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The planar coordination compounds of cobalt(III) with bis(biuretato) ligands are highly unusual due to their intermediate spin triplet ground state. Density functional theory (DFT) and time-dependent DFT have been applied in a study of the structure and electronic spectroscopy of this type of coordination compounds. The investigations included prediction and spectroscopic measurements of the absorption and circular dichroism (CD), as well as an experimental study of the magnetic CD. The results obtained by TD-DFT were in excellent agreement with the observed spectral features, both regarding the d-d and the charge transfer regions. There was noted a systematic blue-shift of the TD-DFT results compared to experiment, corresponding to an offset of ca. 0.5 microm(-1) and a scaling factor of 1.25 for the transition energies. The DFT results are rationalized in terms of a qualitative MO analysis. 相似文献
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Lumduan Mangsup Sutatip Siripaisarnpipat Narongsuk Chaichit 《Analytical sciences》2003,19(9):1345-1346
The reaction between CoCl2 x 6H2O and 2-1-(2-thiazolylazo)-p-cresol (TAC) in acetone resulted in six coordinated cobalt(III) complex, [Co(TAC)2]Cl3. Two TAC ligands coordinate with cobalt ion forming four five membered chelate rings. The cobalt ion is octahedrally coordinated by a phenolic oxygen, azo nitrogen and nitrogen in thiazole rings. Three chloride ions are disordered. 相似文献
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Crystal structure of (C6H5NH3)3[SbCl5]Cl·H2O is determined by X-ray analysis (a = 9.4155(13) Å, b = 11.4344(16) Å, c = 13.1584(18) Å, α = 113.483(2)°, β = 90.383(2)°, γ = 97.323(2)°, space group P \(\bar 1\), Z = 2, ρcalc = 1.642 g/cm3). The crystal structure is based on [SbCl5]2? anions, anilinium cations (C6H5NH3)+, isolated Cl? anions, and water molecules. Structural features responsible for spectral and luminescent properties of the complex are discussed. 相似文献
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Summary The crystal and molecular structure of bis(1-methylimidazole)bis(perchlorato)bis(pyridineN-oxide)copper(II) have been determined using three-dimensional x-ray diffraction data. The complex crystallizes in space group P21/c with Z=2. The cell dimensions area=9.355(3),b=14.363(4),c=9.698(4) Å, and =106.40(3)o. Least-squares refinement of the structure has yielded a final R value of 0.049 for 1235 independent reflections. The centrosymmetric structure consists oftrans pairs of 1-methylimidazole and pyridineN-oxide figands forming a square planar geometry with Cu–N and Cu–O bond lengths of 1.963(4) Å and 1.948(4) Å, respectively. The two perchlorate ions are located above and below the square plane with Cu–O distances of 2.590(5) Å. The uv-vis and i.r. spectra and bonding properties of the title compound are discussed with reference to the structure. 相似文献
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4-Cyano-1-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)-5-methylimidazole ( 4 ) and its corresponding 5-cyano-4-methyl substituted isomer ( 5 ) have been obtained by ribosylation of 4(5)-cyano-5(4)-methylimidazole ( 3 ) via the mercuric cyanide method or by ribosylation of the trimethylsilyl derivative of 3 . Treatment of 4 with methanolic ammonia, ammonium chloride in liquid ammonia and potassium hydrosulfide provided 4-cyano-1-β-D-ribofuranosyl-5-methylimidazole ( 6 ), 1-β-D-ribofuranosyl-5-methylimidazole-4-carboxamide ( 2 ) and 1-β-D-ribofuranosyl-5-methylimidazole-4-thiocarboxamide ( 11 ) respectively. Reaction of 6 with hydroxylamine afforded the corresponding 4-carboxamidoxime substituted nucleoside ( 13 ) which on catalytic reduction in the presence of ammonium chloride, was transformed into 1-β-D-ribofuranosyl-5-methylimidazole-4-carboxamidine ( 14 ) as hydrochloride salt. 相似文献
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The binary complex salt [Co(N2C2H8)3][AuCl4]2Cl has been synthesized. Its crystal structure has been determined. Crystal data for C6H24N6Cl9AuCo: a = 20.8976(14) Å, b = 14.4773(9) Å, c = 7.9944(5) Å; β = 110.809(2)°; V = 2260.9(3) Å3, space group C2/c, Z = 4, d calc = 2.798 g/cm3. The plane square environment of the gold atom of the complex anion is completed to a tetragonal pyramid by the chlorine atom of the neighboring complex anion (Au…Cl 3.538 Å). The structure is layered. Layers of complex cations and complex anions alternate along the X axis. 相似文献
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The electronic structure of a class of compounds based on the bis(biuretato)cobaltate(III) ion has been investigated by spectroscopic methods (UV-vis, CD, MCD), magnetic susceptibility, and ligand field theory. The concept of molecules in molecules has been introduced to account for the conjugated pi system of the whole ligand entity and its perturbation of the metal ion 3d orbitals. The Slater-Condon-Racah scheme was fully exploited; in particular, differences in occupation numbers of the spin orbitals have been used in the spectral assignments of the d-d transitions. The energy calculations used one sigma parameter, two pi parameters, and two Racah parameters. The pi parameters, which were derived from Orgel orbitals of chi and psi type, were found to be positive. The observed charge-transfer transitions are metal <-- ligand. The results of our calculations are in agreement with available experimental data, including the spin triplet ground state and the position of the lower d-d transitions. The approach is general and, for example, applicable to heme iron(II). 相似文献
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Daniel De Moraes Profirio Raphael Enoque Ferraz De Paiva Camilla Abbehausen Alexandre Cuin Norberto Masciocchi Daisy Machado 《Journal of Coordination Chemistry》2016,69(18):2707-2722
A gold(III) complex with N,N′-ethylenebis(pyrrol-2-yl-methyleneamine) (H2pyren) was synthesized and characterized by physicochemical and spectroscopic measurements. Density functional theory (DFT) studies and cytotoxic assays were performed. Infrared, mass spectrometry, and 1H, 13C, and {15N,1H} nuclear magnetic resonance analyses indicate that pyren is deprotonated and gold(III) is four coordinate in a square planar environment, with the pyrrole and imine nitrogens as donors. The structure was confirmed by powder X-ray diffraction and confirmed as a minimum of the potential energy surface by DFT. Cytotoxic activity of [Au(pyren)]+ was active against three tumorigenic cell lines with IC50 values of 35 μM. Interaction studies with CT-DNA by fluorescence and competition with ethidium bromide (EB) showed a quenching of the emission band of DNA with a Stern–Volmer quenching constant value of (3.0 ± 0.1) × 104 M?1 and a decrease in fluorescence quenching of EB-DNA system, respectively, confirming that DNA is a possible target for the complex via an intercalative binding, which was confirmed by DNA conformational changes observed with circular dichroism spectroscopy. 相似文献
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E. Neumann V. Stefov B.
optrajanov B. Engelen H. D. Lutz 《Journal of Molecular Structure》2004,708(1-3):105-111
The crystal structure of dicesium trans-tetraaquadichlorochromium(III) chloride Cs2CrIIICl5·4H2O with trans-[MIIIX2(H2O)4]+ complex ions (space group C2/c, Z=4, a=1915.3(4) pm, b=614.1(1) pm, c=1392.0(3) pm, and β=118.24(3)°, final R1=0.0246 for 2100 unique reflections) was redetermined by single-crystal X-ray diffraction studies. It was found to crystallize in a 2c super structure of the structure reported previously (Inorg. Chem. 20 (1981) 1566; Inorg. Chem. 36 (1997) 2248). The obtained structure data now agree with the results of infrared spectroscopic studies, which has been confirmed in this work, namely that there are two different hydrate H2O molecules in the structure. Phase transitions, static or dynamic disorder of the hydrate H2O molecules, and space group C2/m proposed in the literature were ruled out. The coordinates of the four hydrogen positions derived from the X-ray data have been improved via the O–H distances derived from the wave numbers of the OD stretching modes of matrix isolated HDO molecules (2426, 2323, and 2306 cm−1, 263 K) by using the νOD versus rO–H correlation curve reported in the literature (J. Mol. Struct. 404 (1997) 63). The νOD versus rHCl correlation curve reported by Mikenda (J. Mol. Struct. 147 (1986) 1) should be improved, especially for strong hydrogen bonds. The two hydrate H2O molecules of the title compound are strongly distorted with a weak and a relatively strong O–HCl hydrogen bond each thus intramolecular coupling of the two OH stretching vibrations to coupled ones is largely reduced and, hence, the wavenumbers of the OH and OD stretching modes of the HDO molecules mainly resemble those of the H2O and D2O molecules. The strength of the hydrogen bonds is in accordance with the predictions of the competitive and synergetic effects. Chloro ligands are weaker hydrogen bond acceptor groups than chloride ions. 相似文献
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The crystal structure of the equiatomic compounds EuPdGa and EuPt Ga is TiNiSi type, oP12, and the crystal structure of EuAgGa and EuAuGa is CeCu2 type, OI12. EuCuGa probably has CeCu2-type structure. The Eu atom is divalent in the five compounds, as shown by comparison of the unit cell volume with that of other lanthanide ternary compounds. 相似文献