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171.
Summary. A formalism has been developed that describes spin crossover equilibrium in the solid state by taking into account the effects
of n nearest neighbours of a given molecule on its partition function. In this way binary and many-body interactions of the order
n + 1 are included into the theoretical model and represented by non-ideality parameters connected with the splitting of free
energy levels. Binary interactions are characterised by the main splittings whereas higher order interactions manifest themselves
in asymmetries of splittings within multiplets. The contribution of molecular interactions can also be written in terms of
formal excess free energies of the second, third, fourth and higher orders. Simple relationships between excess free energies
and parameters of multiplets have been found for binary, ternary and quaternary interactions. This formalism is reduced to
that of the model of binary interactions when effects of surroundings are additive leading to equidistant free energy multiplets.
Higher order interactions may cause an abrupt spin crossover but in a limited range of compositions around the transition
point. The regression of experimental transition curves of one-step spin crossover may yield estimates of excess energies
up to the fifth order. 相似文献
172.
Elemental Tellurium reacts with α,α′-dichloro-o-xylene and NaI in 2-methoxyethanol to form 1,1-diiodo-3,4-benzo-1-telluracyclopentane in 83% yield. C8H8TeI2 is molecular in acetone, methylene chloride and methyl ethyl ketone, but ionic in DMF. Two crystalline modifications of the compound have been isolated from 2-methoxyethanol. The yellow-orange or α form is monoclini?, space group P21/c; the orange-red or β form is also monoclinic, space group I2/c. Infrared, optical and mass spectral data, along with solution UV, NMR, molecular weight and conductivity data, suggest that the two crystalline modifications are plymorphs, possibly differing in the degree and type of heavy atom interaction. In 2-methoxyethanol the β form undergoes a solution phase transformation to the stable α form. Both forms are thermochromic. 相似文献
173.
Summary. This review reveals that, in contrast to the general opinion, the aqueous speciation of nickel is poorly known. Besides the
fairly well established first hydrolysis constant, data are scarce and only poor estimates can be derived for higher Ni hydrolysis
constants from a few solubility studies. The situation is even worse in the case of aqueous carbonate complexes. No reliable
experimental study has been published so far and almost all numbers reported in thermodynamic databases are unacceptable estimates.
In this review we scrutinise all these published estimates and propose expectation ranges of nickel carbonate complex stability
through correlation with other known thermodynamic constants. Solubility constants for a few simple nickel solids are known
or have been estimated from thermochemical data. However, none of these simple solids is of geochemical relevance at ambient
conditions. Based on field evidence, classes of solids are identified which potentially govern nickel concentrations in ground
and surface waters. Recent spectroscopic data indicate that magnesium clay minerals and layered double hydroxides are the
most prominent candidates for nickel-bearing solids at ambient conditions.
Corresponding author. E-mail: wolfgang.hummel@psi.ch
Dedicated to the memory of Prof. Rolf Grauer
Received January 14, 2003; accepted January 24, 2003
Published online May 15, 2003 相似文献
174.
Pure rotational transitions of the weakly bound complex He-N(2)O and three minor isotopomers (He-(14)N(15)NO, He-(15)N(14)NO, and He-(15)N(15)NO) were measured in the frequency region from 6 to 20 GHz. Predictions for the microwave transition frequencies were based on the infrared work by Tang and McKellar [J. Chem. Phys. 117, 2586 (2002)]. In the case of (14)N containing isotopomers, nuclear quadrupole hyperfine structure of the rotational transitions was observed and analyzed. The resulting spectroscopic parameters were used to determine geometrical and dynamical information about the complex. An ab initio potential energy surface was calculated at the coupled cluster level of theory with single and double excitations and perturbative inclusion of triple excitations. This surface was constructed using the augmented correlation consistent polarized valence triple zeta basis set for all atoms with the inclusion of bond functions for the van der Waals bond. Bound state calculations were done to determine the energies of low-lying rovibrational levels that are supported by the potential energy surface. The resulting transition energies agree with the experimental values to 1% or better. 相似文献
175.
The new compounds YNi2P2 and LnNi2P2 (Ln = La, Ce, Pr, Nd, Sm, Tb, Dy, Ho, Er, Tm) were prépared by sintering the elemental components in silica tubes. Well-developed crystals were obtained using tin as a flux. They crystallize with the ThCr2Si2 (CeGa2Al2)-type structure which was refined from single-crystal X-ray data for EuNi2P2 to a conventional R value of 0.049 for 118 unique structure factors. While the P atoms in formally isotypic EuCo2P2 are isolated from each other, they form pairs in EuNi2P2. This results in a different ratio and an entirely different bonding situation. A comparison of cell volumes shows that Eu in EuNi2P2 has an intermediate valence. 相似文献
176.
Kayed A. Abu Safieh Ahmad M. Abu Mahthieh Mustafa M. El-Abadelah Mikdad T. Ayoub Wolfgang Voelter 《Monatshefte für Chemie / Chemical Monthly》2007,138(2):157-160
Summary. A novel method for the synthesis of a new series of 5-substituted 1,3-dimethyl pyrazolo[4,3-e][1,2,4]triazines is described. The new synthetic strategy is based on the classical Bischler 1,2,4-benzotriazine synthesis. This approach involves the preparation of 5-hydrazinopyrazole from 5-chloro-1,3-dimethyl-4-nitropyrazole
followed by acylation and nitro group reduction to form the corresponding 4-amino-3-(acylhydrazino)pyrazoles. Intramolecular
oxidative cyclization of the latter derivatives, using polyphosphoric acid, produced the respective target pyrazolotriazines. 相似文献
177.
Kayed A. Abu Safieh Ahmad M. Abu Mahthieh Mustafa M. El-Abadelah Mikdad T. Ayoub Wolfgang Voelter 《Monatshefte für Chemie / Chemical Monthly》2007,21(9):157-160
A novel method for the synthesis of a new series of 5-substituted 1,3-dimethyl pyrazolo[4,3-e][1,2,4]triazines is described. The new synthetic strategy is based on the classical Bischler 1,2,4-benzotriazine synthesis. This approach involves the preparation of 5-hydrazinopyrazole from 5-chloro-1,3-dimethyl-4-nitropyrazole
followed by acylation and nitro group reduction to form the corresponding 4-amino-3-(acylhydrazino)pyrazoles. Intramolecular
oxidative cyclization of the latter derivatives, using polyphosphoric acid, produced the respective target pyrazolotriazines. 相似文献
178.
Ananya Banik Theodosios Famprikis Michael Ghidiu Saneyuki Ohno Marvin A. Kraft Wolfgang G. Zeier 《Chemical science》2021,12(18):6238
The development of high-performance inorganic solid electrolytes is central to achieving high-energy- density solid-state batteries. Whereas these solid-state materials are often prepared via classic solid-state syntheses, recent efforts in the community have shown that mechanochemical reactions, solution syntheses, microwave syntheses, and various post-synthetic heat treatment routines can drastically affect the structure and microstructure, and with it, the transport properties of the materials. On the one hand, these are important considerations for the upscaling of a materials processing route for industrial applications and industrial production. On the other hand, it shows that the influence of the different syntheses on the materials'' properties is neither well understood fundamentally nor broadly internalized well. Here we aim to review the recent efforts on understanding the influence of the synthetic procedure on the synthesis – (micro)structure – transport correlations in superionic conductors. Our aim is to provide the field of solid-state research a direction for future efforts to better understand current materials properties based on synthetic routes, rather than having an overly simplistic idea of any given composition having an intrinsic conductivity. We hope this review will shed light on the underestimated influence of synthesis on the transport properties of solid electrolytes toward the design of syntheses of future solid electrolytes and help guide industrial efforts of known materials.Influence of synthesis and processing on the nature of ultimate product and the ionic transport properties of superionic conductors. 相似文献
179.
Gerhard Buchbauer Johanna Gabmeier Ernst Haslinger Wolfgang Robien Harald Steindl 《Helvetica chimica acta》1985,68(1):231-235
Synthesis and Reactions of the Bicyclo[6.4.0]dodecane-3-carboxylic Acid Derivatives The synthesis and some consecutive reactions of the compounds 5-8 , derivatives of bicyclo[6.4.0]dodecane-3-carboxylic acid ( 1 ), are described. The esters 7 and 8 can be obtained by Baeyer-Villiger oxidation of 2-hydroxy-8-methyltricyclo[7.3.1.02,7]tridecan-13-one ( 4 ) and subsequent hydrolysis of the lactone 5 . The structure and configuration of these compounds has been evaluated by spectroscopic techniques (mainly 2D-NMR methods). The formation of 7 via 1,2-H shift and subsequent isomerization to 8 has been studied. The esters 11 and 13 are formed stereospecifically from 7 and 8 . 相似文献
180.
α-Diazo phosphonates with a conjugated 1,3-diene unit are synthesised by the Bamford-Stevens reaction ( →→). They undergo [4+2]-cycloadditions with the dienophile to form the tetrahydrotriazolopyridazines , which possess an unchanged diazo group. In contrast, dimethyl acetylenedicarboxylate () reacts exclusively with the diazo dipole of to yield the 3H-pyrazoles , which rearrange to by sigmatropic PO-shifts and hydrolyse to form . The diazo compound isomerises to the pyrazole when heated in benzene. 相似文献