Calculation of the energy density function by the method of steepest descent

We present a unified theory of diatomic molecules which reconciles bound state spectroscopy and atomic scattering theory. The total wave-function is expanded in a complete set of atomic channel states which is entirely equivalent to an expansion in Hund's case (e) electronic-rotational states. An analysis of the coupled radial, that is vibrational, functions places strong constraints on the asymptotic properties of the molecular wave-functions. These are presented in terms of the reactance K and scattering S matrices of atomic scattering theory which offers a uniform treatment for open channels (inelastic scattering and continuum spectroscopy), closed channels (bound state spectroscopy) and mixtures of both (predissociation). The normalization of the total wavefunction is derived and related to the asymptotic boundary conditions both for continuum and bound states.     

多金属氧酸盐TBA3[VW5O19]及TBA4[PVW11O40]的固体核磁共振研究

多金属氧酸盐（简称多酸,Polyoxometalates,POMs)是由处于d⁰电子构型的前过渡金属元素通过共边或共角缩聚而成的金属-氧簇类化合物．由于其具有丰富的分子结构和独特的物理化学性质,已经被广泛应用于功能材料、催化化学和药物化学等领域．其中钒取代的多酸阴离子具有很好的催化活性,特别是对烃类的氧化,它的活性主要受钒取代的数目和钒中心的阴离子环境这两个因素影响．该文利用固体核磁技术分析了一取代钒的两类典型结构中⁵¹V的局域结构和化学环境,以及有机阳离子对多酸阴离子结构的影响,特别是对⁵¹V的化学环境的影响,为研究多酸的催化活性和催化机理提供基本的结构信息．     

New thiourea and urea derivatives containing trifluoromethyl- and bis-triflouromethyl-4H-chromen-3-yl substituents

Two new thiourea (1) and urea (2) derivatives, substituted with 2-trifluoromethyl-4H-chromen-3-yl moieties at defined positions, were obtained by convenient synthetic methodologies. The pure compounds were studied in solid state by vibrational spectroscopy (FT-IR and Raman) and in solution by NMR and UV–Vis spectroscopy. The crystal structure of the urea derivative (compound 2) was also determined by X-ray diffraction. The crystal packing is governed by N–H···O intramolecular interactions of moderate strength in a self-assembled dimer of the terminal amide fragment (C(=O)–NH₂). Hirshfeld surface and 2D-fingerprint plots were also performed to characterise the role in the packing stabilisation of all contacts, including weak C–H···F hydrogen bonds and π–π stacking interactions. For both compounds, the tentative assignment of vibrational and electronic spectra was assisted by theoretical calculations. Besides, to evaluate the influence on the pharmacokinetic and pharmacodynamic properties of molecules with –CF₃ groups, the anti-microbial activity of the title compounds was tested against the standard strains of various Gram-positive and Gram-negative organisms with noteworthy antimicrobial effect over Staphylococcus aureus, Klebsiella pneumoniae and Salmonella typhi.     

Synthesis,Physicochemical and Optical Characterization of Novel Fluorescing Complex: <Emphasis Type="Italic">o</Emphasis>-Phenylenediamine—Benzoin

The complex of o-phenylenediamine (o-PDA) and benzoin (BN) was synthesized adopting solid state reaction by mixing of their melt together followed by chilling. The phase diagram study shows the formation of a complex in 1:1 molar ratio with congruent melting point and two eutectics lying on either side of complex. The formation of complex was confirmed using the FTIR, NMR, mass spectroscopy, powder XRD and DSC studies. The optical properties of the parent component, their complex and few other compositions nearby the complex were studied using absorption and laser luminescence techniques. The significantly higher green/yellow emission was noted with newly synthesized complex as compared to that of their parents as well as other compositions of o- PDA and BN.     

An Overview of 195Pt Nuclear Magnetic Resonance Spectroscopy

Abstract

This brief, non‐exhaustive review describes some basic theoretical aspects of ¹⁹⁵Pt nuclear magnetic resonance spectroscopy and also the empirical approach used by the researchers in the field. The different factors which influence the chemical shifts are discussed. The couplings constants between ¹⁹⁵Pt and other isotopes, which have a spin of 1/2 (such as, ¹H and ¹³C) bring further important information on the structures of Pt compounds. Recently, ¹⁹⁵Pt‐NMR spectroscopy in the liquid state has been used successfully in many research fields, e.g., the determination of enantiomeric composition and absolute configuration, in the area of biosensors and biomarkers, in cluster chemistry, in cancer research and in kinetic studies. While liquid‐state ¹⁹⁵Pt‐NMR spectroscopy encompasses a wide range of areas, the parallel solid‐state technique has only been employed over the past few years, mainly in studies of heterogeneous catalysis and is more industrially oriented.     

Vibrational Spectroscopy in Clinical Analysis

Abstract: Vibrational spectroscopy includes several different techniques, the most important of which are mid-infrared (IR), near-IR, and Raman spectroscopy. Raman and mid-IR spectroscopy are complementary techniques and usually both are required to completely measure the vibrational modes of a molecule. Vibrational spectrometry covers a series of well-established analytical methodologies suitable to be employed for both qualitative and quantitative purposes. In the first part of this review, we will focus on theoretical aspects related to vibrational techniques; in the second part, the most important papers, published during the period 2005–2014, related to clinical analysis performed with vibrational spectroscopy techniques will be critically discussed.     

Use of NMR Relaxometry to identify frankfurters of different meat sources

ABSTRACT

Frankfurters are categorised as ready to eat meat products and are prepared by using different meat sources including beef, chicken, turkey or pork or mixtures of them. Due to cost and feasibility, it is very common to adulterate beef-, chicken- and turkey-based frankfurters with pork meat. Since pork is not consumed by some part of the population due to religion, it is important to identify pork frankfurters based on easy quality control methods. In this study, NMR Relaxometry was used to differentiate four different frankfurter types based on their relaxation times. Relaxation measurements were conducted on three permanent field benchtop NMR spectrometers (13.52/20.34/22.35?MHz) and also using an FFC Relaxometer at a frequency range of 40?kHz–8.86?MHz. Physical properties of frankfurters such as moisture and solid fat contents, water activity (a_w) and hardness values were also measured. Results showed that among the permanent field systems, 22.34?MHz was the best to differentiate frankfurters based on both T₁ and T₂ relaxation times. FFC experiments also showed that the dependence of T₁ with respect to frequency follows a well fitted power law behaviour throughout the whole frequency range (R²?>?0.97) and the highest difference on T₁ was observed at the lowest frequency of 40?kHz. Thus the results of the study showed that NMR Relaxometry has the potential to discriminate frankfurters of different meat origin. Further studies are needed to detect the authenticity of the type of mixture in frankfurters.     

A New Benzothiazin-functionalized Calix[4]arene-based Fluorescent Chemosensor for the Selective Detection of Co2+ Ion

Calixarenes, which have a great place in supramolecular chemistry, have become the most prominent macrocyclic compounds in synthetic organic chemistry due to their easy synthesis and functionalization. In this study, p-tert-butyl calix[4]arene dihydrazide derivative was synthesized and then reacted with 3-oxo-3,4-dihydro-2 H-benzo[b][1,4] thiazin-2-ylideneacetyl chloride to prepare new calixarene based chromophore compound 4. The structure of the synthesized compound was elucidated by spectroscopic methods such as ¹H NMR ¹³C NMR and FT-IR spectroscopy. Chromogenic and fluorescence properties of compound 4 were evaluated. It was observed from both studies that compound 4 was Co²⁺ selective and shows fluorescence Switched-off behavior. Stoichiometry, binding constant and the detection limit were calculated. The stoichiometry between compound 4 and Co²⁺ was found to be 1:1. The binding constant value (K) was calculated as 666.67 M^??1 using Benesi–Hildebrand equation, while the detection limit for Co²⁺ ion was calculated as 0.0465 µM.

     

Elastic properties of the premelting phases of the perfluoroalkanes C16F34 and C20F42

The elastic properties of the solid state of linear oligomers are closely related to their special intra-and inter-molecular interactions. This is proved for the perfluoroalkanes C₁₆F₃₄ and C₂₀F₄₂. The elastic tensors of both materials have been measured with Brillouin spectroscopy as a function of temperature. Both systmes show an extremely weak shear stiffnessc ₄₄, indicating the existence of a smectic-B like structure and an unexpected strong elastic anisotropy inversion in the premelting phase. Moreover a Curie-Weiss-law behavior was found for the stiffness constantc ₃₃ indicating the existence of a soft longitudinal acoustic phonon mode. The transition temperatureT _c is for C₂₀F₄₂ below the melting point. The elastic properties are purely static. The observations are tentatively attributed to an intermolecular premelting process.     

Solid state physics at ISOLDE

Radioactive atoms have been used in solid state physics and in materials science for decades. Besides their classical applications as tracers for diffusion studies, nuclear techniques such as Mössbauer spectroscopy, perturbedγγ angular correlation,β-NMR, and emission channeling make use of nuclear properties (via hyperfine interactions or emittedα orβ particles) to gain microscopic information on structural and dynamical properties of solids. During the last decade, the availability of many different radioactive isotopes as clean ion beams at ISOL facilities like ISOLDE/CERN has triggered a new era involving methods sensitive to the optical and electronic properties of solids, especially in the field of semiconductor physics. This overview will browse through ongoing solid state physics experiments with radioactive ion beams at ISOLDE. A wide variety of problems is under study, involving bulk properties, surfaces and interfaces in many different systems like semiconductors, superconductors, magnetic systems, metals and ceramics.

     

Predictability of ion transport properties from the structure of solid electrolytes

The concept of bond valence (BV) is widely used in crystal chemical considerations, e.g. to assess equilibrium positions of atoms in crystal structures from an empirical relationship between bond lengthR _M−X and bond valenceS _A−X =exp [(R ₀ −R _M−X ) /b] as sites where the BV sumV(A)=∑ s _M−X equals the formal valenceV _id of the cationM ⁺ . Our modified BV approach that systematically accounts for the softness of the bond may then be effectively used to study the interplay between structure and properties of solid electrolytes. This is exemplified for correlations to experimental data from IR, NMR, and impedance spectroscopy. Combining the bond valence approach with reverse Monte Carlo (RMC) modeling or molecular dynamics (MD) simulations provides a deeper understanding of ion transport mechanisms, especially in highly disordered or amorphous solids. Local structure models for crystalline electrolytes are derived by combining crystallographic structure information with simulations. A method for the prediction of the activation energy of the ionic conductivity from the bond valence analysis of the crystal structure is proposed. Taking into account the mass dependence of the conversion factor from bond valence mismatch into an activation energy scale, we could establish a correlation that holds for different types of mobile ions. The strong coupling of the H⁺ transfer to the anion motion in proton conductors requires a special treatment. For glassy solid electrolytes RMC structure models are BV-analyzed to assess the total number of equilibrium sites and to identify transport pathways for the mobile ions. Recently, we have reported a correlation between the pathway volume fraction and the transport properties that permits to predict both absolute value and activation energy of the dc ionic conductivities of disordered solids (including mixed alkali glasses) directly from their structural models. Here we discuss a corresponding BV analysis of molecular dynamics simulation trajectories that allows quantifying the evolution of pathways in time and the influence of temperature on the transport pathways. Paper presented at the Patras Conference on Solid State Ionics — Transport Properties, Patras, Greece, Sept. 14 — 18, 2004.     

Spectroscopic (FT‐IR,FT‐Raman,UV, 1H,and 13C NMR) and theoretical studies of m‐anisic acid and lithium,sodium, potassium,rubidium, and caesium m‐anisates

In order to understand the nature of the interactions of biologically important ligands, it is necessary to carry out the physico‐chemical studies of these compounds with their biological targets (e.g., receptors in the cell or important cell components). Results of this study make it possible to predict some properties of a molecule, such as its reactivity, durability of complex compounds, and kinship to enzymes. In this paper the effect of alkali metal cations (Li, Na, K, Rb, and Cs) on the electronic structure of m‐methoxybenzoic acid (m‐anisic acid) was studied. The experimental IR (in solid state and solution), Raman, UV (in solid state and solution), ¹H, and ¹³C NMR spectra of m‐methoxybenzoic acid, and its salts were registered, assigned, and analyzed. Some of the obtained results were compared with published data for o‐anisic acid and o‐anisates. The structures of anisic acid and Li, Na, and K m‐anisates were optimized at the B3LYP/6‐311++G** level. The IR, ¹H, and ¹³C NMR spectra and NPA, ChelpG, and MK atomic charges were calculated. The change of metal along with the series: Li → Na → K → Rb → Cs caused: (1) the change in the electronic charge distribution in anisate anion that is seen via the occurrence of the systematic shifts of several bands in the experimental and theoretical IR and Raman spectra of anisates; (2) systematic ¹H and ¹³C NMR chemical shifts; (3) hypsochromic shifts in UV spectra of salts as compared to ligands. Copyright © 2009 John Wiley & Sons, Ltd.     

Phase-alternated compositeπ/2 pulses for solid state quadrupole echo NMR spectroscopy

Phase-alternated compositeπ/2 pulses have been constructed for spinI=1 to overcome quadrupole interaction effects in solid state nuclear magnetic resonance (NMR) spectroscopy. Magnus expansion approach is used to design these sequences in a manner similar to the NMR coherent averaging theory. It is inferred that the symmetric phase-alternated compositeπ/2 pulses reported here are quite successful in producing quadrupole echo free from phase distortions. This effectiveness of the present composite pulses is due to the fact that most of them are of shorter durations as compared to the ones reported in literature. In this theoretical procedure, irreducible spherical tensor operator formalism is employed to simplify the complexity involved in the evaluation of Magnus expansion terms. It has been argued in this paper that compositeπ/2 pulse sequences for this purpose can also be derived from the broadband inversionπ pulses which are designed to compensate electric field gradient (efg) inhomogeneity in spinI=1 nuclear quadrupole resonance (NQR) spectroscopy.     

Synthesis, Characterization and DNA-binding Properties of Ln(III) Complexes with 6-Ethoxy Chromone-3-Carbaldehyde Benzoyl Hydrazone

A novel 6-ethoxy chromone-3-carbaldehyde benzoyl hydrazone (L) and its Ln(III) complexes, [Ln = Sm (1), Eu (2), Gd (3), Tb (4)], have been synthesized and characterized. The fluorescence properties of the Eu(III) and Sm(III) complexes in solid state and Eu(III) complex in different solutions (DMF, DMSO, methanol and acetonitrile) were investigated. At the same time, the DNA-binding properties of the two complexes are investigated using UV-Vis absorption spectroscopy, fluorescence spectroscopy, viscosity measurement. All the experimental evidences indicate that the two complexes can bind to CT-DNA via an intercalation mechanism. Furthermore, antioxidant activity tests in vitro showed that the complexes have significant antioxidative activity against hydroxyl free radicals from the Fenton reaction.     

Solid-State NMR Studies on the Guest Ordering and Dynamics in α,ω-Dibromoalkane/Urea Inclusion Compounds

Solid-state nuclear magnetic resonance (NMR) spectroscopy is utilized to study the molecular behavior of 1,10-dibromodecane and 1,11-dibromoundecane in their urea inclusion compounds. The guest dynamics and conformational order are explored by ¹³C cross polarization magic-angle spinning (CP/MAS) and ¹H MAS NMR spectroscopy which confirm an all-trans conformation of the guest chains. Dynamic ²H NMR experiments are carried out on two guest molecules selectively deuterated at both end groups. A quantitative analysis of the experimental data, obtained from variable-temperature line shape, spin–spin and spin–lattice relaxation measurements, shows that both guest molecules undergo similar motions within the investigated temperature range between 100 and 298 K. The combination of nondegenerate 6-site (or 3-site) rotational jumps and small-angle overall chain wobbling provides an appropriate motional model for the guest motions in these compounds. It is found that the populations of the jump sites exhibit a characteristic temperature dependence, although a discontinuity is missing at the solid–solid phase transition. The same holds for the guest motions which also remain unaffected by the change of the urea lattice structure. Rather, a discontinuity of the guest dynamics at about 30 and 10 degrees above the corresponding solid–solid phase transition is observed for 1,10-dibromodecane and 1,11-dibromoundecane in urea, respectively. Likewise, there is no clear evidence for an odd–even effect due to the change of the guest chain length on the molecular properties of the present inclusion compounds. As a general result, it is concluded that the intermolecular interactions in the present materials are stronger than in n-alkane/urea inclusion compounds. Authors' address: Klaus Müller, Institut für Physikalische Chemie, Universit?t Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany     

Analysis of hydrogen bonding and weak interactions in the crystal structure of (E)-N-(4-ethylphenyl)-2-(4-hydroxybenzylidene)thiosemicarbazone: experimental and theoretical studies

Hydrogen-bonding interactions play an important role in the rational design of crystal systems with desirable architectures. The novel thiosemicarbazone derivative described herein, namely (E)-N-(4-ethylphenyl)-2-(4-hydroxybenzylidene)thiosemicarbazone, C₁₆H₁₇N₃OS, (I), was prepared and characterised by ¹H NMR, IR and single-crystal X-ray crystallography techniques. The compound is arranged in the lattice by O–H···S and N–H···S bonded polymeric ribbons that extend along the crystal b-axis, and the intermolecular N–H···S hydrogen bonds formed R2 2(8) ring motifs. More importantly, C–H···π interaction stabilises the supramolecular structure of (I). Hirshfeld surface and their associated two-dimensional fingerprint plot analyses are presented to illustrate the supramolecular connectivity in the solid state. The result shows that the short H···H contacts is dominated in the total Hirshfeld surface. As well as we report on n→π* interactions in thiosemicarbazone derivatives by using the reduced density gradient function and natural bond orbital analyses. Besides, molecular electrostatic potential (MEP) and frontier molecular orbital (FMO) analysis of the title compound are also investigated by theoretical calculations.     

Conformational flexibility of xanthene‐based covalently linked dimers

The conformational flexibility of three covalently linked dimers consisting of two xanthene‐based moieties connected by a diphenyl ether linker was studied using NMR spectroscopy, X‐ray crystallography, and density functional theory (DFT) calculations. The three dimers interconvert as a function of pH: the doubly cationic dimer (Xan⁺)₂ exists in acidic solutions (pH < 0.5), the mono‐alcohol monocation Xan⁺–Xan‐OH at intermediate pH values (pH = 1–3), and the neutral diol at the highest pH‐values (pH > 3). Each dimer exhibits conformational degrees of freedom associated with rotations of either the xanthene moiety or of the diphenyl ether (DPE) linker. The barriers for rotation of the xanthylium moiety were evaluated using DFT calculations, yielding values of 23 kcal/mol for (Xan⁺)₂ and 11 kcal/mol for (Xan‐OH)₂, respectively. The rotational barrier for the diphenyl ether linker in Xan⁺–Xan‐OH (15 kcal/mol) was experimentally determined using variable temperature NMR measurements. The relative orientation of the two –OH groups in (Xan‐OH)₂ diol was investigated in solution and the solid state using NMR spectroscopy and X‐ray crystallography. The conformer observed in the solid state was found to be the In–Out conformer, while free rotation of the xanthenol units is thought to occur on the NMR timescale at room temperature. These studies are relevant for the design of linkers for efficient water oxidation catalysts. Copyright © 2016 John Wiley & Sons, Ltd.     

On structural and spectroscopic differences between quinoline‐2‐carboxamides and their N‐oxides in the solution and solid state

Intramolecular hydrogen bonding in the primarily and secondarily substituted quinoline‐2‐carboxamides and their N‐oxides has been studied in the solution by multinuclear NMR spectroscopy. Hydrogen bonding patterns and supramolecular arrangement in the solid state have been determined by single crystal X‐ray analysis. In quinoline‐2‐carboxamides weak, nonlinear intramolecular N? H…N hydrogen bond is present, but in the solid state the intermolecular hydrogen bonds and packing forces are the factors that decide on the properties of 3D structures. In quinoline‐2‐carboxamide N‐oxides the most important structural features are the intramolecular hydrogen bonds. Details of different weak interactions and resulting 3D arrangement of molecules are discussed. In the solution, two separate ¹H signals are observed for the primary quinoline‐2‐carboxamides in the range from ca. 5.8 to 8.1 ppm. The chemical shifts of the NH group's proton for studied R′‐quinoline‐2‐R‐carboxamides are in the range from 8.1 to 8.4 ppm. For the N‐oxide of 4‐R′‐quinoline‐2‐carboxamides (R′ = H, Me, OPh, Cl and Br), the values of the proton chemical shifts of the NH group in the range from 10.78 to 11.38 ppm (for primary amides) indicating that this group forms hydrogen bonds with the oxygen of the N‐oxide group. This bond is stronger than the N? H…N bond in quinoline‐2‐carboxamides. For the secondary amide N‐oxides, the δ(NH) values are increasing from 11.25 to 11.77 ppm in the sequence of substituents 4‐Br < 4‐Cl < 4‐H < 4‐Me < 4‐OPh. For 4‐substituted compounds these values depend also on the substituent effect. Copyright © 2009 John Wiley & Sons, Ltd.     

Structural and magneto-transport properties of LCMO–STO composites

A manganite matrix-based composite series, (1 ? x)La_0.67Ca_0.33MnO₃(LCMO) ? (x)SrTiO₃ (STO), has been prepared by the solid state route. Influence of STO phase on structural and magneto-transport properties of LCMO phase has been investigated. By X-ray diffraction, scanning electron microscopy, and Fourier transform of infrared spectroscopy, we find that there is no interdiffusion between the LCMO and STO phases. Measurements of resistivity on these samples reveal that the parent sample shows a distinct metal–insulator (M–I) transition of intrinsic type at a temperature close to the Curie temperature, whereas composite samples show two possible transitions, intrinsic as well as extrinsic. The series exhibits a conduction threshold at x = x _m ～ 20%, up to which extrinsic M–I transition temperature decreases along with an increase in extrinsic magnetoresistance; whereas, above x _m these trends of variation are reversed.     

Spectroscopic Trends for the Determination of Illicit Drugs in Oral Fluid

Abstract

The present work aims to review all of the articles published so far, focused on the determination of drugs of abuse in oral fluid. This fluid provides a simpler, faster, and more controllable sampling in comparison with the other biological fluids, such as blood or urine. Actually, the main goal of the researchers is to lower the limit of detection (LOD) to detect quantities of drugs smaller than the cut-off limits established by law for drug controls. Advances in Raman, infrared (IR), and nuclear magnetic resonance (NMR) spectroscopy applications are discussed. Surface-enhanced Raman spectroscopy (SERS) has been shown as the most sensitive technique for the detection of illicit drugs in oral fluid. The use of IR spectroscopy for determining drugs of abuse in oral fluid is growing, although the LODs obtained until now do not yet satisfy the necessities in the forensic field. Finally, NMR spectroscopy has seldom been used to determine drugs in oral fluid. Another future trend seems to be related with the use of portable instrumentation, which would allow us to perform in-situ analysis. This last application seems to be particularly promising to perform roadside drug tests and to identify overdose drugs in patients in emergency conditions.