Quantum chemical investigation on complexation of palladium with iminopyridyl ligands: Structural,thermochemical, and electronic aspects

The main purpose of this research is to investigate computationally the structural, thermochemical and electronic properties in complexation process of dichloride {N-[(5-methylthiophen-2-yl)methylidene]?2-(pyridine-2-yl)ethanamine-κ²N,N′}palladium(II) complex. In the first step, we have concentrated on comparative survey of ability of density functional theory (DFT) and also semi-empirical approaches to reproduce the crystal structure of palladium(II) complex. Comparison of our calculated structural parameters of aforementioned complex with the available crystallographical data reveals that both functionals (B3LYP and M06) can well-reproduce x-ray structure of the complex with a near accuracy while PM6-D2 semi-empirical calculated values are not in a reliable agreement with the crystallographical data.

In the next step, we have shown the thermodynamical superiority in using THF as a polar solventin complexation reaction via polarized continuum model (PCM) computations which is in confirmation with experimental observations. Additionally, the bond orders of some selected key bonds in C₁₃H₁₄N₂Sligand andPdCl₂(C₁₃H₁₄N₂S) complex have been evaluated comparatively to analyze the electronic behavior of coordination.

Finally, we focused on topological analysis of electron density function via quantum theory of atoms in molecules (QTAIM) approach to explore the strength and nature of metal-ligand interactions on bond and ring critical points (BCPs).Strictly speaking, QTAIM calculations have been performed to determine the electronic density, its Laplacian and other electronic energy density indicators on some key BCPs to interpret the electronic features of complexation.     

Mass and bond density measurements for PECVD a-SiCx:H thin films using Fourier transform-infrared spectroscopy

The absolute concentration of chemical bonds in Plasma Enhanced Chemically Vapor Deposited (PECVD) a-SiC_x:H thin films have been determined via combining transmission Fourier-Transform Infra-red (FTIR) spectroscopy with X-ray Reflectivity (XRR) and Rutherford Backscattering (RBS) mass density and composition measurements. Specifically, we demonstrate in this paper that the integrated absorbance for the Si-C stretch in FTIR is linearly proportional to the mass density of PECVD a-SiC_x:H films as determined by XRR and RBS. This linear relationship allows us to accurately determine the IR absorption cross section for the Si-C stretch. Using these cross sections in combination with IR proportionality constants/cross sections published by other researchers, we demonstrate that mass densities in agreement with XRR and RBS can be calculated from the integrated absorbances of the Si-C, Si-H, and C-H stretches in FTIR spectra. From additional mass balance relationships, we further demonstrate that the full elemental and bond concentrations can be determined. This analysis reveals the presence of significant Si-Si and C-C bonding in the a-SiC_x:H films that was not clearly identified in previous FTIR investigations due to the low IR activity for these homopolar bonds. The bond and mass density calculations are demonstrated for both 3C-SiC and a-SiC_x:H thin films with mass density values ranging from 1 to 3.2 g/cm³.     

Synthesis and crystal structure of bis(4-methylpiperidine-dithiocarbamato-S,S′)-palladium(II)

The complex bis(4-methylpiperidine-dithiocarbamato-S,S′)-palladium(II) was synthesized by the reaction of 4-methyl-1-piperidine dithiocarbamic acid with palladium(II) chloride. Its structure was determined by X-ray crystal diffraction analysis. It crystallizes in the monoclinic P2₁/c space group with the crystal cell parameters a=8.6491(8) ?, b=18.7305(16) ?, c=11.9933(10) ?, β=107.074(1)°, V=1857.3(3) ?³ and Z=4. The palladium (II) ion is bonded to four sulfur atoms, belonging to two dithiocarbamate ligands, in a distorted square planar geometry. The X-ray data suggest a pronounced electronic delocalization in the two NCS₂ moieties.     

Comparison of the data of X-ray microtomography and fluorescence analysis in the study of bone-tissue structure

The possibility of localizing clusters of heavy atoms is substantiated by comparing the data of X-ray microtomography at different wavelengths, scanning electron microscopy, and X-ray fluorescence analysis. The proximal tail vertebrae of Turner??s thick-toed gecko (Chondrodactylus turneri) have been investigated for the first time by both histological and physical methods, including X-ray microtomography at different wavelengths and elemental analysis. This complex methodology of study made it possible to reveal the regions of accumulation of heavy elements in the aforementioned bones of Turner??s thick-toed gecko.     

Advances in understanding the defects contributing to the tail states in pure amorphous silicon

The tight-binding molecular dynamics simulations and reverse Monte Carlo structural modeling method were applied in order to investigate the existence of small bond angles (like those in triangles and squares) in amorphous silicon networks. The influence of small bond angles on the electronic density of states was analyzed. The presence of a number of smaller bond angles is necessary for a proper reproduction of the neutron diffraction data of amorphous silicon. Semiempirical Hartree–Fock calculations show that these arrangements provide higher energy levels in electronic density of states which are localized on these local structures. Accepting this result we must reconsider the electronic density of states of amorphous semiconductors. The localized mobility gap has structure i.e. two characteristic peaks can be found inside the tail. First larger peak belongs to the squares while the peak at larger energy is formed by triangles.     

Dichloro-{bis(Pyrazol-1-yl)}Palladium(II) Complexes: Structures of a DMSO Solvated Dichloro-{bis(3,5-Dimethylpyrazol-1-yl)Acetic Acid}Palladium(II) and Dichloro-{bis(3,5-Ditertbutylpyrazol-1-yl)Methane}Palladium(II)

Abstract  Two new palladium(II) complexes, dichloro-{bis(3,5-dimethylpyrazol-1-yl)acetic acid}palladium(II)PdCl₂(3,5-Me₂bpza)], (1) (3,5-Me₂bpza = 3,5-dimethylpyrazol-1-yl)acetic acid) and dichloro-{bis(3,5-ditertbutylpyrazol-1-yl)acetic acid}palladium(II), [PdCl₂(3,5-^tBu₂bpza)], (2a) [3,5- ^t Bu₂bpza = 3,5-ditertiarybutylpyrazol-1-yl)acetic acid] complexes, were synthesized from the reactions of pyrazol-1-yl ligands with palladium salts. Attempts to crystallize 2a led to a hydrolyzed product, dichloro-{3,5-ditertbutylpyrazol-1-yl}palladium(II) (2b), in which the acetic acid moiety in the ligand backbone of 1 is lost. Both complexes 1 and 2b have been characterized by single-crystal X-ray crystallography. Both complexes crystallized in triclinic system (P − 1 space group). The cell parameters are: complex 1 (a = 8.7960(14) Å, b = 16.238(2) Å, c = 16.430(2) Å, α = 78.038(10)°, β = 77.817(11)°, γ = 89.970(10)°) and complex 2b (a = 10.1492(2) Å, b = 12.4001(2) Å, c = 13.108(3) Å, α = 103.0690(10)°, β = 97.4120(10)°, γ = 107.2450(10)°). The asymmetric unit of 1 contains two crystallographic independent monomeric units of 1 and three molecules of DMSO solvent, whilst that of 2b has got one monomeric unit with one molecule of chloroform solvent. Index Abstract  Two palladium complexes, dichloro-{bis(3,5-dimethylpyrazol-1-yl)acetic acid}palladium(II), PdCl₂(3,5-Me₂bpza)], (1) (3,5-Me₂bpza = 3,5-dimethylpyrazol-1-yl)acetic acid) and dichloro-{bis(3,5-ditertbutylpyrazol-1-yl)acetic acid}palladium(II), [PdCl₂(3,5- ^t Bu₂bpza)], (3,5- ^t Bu₂bpza = 3,5-ditertiarybutylpyrazol-1-yl)acetic acid) complexes, were synthesized from the reactions of pyrazol-1-yl ligands with palladium salts. Attempt to obtain crystals of tertiarybutylpyrazolyl analogue led to hydrolysis, the crystal structure of the hydrolysis product was established by single crystal X-ray crystallography.      

Structural instability and the metal–non-metal transition in expanded fluid metals

X-ray diffraction, small angle X-ray scattering and inelastic X-ray scattering measurements for fluid Hg in the wide density range up to the supercritical region have been carried out using synchrotron radiation at SPring-8. We obtained the static and dynamic structure factors as a function of temperature, pressure and density. Based on the results we found that there exist medium-range fluctuations accompanying the metal–non-metal transition in fluid Hg. The scale of the fluctuations was about 10 A in space and sub-picoseconds in time. We discuss the possibility that such structural instability induces the metal–non-metal transition in expanded fluid Hg.     

Synthesis, spectral, and single crystal X-ray structural studies on (2,2′-bipyridyl)bis(dimethyldithiocarbamato) zinc(II) and (1,10-phenanthroline) bis(dimethyldithiocarbamato)zinc(II)

Synthesis, spectral, and single crystal X-ray structural studies on (2,2-bipyridyl)bis (dimethyldithiocarbamato)zinc(II) (1) and (l,10-phenanthroline)bis(dimethyldithiocarbamato)zinc(II) (2) complexes are reported in this paper. The complex (1) crystallizes in the orthorhombic lattice, space group Pcca, a = 18.456(3), b = 6.529(2), and c = 17.092(2) Å. The complex (2) crystallizes in the monoclinic space group C2/c, a = 13.372(2), b = 13.850(2), c = 24.680(3) Å, and = 102.71(4)°. IR spectra of the complexes (1) and (2) show the thioureide (C-N) bands at 1489 and 1510 cm^–1, respectively, which are lower than the value observed for the parent bisdithiocarbamate. Reduction in the thioureide stretching frequency is due to the increase in coordination around the zinc ion and the resultant increase in electron density. Thermal studies indicate that the 1,10-phenanthroline adduct is marginally more stable than the other complex. X-ray crystal structures of the two adducts show them to be octahedrally coordinated and monomeric in nature. The Zn-S distances are longer than those observed in the parent bisdithiocarbamate. The thioureide C-N bond distances in (1) and in (2) indicate the partial double bond character. The most important structural changes as a result of the adduct formation are observed in the Zn-S bond distances and S-Zn-S bond angles, in terms of very significant increases in Zn-S bond distances and reductions in S-Zn-S angles, compared to the parent bisdithiocarbamate. The observed changes are indicative of a strong steric force in operation in the adducts rather than electronic effects.     

基于混合配体的镍(Ⅱ)配合物的晶体结构、荧光性质和磁性研究

室温下,以对氯苯乙酸(PCPA)、1,10-邻菲啰啉(phen)和六水合硫酸镍为原料,通过溶剂挥发法合成了镍配合物[Ni(PCPA)₂(phen)H₂O],并用X射线单晶衍射测定了该金属有机配合物的晶体结构。结果显示,配合物属于单斜晶系,P2₁/n空间群,每个不对称单元由一个镍(Ⅱ)离子、两个对氯苯乙酸配体和一个1,10-邻菲啰啉配体组成。荧光光谱分析结果表明,配合物的激发峰和发射峰分别在336 nm和393 nm;热稳定性分析表明,配合物在室温下稳定;磁性测量表明,配合物存在反铁磁相互作用。     

Structural variation in palladium nanoparticles of the C-Pd system when dissolving hydrogen in them

The structure of nanocomposites of the C-Pd system has been studied by X-ray diffraction analysis and transmission electron microscopy. Variations in the lattice period of nanosized palladium, the average amount of hydrogen dissolved in it, and the size distribution of palladium nanoparticles have been analyzed as functions of the nanocomposite fabrication temperature. Based on the structural data, the solubility of hydrogen in nanosized palladium has been estimated.     

Mesomorphic and DFT studies of terminal ester containing salicylaldimines and their copper (II) complexes

In this article, we report synthesis and characterization of a novel homologous series of butyl 4-(4′-(alkoxy)-2-hydroxybenzylideneamino)benzoates, C_nLH (n = 6, 8, 10, 12, 14, 16) and their copper(II) complexes. The mesomorphic properties of these compounds were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and powder X-ray diffraction (XRD) studies. The ligands and their copper(II) complexes exhibit wide range of enantiotropic smectic A mesophase as confirmed by their typical optical texture under polarizing microscope. Thermal stability of the compounds is determined by thermo gravimetric analyses. DFT calculations have been performed using GAUSSIAN-09 program at B3LYP level to obtain the stable electronic structure of the ligand and its copper(II) complex.     

Atomic and electronic structures of nanometer sized silica particles

The Austin Model 1 semi-empirical method combined with geometry optimization procedure was used to study atomic and electronic structures of nanoscale silica particles containing up to 192 atoms (64 Si and 128 O). Twofold Si–O rings were found to dominate in nanometer sized particles. The fraction of larger rings increases with increasing particle sizes. Bond length and bond angle distributions were calculated. The shortest Si–O, O–O and Si–Si interatomic distances are approximately 1.7, 3.0 and 3.3 Å, respectively. Average O–Si–O and Si–O–Si bond angles are approximately 110^∘ and 130^∘. Average electronic energy band gap is 6.9 eV.     

Neutral Organometallic Halogen Bond Acceptors: Halogen Bonding in Complexes of PCPPdX (X = Cl, Br, I) with Iodine (I(2)), 1,4-Diiodotetrafluorobenzene (F4DIBz), and 1,4-Diiodooctafluorobutane (F8DIBu)

The behavior of a sterically crowded neutral pincer {2,6-bis[(di-t-butylphosphino)methyl]-phenyl}palladium (PCPPd) halides, PCPPdX (X = Cl, Br or I), as XB acceptors with strong halogen bond (XB) donors, iodine (I(2)), 1,4-diiodotetrafluorobenzene (F4DIBz), and 1,4-diiodooctafluorobutane (F8DIBu) were studied in the solid state. The co-crystallization experiments afforded high-quality single crystals of XB complexes PCPPdCl-I(2) (1a), PCPPdBr-I(2) (2a), PCPPdI-I(2)(3a), PCPPdCl-F4DIBz (1b), PCPPdBr-F4DIBz (2b), and PCPPdBr-F8DIBu (2c). The 1:1 iodine complexes (1a, 2a, and 3a) all showed a strong halogen bonding interaction, the reduction of the sum of the van der Waals radii of halogen to iodine being 24.6 (1a), 23.9 (2a), and 19.4% (3a) with X···I-I angles of 177, 176, and 179°, respectively. While the pincer palladium chloride 1 and bromide 2 were crystallographically isomorphous and showed similar XB behavior, the palladium iodide complex, 3, exhibited markedly different properties, and unlike 1 and 2 it does not, under similar conditions, result in XB complexes with the weaker XB donors F4DIBz and F8DIBu. The results indicate that PCPPdI is not nucleophilic enough to have XB interactions with other donors than iodine. However, the weaker XB donors F4DIBz and F8DIBu form XB complexes with the chloride 1 and especially with the bromide 2. The prevalence of the halogen bonding with 2 is probably not only electronic in origin, and it seems to offer the best balance between electron poorness and steric availability. The XB interactions with F4DIBz and F8DIBu are much weaker than with iodine, the reduction of the sum of the van der Waals radii of halogen to iodine being 13.5, 12.3, and 14.6% with C-I···X angles between 163 and 179° for 1b, 2b, and 2c, respectively, and results in polymeric (···1···F4DIBz···1···F4DIBz···)(n), (···2···F4DIBz···2···F4DIBz···)(n), and (···2···F8DIBu···2···F8DIBu···)(n) one-dimensional zigzag chains in the solid state.     

基于5-磺基水杨酸的单、双核铜(Ⅱ)三元混配配合物的合成及晶体结构

以5-磺基水杨酸和咪唑衍生物为配体合成了单核、双核结构的三元混配Cu(Ⅱ)配合物:[Cu(H₂biim)(Hssal)(H₂O)₂]·H₂O(1)和{[Cu(MeHbiim)(Hssal)(H₂O)]·0.5H₂O}₂(2)(H₃ssal=5-磺基水杨酸,H₂biim=2,2’-联咪唑,MeHbiim=N-甲基-2,2’-联咪唑),并利用元素分析、红外光谱、紫外-可见光谱、X-射线单晶衍射及热重分析等技术手段对其结构进行了表征。单晶结构解析表明配合物1属于单斜晶系,P2₁／C 空间群,Cu(Ⅱ)离子与1个5-磺基水杨酸根、2个水分子以及1个联咪唑分子形成五配位四角锥构型的单核配合物结构。配合物2属于正交晶系,P2(1)2(1)2(1)空间群,双核Cu(II)离子分别处于五配位四角锥和四配位平面四边形的几何构型的配位环境中,与配合物1不同,5-磺基水杨酸采取μ₂双-单齿配位模式。荧光光谱分析表明配合物2具有较强的荧光性。     

Microstructural analysis of nanostructured amorphous silicon-germanium alloys: Numerical modeling

A detailed microstructural analysis of amorphous silicon-germanium alloys with germanium fraction ranging from 0.1 to 0.5 is performed by means of a numerical modeling technique. By substituting Ge atoms for Si atoms in nanoporous paracrystalline network of amorphous silicon, several amorphous silicon-germanium structures have been generated then relaxed. The main aim of our work is to study the effect of compositional heterogeneities on the structural properties of amorphous silicon-germanium alloys in comparison with the standard case, that of a homogeneous random distribution of the atoms. In the present work we envisage the two-phase amorphous silicon-germanium model proposed by Goerigk and Williamson to interpret their anomalous small-angle X-ray scattering measurements; it consists on a mixture of Ge-rich and Ge-poor domains at the nanoscale. The microstructure of our structural models is analyzed by examining the macroscopic mass density, the X-ray diffraction intensity, the radial distribution functions, the bond lengths and the coordination numbers within the first coordination shell of Si and Ge atoms.     

Diaquabis(5-methoxyindole-2-carboxylato)bis(3-picoline)nickel(II) Complex: Synthesis,Characterization, XRD,TGA, DFT and HSA

A new complex of diaquabis(5-methoxyindole-2-carboxylato)bis(3-picoline)nickel(II) (Ni(5-MeOI2CA)₂(3-pic)₂(H₂O)₂), was synthesized for the first time and characterized by elemental analysis, FT-IR and electronic spectroscopy (UV-Vis) and single-crystal X-ray diffraction (XRD) techniques. The thermal degradation of the Ni(II) complex was investigated using thermogravimetric and differential thermal analyses techniques in oxygen atmosphere. The molecular structure of the complex was determined by single crystal X-ray diffraction technique. Hirshfeld surface analysis (HSA) investigated the packing modes and intermolecular interactions in molecular crystals, as they provide a visual picture of intermolecular interactions. In addition, all computational studies at B3LYP/6-311++G(d,p) were carried out for theoretical characterization of Ni(II) complex. The optimized geometry results, which were well represented the X-ray data, were shown that the chosen of DFT/B3LYP/6-311++G(d,p) was a successful choice for title compound. After a successful optimization, FMOs, chemical activity, non-linear optical properties (NLO), molecular electrostatic potential (MEP), Mulliken population (MPA), natural population analyses (NPA), Fukui function analysis (FFA) and natural bond orbital analysis (NBO), which could not obtained by experimental ways, were calculated and investigated. The computed of net charges and chemical activity studies which helped to identifying the electrophilic/nucleophilic nature.     

X-ray structural,spectroscopic and computational approach (NBO,MEP, NLO,NPA, fukui function analyses) of (E)-2-((4-bromophenylimino)methyl)-3-methoxyphenol

The title compound was isolated and investigated by experimental X-ray diffraction method and density functional theory (DFT) calculational properties and spectroscopic methodologies. The experimental investigations of the compound indicated the molecule seems to be in enol form. DFT calculations are performed both for enol and keto tautomers of the title compound. Additionally chemical activity, electronic transmission and property effect on different solvents, molecular electrostatic potential (MEP), non-linear optical properties (NLO), Mulliken population method, natural population analysis (NPA), natural bond orbital (NBO) and Fukui function analyses have been studied.     

Crystal structure of triethanolammonium bis(1-hydroxyethane-1,1-diphosphonato)diaquazincate pentahydrate, [(OHCH2CH2)3NH][Zn(H2O)2(H2.5 L)2] ⋅ 5H2O

The crystal structure of [(HOCH₂CH₂)₃NH][Zn(H₂O)₂(H_2.5 L)₂] ? 5H₂O, where H₄ L is 1-hydroxyethane-1,1-diphosphonic acid, was determined by X-ray diffraction. The anionic complex has a cis-octahedral structure. The zinc atom is coordinated by four O atoms of two bidentate chelate H_2.5 L ^1.5? ligands and two O atoms of water molecules. The Zn-O(L) bond lengths range between 2.050 and 2.175 Å, and the Zn-O(H₂O) bond lengths are 2.105 and 2.133 Å. The anionic complexes, triethanolammonium cations, and molecules of crystallization water are interlinked by an extensive network of hydrogen bonds. The crystallographic data for isostructural complexes of cobalt and nickel are given.     

Microstructural analysis of atomistic models of Si-rich amorphous silicon-germanium alloys

A detailed microstructural analysis of amorphous silicon-germanium alloys with Ge fraction ranging from 0.1 to 0.5 is performed by means of a numerical modeling technique. By substituting Ge atoms for Si atoms in the nanoporous paracrystalline network of amorphous silicon, several amorphous silicon-germanium structures have been generated. Our main aim in the present work is to study the effect of compositional heterogeneities on the structural properties of amorphous silicon-germanium alloys in comparison with the standard case, that of a homogeneous random distribution of the atoms. We have limited ourselves here to the borderline case, that of segregation of Ge atoms at the nanoscale. The microstructure of our structural models is analyzed by examining the macroscopic mass density, the intensity of X-ray diffraction, the pair distribution functions, the bond lengths and the coordination numbers within the first coordination shell of Si and Ge atoms. Our structural models account for the experimentally derived mass densities regardless of the Ge distribution pattern. They also account for the intense small-angle X-ray scattering observed for some amorphous silicon-germanium samples. The short-range compositional disorder, reflected in the bond lengths and the coordination numbers within the first coordination shell of Ge atoms, is found to be very sensitive to how these atoms are arranged in the alloys.     

AgAlSe2晶体高压相变的第一性原理研究

基于密度泛函理论,采用广义梯度近似法,研究了黄铜矿结构AgAlSe₂在高压下的晶体结构、晶格动力学稳定性与电子结构.结果显示:在0 GPa时AgAlSe₂的晶格参数与实验值吻合,在13.9 GPa附近,质量密度、Se-Ag键长、Se-Al键长、晶格常数a突然增大,相对晶胞体积V/V₀、晶格常数c突然减小,声子谱出现虚频,结构变得不稳定,带隙发生突变,数值呈减小趋势.表明AgAlSe₂晶体在13.9 GPa附近发生结构相变.该研究为AgAlSe₂晶体在理论上所能承受的高压提供信息支撑.