Search results for "Electron configuration"
showing 10 items of 44 documents
Protonation and methylation reactions of 2-pyridyl-palladium(II) and -platinum(II) complexes
1983
Abstract The reactions of strong acids HX and HClO4 with the 2-pyridyl complexes [PdX(μ-C5H4N-C2,N)(PPh3)]2 (X = Cl, Br), trans-[PdCl(C5H4N-C2)(PEt3)2] and [PdCl(C5H4N-C2)(dppe)] yield the N-protonated derivatives cis-[PdX2-(C5H5N-C2)(PPh3)], trans-[PdCl(C5H5N-C2)(PEt3)2]ClO4 and [PdCl-(C5H5N-C2)(dppe)]ClO4, respectively. The terminal 2-pyridyl group of trans-[PdCl(C5H4N-C2)(PEt3)2] and [PdCl(C5H4N-C2)(dppe)] also reacts with Me2SO4/NaClO4 to give trans-[PdClC5H4(l-Me)N-C2(PEt3)2]ClO4 and [PdClC5H4(l-Me)N-C2(dppe)]ClO4. Analogous N-protonation or N-methylation reactions occur with trans-[PtBr(C5H4N-C2)(L)2] (L = PEt3, PPh3). The complexes trans-[MX(C5H5N-C2)(PMe2Ph)2]ClO4 (M = Pd, X = Cl an…
Metal-Controlled Magnetoresistance at Room Temperature in Single-Molecule Devices
2017
The appropriate choice of the transition metal complex and metal surface electronic structure opens the possibility to control the spin of the charge carriers through the resulting hybrid molecule/metal spinterface in a single-molecule electrical contact at room temperature. The single-molecule conductance of a Au/molecule/Ni junction can be switched by flipping the magnetization direction of the ferromagnetic electrode. The requirements of the molecule include not just the presence of unpaired electrons: the electronic configuration of the metal center has to provide occupied or empty orbitals that strongly interact with the junction metal electrodes and that are close in energy to their F…
Ab initio study of the SrTiO3, BaTiO3 and PbTiO3 (001) surfaces
2004
The results of first-principles calculations of the two possible terminations of (0 0 1) surfaces of SrTiO 3 (STO), BaTiO3 (BTO) and PbTiO3 (PTO) perovskites are presented. Surface atomic structures and their electronic configurations have been calculated using ab initio density functional theory (DFT) combined with hybrid (B3PW) exchange-correlation technique. Our results are compared with previous quantum mechanical calculations and available experimental data. Surface relaxations and the electronic states near valence band gap are discussed in details for all three perovskites. © 2004 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Fascinating electronic games in iron complexes
1996
Coordination compounds of transition metal ions with open-shell electron configurations may exhibit dynamic electronic-structure phenomena, depending on the nature of the coordinating ligand sphere. The change of spin state with temperature («thermal spin-crossover»), light-induced electron transfer processes leading to long-lived metastable charge and spin states (e.g., «LIESST» effect), are some of the fascinating electronic games encountered in transition metal compounds, which are presently under extensive study by chemists and physicists. Mossbauer spectroscopy plays a dominant role in the investigation of such phenomena in iron compounds, as will be demonstrated in this paper. This wo…
Hybrid density functional theoretical study of NASICON-type NaxTi2(PO4)3 (x = 1–4)
2020
Sodium Super Ionic Conductor (NASICON) structured phosphate framework compounds represent a very attractive class of materials for their use as Na-ion battery electrodes. A series of NASICON-structured NaxTi2(PO4)3 compounds corresponding to varying degrees of sodiation (x = 1–4) have been investigated using high-level hybrid density functional theory calculations using the Linear Combination of Atomic Orbitals and Gaussian-type basis set formalism together with hybrid B1WC and HSE06 exchange–correlation functionals. Using primitive cells of NaxTi2(PO4)3 compounds with different stoichiometry, sodium sublattice structure and titanium oxidation states are constructed and analyzed using group…
X-Ray Crystallographic Analysis of the Charge-Density Wave Modulated Phases in the NbTe4-TaTe4 System
1999
NbTe4 and TaTe4 belong to the important structural family CuAl2 (tl20) characterized by a tetragonal antiprismatic coordination of the minority component. The basic structures were first described by Selte and Kjekshus [1] and Selte and Bjerkelund [2]. In these structures the Te atoms form 1-D infinite columns of stacked tetragonal antiprisms along [001] which are centered by the metal atoms (Figure 1). The arrangement of the antiprismatic columns in the tetragonal a 1 a 2-plane yields short Te-Te contacts, forming Te2 pairs with covalent bonds of about 2.92 A. Thus, following the usual chemical arguments MTe4 (M=Nb,Ta) is a ditelluride of M(IV), i.e. M4+(Te 2 2- )2. The structure is strong…
Hybrid DFT calculations of the atomic and electronic structure for ABO3 perovskite (001) surfaces
2005
Abstract We present the results of first-principles calculations on two possible terminations of the (0 0 1) surfaces of SrTiO3, BaTiO3, and PbTiO3 perovskite crystals. Atomic structure and the electronic configurations were calculated for different 2D slabs, both stoichiometric and non-stoichiometric, using hybrid (B3PW) exchange-correlation technique and re-optimized basis sets of atomic (Gaussian) orbitals. Results are compared with previous calculations and available experimental data. The electronic density distribution near the surface and covalency effects are discussed in details for all three perovskites. Both SrTiO3 and BaTiO3 (0 0 1) surfaces demonstrate reduction of the optical …
Measurement of the first ionization potential of lawrencium (element 103)
2015
Lawrencium, with atomic number 103, has an isotope with a half-life of 27 seconds; even so, its first ionization potential has now been measured on an atom-at-a-time scale and agrees well with state-of-the-art theoretical calculations that include relativistic effects. The most dramatic modern revision of Mendeleev's periodic table of elements came in 1944 when Glenn T. Seaborg placed a new series of elements, the actinides (atomic numbers 89–103), below the lanthanides. In this issue of Nature, Yuichiro Nagame and colleagues report the first measurement of one of the basic atomic properties of element 103 (lawrencium), namely its first ionization potential. Lawrencium is only accessible vi…
Spin crossover complexes as building units of hydrogen-bonded nanoporous structures
2009
The paper reports on the synthesis, crystal structure, differential scanning calorimetry (DSC) and magnetic properties of a spin crossover salt of formula [Fe(bpp)2](cis,cis-1,3,5-Hchtc)·5.5 H2O (1) (bpp = 2,6-bis(pyrazol-3yl)pyridine; cis,cis-1,3,5-Hchtc = monoprotonated cyclohexanetricarboxylate dianion). The salt shows a porous structure with water molecules sitting in the channels. The electronic configuration of the Fe2+ ions is high-spin (HS). Desolvation of 1 yields a material exhibiting an abrupt spin crossover with a thermal hysteresis loop located near room temperature (T1/2↑ = 319 K and T1/2↓ = 309 K). Rehydration of this desolvated salt yields an essentially low-spin (LS) materi…
High-pressure- and low-temperature-induced changes in [(CH3)2NH(CH2)2NH3][SbCl5].
2006
The structure of N,N-dimethylethylenediammonium pentachloroantimonate(III), [(CH3)2NH(CH2)2NH3][SbCl5], NNDP, was investigated at 100 and 15 K at ambient pressure, as well as at pressures up to 4.00 GPa at room temperature in the diamond-anvil cell. The stable structure at low temperatures and low pressures consists of isolated [SbCl5]2- anions and [(CH3)2NH(CH2)2NH3]2+ cations. The inorganic anions have a distorted square pyramidal geometry. They are arranged in linear chains parallel to the c axis. In contrast to the low-temperature studies, where no phase transition was detected, pressure induces a P2(1)/c --P2(1)/n phase transition between 0.55 and 1.00 GPa, accompanied by a doubling of…