Effect of multivalent cations,temperature, and aging on SOM thermal properties

Multivalent cations are suggested to influence the supramolecular structure of soil organic matter (SOM) via inter- and intra-molecular interactions with SOM functional groups. In this study, we tested the combined effect of cations, temperature treatment, and isothermal aging on SOM matrix properties. Samples from a peat and a mineral soil were either enriched with Na, Ca, and Al or desalinated in batch experiments. After treatment at 25, 40, 60, and 105 °C and after different periods of aging at 19 °C and 31 % relative humidity, we investigated the physicochemical matrix stability and the thermal stability against combustion. We hypothesized that multivalent cations stabilize the SOM matrix, that these structures disrupt at elevated temperatures, and that aging leads to an increase in matrix stability. The results show that cation-specific effects on matrix rigidity started to evolve in the peat only after 8 weeks of aging and were significantly lower than the temperature effects. Temperature treatment above 40 °C caused a non (or not immediately) reversible loss of water molecule bridges (WaMB) and above 60 °C a partly reversible melting process probably of semi-crystalline poly(methylene). Thermal stability increased with increasing cation valence and degree of protonation and was much less affected by temperature. Generally, Na-treated and control samples revealed lower thermal stability and lower increase in matrix rigidity with aging than those treated with Ca, Al, and H. We conclude that drying at elevated temperatures (>40 °C) may irreversibly change SOM structure via disruption of labile cross-links and melting of semi-crystalline domains.     

Synthesis of indium nanoparticles at ambient temperature; simultaneous phase transfer and ripening

Journal of Nanoparticle Research - The increasing demand for optoelectronic devices requires the development of luminescent materials with high luminescence efficiency and low energy demands, and...     

Korrelation zwischen photoelektronen- und elektronen-spektren—VII: Semiempirische berechnung physikalisch-chemischer eigenschaften konjugierter π-systeme

Within the scope of the PPP-SCF-Cl-method the conception of partial bond-localizing on the basis of a structural model of benzene is applied to 34 unsaturated hydrocarbons. It is shown, that the experimental PE- and UV -results, heats of formation and bond-lengths of these compounds can be reproduced with deviations < 2 %.     

In vivo sodium-23 magnetic resonance surface coil imaging: Observing experimental cerebral ischemia in the rat

Sodium-23 magnetic resonance imaging can be used to detect and assess experimental cerebral ischemia in the rat. An imaging technique utilizing a surface coil is described to produce sodium magnetic resonance images of good quality and resolution within 10 min. A novel method of hemispheric occlusion showed edema in the right brain of the rat head within 3 hr after injury. The edema was especially pronounced by 12 hr with effects in the right brain, eye and surrounding muscle evident.     

Korrelation zwischen photoelektronen- und elektronen-spektren : Die zuordnung des A2u-π-orbitals im pe-spektrum des benzols

It has been possible to correlate, by a modified PPP-SCF-CI-method on benzene, PE- and UV-spectroscopical measurements with a deviation of < ± 10^?3 [eV]. In this manner we obtained sets of parameters, of general application to aromatic compounds and we concluded, that the controversial ionisation potential of 12·30 [eV] should be assigned to the π-a_2u-orbital of benzene.     

Silyl anions or silylenoids?--A DFT study of silyllithium compounds with pi-donating substituents

Geometry optimizations at the B3LYP/6-31 + G(d) level for a set of X(SiH3)MeSiLi molecules (X = F, OH, NH2, Cl, SH, and PH2) show that the tetrahedral structure prevails in polar solutions; however, it readily isomerizes into a silylenoid with energy barriers of less than 15 kJ mol(-1). Inverted structures, which predominate in the gas phase, could not be located in solution. Configuration inversion is unfavorable, with energy barriers between 80 and 220 kJ mol(-1). The alpha elimination into a silylene moiety and the corresponding LiX is only likely to occur in solution, particularly for X = Cl and SH.     

Square planar complexes of Cu(II) and Ni(II) with N<Subscript>2</Subscript>O donor set of two Schiff base ligands: synthesis and structural aspects

Abstract Two new square planar Cu(II) and Ni(II) complexes, [CuL¹(NCO)] (1) and [NiL²(N₃)] (2) have been synthesized with two different tridentate N₂O donor Schiff base ligands L ¹ H (1:1 condensation product of benzoylacetone and 2-diethylaminoethylamine) and L ² H (1:1 condensation product of benzoylacetone and 2-dimethylaminoethylamine), respectively. Both the complexes 1 and 2 have been characterized by elemental analysis, IR, UV-Vis spectroscopy, room temperature magnetic susceptibility measurement, electrochemical, thermal, and single crystal X-ray diffraction studies. Structural studies reveal that in both the complexes metal centers have square planar environment with N₂O donor set of Schiff base ligands and terminal pseudohalide anions (isocyanate for 1 and azide for 2) at four coordination sites of square plane. Graphical abstract Square planar complexes of Cu(II) and Ni(II) with N ₂ O donor set of two Schiff base ligands: synthesis and structural aspects Subhra Basak, Soma Sen, Samiran Mitra, C. Marschner, W. S. Sheldrick Two new square planar Cu(II) and Ni(II) complexes, [CuL¹(NCO)] (1) and [NiL²(N₃)] (2) have been synthesized with two different tridentate N₂O donor Schiff base ligands L ¹ H and L ² H respectively. Both the complexes 1 and 2 have been characterized by elemental analysis, IR, UV-Vis spectroscopy, room temperature magnetic susceptibility measurement, electrochemical, thermal and single crystal X-ray diffraction studies.      

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Coordination chemistry of cyclic disilylated stannylenes and plumbylenes to group 4 metallocenes

Reduction of group 4 metallocene dichlorides with magnesium in the presence of cyclic disilylated stannylene or plumbylene phosphine adducts yielded the respective metallocene tetrylene phosphine complexes. Under the same conditions the use of the respective dimerized stannylene or plumbylene gave metallocene ditetrylene complexes. A computational analysis of these reactions revealed for all investigated compounds multiple-bonded character for the M-E(II) linkage, which can be rationalized in the case of the monotetrylene complex with the classical σ-donor/π-acceptor interaction. The strength of the M-E(II) bond increases descending group 4 and decreases going from Sn to its heavier congener Pb. The weakness of the Ti-E(II) bonds is caused by the significantly reduced ability of the titanium atom for d-p π-back-bonding.