their cobalt(II), copper(II), nickel(II) and zinc(II) metal complexes have been synthesized and characterized by their elemental analyses, molar conductances, magnetic moments, IR and electronic spectral measurements. The spectral data indicated the Schiff base ligands ( L 1– L 5) derived by condensation of salicylaldehyde with glycine, alanine, phenylalanine, methionine and cysteine, to act as tridentate towards divalent metal ions (cobalt, copper, nickel and zinc) via the azomethine‐N, deprotonated carboxyl group of the respective amino acid and deprotonated oxygen atom of salicylaldehyde by a stoichiometric reaction of M: L (1:2) to form complexes of the type K2[M( L )2] [where M = Co(II), Cu(II), Ni(II) and Zn(II)]. The magnetic moments and electronic spectral data suggested that all complexes have an octahedral geometry. Elemental analyses and NMR spectral data of the ligands and their Zn (II) complexes agree with their proposed structures. The synthesized ligands, along with their metal complexes, were screened for their in‐vitro antibacterial activity against four Gram‐negative (Escherichia coli, Shigella flexeneri, Pseudomonas aeruginosa and Salmonella typhi) and two Gram ‐ positive (Bacillus subtilis and Staphylococcus aureus) bacterial strains and for in‐vitro antifungal activity against Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani and Candida glaberata. The results of these studies show the metal complexes to be more antibacterial/antifungal against one or more species as compared with the uncomplexed Schiff base ligands. The brine shrimp bioassay was also carried out to study their in‐vitro cytotoxic properties. Only three compounds ( 2, 11 and 17 ) displayed potent cytotoxic activity as LD50 = 8.196 × 10?4, 7.315 × 10?4 and 5.599 × 10?4 M /ml respectively, against Artemia salina. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

12.
The magnetic circularly polarized luminescence (MCPL) and photoluminescence (PL) spectra of achiral (2,3,7,8,12,13,17,18-octaethylporphyrinato)platinum(II), PtOEP , and [2-(4′,6′-difluorophenyl)pyridinato-N,C2′]platinum(II) acetylacetonate-O,O, F2-ppyPt(acac) , in toluene and dichloromethane solutions were recorded under an external magnetic field of 1.6 T with N-up and S-up Faraday geometries. The MCPL signs of PtOEP and F2-ppyPt(acac) were controlled solely by changing the N-up and S-up geometries. The MCPL/PL wavelengths of F2-ppyPt(acac) in solutions were varied by the ratio of the monomeric and excimeric species.  相似文献   

13.
Interpretation of the results of determinations of free fluoride (Ff) and total fluoride (Ft) obtained with fluoride ISE while conducting elemental chemical analysis of bulk material of newly synthesized inorganic fluoride compounds is of crucial importance for the purpose of determination of purity and stoichiometry of these compounds. Knowledge of the properties and behavior of these compounds in aqueous media is therefore essential. Observations are presented on the determinations of the amounts of Ft and Ff in fluorinated compounds, in the particular hexafluoropnictate salts (PnF6, Pn = P, As, Sb, Bi) as found in aqueous media and in some compounds with XeF2, AsF3 ligands. A critical look at the determined amounts of Ff, Ftand calculated amounts of bound fluoride (Fb) is provided.  相似文献   

14.
The rare earth borides RERu4B4 (RE = Ce, Pr, Nd, Sm) were synthesized from the elements by arc‐melting and their crystal structures were studied on the basis of X‐ray powder and single‐crystal diffraction: LuRu4B4 type, I41/acd, a = 747.47(8), c = 1506.4(3) pm, wR2 = 0.0579, 362 F2 values for CeRu4B4, a = 751.3(2), c = 1507.1(5) pm, wR2 = 0.0724, 471 F2 values for PrRu4B4, a = 751.0(2), c = 1506.9(6) pm, wR2 = 0.0598, 384 F2 values for NdRu4B4, and a = 749.1(1), c = 1506.0(3) pm, wR2 = 0.0759, 413 F2 values for SmRu4B4, with 18 variables per refinement. Striking structural motifs of the RERu4B4 structures are Ru4 tetrahedra and B2 dumbbells with Ru–Ru and B–B distances of 271 and 180 pm in CeRu4B4. The intermediate valence of cerium leads to shorter Ce–Ru distances of 292 pm. CeRu4B4 behaves like a Pauli paramagnet with a small room temperature susceptibility of 1.5 × 10–4 emu · mol–1. Chemical bonding analyses shows substantial Ru–B and B–B bonding within the [Ru4B4] substructure.  相似文献   

15.
The design and synthesis of 3d–4f heterometallic coordination polymers have attracted much interest due to the intriguing diversity of their architectures and topologies. Pyridine‐2,6‐dicarboxylic acid (H2pydc) has a versatile coordination mode and has been used to construct multinuclear and heterometallic compounds. Two isostructural centrosymmetric 3d–4f coordination compounds constructed from pyridine‐2,6‐dicarboxylic acid and 4,4′‐bipyridine (bpy), namely 4,4′‐bipyridine‐1,1′‐diium diaquabis(μ2‐pyridine‐2,6‐dicarboxylato)tetrakis(pyridine‐2,6‐dicarboxylato)bis[4‐(pyridin‐4‐yl)pyridinium]cobalt(II)dieuropium(III) octahydrate, (C10H10N2)[CoEu2(C10H9N2)2(C7H3NO4)6(H2O)2]·8H2O, (I), and 4,4′‐bipyridine‐1,1′‐diium diaquabis(μ2‐pyridine‐2,6‐dicarboxylato)tetrakis(pyridine‐2,6‐dicarboxylato)bis[4‐(pyridin‐4‐yl)pyridinium]cobalt(II)diterbium(III) octahydrate, (C10H10N2)[CoTb2(C10H9N2)2(C7H3NO4)6(H2O)2]·8H2O, (II), were synthesized under hydrothermal conditions and characterized by IR and fluorescence spectroscopy, thermogravimetric analysis and powder X‐ray diffraction. Both compounds crystallize in the triclinic space group P. The EuIII and TbIII cations adopt nine‐coordinated distorted tricapped trigonal–prismatic geometries bridged by three pydc2? ligands. The CoII cation has a six‐coordination environment formed by two pydc2? ligands, two bpy ligands and two coordinated water molecules. Adjacent molecules are connected by π–π stacking interactions to form a one‐dimensional chain, which is further extended into a three‐dimensional supramolecular network by multipoint hydrogen bonds.  相似文献   

16.
The cadmium(II) coordination polymer poly[[(pyrazino[2,3‐f][1,10]phenanthroline‐κ2N8,N9)cadmium(II)]‐μ3‐naphthalene‐1,4‐dicarboxylato‐κ5O1:O1,O1′:O4,O4′], [Cd(C12H6O4)(C14H8N4)]n, contains two CdII cations, two pyrazino[2,3‐f][1,10]phenanthroline (L) ligands and two naphthalene‐1,4‐dicarboxylate (1,4‐ndc) anions in the asymmetric unit. Both CdII ions are in a distorted CdO5N2 monocapped octahedral coordination geometry. Both unique 1,4‐ndc ligands are bonded to three CdII ions. In these modes, tetranuclear clusters are formed in which four CdII ions are bridged by the carboxylate groups of the 1,4‐ndc ligands to form discrete rods. The tetranuclear cadmium carboxylate clusters act as rod‐shaped secondary building units (SBUs) within the structure. The SBUs are connected together by the aromatic backbone of the dicarboxylate ligands, connecting the clusters into a three‐dimensional α‐polonium net. The title compound represents the first α‐polonium net constructed from rod‐like clusters in coordination polymers. The result indicates that an appropriate combination of dicarboxylate and aromatic chelating ligands is critical to the formation of high‐dimensional structures based on metal clusters in these systems.  相似文献   

17.
The CoII cation in poly[[aqua(μ‐benzene‐1,2‐dicarboxylato‐κ3O1,O2:O1)(μ‐4,4′‐bipyridine‐κ2N:N′)cobalt(II)] trihydrate], {[Co(C8H4O4)(C10H8N2)(H2O)]·3H2O}n, is octahedrally coordinated by two N atoms of two 4,4′‐bipyridine ligands, three O atoms from phthalate anions and a fourth O atom from a coordinated water molecule. The packing consists of planes of coordination polymers linked by hydrogen bonds mediated by three solvent water molecules; the linkage is achieved by the water molecules forming intricate oligomeric clusters which also involve the O atoms of the phthalate ligands.  相似文献   

18.
Binuclear cobalt(II), nickel(II), copper(II) and zinc(II) complexes of general composition [M2L1-2(μ-Cl)Cl2] · nH2O with the Schiff-base ligands (where L1H and L2H are the potential pentadentate ligands derived by condensing 2,6-diformyl-4-methylphenol with 4-amino-3-antipyrine and 2-hydroxy-3-hydrazinoquinoxiline, respectively) have been synthesized and characterized. Analytical and spectral studies support the above formulation. 1H-NMR and IR spectra of the complexes suggest they have an endogenous phenoxide bridge, with chloride as the exogenous bridge atom. The electronic spectra of all the complexes are well characterized by broad d–d and a high intensity charge-transfer transitions. The complexes are chloro-bridged as evidenced by two intense far-IR bands centered around 270–280 cm−1. Magnetic susceptibility measurements show that complexes are antiferromagnetic in nature. The compounds show significant growth inhibitory activity against fungi Aspergillus niger and Candida albicans and moderate activity against bacteria Bacillus cirroflagellosus and Pseudomonas auresenosa.  相似文献   

19.
The two title complexes, catena‐poly[[{2,2′‐[1,3‐propane­diylbis(nitrilo­methyl­idyne)]diphenolato}cobalt(III)]‐μ‐azido], [Co(C17H16N2O2)(N3)]n, (I), and catena‐poly[[{2,2′‐[1,3‐propane­diylbis(nitrilo­methyl­idyne)]diphenolato}cobalt(III)]‐μ‐thio­cyanato], [Co(C17H16N2O2)(NCS)]n, (II), are isomorphous polynuclear cobalt(III) compounds. In both structures, the CoIII atom is six‐coordinated in an octa­hedral configuration by two N atoms and two O atoms of one Schiff base, and two terminal N or S atoms from two bridging ligands. The [N,N′‐bis­(salicyl­idene)propane‐1,3‐diaminato]cobalt(III) moieties are linked by the bridging ligands, viz. azide in (I) and thio­cyanate in (II), giving zigzag polymeric chains with backbones of the type [–Co—N—N—N—Co]n in (I) or [–Co—N—C—S—Co]n in (II) running along the c axis.  相似文献   

20.
The crystal structure of the title compound, triacetato‐1κO;3κ4O,O′‐(2,2′‐imino­diethanol)‐1κ3O,N,O′‐bis­(μ‐2,2′‐iminodi­ethanol­ato)‐1κ2O:2κ6O,N,O′:3κ2O′‐cobalt(III)copper(II)zinc(II), [CoCuZn(C4H9NO2)2(C2H3O2)3(C4H11NO2)], shows a mol­ecule with a triangular three‐metal core. The metal sites were refined with full occupancies, but the possibility that the Zn and Cu positions are actually mixed Cu/Zn sites cannot be excluded. The inter­metallic Cu⋯Co and Co⋯Zn distances are 2.924 (3) and 2.906 (3) Å, respectively. The neutral mol­ecules are held together by N—H⋯O hydrogen bonds involving amine groups from the 2,2′‐iminodiethanol ligands and acetate groups to build two‐dimensional layers.  相似文献   

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