Coordination chain polymeric assemblies of trivalent lanthanides with multidentate Schiff base synthetic, spectral investigation and thermal aspects

The coordination chain polymers of La(III), Ce(III), Pr(III), Nd(III) and Sm(III) with N,N’-di(o-thiophenyl)terephthalaldehydediimine have been prepared and characterized by elemental analysis, ¹H NMR, ¹³C NMR, magnetic measurements, infrared spectra, reflectance spectra and thermogravimetric analysis. A coordination number of seven around the metal ion is suggested. The thermal decompositions of the coordination polymers have been studied. The kinetic parameters have been calculated using Freeman-Carroll method. The thermodynamic activation parameters such as entropy (S*), preexponential factor (A), enthalpy (H*) and free energy of the decomposition (G*) have been evaluated.     

Author Index to Volume 24

Abstract

The preparation of fairly monodisperse nanoparticles of zinc sulfide, cadmium sulfide, and lead chromate using a polymer–surfactant gel matrix as the template to resist particle clustering is been described. A hydrophobically modified polymer (chloride salt of N,N′‐dimethyl‐N‐methyl derivative of hydroxymethyl cellulose, JR 400) and a surfactant (sodium dodecyl sulfate, SDS) have been used to form the gel matrix. The nanodispersions formed in the gel at different precursor concentrations have been characterized by the TEM and SEM. Their UV‐visible and fluorescence spectra have been measured and analyzed. The band gaps and other characteristic properties of the nanomaterials have been estimated from the spectral data. A procedure for isolation of the products from the gel is described.     

Application of chemical and chemometric analytical techniques to the study of ancient ceramics from Dougga (Tunisia)

In the present paper chemical characterization has been carried out on 67 shards of archaeological pottery from Dougga (North Tunisia). The analysed shards, dated to the Byzantine period (VI–VII century A.D.), belong to the three ceramic classes African Red Slip Ware, Dougga Ware and African cooking Ware. Fourteen elements have been determined by both atomic emission spectroscopy with flame as source (AES) and by using an inductively coupled plasma source (ICP-OES). The data acquired have been treated by statistical techniques in order to define grouping for the examined shards. Both unsupervised and supervised methods have been employed in order to define groups of different pottery shards. As a comparison, some samples (control group) coming from Southern Tunisia have been examined. All the statistical methods employed have evidenced how the control group, as concerns the chemical composition, is clearly distinguishable from Ain Wassel samples which are highly homogeneous. In fact because of the compositional homogeneity of the Northern Tunisia productions, it is quite difficult to establish a good classification and distribution of the samples in well defined cluster. Nevertheless supervised analysis has evidenced how, among the three classes, the African cooking Ware is the more distinguishable one confirming the archaeologists' hypothesis that Dougga Ware is an imitation of African Red Slip Ware.     

Dielectric relaxation study of formamide–propylene glycol using time domain reflectometry

Using picoseconds time domain reflectometry, dielectric relaxation studies have been carried out for formamide (FMD)–propylene glycol (PLG) mixtures over the frequency range from 10?MHz to 20?GHz at various temperatures. The dielectric parameters, i.e. static dielectric constant (ε ₀) and relaxation time (τ), have been obtained by Fourier transform and least squares fit methods. The excess dielectric properties and Kirkwood correlation factor of the mixtures have also been determined. The Kirkwood angular correlation factor is greater than one (g ^eff?>?1) in FMD-rich region and less than one (g ^eff?<?1) in PLG-rich region, which indicates that in the mixture the dipole pairs have been formed in such a way that their orientation is parallel in FMD-rich region and antiparallel in the PLG-rich region.     

Diazo-, azo- and azidoazoles,and related compounds. 1. Synthesis of naphthoazolo-as-triazines from diazoazoles and 2-naphthol

Azo derivatives prepared by coupling 2-diazoimidazole, 3(5))diazopyrazole, 3(5)diazo-s-triazole, 4(5)diazo-v-triazole and diazotetrazole with β-naphthol have been cyclized to the corresponding naphthoazolo-as-triazines, an heterocyclic system related to azasteroids. The structure of the products have been elucidated. A consistent mechanism for the cyclization is proposed.     

Dynamical Structure Factor of Fluid Ar36

Abstract

The continued fraction representation of the correlation function and a secant hyperbolic form of the memory function have been used to calculate the dynamical structure factor S(q, ω) of fluid Ar³⁶ for the densities ranging from n? = 0.668 to 0.763 and a temperature to 120 K. The parameters of the memory function have been determined from the fourth and sixth frequency sum rules of S(q, ω). The predicted results for S(q, ω) have been compared with recent neutron scattering data. A good agreement has been achieved. Further, it is also found that the position of first minima of full width at half maxima of S(q, ω) shifts towards smaller wave number side with decrease in density while, the position of first maxima is independent of density.     

Calixarenes with nitrogen or phosphorus substituents on the lower rim

Calix[n]arenes (n=4,6) with diphenylphosphinite groups appended to their lower rim have been synthesized by reaction first with base, followed by chlorodiphenylphosphine. The reaction has also been carried out with the partially methoxylated calix[n]arenes. Calix[6]arenes with phosphate groups selectively bridging adjacent pairs of oxygens have been synthesized by reaction first with base, followed by ethyl dichlorophosphate. Calix[n]arenes (n=4,6) with 2-aminoethyloxy groups appended to the lower rim have been synthesized both by the reduction of an amide or nitrile group. Calixarenes with 2-hydroxyethyloxy and 2-bromoxyethyloxy groups appended to the lower rim have also been prepared. A route to preparing calixarene-functionalized polymers by the alkylation of polyethyleneimine is also described.This paper is dedicated to the commemorative issue on the 50th anniversary of calixarenes.     

Surface Tension of the 4-Methyl-2-Pentanone/Ethyl Benzoate Binary System in the Temperature Range from 278.15 to 308.15K

Surface tensions (σ) and densities (ρ) of 4-methyl-2-pentanone/ethyl benzoate binary mixtures have been measured over the entire composition range at 278.15, 288.15, 298.15, and 308.15 K. Values of the excess surface tensions (σ^E) and excess molar volumes (V^E) have been calculated. The σ^E and V^E values were fitted by to the Redlich–Kister polynomial equation and the A_k coefficients have been derived. The standard deviations between the calculated and the experimental excess properties have also been derived. The surface tension values have been further used to calculate the surface entropies (S^S) and surface enthalpies (H^S) per unit surface area. The lyophobicity (β) and the surface mole fractions (x₁^S) of the surfactant 4-methyl-2-pentanone have been derived using the extended Langmuir model. The obtained results are discussed from the viewpoint of the existence of specific interactions between unlike molecules in the bulk region and the surface.     

Twinning in macroscopic polymer single crystals

Twinning in macroscopic single crystals of poly(TSHD) has been investigated using scanning electron microscopy. Two particular chain-axis rotation twins have been identified unambiguously. They have K₁ twinning planes of (012) and (212). It is also thought that twins with K₁ planes of (21 2) and (202) may possibly occur. The possible mechanisms of twinning in polymer crystals have been discussed and chain-axis rotation twinning in poly(TSHD) has been compared with a similar type of deformation that has been suggested to take place in polyethylene crystals.     

Mössbauer effect studies on thermal decomposition of iron(III) hydroxy- and amino-benzoates

The thermal decomposition of iron(III) aminobenzoates (o-, m-, p-) and iron(III) hydroxybenzoates (p-, m-, p-) have been investigated from ambient temperature to 873 K in air using derivatography DTG-DTA-TG, Mössbauer, IR spectroscopy and XRD. The importance of Mössbauer spectra recorded at various stages of heating, without separating the product mixture, in studying the mode of decomposition is highlighted. The intermediates (e.g., Fe(II)-species) were confirmed. The nature of water of hydration and the order of stability (p->m->o-) have been investigated from decomposition temperatures. The kinetic model and parameters have been investigated for dehydration.P.U. and G.K.B. thank to Guru Nanak Dev. University, Amritsar for financial assistance.     

13C?13C coupling constants in diacetylene (1,3-butadiyne) and its bis(triethylsilyl) derivative

Completely ¹³C-labelled diacetylene and its bis(triethylsilyl) derivative have been synthesized and all the possible spin–spin couplings between the acetylenic carbon nuclei have been determined from their Fourier transform ¹³C NMR spectra. J(CC) values in diacetylene have been also computed by means of the finite perturbation INDO method. Carbon–proton coupling constants in diacetylene have been determined from the spectrum at natural abundance. It has been established that J(CC) values across the triple bond in diacetylene and bis(triethylsilyl)diacetylene are greater than in acetylene and triethylsilylacetylene, respectively. The increase is interpreted in terms of σ- and π-electronic changes which occur with the coupling of two isolated triple bonds into a dimer-like system. All CC coupling constants are greater in diacetylene than in bis(triethylsilyl)diacetylene, which indicates that strong (p→d)π interaction takes place in the latter compound.     

Mixed-ligand Copper(II) Complexes: Investigation of their Spectroscopic, Catalysis, Antimicrobial and Potentiometric Properties

Schiff base ligands HL¹–HL⁶ have been prepared from the reaction of 2,6-diformyl-4-t-butylphenol and 2,6-di-formyl-4-methylphenol with various aromatic amines in ethanolic solution. The Schiff base ligands 2,2′-dipyridine (dp) mixed-ligand Cu^II complexes have been obtained. Mixed-ligand Cu^II complexes containing the dp ligand have ionic nature and they conduct the electricity in solution media. The complexes have been obtained in two different forms: one of them is [Cu₂(Lⁿ)Cl₃] (n: 1, 2, 3, 4, 5 and 6) and other complexes have the general formula [Cu₂(Lⁿ)(dp)₂]3Cl. Ligands and their complexes have been characterized by elemental analyses, FT-IR, electronic spectra, molar conductance, ¹H(¹³C)-n.m.r. and mass spectral data. Their stoichiometric protonation constants have been determined potentiometrically in dioxan using a combined pH electrode at 25 °C, under a nitrogen atmosphere. For the calculation of the protonation constants, PKAS computer programme has been used. The effects of the substituents on the protonation constants and the additivities of these effects are discussed. The antimicrobial activity studies of the ligands and their complexes have been studied against the Bacillus megaterium, Micrococcus luteus, Corynebavterium xenosis, Enterococcuc faecalis, bacteria and Saccoramyces cerevisia, yeast. The catalytic properties of the complexes have been studied on the ascorbic acid, catechol and 2,6-di-t-butylphenol substrates. Thermal behaviour of the complexes has been studied by thermal techniques.     

Thermal analysis of flammability

The present article describes the synthesis, structural features and thermal studies of the complexes of the type [M(SB)₂(H₂O)₂]·nH₂O [where HSB=pyridine-m-carboxaldene-o-aminobenzoic acid and M=Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II)]. The complexes have been characterized on the basis of elemental analyses, magnetic susceptibility measurements, (FTIR and electronic) spectra and thermal studies. The nature of the bonding has been discussed on the basis of infrared spectral data. Magnetic susceptibility measurements and electronic spectral data suggest a six-coordinated structure of these complexes. The complexes of Mn(II), Co(II), Ni(II), Cu(II) are paramagnetic, while Zn(II) and Cd(II) are diamagnetic in nature. The thermal decomposition of the complexes have been studied and indicates that not only the crystallization and coordinated water are lost but also that the decomposition of the ligand from the complexes is necessary to interpret the successive mass losses. The kinetic parameters such as order of reaction (n) and the energy of activation (E _a) have been reported using Freeman–Carroll method. The entropy (S*), the pre-exponential factor (A), the enthalpy (H*) and the Gibbs free energy (G*) have been calculated.     

Acoustical Parameters of CuCl-KCl System in Acetonitrile-Water Solvent Mixture

Abstract

Ultrasonic velocity (U) and density (d) have been measured for CuCl-KCl in. acetonitrile water co-solvent at various temperatures from 298.15 to 318.15K. The adiabatic compressibility (β_ad), molar compressibility (β) specific acoustical impedance (Z), Rao Number (R) and Van der Waals Constant (b) have been computed. The variation of d, β_ad, β, Z, R and b with molarity of CuCl have been studied. The association between the components and the formation of complexes are treated.     

A study of thermal crystallization in glassy Se80Te20 and Se80In20 using DSC technique

Different methods have been used by various workers to determine the activation energy of thermal crystallization (E_c) in chalcogenide glasses using non-isothermal DSC data. In the present work, the crystallization kinetics of two important binary alloys Se₈₀Te₂₀ and Se₈₀In₂₀ is studied using non-isothermal DSC data. DSC scans of these alloys have been taken at five different heating rates. The values of activation energy of crystallization (E_c) have been determined by four different methods, i.e., Kissinger's method, Matusita-Sakka method, Augis-Bennett's method and Ozawa's method, have been used to calculate E_c. The results obtained have been compared with each other to see the effect of using different methods in the determination of E_c.     

Recent Development of Relativistic Molecular Theory

Summary. Today it is common knowledge that relativistic effects are important in the heavy-element chemistry. The continuing development of the relativistic molecular theory is opening up rows of the periodic table that are impossible to treat with the non-relativistic approach. The most straightforward way to treat relativistic effects on heavy-element systems is to use the four-component Dirac-Hartree-Fock approach and its electron-correlation methods based on the Dirac-Coulomb(-Breit) Hamiltonian. The Dirac-Hartree-Fock (DHF) or Dirac-Kohn-Sham (DKS) equation with the four-component spinors composed of the large- and small-components demands severe computational efforts to solve, and its applications to molecules including heavy elements have been limited to small- to medium-size systems. Recently, we have developed a very efficient algorithm for the four-component DHF and DKS approaches. As an alternative approach, several quasi-relativistic approximations have also been proposed instead of explicitly solving the four-component relativistic equation. We have developed the relativistic elimination of small components (RESC) and higher-order Douglas-Kroll (DK) Hamiltonians within the framework of the two-component quasi-relativistic approach. The developing four-component relativistic and approximate quasi-relativistic methods have been implemented into a program suite named REL4D.In this article, we will introduce the efficient relativistic molecular theories to treat heavy-atomic molecular systems accurately via the four-component relativistic and the two-component quasi-relativistic approaches. We will also show several chemical applications including heavy-element systems with our relativistic molecular approaches.     

Conformational Studies of Cyclopropylmethyl Ketone from Temperature-Dependent FT–IR Spectra of Xenon Solutions

Variable temperature (–60 to –100°C) studies of the infrared spectra (3500–400 cm^–1) of cyclopropylmethyl ketone, c-C₃H₅C(CH₃)O, dissolved in liquid xenon have been recorded. Utilizing several doublets due to the cis and near-trans conformers, the enthalpy difference has been determined to be 269 ± 26 cm^–1 (3.22 ± 0.31 kJ/mol) with the cis conformer (oxygen atom cis to the three-membered ring) the more stable rotamer. From these data it is estimated that 79 ± 3% of the cis form is present at ambient temperature. Ab initio calculations have been carried out with different basis sets up to 6-311+G(2df,2pd) at the restricted Hartree–Fock and/or with full electron correlation by the perturbation method to second order (MP2) from which structural parameters and conformation stabilities have been determined. These calculations support the experimental conformational conclusions that the cis form is the more stable conformer. A complete vibrational assignment is given for the cis conformer, which is supported from a normal coordinate calculation utilizing ab initio force constants. Several of the fundamentals of the near-trans conformer have been identified and assigned. Adjusted r ₀ structural parameters have been obtained from combined ab initio predicted values and previously reported rotational constants from the microwave investigation. The spectroscopic and theoretical results are compared to the corresponding quantities for some similar molecules.     

Recent Development of Relativistic Molecular Theory

Today it is common knowledge that relativistic effects are important in the heavy-element chemistry. The continuing development of the relativistic molecular theory is opening up rows of the periodic table that are impossible to treat with the non-relativistic approach. The most straightforward way to treat relativistic effects on heavy-element systems is to use the four-component Dirac-Hartree-Fock approach and its electron-correlation methods based on the Dirac-Coulomb(-Breit) Hamiltonian. The Dirac-Hartree-Fock (DHF) or Dirac-Kohn-Sham (DKS) equation with the four-component spinors composed of the large- and small-components demands severe computational efforts to solve, and its applications to molecules including heavy elements have been limited to small- to medium-size systems. Recently, we have developed a very efficient algorithm for the four-component DHF and DKS approaches. As an alternative approach, several quasi-relativistic approximations have also been proposed instead of explicitly solving the four-component relativistic equation. We have developed the relativistic elimination of small components (RESC) and higher-order Douglas-Kroll (DK) Hamiltonians within the framework of the two-component quasi-relativistic approach. The developing four-component relativistic and approximate quasi-relativistic methods have been implemented into a program suite named REL4D.In this article, we will introduce the efficient relativistic molecular theories to treat heavy-atomic molecular systems accurately via the four-component relativistic and the two-component quasi-relativistic approaches. We will also show several chemical applications including heavy-element systems with our relativistic molecular approaches.     

Carbon-13 NMR. The analysis of the relaxation times T1 of benzofuran and of a series of its methyl derivatives. Correlations between molecular motions and structural properties

Carbon-13 relaxation times (T₁) and nuclear Overhauser enhancements (η) have been measured for benzofuran and a series of its methyl derivatives. The contributions of dipolar (T₁ ^DD) and spin rotation (T₁^SR) mechanisms have both been determined. The temperature dependence of T₁ has been studied. The relationships between molecular motions and structural properties have been emphasized. The overall motional anisotropy of the benzofuran molecule is increased by substitution in positions 2 and 5. The internal rotation of a methyl group may change depending on its position in the molecule and on the influence of other methyl groups in its close neighbourhood.