Predicting core level binding energies shifts: Suitability of the projector augmented wave approach as implemented in VASP

Here, we assess the accuracy of various approaches implemented in Vienna ab initio simulation package code to estimate core‐level binding energy shifts (ΔBEs) using a projector augmented wave method to treat core electrons. The performance of the Perdew–Burke–Ernzerhof (PBE) and the Tao–Perdew–Staroverov–Scuseria (TPSS) exchange‐correlation density functionals is examined on a dataset of 68 molecules containing B→F atoms in diverse chemical environments, accounting for 185 different 1s core level binding energy shifts, for which both experimental gas‐phase X‐ray photoemission (XPS) data and accurate all electron ΔBEs are available. Four procedures to calculate core‐level shifts are investigated. Janak–Slater transition state approach yields mean absolute errors of 0.37 (0.21) eV at PBE (TPSS) level, similar to highly accurate all electron ΔSCF approaches using same functionals, and close to XPS experimental accuracy of 0.1 eV. The study supports the use of these procedures to assign ΔBEs of molecular moieties on material surfaces of interest in surface science, nanotechnology, and heterogeneous catalysis. © 2017 Wiley Periodicals, Inc.     

Sol‐Gel Synthesis and Photocatalytic Study of Visible Light Active N‐Doped KSbWO6

KSbWO₆ was prepared by sol‐gel method. N‐doped KSbWO₆ (KSbWO_6–xN_x) was obtained by heating KSbWO₆ and urea at 400 °C. Both the compounds are characterized by powder X‐ray diffraction (XRD), TEM, SEM‐EDS, X‐ray photo electronic spectroscopy (XPS), and UV/Vis diffuse reflectance spectroscopy (UV‐DRS). A shift in the peak positions of powder XRD and XPS spectra was observed. The band gap energy (E_g) of KSbWO₆ and N‐doped KSbWO₆ was obtained from their diffused reflectance spectra.E_g was reduced from 3.17 eV to 2.56 eV upon nitrogen doping in KSbWO₆. The reduction of the E_g is attributed to the lifting of valence band of N‐doped KSbWO₆, due to the mixing of O 2p states with N 2p states. The photocatalytic activity of both the samples was studied by degradation of methylene blue (MB). The nitrogen doped KSbWO₆ shows higher photocatalytic activity compared to that of KSbWO₆.     

Structures and Dynamic Solution Behavior of Cationic,Two‐Coordinate Gold(I)–π‐Allene Complexes

A family of seven cationic gold complexes that contain both an alkyl substituted π‐allene ligand and an electron‐rich, sterically hindered supporting ligand was isolated in >90 % yield and characterized by spectroscopy and, in three cases, by X‐ray crystallography. Solution‐phase and solid‐state analysis of these complexes established preferential binding of gold to the less substituted C?C bond of the allene and to the allene π face trans to the substituent on the uncomplexed allenyl C?C bond. Kinetic analysis of intermolecular allene exchange established two‐term rate laws of the form rate=k₁[complex]+k₂[complex][allene] consistent with allene‐independent and allene‐dependent exchange pathways with energy barriers of ΔG^≠₁=17.4–18.8 and ΔG^≠₂=15.2–17.6 kcal mol^?1, respectively. Variable temperature (VT) NMR analysis revealed fluxional behavior consistent with facile (ΔG^≠=8.9–11.4 kcal mol^?1) intramolecular exchange of the allene π faces through η¹‐allene transition states and/or intermediates that retain a staggered arrangement of the allene substituents. VT NMR/spin saturation transfer analysis of [{P(tBu)₂o‐binaphthyl}Au(η²‐4,5‐nonadiene) ]⁺SbF₆^? ( 5 ), which contains elements of chirality in both the phosphine and allene ligands, revealed no epimerization of the allene ligand below the threshold for intermolecular allene exchange (ΔG^≠_298K=17.4 kcal mol^?1), which ruled out the participation of a η¹‐allylic cation species in the low‐energy π‐face exchange process for this complex.     

Stable N‐Heterocyclic Germylenes of the Type [Fe{(η5‐C5H4)NR}2Ge] and Their Oxidation Reactions with Sulfur,Selenium, and Diphenyl Diselenide

Three new N‐heterocyclic germylenes of the type [Fe{(η⁵‐C₅H₄)NR}₂Ge] ( 1R Ge) containing particularly bulky alkyl [R = 2‐adamantyl (Ad), 1,1,2,2‐tetramethylpropyl (Pr*)] or aryl substituents [R = 2,6‐diisopropylphenyl (Dipp)] were prepared and structurally characterized, in two cases (R = Ad, Dipp), by single‐crystal X‐ray diffraction. Together with the previously described homologues with R = trimethylsilyl (TMS), tert‐butyl (tBu), and mesityl (Mes) their oxidative addition reactions with S₈ and Se₈ were studied, which afforded compounds of the type [ 1R Ge(μ‐E)]₂ (E = S, Se). The low solubility of most of these products severely hampered their purification and characterization. Nevertheless, their structural characterization by single‐crystal X‐ray diffraction was possible in six cases (E = S, R = Ad, Pr*; E = Se, R = Ad, Pr*, Mes, Dipp). No solubility problems were encountered in oxidative addition reactions with diphenyl diselenide, affording products of the type 1R Ge(SePh₂)₂, whose crystal structures could be determined in four cases (R = TMS, tBu, Mes, Dipp). Short intramolecular CH ··· Se contacts compatible with hydrogen bonds were observed for [ 1Ad Ge(μ‐Se)]₂, [ 1Pr* Ge(μ‐Se)]₂, and 1tBu Ge(SePh₂)₂.     

Synthesis and Characterization of Two Formyl 2‐Tetrazenes

The synthesis of two formyl 2‐tetrazenes, namely, (E)‐1‐formyl‐1,4,4‐trimethyl‐2‐tetrazene ( 2 ) and (E)‐1,4‐diformyl‐1,4‐dimethyl‐2‐tetrazene ( 3 ), by oxidation of (E)‐1,1,4,4‐tetramethyl‐2‐tetrazene ( 1 ) using potassium permanganate in acetone solution is presented. Compound 3 was also synthesized in an improved yield from the oxidation of 1‐formyl‐1‐methylhydrazine ( 4a ) using potassium permanganate in acetone. Both compounds 2 and 3 were characterized by analytical (elemental analysis, GC‐MS) and spectroscopic methods (¹H, ¹³C, and ¹⁵N NMR spectroscopy, and IR and Raman spectroscopy). In addition, the solid‐state structures of the compounds were confirmed by low‐temperature X‐ray analysis. (Compound 2 : triclinic; space group P‐1; a=5.997(1) Å, b=8.714(1) Å, c=13.830(2) Å; α=107.35(1)°, β=90.53(1)°, γ=103.33(1)°; V_UC=668.9(2) ų; Z=4; ρ_calc=1.292 cm^?3. Compound 3 : monoclinic; space group P2₁/c; a=5.840(2) Å, b=7.414(3) Å, c=8.061(2) Å; β=100.75(3)°; V_UC=342(2) ų; Z=2; ρ_calc=1.396 g cm^?3.) The vibrational frequencies of compounds 2 and 3 were calculated using the B3LYP method with a 6‐311+G(d,p) basis set. We also computed the natural bond orbital (NBO) charges using the rMP2/aug‐cc‐pVDZ method and the heats of formation were determined on the basis of their electronic energies. Furthermore, the thermal stabilities of these compounds, as well as their sensitivity towards classical stimuli, were also assessed by differential scanning calorimetry and standard BAM tests, respectively. Lastly, the attempted synthesis of (E)‐1,2,3,4‐tetraformyl‐2‐tetrazene ( 6 ) is also discussed.     

Spectral,crystallographic, theoretical and antibacterial studies of palladium(II)/platinum(II) complexes with unsymmetric diphosphine ylides

The reaction of α‐keto‐stabilized diphosphine ylides [Ph₂P(CH₂)_nPPh₂═C(H)C(O)C₆H₄‐p‐CN] (n = 1 (Y¹); n = 2 (Y²)) with dibromo(1,5‐cyclooctadiene) palladium(II)/platinum(II) complexes, [Pd/PtBr₂(cod)], in equimolar ratio gave the new cyclometalated Pd(II) and Pt(II) complexes [Br₂Pd(κ²‐Y¹)] ( 1 ), [Br₂Pt(κ²‐Y¹)] ( 2 ), [Br₂Pd(κ²‐Y²)] ( 3 ) and [Br₂Pt(κ²‐Y²)] ( 4 ). These compounds were screened in a search for novel antibacterial agents and characterized successfully using Fourier transfer infrared and NMR (¹H, ¹³C and ³¹P) spectroscopic methods. Also, the structures of complexes 1 and 2 were characterized using X‐ray crystallography. The results showed that the P,C‐chelated complexes 1 and 2 have structures consisting of five‐membered rings, while 3 and 4 have six‐membered rings, formed by coordination of the ligand through the phosphine group and the ylidic carbon atom to the metal centre. Also, a theoretical study of the structures of complexes 1 – 4 was conducted at the BP86/def2‐SVP level of theory. The nature of metal–ligand bonds in the complexes was investigated using energy decomposition analyses (EDA) and extended transition state combined with natural orbitals for chemical valence analyses. The results of EDA confirmed that the main portions of ΔE_int, about 57–58%, in the complexes are allocated to ΔE_elstat.     

X‐Ray Emission Spectroscopy: A Spectroscopic Measure for the Determination of NO Oxidation States in Fe–NO Complexes

Extensive study of the electronic structure of Fe‐NO complexes using a variety of spectroscopic methods was attempted to understand how iron controls the binding and release of nitric oxide. The comparable energy levels of NO π* orbitals and Fe 3d orbitals complicate the bonding interaction within Fe? NO complexes and puzzle the quantitative assignment of NO oxidation state. Enemark–Feltham notation, {Fe(NO)_x}ⁿ, was devised to circumvent this puzzle. This 40‐year puzzle is revisited using valence‐to‐core X‐ray emission spectroscopy (V2C XES) in combination with computational study. DFT calculation establishes a linear relationship between ΔE_σ2s*‐σ2p of NO and its oxidation state. V2C Fe XES study of Fe? NO complexes reveals the ΔE_σ2s*‐σ2p of NO derived from NO σ_2s*/σ_2p→Fe_1s transitions and determines NO oxidation state in Fe? NO complexes. Quantitative assignment of NO oxidation state will correlate the feasible redox process of nitric oxide and Fe‐nitrosylation biology.     

Development of a simultaneous measurement system of x‐ray diffraction and raman spectra: Application to structural study of crystalline‐phase transitions of chain molecules

The development of a bench‐top‐type system for simultaneous measurement of X‐ray diffraction and Raman spectra has been made to investigate structural changes in the phase transitions of chain molecules such as polyethylene, n‐alkane, and so forth from various viewpoints. For the X‐ray diffraction measurement an imaging plate or a charge‐coupled device camera was used as a two‐dimensional detector. For the Raman spectral measurement a miniature Raman spectrometer was used with optical fibers for the irradiation of incident laser beams and collection of scattered signals. For example, in the heating process of the n‐C₃₀H₆₂ sample, the phase transition from orthorhombic‐to‐hexagonal lattices could be detected clearly by the X‐ray and Raman measurements. By comparing these two different types of data in detail, an intimate relationship between conformational disordering and rotational motion of molecular chains is detected more clearly than before. Also, similar discussion can be made for the orthorhombic‐to‐hexagonal phase transition of the geometrically constrained polyethylene sample occurring immediately below the melting point. Another example concerns the structural change in the photoinduced solid‐state polymerization of cis,cis‐diethylmuconate single crystal. From the shifts in the X‐ray reflection position and Raman frequency characteristic of the produced polymer, it was found that the molecular deformation of the polymer chains and lattice strain was induced in the early stage of the polymerization reaction. For the ferroelectric‐phase transition of vinylidene fluoride copolymer, the simultaneous measurement was made for collecting triple information of small‐angle and wide‐angle X‐ray scatterings and Raman spectra to know the relationship between the structural change in the crystal lattice and the morphological change in the lamellar stacking mode. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 495–506, 2002; DOI 10.1002/polb.10112     

Exact electronic properties in the classically forbidden region of a metal surface

We derive exact properties of the inhomogeneous electron gas in the asymptotic classically forbidden region at a metal–vacuum interface within the framework of local effective potential energy theory. We derive a new expression for the asymptotic structure of the Kohn–Sham density functional theory (KS‐DFT) exchange‐correlation potential energy v_xc(r) in terms of the irreducible electron self‐energy. We also derive the exact asymptotic structure of the orbitals, density, the Dirac density matrix, the kinetic energy density, and KS exchange energy density. We further obtain the exact expression for the Fermi hole and demonstrate its structure in this asymptotic limit. The exchange‐correlation potential energy is derived to be v_xc(z → ∞) = ?α_KS,xc/z, and its exchange and correlation components to be v_x(z → ∞) = ?α_KS,x/z and v_c(z → ∞) = ?α_KS,c/z, respectively. The analytical expressions for the coefficients α_KS,xc and α_KS,x show them to be dependent on the bulk‐metal Wigner–Seitz radius and the barrier height at the surface. The coefficient α_KS,c = 1/4 is determined in the plasmon‐pole approximation and is independent of these metal parameters. Thus, the asymptotic structure of v_xc(z) in the vacuum region is image‐potential‐like but not the commonly accepted one of ?1/4z. Furthermore, this structure depends on the properties of the metal. Additionally, an analysis of these results via quantal density functional theory (Q‐DFT) shows that both the Pauli W_x(z → ∞) and lowest‐order correlation‐kinetic W(z → ∞) components of the exchange potential energy v_x(z → ∞), and the Coulomb W_c(z → ∞) and higher‐order correlation‐kinetic components of the correlation potential energy v_c(z → ∞), all contribute terms of O(1/z) to the structure. Hence correlations attributable to the Pauli exclusion principle, Coulomb repulsion, and correlation‐kinetic effects all contribute to the asymptotic structure of the effective potential energy at a metal surface. The relevance of the results derived to the theory of image states and to KS‐DFT is also discussed. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Synthesis and Crystal Structure of [Nd(η6‐1, 3, 5‐C6H3Me3)‐(AlCl4)3](C6H6) and Structural Comparison of Ln(η6‐arene)‐(AlCl4)3

Reaction of Ndcl₃ with AlCl₃ and mesitylene in benzene gives complex [Nd(η⁶‐1, 3, 5‐C₆H₃Me₃)‐(AlCl₄)₃](C₆H₆) (1) which was characterized by elemental analysis, IR spectra, MS and X‐ray diffractions. The X‐ray determination indicates that 1 has a distorted pentagonal bipyramidal geometry and crystallizes in the monoclinic, space group P2₁/n with a = 0.9586(2), b = 1.1717(5), c = 2.8966(7) nm, β = 90.85 (2)°, V = 3.2529 (6) nm³,D_c= 1.573 g/cm³, Z = 4. A comparison of bond parameters for all the reported Ln (η⁶‐Ar) (AlCl₄)₃ complexes indicates that the bond distance of La? C is shortened with the increasing of methyl group on benzene and with the decreasing of radius of lanthanide ions.     

Easy Entry into Reduced Ar‐BIANH2 Compounds: A New Class of Quinone/Hydroquinone‐Type Redox‐Active Couples with an Easily Tunable Potential

Ar‐BIANH₂ bearing different substituents on the aryl rings have been synthesized in high yield by reduction of the corresponding bis(aryl)acenaphthenequinonediimine (Ar‐BIAN) compounds. The structure of p‐CH₃C₆H₄‐BIANH₂ in the solid state was determined by X‐ray diffraction. An exhaustive voltammetric investigation of the two parallel BIAN and BIANH₂ series afforded a first rationalization of the redox properties of these molecules, highlighting their analogies with quinone/hydroquinone systems. Such analogies, in combination with the much more negative reduction potential range of Ar‐BIAN compounds with respect to quinones, can afford to extend the range of reduction potentials so far obtainable by the use of quinones.     

Direct Synthesis of PbO Nanoparticles From a Lead(II) Nano Coordination Polymer Precursor: Synthesis,Crystal Structure,and DFT Calculations of [Pb2(dmp)2(μ‐N3)2(μ‐ClO4)2]n with the First Pb2‐(μ‐ClO4)2 Unit

Nanostructures of a new coordination polymer of divalent lead with the ligand 2, 9‐dimethyl‐1, 10‐phenanthroline (dmp) containing the first Pb₂‐(μ‐ClO₄)₂ motif, [Pb₂(dmp)₂(μ‐N₃)₂(μ‐ClO₄)₂]_n ( 1 ), was synthesized by a sonochemical method that produces the coordination polymers at nano size. The new nanostructure was characterized by scanning electron microscopy, X‐ray powder diffraction, IR, ¹H NMR and ¹³C NMR spectroscopy, and elemental analysis. Compound 1 was structurally characterized by single‐crystal X‐ray diffraction and the single‐crystal X‐ray data shows that the coordination number of Pb^II ions is six, (PbN₄O₂), with two N‐donor atoms from aza‐aromatic base ligands and four O‐donors from two perchlorate anions and two N‐donors from two azide anions. It has a “stereo‐chemically active” electron lone pair, and the coordination sphere is hemidirected. The supramolecular features in these complexes are guided and controlled by weak directional intermolecular interactions. The chains interact with each other through π–π stacking interactions creating a 3D framework. The structure of the title complex was optimized by density functional theory calculations. Calculated structural parameters and IR spectra for the title complex are in agreement with the crystal structure. The PbO nanoparticles were obtained by thermolysis of 1 at 180 °C with oleic acid as a surfactant. The average diameter of the nanoparticles was estimated by the Scherrer equation to be 23 nm. The morphology and size of the prepared PbO samples were further observed using SEM.     

A New Energetic Complex [Co(2,4,3‐tpt)2(H2O)2]·2NO3: Synthesis,Structure, and Catalytic Thermal Decomposition for Ammonium Perchlorate

The energetic complex, [Co(2,4,3‐tpt)₂(H₂O)₂] · 2NO₃ ( 1 ) [2,4,3‐tpt = 3‐(2‐pyridyl)‐ 4‐(4'‐pyridyl)‐5‐(3′‐pyridyl)‐1H‐1,2,4‐triazole], was synthesized and characterized by single‐crystal X‐ray diffraction, thermogravimetric analyses, elemental analysis, X‐ray powder diffraction, and IR spectroscopy. The title complex is a 0D motif with a unit of [Co(2,4,3‐tpt)₂(H₂O)₂]²⁺, whereas NO₃^– ions not only act as counter anions to balance the charge of the Co^II cations, but also provide hydrogen bond interactions, which make the 0D motif into a 1D chain. Furthermore, the thermal decomposition of ammonium perchlorate (AP) with complex 1 was explored by differential scanning calorimetry (DSC) over the temperature range from 50–500 °C. AP is completely decomposed in a shorter time in the presence of complex 1 , and the decomposition heat of the mixture is 2.143 kJ g^–1, significantly higher than pure AP. By Kissinger's method, the ratio of E_a/ln(A) is 11.87 for the mixture, which indicates that complex 1 shows good catalytic activity toward AP decomposition.     

An experimental and theoretical approach to the molecular structure of 3‐{[4‐(3‐Methyl‐3‐phenyl‐cyclobutyl)‐thiazol‐2‐yl]‐hydrazono}‐1,3‐dihydro‐ indol‐2‐one

The title molecule, 3‐{[4‐(3‐methyl‐3‐phenyl‐cyclobutyl)‐thiazol‐2‐yl]‐hydrazono}‐1,3‐dihydro‐indol‐2‐one (C₂₂H₂₀N₄O₁S₁), was prepared and characterized by ¹H NMR, ¹³C NMR, IR, UV–visible, and single‐crystal X‐ray diffraction. The compound crystallizes in the monoclinic space group P21 with a = 8.3401(5), b = 5.6976(3), c = 20.8155(14) Å, and β = 95.144(5)°. Molecular geometry from X‐ray experiment and vibrational frequencies of the title compound in the ground state has been calculated using the Hartree–Fock with 6‐31G(d, p) and density functional method (B3LYP) with 6‐31G(d, p) and 6‐311G(d, p) basis sets, and compared with the experimental data. The calculated results show that optimized geometries can well reproduce the crystal structural parameters, and the theoretical vibrational frequencies values show good agreement with experimental data. Density functional theory calculations of the title compound and thermodynamic properties were performed at B3LYP/6‐31G(d, p) level of theory. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

Neue [{Cp(CO)2Mo}2ESbCl]‐Cluster mit tetraedrischem Mo2SbE‐Gerüst (E = S,Se)

Reaction of [{Cp(CO)₃Mo}₂SbCl] with S₈ or Se₈ leads to the formation of cluster compounds [{Cp(CO)₂Mo}₂ESbCl] (E = S, Se). [{Cp(CO)₂Mo}₂SSbCl] crystallizes monoclinic, space group P2₁/n with a = 812.28(3), b = 855.65(4), c = 2441.01(9) pm and β = 90.149(3)°; [{Cp(CO)₂Mo}₂SeSbCl] · CH₂Cl₂ crystallizes triclinic, space group P$\bar{1}$ with a = 828.82(9), b = 1002.8(1), c = 1340.0(2) and α = 109.24(1), β = 100.87(1), γ = 96.81(1)°. For both compounds X‐ray crystal structure analysis reveals tetrahedral Mo₂SbE cluster cores with Sb–E bond lengths of 256.8(1) pm (E = S) and 265.3(1) (E = Se). According to the 18 electron rule the [{Cp(CO)₂Mo}₂ESbCl] clusters can be regarded as complexes of the 4 electron donator ESbCl that is coordinated “side‐on” to a {Cp(CO)₂Mo}₂ fragment.     

XANES Spectroscopic Studies of the Phase Transition in Gd2Zr2O7

The structural phase transition from fluorite to pyrochlore and the strength of the coordination bond of Zr–O in Gd₂Zr₂O₇ were investigated by XANES spectra of both O and Zr K‐edge. The energy difference of the O K‐edge absorption spectra at 532 and 536 eV was assigned to the crystal field splitting energy of the 4d orbital (ΔE_4d, t_2g and e_g) of the Zr ion. Also, in the samples prepared at higher temperatures, the 536 eV peak moves slightly to higher energy, whereas the absorption energy of 532 eV peak does not shift. A correlation between ΔE_4d and the strength of interaction between Zr (4d) and O (2p) orbitals has been found. Furthermore, two Zr K‐edge absorptions at 18020 and 18030 eV of Gd₂Zr₂O₇ have been observed; the splitting energy (ΔE), peak intensity ratio (I₁₈₀₃₀/I₁₈₀₂₀), and FWHM of the first derivative of the absorption curve depend on the preparation temperatures. The effect of crystal symmetry and Zr‐O bonding character on the XANES spectral profile was discussed.     

Synthesis and Characterization of N,N‐Di‐substituted Acylthiourea Copper(II) Complexes

A series of six N,N‐di‐substituted acylthiourea ArC(O)NHC(S)NRR′ ligands (denoted as HLⁿ) [Ar = 1‐Naph: NRR′ = NPh₂, HL¹ ( 1 ); N(iPr)Ph, HL² ( 2 ). Ar = Mes: NRR′ = NPh₂, HL⁴ ( 3 ); N(iPr)Ph, HL⁵ ( 4 ); NEt₂, HL⁶ ( 5 ). Ar = Ph: NRR′ = N(iPr)Ph, HL⁸ ( 6 )] were synthesized and characterized. These ligands were deprotonated to form Cu^II complexes through metathesis or combined redox reaction with copper halides. The structures of the complexes were investigated with single‐crystal X‐ray diffraction. The reaction of the 1‐naphthalene derivative HL¹ ( 1 ) with CuBr in the presence of sodium acetate produced cis‐CuL¹₂ ( 7 ), where the deprotonated ligand is bound to the Cu^II atom in a bidentate‐(O, S) coordination mode. Similarly treatment of HL² ( 2 ) with NaOAc and CuCl resulted in the formation of the cis‐arranged product [cis‐CuL²₂ ( 8 )]. The reaction of mesityl derivative HL⁴ ( 3 ) and CuBr with and without the addition of NaOAc gave the cis‐CuL⁴₂ ( 9 ) and cis‐(HL⁴)₂CuBr ( 10 ), respectively. In contrast, reaction of HL⁵ ( 4 ) and CuI in the presence of NaOAc resulted in trans‐CuL⁵₂ ( 11 ). Alternatively trans‐CuL⁶₂ ( 12 ) was obtained by the reaction of diethyl‐substituted HL⁶ ( 5 ) with CuCl₂ in the absence of a base.     

Visualization of the Heterogeneity of Cerium Oxidation States in Single Pt/Ce2Zr2Ox Catalyst Particles by Nano‐XAFS

The cerium oxidation states in single catalyst particles of Pt/Ce₂Zr₂O_x (x=7 to 8) were investigated by spatially resolved nano X‐ray absorption fine structure (nano‐XAFS) using an X‐ray nanobeam. Differences in the distribution of the Ce oxidation states between Pt/Ce₂Zr₂O_x single particles of different oxygen compositions x were visualized in the obtained two‐dimensional X‐ray fluorescent (XRF) mapping images and the Ce L_III‐edge nano X‐ray absorption near‐edge structure (nano‐XANES) spectra.     

On the optimal mixing of the exchange energy and the electron-electron interaction part of the exchange-correlation energy

The optimal mixing coefficient C of the exchange energy E_x and the electron-electron interaction part of the exchange-correlation energy W¹_xc in the formula for the total exchange-correlation energy E_xc was expressed through the ratio of the kinetic T_c and potential W_c contributions to the correlation energy E_c. This expression can be derived from a Heavyside step function model of the dependence of W^λ_xc on the coupling parameter of the electron interaction λ. Values of T_c and W_c obtained from ab initio wave functions were used to estimate C for a number of atoms and molecules. A strong dependence of T_c, W_c, and C on the bond distance was demonstrated for the case of the H₂ molecule. T_c and C approach zero in the bond-dissociation limit; so for an electron-pair bond, the admixing of exact exchange to obtain an accurate E_xc is strongly dependent on the bond length and has to disappear for weak interaction/large bond distances. The potential of the exchange-correlation hole constructed for H₂ from an ab initio second-order density matrix was compared with its generalized gradient approximation (GGA). © 1996 John Wiley & Sons, Inc.     

Intrakonfigurations‐, Trip‐Multiplett‐ sowie anomal polarisierte A1gund A2g‐Übergänge in elektronischen und vibratorischen Resonanz‐Raman‐Spektren von (spinentarteten) trans‐Di(cyano)phthalocyaninatorhenaten

Intraconfigurational, Trip‐Multiplet, and Anomalously Polarised A_1g and A_2g Transitions in Electronic and Vibrational Resonance Raman Spectra of (Spin‐Degenerate) trans ‐Di(cyano)phthalocyaninatorhenates Brown bis(tetra(n‐butyl)ammonium) trans‐di(cyano)phthalocyaninato(2‐)rhenate(II) ( 1 ) is prepared by melting bis(phthalocyaninato(2‐)rhenium(II)) with tetra(n‐butyl)ammonium cyanide. According to electrochemical data, 1 is oxidised by iodine to yield blue tetra(n‐butyl)ammonium trans‐di(cyano)phthalocyaninato(2‐)rhenate(III) ( 2 ), whose cation exchange in the presence of bis(triphenylphosphine)iminium salts has been confirmed by x‐ray structure determination. 1 and 2 dissolve without dissociation of the cyano ligands in conc. sulfuric acid. Dilution with cold water precipitates blue trans‐di(cyano)phthalocyaninato(2‐)rhenium(III) acid. 1 and 2 are oxidised by bromine yielding violet trans‐di(cyano)phthalocyaninato(1‐)rhenium(III). Oxidation of 2 with dibenzoylperoxide and N‐chlorsuccinimide is described. 1 and 2 are characterised by polarised resonance Raman(RR) spectra, FIR/MIR spectra, and UV‐Vis‐NIR spectra. Due to a Kramers degenerate ground electronic state of low‐spin Re^II, a polarisation anomaly of the totally symmetric vibrations a_1g at 598 and 672 cm^–1 with depolarisation ratios ρ_l > 3 is observed in the RR spectra of 1 . Weak bands in the unusual UV‐Vis‐NIR spectrum of 1 , starting at 10200 cm^–1, are attributed to trip‐multiplet (TM) transitions. An electronic RR effect is detected for 2 . The selectively enhanced anomalously polarised line at 1009 cm^–1 with ρ_l ≈ 15 and the (de)polarised lines between 1688 and 2229 cm^–1 are attributed to intraconfigurational transitions A_1g → A_2g > A_1g, B_1g, B_2g, E_g arising from the ³T_1g ground electronic state of low‐spin Re^III split by spin‐orbit coupling and low symmetry (D ). Some of their vibronic bands are detected in the IR spectrum between 1900 and 4000 cm^–1. B and Q transitions of 2 at 16700 and 31900 cm^–1, respectively, as well as eight weak TM transitions are observed between 5050 and 26100 cm^–1.