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排序方式: 共有330条查询结果,搜索用时 187 毫秒
1.
Dr. Christiane Stoll Prof. Dr. Mihail Atanasov Jascha Bandemehr Prof. Dr. Frank Neese Clemens Pietzonka Prof. Dr. Florian Kraus Prof. Dr. Antti J. Karttunen Dr. Markus Seibald Assoc. Prof. Dr. Gunter Heymann Prof. Dr. Hubert Huppertz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(38):9801-9813
As a consequence of the static Jahn-Teller effect of the 5E ground state of MnIII in cubic structures with octahedral parent geometries, their octahedral coordination spheres become distorted. In the case of six fluorido ligands, [MnF6]3− anions with two longer and four shorter Mn−F bonds making elongated octahedra are usually observed. Herein, we report the synthesis of the compound K3[MnF6] through a high-temperature approach and its crystallization by a high-pressure/high-temperature route. The main structural motifs are two quasi-isolated, octahedron-like [MnF6]3− anions of quite different nature compared to that met in ideal octahedral MnIII Jahn-Teller systems. Owing to the internal electric field of Ci symmetry dominated by the next-neighbour K+ ions acting on the MnIII sites, both sites, the pseudo-rhombic (site 1) and the pseudo-tetragonally elongated (site 2) [MnF6]3− anions are present in K3[MnF6]. The compound was characterized by single-crystal and powder X-ray diffraction, and magnetometry as well as by FTIR, Raman, and ligand field spectroscopy. A theoretical interpretation of the electronic structure and molecular geometry of the two Mn sites in the lattice is given by using a vibronic coupling model with parameters adjusted from multireference ab-initio cluster calculations. 相似文献
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Benjamin Wenn Gunter Reekmans Peter Adriaensens Thomas Junkers 《Macromolecular rapid communications》2015,36(16):1479-1485
The branching stemming from midchain radical formation in n‐butyl acrylate polymerization is investigated via melt‐state 13C NMR measurements. The dependence of the degree of branching (DB) on the monomer conversion of the system is examined for photoinduced polymerizations, revealing a steady increase in branching with conversion. For polymerization at moderate light intensities, an increase in branching from 0.03% to 0.37% is observed for polymerizations at 60 °C, which is fivefold below the level of branching observed in thermally initiated polymerizations under otherwise identical reaction conditions. The reason for this overall reduction in branching remains momentarily unclear; yet, a strong dependence of branching on light intensity is observed. While polymerization under a 1 W LED lamp results at almost full monomer conversion in branching degrees of 0.22%, polymerization under a 400 W lamp yields 1.81% of chain branches.
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Dr. Sebastian Sobottka Maite Nößler Dr. Andrew L. Ostericher Dr. Gunter Hermann Noah Z. Subat Julia Beerhues Dr. Margarethe Behr-van der Meer Dr. Lisa Suntrup Dr. Uta Albold Dr. Stephan Hohloch Dr. Jean Christophe Tremblay Prof. Dr. Biprajit Sarkar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(6):1314-1327
Asymmetric platinum donor–acceptor complexes [(pimp)Pt(Q2−)] are presented in this work, in which pimp=[(2,4,6-trimethylphenylimino)methyl]pyridine and Q2−=catecholate-type donor ligands. The properties of the complexes are evaluated as a function of the donor ligands, and correlations are drawn among electrochemical, optical, and theoretical data. Special focus has been put on the spectroelectrochemical investigation of the complexes featuring sulfonyl-substituted phenylendiamide ligands, which show redox-induced linkage isomerism upon oxidation. Time-dependent density functional theory (TD-DFT) as well as electron flux density analysis have been employed to rationalize the optical spectra of the complexes and their reactivity. Compound 1 ([(pimp)Pt(Q2−)] with Q2−=3,5-di-tert-butylcatecholate) was shown to be an efficient photosensitizer for molecular oxygen and was subsequently employed in photochemical cross-dehydrogenative coupling (CDC) reactions. The results thus display new avenues for donor–acceptor systems, including their role as photocatalysts for organic transformations, and the possibility to introduce redox-induced linkage isomerism in these compounds through the use of sulfonamide substituents on the donor ligands. 相似文献
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Birgit Fuchs Prof. Dr. Gunter Heymann Xuefei Wang Abudukadi Tudi Dr. Lkhamsuren Bayarjargal Dr. Renée Siegel Adrian Schmutzler Prof. Dr. Jürgen Senker Dr. Bastian Joachim-Mrosko Dr. Andreas Saxer Prof. Dr. Zhihua Yang Prof. Dr. Shilie Pan Prof. Dr. Hubert Huppertz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(30):6851-6861
La3B6O13(OH) was obtained by a high-pressure/high-temperature experiment at 6 GPa and 1673 K. The compound crystallizes in the space group P21 (no. 4) with the lattice parameters a=4.785(2), b=12.880(4), c=7.433(3) Å, and β=90.36(10)°, and is built up of corner- as well as edge-sharing BO4 tetrahedra. It represents the first acentric high-pressure borate containing these B2O6 entities. The compound develops borate layers of „sechser“-rings with the La3+ cations positioned between the layers. Single-crystal and powder X-ray diffraction, vibrational and MAS NMR spectroscopy, second-harmonic generation (SHG) and thermoanalytical measurements, as well as computational methods were used to affirm the proposed structure and the B2O6 entities. 相似文献
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Fernando Pigeard de Almeida Prado Gunter M. Schütz 《Journal of statistical physics》2011,142(5):984-999
We consider a kinetic Ising model which represents a generic agent-based model for various types of socio-economic systems.
We study the case of a finite (and not necessarily large) number of agents N as well as the asymptotic case when the number of agents tends to infinity. The main ingredient are individual decision thresholds
which are either fixed over time (corresponding to quenched disorder in the Ising model, leading to nonlinear deterministic
dynamics which are generically non-ergodic) or which may change randomly over time (corresponding to annealed disorder, leading
to ergodic dynamics). We address the question how increasing the strength of annealed disorder relative to quenched disorder
drives the system from non-ergodic behavior to ergodicity. Mathematically rigorous analysis provides an explicit and detailed
picture for arbitrary realizations of the quenched initial thresholds, revealing an intriguing “jumpy” transition from non-ergodicity
with many absorbing sets to ergodicity. For large N we find a critical strength of annealed randomness, above which the system becomes asymptotically ergodic. Our theoretical
results suggests how to drive a system from an undesired socio-economic equilibrium (e.g. high level of corruption) to a desirable
one (low level of corruption). 相似文献
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