Vibrational Spectra and Molecular Vibrational Behaviors of Dibenzyl Disulfide,Dibenzyl Sulphide and Bibenzyl

The vibration spectroscopy (Raman and infrared) of widely concerned molecules in sulfur corrosion phenomenon (Dibenzyl Disulfide, Dibenzyl Sulphide, and Bibenzyl) is detailedly analyzed based on density functional theory and experimental measurement. The dominant conformations of these molecules are determined according to Boltzmann distribution in relative Gibbs free energy. Additionally, noncovalent interaction analysis is conducted to indicate intramolecular interaction. Vibration normal mode is assigned based on potential energy distribution, which comprehensively reveals the molecular vibrational behaviors. Conformations weighted spectra are obtained and compared with experimentally measured spectra. We found that experimental spectra are in good agreement with the theoretical spectra in B3LYP-D3(BJ)/6-311G** level with a frequency correction factor. Furthermore, the divergence among these molecules is discussed. The vibrational behavior of the methylene group in the molecule shows a trend with the presence of the sulfur atom.     

Vibrational Spectra of Spodiosite Analogs

Spodiosite analogs are a class of compounds related to the apatite family. The ir spectra (4000 to 200 cm⁻¹) and the laser-Raman spectra were obtained for several analogs (Ca₂(XO₄)Cl in which X=P, As, or V) prepared by a reaction flux technique. Fundamental modes were identified, and empirical band assignments were made. Unquestionable band assignment of the v ₂ modes can be made using Raman spectra. Effects of solid-state interactions were noted in the spectra and interpreted by factor-group analysis using the factor group D_2h. The spectra of chlorspodiosite (Ca₂(PO₄)Cl) were compared with the spectra of synthetically prepared chlorapatite.     

Pharmaceutical Cocrystals of Ethenzamide: Molecular Structure Analysis Based on Vibrational Spectra and DFT Calculations

Pharmaceutical cocrystals can offer another advanced strategy for drug preparation and development and can facilitate improvements to the physicochemical properties of active pharmaceutical ingredients (APIs) without altering their chemical structures and corresponding pharmacological activities. Therefore, cocrystals show a great deal of potential in the development and research of drugs. In this work, pharmaceutical cocrystals of ethenzamide (ETZ) with 2,6-dihydroxybenzoic acid (26DHBA), 2,4-dihydroxybenzoic acid (24DHBA) and gallic acid (GA) were synthesized by the solvent evaporation method. In order to gain a deeper understanding of the structural changes after ETZ cocrystallization, terahertz time domain spectroscopy (THz-TDS) and Raman spectroscopy were used to characterize the single starting samples, corresponding physical mixtures and the cocrystals. In addition, the possible molecular structures of ETZ-GA, ETZ-26DHBA and ETZ-24DHBA cocrystals were optimized by density functional theory (DFT). The results of THz and Raman spectra with the DFT simulations for the three cocrystals revealed that the ETZ-GA cocrystal formed an O−H∙∙∙O hydrogen bond between the -OH of GA and oxygen of the amide group of the ETZ molecule, and it was also found that ETZ formed a dimer through a supramolecular amide–amide homosynthon; meanwhile, the ETZ-26DHBA cocrystal was formed by a powerful supramolecular acid–amide heterosynthon, and the ETZ-24DHBA cocrystal formed the O−H∙∙∙O hydrogen bond between the 4-hydroxy group of 24DHBA and oxygen of the amide group of the ETZ molecule. It could be seen that in the molecular structure analysis of the three cocrystals, the position and number of hydroxyl groups in the coformers play an essential role in guiding the formation of specific supramolecular synthons.     

Theoretical Vibrational Spectra of Carbon Fullerenes

This article investigates the stretching vibrational modes of carbon fullerenes (C₂₄, C₂₈, C₃₂, and C₅₀) by using one-dimensional U(2) algebra. Considering the molecular symmetry, the model Hamiltonian is constructed which is able to describe the fundamental “stretching modes” of the physical system with less number of algebraic parameters. The calculated energies find an excellent agreement with the theoretical data of harmonic force constant calculation.     

Vibrational Spectra of Hydrothermally Prepared Hydroxyapatites

Apatites can be used as bioceramic materials for tooth and bone implants. Infrared (4000 to 400 cm⁻¹) and laser-Raman spectra were obtained for hydrothermally prepared hydroxyapatites with the general formula X₁₀(PO₄)₆(OH)₂ where X= Ca²⁺ Sr²⁺, Ba²⁺, or Pb²⁺ Fundamental vibrational modes were identified and empirical band assignments made. Analysis of the vibrational spectra led to the reassignment of the v₂ mode to a higher wave-number, lower-intensity band (e.g. ∼470 cm⁻¹ for Ca hydroxyapatite). Effects of solid-state interaction were noted in the vibrational spectra and interpreted by factor-group analysis. An "effective" factor group C_6h, which neglects the locations of the OH⁻ ions, best describes the vibrational spectra of the hydroxyapatites.     

Study of the Preparation of Flavone Imprinted Silica Microspheres and Their Molecular Recognition Function

The aim of this study is to prepare flavone imprinted silica with good sphericity. Previous studies have demonstrated that imprinted silica can be synthesized using a simple sol‐gel method and a grinding‐sieving process. Despite the simplicity of the synthetic method, the appearance of the final product obtained is often very irregular and nonuniform. This product has many utilization issues and problems, e.g., residues and low operability. In this study, one type of novel spherical flavone imprinted silica was synthesized. A sol‐gel method and molecular imprinting technique were employed. By using luteolin as a template molecule, aminopropyltriethoxysilane (APTS) as the functional monomer, tetraethoxysilane (TEOS) as the cross‐linking agent, molecularly imprinted silica microspheres were prepared via a two‐stage reaction. The preparation conditions were monitored by the appearance of the products. SEM images show that under optimum conditions, the diameters of these microspheres are ca. 20–30 μm. The amino group adsorption peaks can be seen from the IR spectra. Results from elemental analysis indicate that 3.206 μmol of amino groups were successfully introduced into 1 g of product. This microspheric adsorbent has a high adsorption capacity to the template molecule, high adsorption selectivity and reproducibility. The adsorption capacity amounted to 32.987 mg/g and the separation factor was up to 84.3, while the adsorption capacity hardly decreased after 15 cycles.     

Vibrational Spectra and Thermodynamic Functions of the Three Isomeric Methoxyphenols

Infrared absorption spectra in the range of 250-4000 cm^?1 of the three isomeric methoxyphenols are reported. The para methoxyphenol is in the solid phase at room temperature and its spectrum has been investigated in the range of 700-4000 cm^?1 in chloroform solution in addition to the spectrum recorded for its nujol mull. Under the usual approximation of the two substituent groups taken as point masses the observed bands have been assigned to different modes of vibration. These assignments have been used to calculate the molar thermodynamic functions for these compounds.     

Deuterium Treatment and Infrared Transmission Spectra of Fused Silica

The effects of deuterium treatment on the in absorption bands infused silica were measured. The deuterium treatment progressively replaces the OH group by the OD group as determined by reduction in the intensity of OH bands. New OD bands of lower intensity were developed at longer wavelengths. The extinction coefficient of the OD group was determined to be 0.57 times lower than that of the OH group .     

Application of Molecular Orbital Calculations to Fracture Mechanics: Effect of Applied Strain on Charge Distribution in Silica

To further our understanding of the mechanism of environmentally enhanced crack growth, molecular oribital calculations (MO) using the ab initio self-consistent-field (SCF) technique have been employed to investigate the effect of applied strain on the atomic charge distribution and the bond overlap population of the Si–O bond at the crack tip of silica. Pyrosilicic acid (H₆Si₂O₇) with eclipsed conformation has been employed as the model molecule. Strain effects up to 20% were simulated in terms of bond stretching and angle distortion. The results indicate that, regardless of how the external strain is applied on the model molecule, the gross electron population on the bridged oxygen increases as strain increases and that on the silicon decreases.     

Interpretation of the Infrared Spectra of Fused Silica

A vibrational analysis was performed for fused silica assuming short-range order in the glassy network. This order is described by an average structural unit based on the model α-quartz. The analysis uses a group theoretical method and the Wilson FG-matrix techniques to predict 16 normal mode vibrational frequencies based on a diagonal force field. The most probable values of the force constants, which were obtained from the best fit between the calculated vibrational frequencies and the measured spectral values, are:

Although the selection rules are not adhered to, 15 predicted frequencies are within the ranges of the spectra of fused silica reported in the literature.     

Molecular Structures,Vibrational Spectra,Electronic Properties,and Molecular Docking of Two Pyrazoline Derivatives Containing 1-Carboxamide and 1-Carbothioamide: A Comparative Study

Pyrazolines derivatives are nitrogen-containing heterocyclic compound, which exhibit the broad spectrum of biological activities such as antibacterial, antifungal, antiprotozoal, and anti-inflammatory. The optimized geometry, frequency, and intensity of vibrational bands of these compounds are obtained by the density function theory (DFT) using 6–31+G(d,p) basis set. The scaled harmonic vibrational frequencies have been compared with experimental Fourier transform infrared spectroscopy (FTIR) values and found to be in good agreement. The electronic properties of these molecules are discussed with the help of highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), and molecular electrostatic potential (MESP) surfaces, and a number of electronic and thermodynamic parameters are calculated, which are closely related to their chemical reactivity and reaction path. We also notice that pyrazoline derivatives show biological activity for preventing dyskinesia. This study may provide a further investigation on pyrazolines derivatives for pharmacological importance.     

A DFT Study of Vibrational Spectra and Mutagenicity Predictions of Mononitrated Fluoranthenes

The Raman and infrared (IR) spectra of the mononitrated fluoranthenes (1-, 2-, 3-, 7-, and 8-nitrofluoranthene), important environmental pollutants that induce mutagenic/carcinogenic effects upon mammalian and bacterial cells, were studied via density functional theory, using optimized geometries at the B3LYP/6-311+G(d,p) and PBE0/6-311+G(d,p) levels of theory. The predicted harmonic vibrational frequencies were used in normal mode assignments. To validate the spectra, experimental fluoranthene and 3-nitrofluoranthene were used to benchmark the predicted spectra. The scaled harmonic frequencies below 2000 cm^?1are in good agreement to experiment to <5 cm^?1and 10 cm^?1or better at the B3LYP/6-311+G(d,p) and PBE0/6-311+G(d,p) levels, respectively. The high intensity nitro asymmetric/symmetric stretch modes (ν_asym/ν_symNO₂), ν(C?C) and ν(C?H) stretch frequencies were then considered, and used in distinguishing nitrofluoranthene isomers. The ν_sym(NO₂) frequency shifts are correlated to the observed mutagenic potencies, thus shedding light on their relative reactivity. The observed differential mutagenic-vibrational correlations, and implications of the ν_NO2shifts/biological mutagenic potencies between nitrofluoranthene isomers are then discussed.

Supplemental materials are available for this article. Go to the publisher's online edition of Polycyclic Aromatic Compounds to view the supplemental file.     

Structural and Molecular Orbital Studies of Si-Phenyl Silaanthracenes

The Si-phenyl derivatives of 1-, 2-, 9- silaanthracenes have been subjected to theoretical analysis with density functional theory (B3LYP/6-31G(d)) to obtain their molecular orbital properties. 2-silaanthracene has been found to be thermodynamically the most stable derivative among the trio. Moreover, the effects of the position of the Si substitution and phenyl attachment on the aromaticity of the parent anthracene have been investigated by NICS calculations at ring centers. The structures have been found to be less aromatic with respect to their unsubstituted counterparts.     

二氧化硅介孔膜材料的研究进展及应用前景

重点介绍了国内外近年来在二氧化硅介孔膜的制备与应用方面的最新进展,并对其制备与应用研究前景进行了展望。     

Synthesis of Amorphous Silica Nanosheets and Their Photoluminescence

We demonstrate the synthesis of silica nanosheets (SiONSs) by exfoliation and oxidation with layered polysilane, (SiH) _n . The resulting silica was produced in the form of amorphous nanosheets with a uniform thickness of 0.68 nm, which was constructed of six-membered rings of SiO₄ tetrahedra. The thickness is an order magnitude smaller than previously reported silica nanoparticles prepared by a variety of other methods. Strong photoluminescence (PL) was observed, and the PL spectra had maxima at 2.7 and 3.1 eV. This strong emission may be because of the defect center of oxygen deficiency in the sheets. The SiONSs may have potential applications in future integrated optical devices.     

The Vibrational Spectra of Monomer and Dimer of Benzene: An Algebraic Approach

In this article, we calculate the different fundamental modes of benzene monomer and dimers using the algebraic method by considering the symmetry and Wilson numbering. The model Hamiltonian constructed describes the C?C and C?H stretching modes accurately with only four numbers of algebraic parameters. The present calculation not only predicts the different fundamental modes but also shows good agreement with the few observed DFT data.     

价键法融合分子轨道理论及轨道杂化概念对O_3分子结构和性质的阐释

物质性构相依是化学的重要学科思想。根据现代价键理论,并融合轨道杂化的概念及分子轨道理论的处理方法,分析讨论了O_3的分子结构,阐释了该分子各键参数的特点及分子理化性质的内在原因。     

Differential Membrane Lipid Profiles and Vibrational Spectra of Three Edaphic Algae and One Cyanobacterium

The membrane glycerolipids of four phototrophs that were isolated from an edaphic assemblage were determined by UPLC–MS after cultivation in a laboratory growth chamber. Identification was carried out by 18S and 16S rDNA sequencing. The algal species were Klebsormidium flaccidum (Charophyta), Oocystis sp. (Chlorophyta), and Haslea spicula (Bacillariophyta), and the cyanobacterium was Microcoleus vaginatus (Cyanobacteria). The glycerolipid profile of Oocystis sp. was dominated by monogalactosyldiacylglycerol (MGDG) species, with MGDG(18:3/16:4) accounting for 68.6%, whereas MGDG(18:3/16:3) was the most abundant glycerolipid in K. flaccidum (50.1%). A ratio of digalactosyldiacylglycerol (DGDG) species to MGDG species (DGDG/MGDG) was shown to be higher in K. flaccidum (0.26) than in Oocystis sp. (0.14). This ratio increased under high light (HL) as compared to low light (LL) in all the organisms, with its highest value being shown in cyanobacterium (0.38–0.58, LL−HL). High contents of eicosapentaenoic acid (EPA, C20:5) and hexadecenoic acid were observed in the glycerolipids of H. spicula. Similar Fourier transform infrared (FTIR) and Raman spectra were found for K. flaccidum and Oocystis sp. Specific bands at 1629.06 and 1582.78 cm⁻¹ were shown by M. vaginatus in the Raman spectra. Conversely, specific bands in the FTIR spectrum were observed for H. spicula at 1143 and 1744 cm⁻¹. The results of this study point out differences in the membrane lipid composition between species, which likely reflects their different morphology and evolutionary patterns.