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21.
Catherine P. Raptopoulou Athanassios K. Boudalis Katerina N. Lazarou Vassilis Psycharis Nikos Panopoulos Michael Fardis George Diamantopoulos Jean-Pierre Tuchagues Alain Mari George Papavassiliou 《Polyhedron》2008,27(18):3575-3586
The use of salicylaldehyde oxime (H2salox) in manganese(III) carboxylate chemistry has yielded new members of the family of hexanuclear compounds presenting the [Mn6(μ3-O)2(μ2-OR)2]12+ core, complexes [MnIII6(μ3-O)2(O2CPh)2(salox)6(L1)2(L2)2] (L1 = py, L2 = H2O (1); L1 = Me2CO, L2 = H2O (2); L1 = L2 = MeOH (3)). Addition of NaOMe to the acetonitrile reaction mixture, afforded the 1D complex [MnIII3Na(μ3-O)(O2CPh)2(salox)3(MeCN)]n (4), whereas addition of NaClO4 to the acetone reaction mixture afforded an analogous 1D complex [MnIII3Na(μ3-O)(O2CPh)2(salox)3(Me2CO)]n (5). The structures of 1–3 present the [Mn6(μ3-O)2(μ2-OR)2]12+ core and can be described as two [Mn3(μ3-O)]7+ triangular subunits linked by two μ2-oximato oxygen atoms of the salox2− ligands, which show the less common μ3-κ2O:κO′:κN coordination mode. The benzoato ligands are coordinated through the usual syn,syn-μ2-κO:κO′ mode. The 1D polymeric structures of 4 and 5 consist of alternating [Mn3(μ3-O)]7+ subunits and Na+ atoms linked through two μ3-κ2O:κO′:κN and one μ4-κ2O:κ2O′:κN salox2− ligands as well as one syn,anti-μ2-κO:κO′ benzoato ligand. DC and AC magnetic susceptibility studies on 1 revealed the stabilization of an S = 4 ground state, and indications of single-molecule magnetism behavior, whereas the DC experimental data from polycrystalline sample of 5 are indicative of antiferromagnetic interactions within the [Mn3] subunit. Solid state 1H NMR data of 1 were used to probe the spin-lattice relaxation of the system. 相似文献
22.
Stamatatos TC Diamantopoulou E Raptopoulou CP Psycharis V Escuer A Perlepes SP 《Inorganic chemistry》2007,46(7):2350-2352
The use of di-2-pyridyl ketone oxime [(py)2CNOH] in reactions with Ni(O2CMe)2.4H2O, in the presence or absence of extra inorganic anions (N3- and SCN-) has led to Ni4, Ni5, and Ni7 clusters; the magnetic study of the heptanuclear nickel(II) complex reveals an S = 3 ground state. 相似文献
23.
Afrati T Dendrinou-Samara C Raptopoulou C Terzis A Tangoulis V Kessissoglou DP 《Dalton transactions (Cambridge, England : 2003)》2007,(44):5156-5164
The use of phenyl 2-pyridyl ketoxime (PhPyCNO)/X(-)"blends" (X(-) = OH(-), Cl(-), ClO(4)(-)) in copper chemistry has yielded trinuclear clusters that have been characterized as inverse-9-metallacrown-3 accommodating one or two anions. The magnetic behaviour has shown a large antiferromagnetic interaction. The discrepancy between the Brillouin curve and the experiment has been assigned to the influence of the antisymmetric interaction. By introducing in the magnetization formula the antisymmetric terms derived from the fitting of the susceptibility data the simulated curve become almost superimposable to the experimental one. From the EPR findings it has been shown that the compound [Cu(3)(PhPyCNO)(3)(OCH(3))(Cl)(ClO(4))] () having isosceles magnetic symmetry or lower (delta not equal 0), the antisymmetric exchange is important (G not equal 0) and DeltaE > hv. The structures of the two complexes have been determined by single-crystal X-ray crystallography. 相似文献
24.
Vassilis Kostakos 《Physica A》2009,388(6):1007-1023
We introduce the idea of temporal graphs, a representation that encodes temporal data into graphs while fully retaining the temporal information of the original data. This representation lets us explore the dynamic temporal properties of data by using existing graph algorithms (such as shortest-path), with no need for data-driven simulations. We also present a number of metrics that can be used to study and explore temporal graphs. Finally, we use temporal graphs to analyse real-world data and present the results of our analysis. 相似文献
25.
26.
The reaction of Zn(acac)2 with btaH (1,2,3-benzotriazole) in dmf yielded the pentanuclear complex [Zn5(bta)6(acac)4(dmf)]·dmf (1·dmf). In the presence of pyrazine, the pentanuclear [Zn5(bta)6(acac)4(dmf)]·3.7dmf (2·3.7dmf) and enneanuclear [Zn9(bta)12(acac)6]·6dmf (3·6dmf) complexes were formed, whereas in the presence of 4,4′-bpy the 1D coordination polymer [Zn(acac)2(4,4′-bpy)]n (4) was isolated. The molecular structures of 1·dmf and 2·3.7dmf reveal that the [Zn5] clusters consist of four ZnII ions which span the corners of a tetrahedron and the fifth resides at its centre. The molecular structure of 3·6dmf reveals that the [Zn9] clusters consist of two corner sharing tetrahedra and the structure can be described as the addition of two [Zn5] clusters of 1·dmf and/or 2·3.7dmf followed by the simultaneous abstraction of [Zn(acac)2] and dmf molecules; this alternative was accomplished by recrystallization of 1·dmf from dmf which yielded 3·6dmf. Each of the μ3-κN:κN′:κN′′ benzotriazolate ligands in 1·dmf, 2·3.7dmf and 3·6dmf spans an edge of the tetrahedron. The molecular structure of 4 reveals mononuclear [Zn(acac)2] units bridged via 4,4′-bpy molecules to 1D coordination polymer. Characteristic IR bands of the four complexes are discussed in terms of the coordination modes of the ligands and known structures. 相似文献
27.
Estrader M Ribas J Tangoulis V Solans X Font-Bardía M Maestro M Diaz C 《Inorganic chemistry》2006,45(20):8239-8250
The reaction of Ln(NO3)3.aq with K3[Cr(CN)6] and 2,2'-bipyridine (bpy) in a water/ethanol solution led to two families of complexes: 4 one-dimensional (1D) complexes of the formula trans-[Cr(CN)4(mu-CN)2Ln(H2O)3(bpy)2]n.4nH2O.3.5nbpy (Ln3+ = La, Ce, Pr, and Nd) and 10 1D complexes of the formula trans-[Cr(CN)4(mu-CN)2Ln(H2O)4(bpy)]n.3.5nH2O.1.5nbpy (Ln3+ = Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu). The structures for the fourteen complexes [LaCr]n (1), [CeCr]n (2), [PrCr]n (3), [NdCr]n (4), [NdCr]n (4'), [SmCr]n (5), [EuCr]n (6), [TbCr]n (7), [DyCr]n (8), [HoCr]n (9), [ErCr]n (10), [TmCr]n (11), [YbCr]n (12), and [LuCr]n (13) have been solved. Complexes 1-4 crystallize in the orthorhombic space group Pbam and are isomorphous; complexes 4'-13 crystallize in the triclinic space group PI and are isomorphous. The X-ray structural characterization of complexes 1-4 shows the presence of a discrete decameric water cluster built around a cyclic hexameric core stabilized by the solid-state structure, which represents another new mode of association of water molecules. The Ln3+-Cr3+ magnetic interaction is negligible in 6 and 12, antiferromagnetic in 2, 4', 7, 8, 9, 10, and 11, and unresolved for 3. The complex 5 is a ferrimagnet because its magnetic studies suggest the onset of a very weak ferromagnetic three-dimensional ordering. 相似文献
28.
Methodology to Assess the Effects of Rice Cultivation Under Flooded Conditions on van Genuchten’s Model Parameters and Pore Size Distribution 总被引:1,自引:0,他引:1
Vassilis G. Aschonitis Sofia K. Kostopoulou Vassilis Z. Antonopoulos 《Transport in Porous Media》2012,91(3):861-876
The effects of rice (Oryza sativa L.) cultivation under flooded conditions on soil’s physical-hydraulic properties were studied in this article, using a new
methodology based on a combined analysis on soil water retention curve (WRC) and pore size distribution (PSD). WRC analysis
was carried out through the changes of van Genuchten’s model parameters, the characteristics of WRC at the inflection point,
and the specific water capacity curve. Analysis of PSD was performed on the volume changes of porosity fractions through a
detailed pore size classification, while different pore size classifications based on their hydraulic and structural characteristics
were also used. The methodology was applied using a small dataset obtained from fine-textured Entisol soils which were subjected
to rice cultivation under flooded conditions in Axios River plain (Northern Greece). Measurements of WRC were obtained at
four depths of the soil profile from two fields, before and after the growing season of rice. The analysis indicated that
the van Genuchten’s model parameters (θ
s, a, and n) and the WRC characteristics at the inflection point (pressure head h
i
, pore equivalent diameter D
i
, and slope S
i
) significantly changed after the growing season following similar patterns, along the soil profile in both fields. The parameters
θ
s, a, D
i
, and S
i
were decreased, while n and h
i
were increased. The h
i
and a were the most sensitive parameters, while the values of (h
i
and 1/a) in each layer before and after the growing season for each field were linearly correlated and shifted to higher values because
of compaction, indicating that it could be applied as a tool to evaluate the degree of soil compaction to similarly textured
soils. The peaks of the specific water capacity curves were compressed (lower values of slope S
i
) and shifted to lower water potentials (h
i
) that corresponded to pores of equivalent diameter D
i
between 2 and 6 μm. The soils had few structural pores (>9 μm) and low air-filled porosity (>30 μm) before the growing season,
which presented accessory reduction after the growing season in both fields. Total porosity was reduced at the expense of
structural porosity along the soil profile, while the pore size class of 5–3 μm was identified as the threshold where the
smaller pores’ volume started to increase in all layers of both fields. The results indicated that the changes in the WRC
and the PSD follow specific trends, which can be used in future studies to model temporal variability of soil’s physical-hydraulic
properties. 相似文献
29.
An analytical method for the determination of both sulfadiazine (SDZ) and trimethoprim (TMP), and also N4-acetyl-sulfadiazine (AcSDZ), the main metabolite of SDZ, in fish muscle plus skin has been developed and validated. Dapsone was used as internal standard. The method involves extraction of the analytes from fish tissue by pressurized liquid extraction using water as extractant. Sample cleanup was carried out by solid phase extraction using Abselut Nexus cartridges. Target analytes were quantitatively determined by liquid–chromatography mass spectrometry using single ion monitoring. The developed method was validated according to the European Union requirements (decision 2002/657/EC). The limit of detection for SDZ and AcSDZ was 3.0 and 2.5 µg kg?1 for TMP. The limit of quantification (LOQ) was 10 µg kg?1 for SDZ and AcSDZ and 7.5 µg kg?1 for TMP. The recovery experiments carried out included the concentration levels of 0.5, 1 and 1.5 times the MRLs for SDZ and TMP. Concentration levels for AcSDZ were the same as SDZ. The values obtained were higher than 92.0% with coefficient of variation (CV, %) below 8.6%. The precision of the method, calculated as CV (%), ranged from 0.2 to 6.8% and from 0.8 to 8.9% for intra–day and inter–day analysis, respectively. Decision limit (CCα) was calculated as 104.3, 53.7 and 105.3 µg kg?1 for SDZ, TMP and AcSDZ, respectively. Detection capability (CCβ) was calculated as 110.0, 58.8 and 109.7 µg kg?1 for SDZ, TMP and AcSDZ, respectively. “Matrix effect” and “relative matrix effect” were also evaluated. The method was used for the analysis of fish samples purchased from local markets. 相似文献
30.