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Magnetic Properties and Electronic Structure of Neptunyl(VI) Complexes: Wavefunctions,Orbitals, and Crystal‐Field Models 下载免费PDF全文
Dr. Frédéric Gendron Dr. Dayán Páez‐Hernández Dr. François‐Paul Notter Dr. Ben Pritchard Dr. Hélène Bolvin Prof. Dr. Jochen Autschbach 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(26):7994-8011
The electronic structure and magnetic properties of neptunyl(VI), NpO22+, and two neptunyl complexes, [NpO2(NO3)3]? and [NpO2Cl4]2?, were studied with a combination of theoretical methods: ab initio relativistic wavefunction methods and density functional theory (DFT), as well as crystal‐field (CF) models with parameters extracted from the ab initio calculations. Natural orbitals for electron density and spin magnetization from wavefunctions including spin–orbit coupling were employed to analyze the connection between the electronic structure and magnetic properties, and to link the results from CF models to the ab initio data. Free complex ions and systems embedded in a crystal environment were studied. Of prime interest were the electron paramagnetic resonance g‐factors and their relation to the complex geometry, ligand coordination, and nature of the nonbonding 5f orbitals. The g‐factors were calculated for the ground and excited states. For [NpO2Cl4]2?, a strong influence of the environment of the complex on its magnetic behavior was demonstrated. Kohn–Sham DFT with standard functionals can produce reasonable g‐factors as long as the calculation converges to a solution resembling the electronic state of interest. However, this is not always straightforward. 相似文献
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Using the generalized gradient approximation to density functional theory (DFT), molecular and dissociative oxygen adsorptions on a Pu (111) surface has been studied in detail. Dissociative adsorption with a layer‐by‐layer alternate spin arrangement of the plutonium layer is found to be energetically more favorable, and adsorption of oxygen does not change this feature. Hor1 (O2 is parallel to the surface and lattice vectors) approach on the center2 (center of the unit cell, where there is a Pu atom directly below on the third layer) site, both without and with spin polarization, was found to be the preferred chemisorbed site among all cases studied with chemisorption energies of 8.365 and 7.897 eV, respectively. The second‐highest chemisorption energy occurs at the Ver (O2 is vertical to the surface) approach of the bridge site with chemisorption energies of 8.294 eV (non‐spin‐polarized) and 7.859 eV (spin‐polarized), respectively. We find that 5f electrons are more localized in the spin‐polarized case than the non‐spin‐polarized counterparts. Localization of the 5f electrons is higher in the oxygen‐adsorbed plutonium layers compared with the bare layers. The ionic part of O? Pu bonding plays a significant role in the chemisorption process, along with Pu 5f? O 2p hybridization. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 相似文献
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Dr. Samir Safi Dr. Gaëlle Creff Dr. Aurélie Jeanson Lei Qi Christian Basset Dr. Jérome Roques Dr. Pier Lorenzo Solari Prof. Eric Simoni Dr. Claude Vidaud Prof. Christophe Den Auwer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(34):11261-11269
Herein, we describe the structural investigation of one possible uranyl binding site inside a nonstructured protein. This approach couples spectroscopy, thermodynamics, and theoretical calculations (DFT) and studies the interaction of uranyl ions with a phosphopeptide, thus mimicking a possible osteopontin (OPN) hydroxyapatite growth‐inhibition site. Although thermodynamical aspects were investigated by using time‐resolved laser fluorescence spectroscopy (TRLFS) and isothermal titration calorimetry (ITC), structural characterization was performed by extended X‐ray absorption fine structure (EXAFS) at the U LIII‐edge combined with attenuated total reflection Fourier transform infrared (ATR‐FTIR) spectroscopy. From the vibrational and fluorescence spectra, several structural models of a UO22+/peptide complex were developed and subsequently refined by using theoretical calculations to fit the experimental EXAFS obtained. The structural effect of the pH value was also considered under acidic to moderately acidic conditions (pH 1.5–5.5). Most importantly, the uranyl/peptide coordination environment was similar to that of the native protein. 相似文献
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Quantum Size Effects in the Size–Temperature Phase Diagram of Gallium: Structural Characterization of Shape‐Shifting Clusters 下载免费PDF全文
Dr. Krista G. Steenbergen Dr. Nicola Gaston 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(7):2862-2869
Finite temperature analysis of cluster structures is used to identify signatures of the low‐temperature polymorphs of gallium, based on the results of first‐principle Born–Oppenheimer molecular dynamics simulations. Pre‐melting structural transitions proceed from either the β‐ and/or the δ‐phase to the γ‐ or δ‐phase, with a size‐ dependent phase progression. We relate the stability of each isomer to the electronic structures of the different phases, giving new insight into the origin of polymorphism in this complicated element. 相似文献
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Characterization of Paramagnetic Reactive Intermediates: Predicting the NMR Spectra of Iron(IV)–Oxo Complexes by DFT 下载免费PDF全文
Dr. Andrea Borgogno Dr. Federico Rastrelli Prof. Alessandro Bagno 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(37):12960-12970
The relative energies of spin states of several iron(IV)–oxo complexes and related species have been calculated with DFT methods by employing the B3LYP* functional. We show that such calculations can predict the correct ground spin state of FeIV complexes and can then be used to determine the 1H NMR spectra of all spin states; the spectral features are remarkably different, hence calculated paramagnetic 1H NMR spectra can be used to support the structure elucidation of numerous paramagnetic complexes. Applications to a number of stable and reactive iron(IV)–oxo species are described. 相似文献
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Gorden AE Shuh DK Tiedemann BE Wilson RE Xu J Raymond KN 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(9):2842-2848
The first single-crystal X-ray diffraction analysis of a hydroxypyridonate plutonium(IV) complex is presented, that of the tetradentate ligand 5LIO(Me-3,2-HOPO) with Pu(IV). The [Pu(IV){5LIO(Me-3,2-HOPO)}(2)] complex crystallizes in the space group Pna2(1) with the asymmetric unit cell containing two unique eight-coordinate plutonium complexes and one perchlorate anion. According to shape measure analysis, the geometry of both Pu centers is closest to a bicapped trigonal prism (C(2v) symmetry, for Pu 1: S(C(2v))=13.48 degrees , S(D(4d))=15.43 degrees , S(D(4d))=16.10 degrees ). The average bond length for the Pu--O(phenolic) is 2.31(4) A, whereas the Pu--O(amide) distances are slightly longer, averaging 2.40(2) A. The preparative chemistry of this compound and the implications of the structure are discussed. 相似文献
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The electronic properties of α‐LixV2O5 (x=0.5 and 1) are investigated using first principle calculations based on density functional theory with local density approximation. Different intercalation sites for Li in the V2O5 lattices are considered, showing different influences on the electronic structures of LixV2O5. The lowest total energy is found when Li is only intercalated along the c axis between two bridging oxygen ions of sequential V2O5 layers. The intercalation of Li into V2O5 does not change the electron transition property of V2O5, which is an indirect band gap semiconductor, but leads to a reduction of vanadium ions and an increase of the Fermi level of LixV2O5 arising from the electron transfer from the Li 2 s orbital to the initially empty conduction band of the V2O5 host. 相似文献