共查询到20条相似文献,搜索用时 31 毫秒
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Iurii L. Malaestean Manfred Speldrich Arkady Ellern Svetlana G. Baca Paul Kögerler 《Polyhedron》2010,29(8):1990-1997
Four hexanuclear coordination clusters containing cores of edge-sharing coordination octahedra exemplify how mixed-spin derivatives of a homonuclear parent structure, [(N–O)4], can be realized by a ligand ‘shrink-wrapping’ approach, resulting in [(N–O)4]- and [(N-O)4]-type clusters (L = isobutyrate, N–O = methyldiethanolamine, n-butyldiethanolamine, or triethanolamine). The resulting core structures are either virtually isostructural to the parent structure or differ in the placement of the peripheral metal ions, depending on the mix of structure-directing carboxylate and alkoxyamine ligands with large, flexible alkyl chains. Whereas the and {} complexes show dominant antiferromagnetic exchange, ferrimagnetic coupling features are exhibited by two {} clusters. 相似文献
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《Journal of organometallic chemistry》2007,692(1-3):111-121
New hexadentate dinucleating ligands having a xylyl linker, X–L–R, were synthesized, where X–L–R = 1,3-bis[bis(6-methyl-2-pyridylmethyl)aminomethyl]-2,4,6-trimethybenzene (Me2–L–Me) and 1,3-bis[bis(6-methyl-2-pyridylmethyl)aminomethyl]-2-fluorobenzene (H–L–F). They form dinuclear copper(I) complexes, [Cu2(X–L–R)]2+ (Me2–L–Me (1) and H–L–F (2)). The copper(I) complexes in acetone at −78 °C react with O2 to produce intra- and intermolecular (μ-η2:η2-peroxo)dicopper(II) species depending on the concentrations of the complexes: both complexes generate intramolecular (μ-η2:η2-peroxo)dicopper(II) species [Cu2(O2)(X–L–R)]2+ (1-O2 and 2-O2) at the concentrations below ∼5 mM, whereas at ∼60 mM, both complexes produce intermolecular (μ-η2:η2-peroxo)dicopper(II) species, which were confirmed by the electronic and resonance Raman spectroscopies. The electronic spectrum of 1-O2 in acetone at concentrations below ∼5 mM showed an absorption band at (λmax = 442 nm, ε = 5600 M−1 cm−1) assignable to the (O–O)-to-Cu(II) ( component) LMCT transition in addition to an intense band attributable to the (O–O)-to-Cu(II) ( component) LMCT transition (λmax = 359 nm, ε = 21000 M−1 cm−1), indicating that the (μ-η2:η2-peroxo)Cu(II)2 core of 1-O2 takes a butterfly structure. Decomposition of 1-O2 resulted in hydroxylation of the 2-position of the xylyl linker with 1,2-methyl migration (NIH shift), suggesting that the hydroxylation reaction proceeds via a cationic intermediate as proposed for closely related (μ-η2:η2-peroxo)Cu(II)2 complexes having a xylyl linker. Kinetic study of the decomposition (hydroxylation of the xylyl linker) of 1-O2 suggests that a stereochemical effect of the methyl group in the 2-position of the xylyl linker has a significant influence on a transition state for decomposition (hydroxylation of the xylyl linker). 相似文献
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《Polyhedron》2007,26(9-11):1805-1810
The reaction of 1-(2-pyridyl)-3-(p-tolyl)propane-1,3-dione (HL) with [Mn3O(O2CPh)6(H2O)(py)2] in CH2Cl2 affords a mixed-valence hexanuclear complex [Mn6O2(O2CPh)8L3] (1). Complex 1 contains a core, which is a new structural type in the family of Mn6 complexes. Variable temperature magnetic susceptibility and magnetization measurement of complex 1 have been carried out. The magnetic data indicate that complex 1 has a ground state spin value of S = 7/2 with significant magnetoanisotropy as gauged by the D value of −0.46 cm−1. The frequency dependence of the out-of-phase component in alternating current magnetic susceptibilities for complex 1 indicates the slow magnetic relaxation of a superparamagnetic molecule. 相似文献
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《The Journal of chemical thermodynamics》2006,38(11):1484-1488
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《Polyhedron》2005,24(16-17):2455-2458
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《The Journal of chemical thermodynamics》2006,38(8):1054-1061
The enthalpies of solution in water, ΔsolHm, of some small peptides, namely the amides of five N-acetyl substituted amino acids of glycine, l-alanine, l-proline, l-valine, l-leucine and two cyclic anhydrides of glycine and l-sarcosine (diketopiperazines), were measured by isothermal calorimetry at T = (296.84, 306.89, and 316.95) K. The enthalpies of solution at infinite dilution at T = 298.15 K were derived and added to the enthalpies of sublimation, , at the same temperature, to obtain the corresponding solvation enthalpies at infinite dilution, . Moreover, the partial molar heat capacities at infinite dilution at T = 298.15 K, , were calculated by adding molar heat capacities of solid small peptides, Cp,m(cr), to the values obtained from our experimental data. CH2 group contributions, in terms of solvation enthalpy and partial molar heat capacity, were −3.2 kJ · mol−1 and 89.3 J · K−1 · mol−1, respectively, in good agreement with the literature data. Simple additive methods were used to estimate the average molar enthalpy of solvation and partial molar heat capacity at infinite dilution for the 1/2CONH⋯CONH functional group in the small peptides. Values obtained were −46.7 kJ · mol−1 for solvation enthalpy and −42.4 J · K−1 · mol−1 for partial molar heat capacity, significantly lower than values obtained for the CONH functional group in monofunctional model compounds. 相似文献
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The standard molar enthalpies of formation, (298.15 K) of Pb2Fe2O5(s) and PbFe5O8.5(s) have been determined using acid solution calorimetry. The enthalpies of solution of the compounds Pb2Fe2O5(s) and PbFe5O8.5(s), as well as those of mixtures of Fe2O3(s) and Pb3O4(s) in HCl (aq, 6 mol·dm−3) at 298.15 K were measured. Using these values, the standard enthalpies of formation () of Pb2Fe2O5(s) and PbFe5O8.5(s) were determined as −(1324.2 ± 11.1) kJ·mol−1 and −(2347.8 ± 10.7) kJ·mol−1, respectively. 相似文献
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《Polyhedron》2007,26(9-11):1830-1834
The use of 2-pyridyloximate(-1) ligands, (py)C(R)NO− [R = H, Ph, 2-pyridyl (py)] in cobalt and nickel(II) chemistry has been investigated and led to four families of clusters. A representative member of each family, namely (1), (2), [Ni9(OH)4{(py)CHNO}10(H2O)8]{N(CN)2}3(ClO4) [3{N(CN)2}3(ClO4)] and [Ni4(O2CMe)4{(py)C(ph)NO}4(MeOH)2] (4) is briefly structurally and magnetically described. 相似文献