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151.
Room temperature and low temperature magnetic circular dichroism (MCD) in the intraligand spin-forbidden singlet-triplet π-π∗ transition for the coordinated β-diketonate ligands were observed for the β-diketonato Ni(II) complexes with a chelated imino or nitronyl nitroxide radical, but not for the β-diketonato Ni(II) complexes without the radical ligands. This is elucidated by the borrowing mechanism from the singlet-singlet π-π∗ transition through the hypothetical interligand β-diketonate-to-radical charge transfer (LLCT) in contrast to the case of Cr(III) complexes. 相似文献
152.
Sergey V. Kolotilov Stéphane Golhen Vladimir G. Ilyin Lahcène Ouahab 《Inorganica chimica acta》2007,360(6):1883-1889
(ML)2(bipy) complexes (LH2 = thiosemicarbazone of 2-hydroxybenzaldehyde, bipy = 4,4′-bipyridine, M = Ni(II), 1, or Cu(II), 2) were synthesized and characterized by X-ray crystallography. Compound 1 possessed porous structure due to peculiarities of crystal packing, whereas 2 formed infinite zig-zag chains with dense non-porous packing. It was shown that 1 absorbed 0.013 cm3/g of methanol vapor in two steps. Complex 1 was diamagnetic; for 2, the dependency of χ versus T could be interpreted by Bleaney-Bowers expression in 20-300 K temperature range (J = −6.8 cm−1, g = 2.07). 相似文献
153.
This paper reports two tetranuclear manganese clusters, namely, [Mn4O2(O2CCH3)4(O3PC6H11)2(phen)2] (1) and [Mn4O2(O2CPh)4 (O3PC6H11)2(bpy)2] (2). Both contain a butterfly-like [Mn4(μ3-O)2]8+ core. The neighboring Mn atoms within the core are bridged by the carboxylate groups, forming approximately a plane. The phosphonate ligands locate above and below the plane, and cap on top of the Mn3O triangles by using its three phosphonate oxygen atoms. The magnetic measurements of complexes 1 and 2 reveal that dominant antiferromagnetic interactions are propagated between the magnetic centers. 相似文献
154.
Two organic-inorganic hybrid polymers, {[Tb(μ2-bp3dc)(NO3)(H2O)4] · 2H2O}n (1) and {[Ni(μ2-η2-bp3dc)(H2O)3] · H2O}n (2) (bp3dc = 2,2′-bipyridine-3,3′-dicarboxylate) have been hydrothermally synthesized from 2,2′-bipyridine-3,3′-diformylhydrazide (bp3dh) and characterized by the elemental analyses, IR spectrum, TG analysis and the single crystal X-ray diffraction. Polymer 1 shows a 1D linear chain structure, in which extensive hydrogen bonding between the deprotonated carboxylates, nitrate ions, and coordinated water molecules result in a 3D network which also contains face-to-face π-π interactions between adjacent bp3dc ligands. Polymer 2 is a 1D helical chain, and the interchain hydrogen bonding interactions also contribute to the final 3D network. The bridging bp3dc ligands in 1 adopt the anti-bridging bidentate mode, while that in 2 adopt the chelating bridging tridentate mode. The solid-state magnetic properties of the Tb and Ni complexes demonstrated the presence of weak antiferromagnetic exchange interactions, caused by interaction between the neighbouring ions along the 2,2′-bipyridine-3,3′-dicarboxylate bridged chain. 相似文献
155.
Pei-Xiu Yin Jian Zhang Jian-Kai Cheng Lei Zhang Yuan-Gen Yao 《Inorganica chimica acta》2007,360(11):3525-3532
Although the 2,2′-biphenyldicarboxylate ligand (2,2′-dpa) has been widely used to construct metal-organic frameworks (MOFs) with helical sub-structure, the effect of the helical arrangement of spin carriers on the magnetic properties remains rarely scarce. In this article, two unique magnetic metal-organic supramolecular frameworks with different structural features, [Cu2(dpa)2(H2O)2(4,4′-dpdo)0.5]n (1) and [Ni(H2O)4(dpa)] · (4,4′-dpdo)(H2O) (2) (dpdo = 4,4′-dipyridine-N,N′-dioxide), have been isolated from the direct reaction of H2dpa with their corresponding salts in the presence of dpdo. In complex 1, the Cu-dpa double-helical chains, which are bridged by long flexible μ2-dpdo ligands to give rise to a regular 63 covalent layer, exhibit strong antiferromagnetic coupling interactions. Whereas the 1D [Ni(dpa)]n helical chains in complex 2 exhibit weak antiferromagnetic coupling interactions. Rich hydrogen bonds between perpendicular 1D [Ni(dpa)]n helical chains and quasi-1D (dpdo)n chains result in an intricate 3D supramolecular network. 相似文献
156.
硫对石灰性土壤化学性质的影响 总被引:4,自引:0,他引:4
通过连续两茬油菜盆栽试验,分析了硫对土壤pH、电导率、交换性阳离子和水溶性阴离子等指标的影响.结果表明:硫能显著降低土壤pH、增加土壤电导率;施硫会使土壤交换性Na+和交换性K+含量升高,并加剧土壤水溶性阴离子总量的累积;施硫对交换性Ca2+和Mg2+含量影响较小,也未能显著改变土壤阳离子交换量和土壤碱化度.与尿素相比,硫包膜尿素对土壤pH和电导率的影响不显著,但对交换性阳离子和水溶性阴离子影响较大;与尿素处理相比,施硫未表现出明显的增产效应;施硫较多时,油菜产量显著降低. 相似文献
157.
Halotolerant and halophilic microorganisms may be expected to be present on the external walls of buildings, especially in
dry and/or hot climates. They have been detected in Europe in various molecular biological studies. Using plating on specific
salt-supplemented medium (10 and 15%), bacteria and fungi were detected in winter, spring and summer months on the discoloured
external walls of 5 historic buildings in Porto Alegre, South Brazil. Microbial biodiversity in the samples was calculated
using the Simpson Index. Halotolerant non-phototroph diversity was highest in the winter (September), when environmental conditions
are less extreme. Some collections yielded organisms that grew on media with 15% added salt; diversity in this case was lower.
Frequently, and in all winter collections, only one type of microorganism grew; this was a brown-pigmented fungus, probable
genus Cladosporium. Greater diversity was found at 15% salt in 2 collections made in the summer month of January. It is suggested that this
results from the selection of organisms able to resist the more extreme conditions of high temperature and lower relative
humidity. 相似文献
158.
The landward changes of soil enzyme activities and physico-chemical properties of the surface sediment in Chongming Dongtan of the Yangtze River Estuary, were studied. Along the elevation gradient or succession series, the contents of total phosphorus (TP), total nitrogen (TN) and organic matter (OM) in the sediment increased, but the average grain size (AGS) of the sediment and the content of the dissolved inorganic phosphorus (DIP) decreased. The activity of alkaline phosphatase increased gradually along the elevation gradient, and was positively correlated with the values of TP, TN and OM (P<0.05), but negatively to AGS and DIP (P<0.05). It was correlated with a mechanism of substrate inductivity and product inhibition. Catalase activity had the similar trend of gradual increase along the elevation gradient, enhancing the fertility of the soil and the oxidative process of OM in the sediment. Along the succession series, from the tidal flat to the bulrush (Scirpus mariqueter) zone, and then to the reed (Phragmites australis) zone, the activity of sucrase only changed insignificantly, but there was a higher activity in the bulrush zone than in other zones. The activity of proteinase decreased from the tidal flat to the reed zone, and the activity was negatively correlated with OM and TN (P<0.05), but positively with DIP (P<0.05). Through the succession zones a decrease in the number of diatoms resulted in a decline in the concentration of protein, which influenced the proteinase activity, suggesting that the proteinase in the sediment was produced by diatoms. 相似文献
159.
Questions: (1) What are the most important abiotic environmental variables influencing succession in central European man‐made habitats? (2) How do these variables interact with one another and with variation in community properties? Location: Central, western and southern parts of the Czech Republic. Habitats included old fields, urban sites, spoil heaps after coal mining, sites at water reservoirs, extracted sand pit and peatland and reclaimed sites in areas deforested by air pollution. Methods: We investigated vegetation patterns on 15 succes‐sional seres, sampled by the same methods. Time of succession over which the data were available ranged from 12 to 76 years. The cover of vascular plant species (in %) was estimated in 5 m × 5 m plots. The relationships between vegetation characteristics (species composition, total cover, cover of woody species, species number and rate of dominant species turnover) and 13 abiotic site factors, including climatic and soil variables, were tested using CCA ordination and regression models. Results: Substratum pH, the only substratum characteristic, and climate were the environmental variables significantly affecting the vegetation patterns in the course of succession. The rate of succession, measured as the turnover of dominant species, was significantly more rapid in lowland than in mountain climates. On alkaline soils, species numbers in succession increased towards warmer climates. However, acid soils prevented any increase in species numbers, regardless of the climate. Surprisingly, forms of nitrogen and contents of C, P and cations did not exhibit any significant effect on the vegetation characteristics studied. Conclusions: Our approach, to compare a number of seres, can contribute not only to our understanding of succession, but also to help restoration projects to predict vegetation change because the crucial environmental variables, as identified by this study, are easy to measure. 相似文献
160.
Pyruvate dehydrogenase complex (PDC) deficiency is an inborn metabolic disorder that causes neurological abnormalities. In
this report, a murine model of PDC deficiency was analyzed using histology, magnetic resonance (MR) imaging and MR spectroscopy
(MRS) and the results compared to PDC-deficient female patients. Histological analysis of brains from PDC-deficient mice revealed
defects in neuronal cytoarchitecture in grey matter and reduced size of white matter structures. MR results were comparable
to previously published clinical MR findings obtained from PDC-deficient female patients. Specifically, a 15.4% increase in
relative lactate concentration, 64.4% loss of N-acetylaspartate concentration and a near complete loss of discernable glutamine plus glutamate concentration were observed
in a PDC deficient mouse compared to wild-type control. Lower apparent diffusion coefficients (ADCs) were observed within
the brain consistent with atrophy. These results demonstrate the usefulness of this murine model to systematically evaluate
the beneficial effects of dietary and pharmacological interventions.
Special issue dedicated to John P. Blass.
Lioudmila Pliss and Richard Mazurchuk are two investigators who contributed equally. 相似文献