On the inner and outer radial density functions

Starting from the two-electron radial density D ₂(r ₁,r ₂), a generalized partitioning of the one-electron radial density function D(r) into two component densities D _a (r) and D _b (r) is discussed for many-electron systems. The literature partitioning (Koga and Matsuyama Theor Chem Acc 115:59, 2006) of D(r) into the inner D _<(r) and outer D _>(r) radial densities is shown to minimize the average variance of the two component density functions D _a (r) and D _b (r). It is also found that the average radial separation halved, , constitutes a lower bound to the standard deviation σ of D(r).     

Approximate analytical solutions for arbitrary l-state of the Hulthén potential with an improved approximation of the centrifugal term

An approximate analytical solution of the radial Schr?dinger equation for the generalized Hulthén potential is obtained by applying an improved approximation of the centrifugal term. The bound state energy eigenvalues and the normalized eigenfunctions are given in terms of hypergeometric polynomials. The results for arbitrary quantum numbers n _r and l with different values of the screening parameter δ are compared with those obtained by the numerical method, asymptotic iteration, the Nikiforov-Uvarov method, the exact quantization rule, and variational methods. The results obtained by the method proposed in this work are in a good agreement with those obtained by other approximate methods.      

Synthesis,crystal structure,spectroscopic and thermal investigations of neodymium(III) biphenyl-4,4′-dicarboxylate framework

The three-dimensional complex {[Nd(bpdc)_1.5(DMF)]·1.4DMF}_n (DMF=N,N′-dimethylformamide, bpdc=biphenyl-4,4′-dicarboxylate) was synthesized using the solvothermal method. The crystal structure of the neodymium(III) complex has been determined by single-crystal X-ray diffraction method at 100(2) K. The polymeric structure consists of neodymium polyhedra bridged by bpdc ligands. Eight-coordinated Nd(III) atoms are surrounded by seven oxygen atoms from six bpdc moieties and one oxygen atom from the DMF molecule. The 3D structure of the complex contains two types of channels occupied by DMF molecules. Thermal analysis revealed that DMF molecules are lost in a stepwise manner. The infrared spectrum confirmed full deprotonation of acid and presence of DMF molecules in the structure.      

Spectroscopic characterization and <Emphasis Type="Italic">Ab initio</Emphasis> calculations of new diazaphosphole and diazaphosphorinane

Phosphoryl chloride is used as a starting material to synthesize new diazaphosphole, (1) and diazaphosphorinane, (2). The products are characterized by ¹H, ¹³C, ³¹P NMR, and IR spectroscopy. A high value ² J(PNH) = 17.0 Hz, 17.2 Hz is measured for two non-equivalent NH protons of endocyclic nitrogen atoms in compound 1, while it greatly decreases to 4.5 Hz in 2. Also, great amounts are obtained for two ² J(P,C) as well as two ³ J(P,C) in the ¹³C NMR spectrum of 1, but they are zero in 2. Here, the effect of ring strain and ring size on the structural and spectroscopic parameters is observed. The ³¹P NMR spectra reveal that δ(³¹P) of compound 1 is far much more downfield (12.63 ppm) relative to that of compound 2 (−10.39 ppm). Furthermore, ab initio quantum chemical calculations are performed to optimize the structures of these molecules by density functional theory (B3LYP) and Hartree-Fock (HF) methods, using the standard 6−31+G** basis set. The stabilization energies are calculated by the equation ΔE _{stabilization} = E _molecule − ΣE _i , where i = atom. To obtain the atomic hybridizations, NBO computations are made at the B3LYP/6−31+G** level. Also, by NMR calculations the ¹H, ¹³C, ³¹P chemical shifts are obtained and compared with the experimental ones.     

Synthesis by self-assembly and structural characterization of a new co-crystal system {[Cu(NO3)2(H2O)2]L1(NO3)2} (L1 = 1,1′-dibenzyl-3,3′-butyl-diimidazolium-2,2′-diylidene) from copper nitrate and a carbene precursor

Herein, the first example of a co-crystal system formed by an imidazolium nitrate, a carbene precursor, and copper (II) nitrate, {[Cu(NO₃)₂(H₂O)₂]L1(NO₃)₂} (1) (L1 = 1,1′-dibenzyl-3,3′-butyl-diimidazolium-2,2′-diylidene) is reported. These two building blocks are connected in the solid state through hydrogen bonds to generate a three-dimensional supramolecular network.      

Thermogravimetric study of the dehydration reaction of LiCl·H<Subscript>2</Subscript>O

The dehydration of LiCl·H₂O was studied under inert helium atmosphere by DTA/TG for different heating rates. The dehydration of LiCl·H₂O proceeds through a two step reaction between 99–110 and 160–186°C, respectively. It leads to the formation of LiCl·0.5H₂O as intermediate compound. The proposed mechanism is: and Based on the temperature peak of the DTA signals the activation energies of the two reactions were determined to be 240 kJ mol⁻¹ (step 1) and 137 kJ mol⁻¹ (step 2), respectively.     

Sol-gel bioactive glass-ceramics Part I: Calcium phosphate silicate/wollastonite glass-ceramics

In this work we present experimental results about synthesis, structure evolution and in vitro bioactivity of new calcium phosphate silicate/wollastonite (CPS/W) glass-ceramics. The samples obtained were synthesized via polystep sol-gel process with different Ca/P+Si molar ratio (R). The structure of the materials obtained was studied by XRD, FTIR spectroscopy and SEM. XRD showed the presence of Ca₁₅(PO₄)₂(SiO₄)₆, β-CaSiO₃ and α-CaSiO₃ for the sample with R=1.89 after thermal treatment at 1200°C/2h. The XRD results are in good agreement with FTIR analysis. SEM denotes that apatite formation can be observed after soaking in simulated body fluid (SBF).      

A new zinc complex of 1-propyl-1H-benzo[d] imidazole: synthesis, characterization and electrocatalysis

The present work reports the synthesis, characterization and performance of a new zinc(II) complex of [Zn(C₃H₇-bim)₂Br₂] (bim = benzimidazole) as electrocatalyst for trichloroacetic acid and bromate reduction. Its structure was characterized by X-ray crystallography, IR spectroscopy and elemental analysis. The zinc atom adopts a distorted tetrahedral geometry by coordinating to two bromine atoms and two nitrogen atoms from two 1-propyl-1H-benzo[d]imidazole ligands. The electrochemical behavior and electrocatalysis of the zinc complex bulk-modified carbon paste electrode (Zn-CPE) have been studied by cyclic voltammetry. The Zn-CPE shows good electrocatalytic activities toward the reduction of trichloroacetic acid and bromate. The detection limit and the sensitivity are 0.05 μM, 67.43 μA μM⁻¹ for trichloroacetic acid detection, and 0.02 μM, 69.94 μA μM⁻¹ for bromate detection, respectively. This modified electrode shows good reproducibility, high stability, low detection limit, technical simplicity and possibility of rapid preparation, which is important for practical applications.      

Ionic liquid-functionalized SBA-15 mesoporous material: efficient heterogeneous catalyst in versatile organic reactions

Ionic liquid-functionalized mesoporous materials exhibited high catalytic activity in versatile organic reactions, such as cycloaddition of carbon dioxide (CO₂) with epoxide, aza-Michael addition of amines to α, β-unsaturated carbonyl compounds, and the Biginelli reaction of aldehyde, ethyl acetoacetate and urea. Recycling of the catalyst in these reactions could be carried out and the catalyst used at least five times without significant loss in activity.      

Efficient and solvent-free synthesis of 1-amidoalkyl-2-naphthols using <Emphasis Type="Italic">N,N,N’,N’</Emphasis>-tetrabromobenzene-1,3-disulfonamide

N,N,N,’N’-Tetrabromobenzene-1,3-disulfonamide [TBBDA] is found to be a reusable catalyst for efficient synthesis of various amidoalkyl naphthols from β-naphthol, aromatic aldehydes and urea in good to high yields under solvent-free conditions.      

Synthesis,characterization and crystal structure analysis of a novel oxo-centered mixed-metal complex containing unsaturated bridging carboxylates

A novel oxo-centered trinuclear mixed-metal carboxylate complex with unsaturated bridging ligands [Fe₂Cr(μ₃-O)(C₃H₃O₂)₆(H₂O)₃]·NO₃·4H₂O has been synthesized and characterized by means of Elemental analyses, Infrared spectroscopy and Crystal structure analysis. The compound crystallizes isotypically in the monoclinic space group type P2₁/c. In the compound, each M^(III) cation is coordinated by six O atoms from four unsaturated carboxylate groups as bridging ligands, one water molecule as the terminal ligand, and a μ₃-oxygen atom in the center of an equilateral triangle. The infrared spectra show resolved bands arising from ν_asym(COO) and ν_sym(COO) vibration of bridging carboxylate ligands along with those of ν_asym(M₂M′O) vibration in the complex. The difference between symmetrical and asymmetrical (COO) ligands indicate that the acrylate bridge is present in the structure of complex.      

Preparation and crystal structure of bis[(dibenzo-18-crown-6)potassium]bis(μ<Subscript>2</Subscript>-chloro)-tetrachlorodicuprate(II)

A new complex compound bis[(dibenzo-18-crown-6)potassium]bis(μ₂-chloro)-tetrachlorodicuprate( II), {[K(Db18c6)]₂Cu₂Cl₆} (I) was prepared and its crystal structure was investigated by XRD analysis. Complex molecule I consist of anion [Cu₂Cl₆]²⁻ located in a crystallographic center of inversion, and two centrosymmetrical to each other complex cations [K(Db18c6)]⁺ of “guest-host” type: the cation K⁺ is located in the cavity of the crown-ligand Db18c6 and is coordinated by all its six O atoms, and also by one Cl atom of anion [Cu₂Cl₆]²⁻. The coordination of this cation K⁺ is enlarged up to hexagonal-bipyramidal due to the formation of unusual coordination bond K⁺ → π(      

The homogeneity range of lyonsite-type phase existing in the CrVO4 - Co3V2O8 system

In the work presented here, the way of obtaining the phase with general formula Co_3+1.5xCr_2–x(VO₄)₄ (0 ≤ × < 0.4) is demonstrated. A new phase is detected in CrVO₄ - Co₃V₂O₈ that is formed in one of the intersection of the ternary CoO - V₂O₅ - Cr₂O₃ system. Monophasic Co₃Cr₂(VO₄)₄ (Co_3+1.5xCr_2−x(VO₄)₄, where × = 0) was obtained from both a mixture comprising CrVO₄ and Co₃V₂O₈ as well as from the mixture of CoV₂O₆ with CoCr₂O₄. The Co_3+1.5xCr_2−x(VO₄)₄ is isotypic with the those demonstrating the lyonsite-type structure. The temperature of melting for the new compound was established using the DTA methods.      

Metathesis transformations of unsaturated derivatives of β-diketones

Selected β-diketones bearing unsaturated derivatives have been demonstrated to undergo homo-metathesis and cross-metathesis with selected olefins in the presence of Grubbs catalysts. The reactions led to respective homo- and cross-metathesis products mainly with good yields and selectivities.      

Molecular dynamics simulation study of the diamond D<Subscript>5</Subscript> substructures

Diamond D₅ is the name proposed by Diudea for hyper-diamonds having their rings mostly pentagonal. Within D₅, in crystallographic terms: the mtn structure, known in clathrates of type II, several substructures can be defined. In the present work, the structural stability of such intermediates/fragments appearing in the construction/destruction of D₅ net was investigated using molecular dynamics simulation. Calculations were performed using an empirical many-body potential energy function for hydrocarbons. It has been found that, at normal temperature, the hexagonal hyper-rings are more stable while at higher temperature, the pentagonal ones are relatively more resistant against heat treatment.      

Large cation model of dissociative reduction of electrochromic WO3−x films

Studies of dissociative reduction processes of electrochromic WO_3−x films were conducted to: (i) evaluate their utility for electroetching and (ii) determine their fundamental mechanistic features to reduce or eliminate their occurrence in normal optical switching and modulation operation of WO_3−x films. We have found that while the small intercalating cations stabilize WO_3−x structure, the large nonintercalating surfactant cations (Et₄N+, CtMe₃N+) contribute to the dissociative reduction. While these cations do not affect WO_3−x structure of anodically protected films (E > 0.2 V), they cause surface lattice polarization on electron injection to the conduction band of WO_3−x at lower electrode potentials, in the absence of intercalating cations. We have found that this process is limited to the surface and no structural damage occurs to the underlying film. The mechanistic aspects of the process have been discussed on the basis of experimental voltammetric and electrochemical quartz crystal nanogravimetric (EQCN) measurements and ab initio quantum mechanical calculations.      

Subsolidus area of the system CdO - V2O5 - Fe2O3

Phase diagrams in the subsolidus area of the systems FeVO₄ - CdO and FeVO₄ - Cd₂V₂O₇ have been deduced using the results of XRD and DTA analyses. On the basis of these diagrams and some additional verifying research, a projection of the subsolidus area of the CdO - V₂O₅ - Fe₂O₃ system onto the plane that comprises the components’ concentration triangle has been presented. The H-type phase is the only phase formed in this system. It co-exists at equilibrium with other phases in six subsidiary subsystems.      

Thermal synthesis and characterization of Al χ La1-χ P3O9

New binary lanthanum-aluminum triphosphates were synthesized by thermal-condensation method from H₃PO₄, La₂O₃ and Al(OH)₃. These pigments could be potentially used as special inorganic pigments; their corrosion-inhibition properties were widely studied. Synthesis conditions were determined on the basis of DTA and TG measurements. The products were also characterized by X-ray diffraction analysis. Physical properties — density by pycnometric method, particle size distribution, oil number and critical pigment volume concentration (CPVC), pH and specific conductivity of their aqueous extracts were also determined.      

Electrochemical dissolution of Co<Subscript>3</Subscript>O<Subscript>4</Subscript> in acidic solutions

The cyclic voltammetry method was used to study the regularities of the electrochemical behavior of cobalt cobaltite in an acidic medium. It is shown that cathodic reduction of Co₃O₄ in the studied range of potentials of +1.0 to −0.8 V is a multistage process occurring according to the scheme:      

Density and temperature effect on hydrogen-bonded clusters in water - MD simulation study

Molecular dynamics NVE simulations have been performed for five thermodynamic states of water including ambient, sub-and supercritical conditions. Clustering of molecules via hydrogen bonding interaction has been studied with respect to the increasing temperature and decreasing density to examine the relationship between the extent of hydrogen bonding and macroscopic properties. Calculations confirmed decrease of the average number of H-bonds per molecule and of cluster-size with increasing temperature and decreasing density. In the sub-and supercritical region studied, linear correlations between several physical quantities (density, viscosity, static dielectric constant) and the total engagement of molecules in clusters of size k > 4, P _k>4, have been found. In that region there was a linear relationship between P _k>4 and the average number of H-bonds per water molecule. The structural heterogeneity resulting from hydrogen bonding interactions in low-density supercritical water has been also discussed.