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[Display omitted] • Shortwave infrared micro spectroscopy (SWIR) enables the measurement of water rotational relaxation time. • Water relaxation time measured by SWIR agrees with that measured by dielectric spectroscopy up to 100psec within 20% accuracy. • SWIR allows the sub-zero measurement of water relaxation time in solutions where ice and solution form a slurry. The shortwave infrared spectroscopy (SWIR) is the noble method which allows to evaluate the rotational relaxation time of water (RRTW) in a sample. Because SWIR requires the reference sample of pure water, the measurement temperature is limited only at above 0 °C. In this study, we expanded this temperature limitation of SWIR by using alternative reference solutions with freezing points below 0 °C, including sugar and glycerol solutions. The results showed that some reference sample solutions are useable for evaluating RRTW in samples below 0 °C. It was found that RRTW in solution measured by newly proposed SWIR agrees with RRTW measured by dielectric spectroscopy in 10% accuracy when it is shorter than 100psec. [ABSTRACT FROM AUTHOR]

[Display omitted] • Combined with the theoretical calculation of TD-DFT, the orbital characteristics of the Rydberg states are attributed and analyzed. • The vibration types related to the umbrella mode of N-methylpyrrole are analyzed by vibration spectroscopy. The umbrella mode mainly includes Out-of-plane rocking vibration, In-plane rocking vibration and Stretching vibration, which may cause molecular oscillation. • By scanning the potential energy surfaces of three vibration scales, it is found that only the out-of-plane rocking vibration and in-plane rocking vibration of the umbrella mode can cause the vibration of the molecule, and the stretching vibration of the umbrella mode may cause the dissociation of the molecule. Quantum chemical calculations are utilized to analyze the potential causes of N-methylpyrrole oscillations, focusing on vibration spectra and potential energy curves. Optimization of the ground state, ionic state and 3s state structure reveal mostly sp2 hybridization. An analysis of the 3s state vibration spectrum and adiabatic binding energy indicate that changes in dihedral angles D 2,3,4,1 and plane angle A 3,2,1 are potential factors contributing to molecular oscillations. The role of vertical binding energy and adiabatic binding energy in the oscillation process are also discussed, shedding light on the possible dynamic processes of N-methylpyrrole. [ABSTRACT FROM AUTHOR]

Mononuclear and dinuclear dioxidomolybdenum(VI) complexes of an aroylhydrazone are prepared and their experimental results are correlated by theoretical studies [Display omitted] Four dioxidomolybdenum(VI) complexes, [MoO 2 (L)] 2 ·H 2 O (1), [MoO 2 (L)(py)] (2), [MoO 2 (L)(3-pic)]·H 2 O (3) and [MoO 2 (L)(4-pic)] (4) of a dibasic tridentate ONO donor aroylhydrazone, H 2 L (where H 2 L = 3-methoxy-2-hydroxybenzaldehyde-2-furoic acid hydrazone) have been synthesized and well characterized. The stoichiometric reaction of aroylhydrazone with MoO 2 (acac) 2 in methanolic medium yielded phenoxobridged binuclear complex 1 whereas monomeric complexes, 2 , 3 and 4 were formed as a result of incorporating different monodentate heterocyclic bases. The tridentate aroylhydrazone coordinates to the MoO 2 2+ core through phenolate oxygen, azomethine nitrogen and iminolate oxygen atoms. Single crystal XRD studies established the coordination geometry of mononuclear dioxidomolybdenum(VI) complexes as distorted octahedron. The crystal structures and various solid state interactions were also investigated here. DFT investigations were conducted to explore the reactivity parameters of the studied aroylhydrazone and complexes. Furthermore, molecular docking analyses unveiled the superior putative binding energy of the investigated compounds in contrast to cisplatin. These findings were particularly pronounced in relation to the selected target proteins, which are indicative of their potential efficacy against lung and breast cancer cell lines. [ABSTRACT FROM AUTHOR]

The electronic structure and the equilibrium geometry of the VN 3 defect in diamond are computed by using a quantum mechanical approach, the main ingredients being an all electron gaussian type basis set, a global hybrid functional, the supercell scheme (216 atoms) and the CRYSTAL code. For the first time the Fermi contact and the hyperfine coupling tensor B of the open shell structure (S z = 1/2) are evaluated and compared with available experimental EPR (electron paramagnetic resonance) data. The agreement is excellent. The infrared (IR) spectrum is also computed. It results to be very close to the one of the so called B defect (VN 4), and with similarities to the one of the other members of the VN x (x = 0, 1, 2) family, so that the attribution of specific experimental peaks to one of the five mentioned compounds is difficult and questionable. The peaks measured by Sutherland (Nature, 174 , 901, 1954) and attributed to the B center might, at least in part, come from both VN 3 and VN 4. Being the ground state of the latter a closed shell, and then EPR inactive, a combined use of the two spectroscopies (IR and EPR) is mandatory for the identification of the relative weight of the two defects. Image 1 [ABSTRACT FROM AUTHOR]

The VN 2 − defect in diamond consists of a vacancy surrounded by two substitutional nitrogen atoms, which lower the local symmetry from T d to C 2v. Calculations of the doublet ground state geometry, electronic structure, EPR parameters, and IR spectra of this defect are reported along with a preliminary investigation of the observed optical transition. For the most part our results were obtained using a uniform charge compensated supercell approach together with the B3LYP functional and all-electron Gaussian basis sets designed for the properties studied. In particular, the computed hyperfine and quadrupolar EPR parameters for the carbon and nitrogen atoms adjacent to the vacancy agree very well with the experiments (Fermi contact values are 245 MHz vs 241 for 13C, and 4.1 vs 4.0 for 15N). The accompanying spin distribution may be described as a damped spherical spin wave with little spin density on the nitrogen atoms. IR spectra show some interesting features in the range of approximately 360–1310 cm−1, which are absent in the pristine diamond. Functionals without exact exchange, such as PBE, better reproduce the observed zero phonon line. Image 1 [ABSTRACT FROM AUTHOR]

Monomers of indigo were investigated using experimental (matrix-isolation) and theoretical methods. For the first time, the infrared spectrum of indigo molecules isolated in low-temperature Ar matrices was recorded and subjected to a detailed theoretical analysis. An excellent agreement between the experimental spectrum of indigo monomers and the spectrum theoretically predicted for the highly-symmetric (C 2h) most stable dioxo form of the compound allowed a very reliable assignment of the observed infrared absorption bands. Matrix-isolated monomers of indigo were exposed to UV–vis radiation of different wavelengths. The conducted experiments demonstrated that molecules of indigo do not undergo any structural changes, even under irradiation with short-wavelength UV (λ > 200 nm) light. Theoretical calculations concerning the stability of photoproducts that could be potentially generated from indigo were conducted. The calculations carried out for the species generated by hydrogen-atom transfer from N1′ to O atom attached to the opposite ring revealed that both the oxo-hydroxy and dihydroxy tautomers of indigo should be unstable in the ground electronic state. The calculations carried out for the C2H tautomer (which may be generated by a hydrogen atom shift from N1′ to C2 of the opposite ring) led to optimization of the structure that is potentially stable, but very much distorted from planarity. [Display omitted] • Infrared spectrum of indigo monomers isolated in cryogenic argon matrix is reported. • The mid-infrared spectrum of the dioxo indigo tautomer has been fully assigned. • Photostability of indigo in the electronic ground state is analyzed computationally. • The isomerization pathways via deprotonated indigoyl radical have been explored. • Hydroxy-oxo and dihydroxy tautomers are unstable and collapse back to dioxo form. [ABSTRACT FROM AUTHOR]

Calcite, magnesite and dolomite are important in Earth's evolutionary history, so they are significant in sediments and biominerals. As we know, the experimental investigations of calcite, dolomite, magnesite with Raman spectra are widespread. In order to show microprocess about Raman spectra, the first-principles vibration calculations deserve further discussion. So, the first-principles density functional perturbation theory is employed to calculate the phonon dispersion, IR spectrum, Raman spectrum, thermodynamic properties and dielectric permittivity. The vibration modes of phonon dispersion curves are investigated through symmetry system. The vibration type from group theory is used to discuss the IR activity and Raman activity, where the minerals space group are R 3 ¯ c , R 3 ¯ c and R 3 ¯ for clacite, magnesite and dolomite, respectively. The calculated phonon dispersions show that minerals with ionic and covalent bonds are dynamically stable. The vibration analysis of IR modes and Raman modes reveals the strongest covalent bond in (001) plane, and it can produce bigger shear modulus. In addition, the differently cationic masses have a little effect on thermodynamic and dielectric properties for minerals. The investigated results in this paper can promote the analysis of minerals at microscopic level, where the information of vibration can expound the stably combinative direction of electron cloud of minerals. So it can present the macroscopically mechanical property, which would help researchers to research earth mantle. • Raman and IR spectra of minerals are used to analyze the phonon vibration modes with group theory. • We find the strongest covalent bond in (001) plane can produce bigger shear modulus. • Thermodynamic and dielectric properties show that the cationic mass of minerals have few contributions. [ABSTRACT FROM AUTHOR]

Abstract The dependence of the bond characters and crystal structure on microwave dielectric properties of NdNb 1- x (Mg 1/4 W 3/4) x O 4 (x = 0.02–0.06) solid solution ceramics is investigated. X-ray diffraction and Rietveld refinement analysis both indicate a formation of single monoclinic phase in the whole range. Based on complex chemical bond theory, theoretical dielectric constant of the complex crystal is slightly lower than observed one, which is consistent with the analysis of infrared reflectivity spectra. The Q × f (quality factor) values are associated with the total lattice energy and average grain size. Increment of Nb-site bond energy generates a more stable structure, which makes τ f (temperature coefficient of resonant frequency) continuously move towards zero. Besides, far-infrared reflectivity spectra illustrates that low-frequency modes play primary role of intrinsic dielectric properties. Excellent microwave dielectric properties and an optimal combination are: ε r = 19.59, Q × f = 50339 GHz, τ f = −39.62 ppm/°C at x = 0.04. Highlights • NdNb 1- x (Mg 1/4 W 3/4) x O 4 (x = 0.02–0.06) solid solution ceramics have excellent microwave dielectric properties. • Far-infrared reflectivity spectra illustrates that low-frequency modes play primary role of intrinsic dielectric properties. • The relationship between microwave dielectric properties and the chemical bonds characteristics is investigated. [ABSTRACT FROM AUTHOR]

By the introduction of Rb+ with large ionic radius and rigid SiO 4 unit into borate, a noncentrosymmetric crystal, RbBSi 2 O 6 polymorph has been obtained. Its structure was determined by single crystal X-ray diffraction technique, and it can be described as a three dimensional (3D) framework constructed by the Si/BO 4 tetrahedra via corner-sharing O atoms, the Rb atoms reside in the tunnels and large cavities of the 3D framework. In addition, the optical properties of RbBSi 2 O 6 and CsBSi 2 O 6 , including IR spectra, UV–Vis–NIR diffuse reflectance spectra, have been reported in this work. Both RbBSi 2 O 6 and CsBSi 2 O 6 reveal short deep ultraviolet (UV) cutoff edges (below 180 nm and 185 nm, respectively), so they may have potential application in deep UV fields. Furthermore, the first-principle theoretical studies on band structure and density of states have also been performed for RbBSi 2 O 6. By the introduction of Rb+ with large ionic radius and rigid SiO 4 unit into borate, a noncentrosymmetric crystal, RbBSi 2 O 6 has been obtained. Its structure can be described as a three dimensional (3D) framework constructed by the Si/BO 4 tetrahedra via corner-sharing O atoms, the Rb atoms reside in the tunnels and large cavities of the 3D framework. Image 1 • Both RbBSi 2 O 6 and CsBSi 2 O 6 reveal short deep ultraviolet (UV) cutoff edges (below 180 nm and 185 nm, respectively), so they may have potential application in the deep ultraviolet areas. • IR spectra of RbBSi 2 O 6 and CsBSi 2 O 6 are measured for the first time. • Band structures and density of states have been calculated for RbBSi 2 O 6. [ABSTRACT FROM AUTHOR]

Abstract Partial least squares-discriminant analysis (PLS-DA) is a favored modeling tool for high-dimensional data, e.g. infrared and Raman spectra. Prior to prediction, one needs to pre-select one decision rule (DR) for the PLS-DA model. The purpose of this work is to evaluate statistical differences of four novel DRs and the naïve DR in PLS2-DA prediction models for classification of blue gel pen inks based on attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectra. The performances of the DRs have been estimated using forty sub-datasets that were prepared from the principal ATR-FTIR spectra. The global region together with three mutually exclusive spectral windows were preprocessed independently via nine different data preprocessing methods (i.e. mean centering, autoscaling, Pareto scaling, robust scaling, multiplicative scatter correction, normalization to sum, normalization to constant vector length, standard normal variate and asymmetric least squares). Then a series of 50 models (i.e. by including the first 50 PLS components incrementally) was constructed using the forty sub-datasets independently. Each model was evaluated using six different variants of v -fold cross-validation and external testing; and selected models were also assessed using iterative random sampling approach. Eventually, each DR was presented with a number of model estimates that describe the model accuracy and stability. Performances of the DRs were discussed according to summary statistics and ANOVA tests that were derived from the model estimates. Results show that the novel DRs are more accurate but relatively less stable than the naïve DR. The differences are statistically significant at the 0.05 significance level. In conclusion, both novel and naïve DRs are competitive with each other; and one has to decide on a trade-off between model stability and model accuracy. Highlights • The performances of different decision rules (DRs) in PLS2-DA modeling are explored using spectral data. • The difference between naïve DR and four novel DRs is assessed using ANOVA test. • Naïve DR underperforms novel DRs in terms of model accuracy. • Naïve DR outperforms novel DRs in terms of model stability. [ABSTRACT FROM AUTHOR]

Abstract In response to our review paper [L.C. Lee et al., Chemom. Intell. Lab. Systs. 163 (2017) 64–75], we present a study that explores practical impacts of data preprocessing (DP) methods in ATR-FTIR spectra. Nine common DP methods, i.e. mean centering (MC), autoscaling (AS), Pareto scaling, robust scaling, multiplicative scatter correction (MSC), normalization to sum (NS), normalization to constant vector length (NV), standard normal variate and asymmetric least squares (AsLS), were chosen on the sake of their availability in the R software and the rather simple computation steps. An ATR-FTIR spectral dataset of blue gel pen inks that is originated from 10 different manufacturers (i.e. brands) was used in this work. The dataset is colossal (N = 1361), high dimensional (J = 5401), multi-class (C = 10), and imbalanced. In order to examine the impacts of substrate interferences, the global spectral region was further divided, arbitrarily, into three mutually exclusive local regions and analyzed independently. Following that, the resulting four sub-datasets (i.e. one based on global and three based on local regions) were preprocessed via the DP methods independently to produce 40 different sub-datasets including the raw counterparts. Partial least squares-discriminant analysis (PLS-DA) was chosen to construct a series of 50 models by including the first 50 PLS components incrementally. The modeling was performed independently for each of the 40 sub-datasets. Each model was evaluated repeatedly using autoprediction, six variants of v -fold cross validation (v = 2, 4, 5, 7, 10, 15) and external testing schemes. As a results, empirical performances of each DP methods are represented by 400 different error rates (8 model validation schemes × 50 models). Performances of each DP method was then compared against its raw counterparts according to summary statistics and hypothesis tests. In addition, principal component analysis and hierarchical clustering analysis were also employed, respectively, to illustrate the spatial distribution and the similarity between the nine DP methods and the raw counterparts. Several important remarks have been drawn from the rigorous comparative analyses. First, due to the inherent properties of ATR-FTIR spectra, DP methods that handling slope, e.g. MSC and AsLS, have appeared to be the most excellent DP methods. Second, normalization methods, either NS or NV, ranked the second best-performing DP method. Third, MC shows no impact on the raw IR spectral dataset. Fourth, it is shown that outliers in the ATR-FTIR spectra of pen inks could be localized. Last but not least, removal of irrelevant signals arising from sample substrate is best achieved via region truncation rather than via PLS or DP methods alone. Highlights • ATR-FTIR spectra of pen inks is seriously overlapped with substrate interference. • ATR-FTIR spectra is best preprocessed via slope correcting algorithms. • Normalization methods are the second best-performing data preprocessing method. • Mean centering shows no effect on ATR-FTIR spectral dataset. • Outliers in the ATR-FTIR spectra of pen inks could be localized. [ABSTRACT FROM AUTHOR]

External testing (ET), known also as the hold-out validation, is currently considered to be one of the most reliable ways to estimate predictive ability of a statistical model. One safeguard to prevent impermissible peeking in ET is to ensure all replicates of a particular sample is only included in either the test or the training set. Assuming a sample X1 consists of two replicates (i.e. X1a and X1b). The model is claimed to enjoy impermissible peeking if the X1a and X1b are split into the training and the test sets, respectively. Eventually, the resulting prediction model is expected to predict the test sets easily and presents an over-optimistic model performance. In forensic document examinations, an individual pen (IP) can be used to produce multiple ink strokes. In real-world practice, pens are manufactured via bulk production such that one big tank of ink is used to produce a wealth of IPs. In other words, ink strokes produced by varying IPs but of the same pen model are indeed originated from one single source (i.e. the same tank of ink). Eventually, with respect to the aforementioned safeguard, how shall one treat the ink strokes? Are they replicates or independent samples? In this context, the aim of the work is to investigate the validity of the safeguard in splitting dataset for hold-out validation strategy (i.e. ET) in the domain of forensic pen ink analysis. An infrared (IR) spectra of blue gel pen inks was used to demonstrate the practical aspect. The IR spectral data were collected from 1361 ink strokes that originated from 273 IPs of 23 pen models and 10 pen brands. Iterative stratified random sampling was employed to prepare 1000 pairs of training and test sets that were split at ratio 7:3 using two different principles: (a) set IP - selection was conducted at IP level to ensure all the ink strokes originated from a particular IP must be included into either the training or the test sets only; and (b) set NIP - ink strokes of a particular IP were allowed to be spread between the training and the test sets. For each dataset, a series of 50 PLS-DA models were constructed by including the first 50 PLS components incrementally, which were then validated via auto-prediction and ET. Following that, the performances between IP and NIP model series were compared with respect to: (a) model accuracy; (b) model stability; and (c) model fitting. In conclusion, the NIP model series do not show any evidence of advantages from the impermissible peeking since both the NIP and IP model series exhibit quite similar performances in all the three model aspects. [ABSTRACT FROM AUTHOR]

The development of an effective and mechanically robust organogel coating that is both superoleophilic and under-oil superhydrophobic is presented. The organogel was shown to absorb and retain oil, and as a consequence render the surface superhydrophobic. The coating showed high repellence against water while letting oil pass through without the need to apply pressure. Utilization of the coating in oil and water separation was investigated and exhibited ≥ 99% separation efficiency for a wide variety of commercial oil. The coating was also shown to be mechanically robust and can withstand shear tests of different strengths and duration. [ABSTRACT FROM AUTHOR]

Crystal structure of orthorhombic γ-CdC 2 O 4 (sp.gr. Pmna , a = 7.3217(1), b = 6.0231(1), c = 9.2545(2) Å, V = 408.12(1) Å 3 , Z = 8, D x = 3.262 Μg·m −3 ) was solved from the powder diffraction pattern. Each metal atom in the structure is co-ordinated by seven oxygen atoms which belong to five oxalate-ions. Crystal packing containing the noticeable cavities in the [101] and [001] directions is not close and essentially differs from the known disordered α- and ordered β-modifications of transition metal oxalates. This modification seems to be meta-stable. It was found that spontaneous γ→β phase transition takes place for the γ-CdC 2 O 4 aged during 6 month in air. This transition may be accelerated via the heating of γ-CdC 2 O 4 with excessive amounts of oxalic acid. [ABSTRACT FROM AUTHOR]

Electronic structure of para-methoxybenzylidine p -ethylaniline (MBEA), a pure nematic liquid crystal has been examined using ab–initio, HF/6-31G(d,p) and DFT B3LYP/6-31G(d,p) techniques with GAMESS program. MBEA transforms from crystal to nematic at 28 °C and nematic to isotropic phase at 57 °C. Potential Energy Surface (PES) in terms of various conformations and charge distribution analysis have been carried out. Molecular Electrostatic Potential (MEP), Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) surfaces have been scanned. Ionization potential, electron affinity, electronegativity, global hardness and softness parameters of the liquid crystal molecule have been determined. Molecular and thermodynamic properties such as total energy, dipole moment, entropy, enthalpy and Gibbs free energy have been calculated at 298.15 K temperature. FTIR showed that calculated and experimental frequencies are in agreement. Stacking, side by side and end to end interactions between a molecular pair have been evaluated employing modified second order perturbation theory along with multicentred-multipole expansion technique. Results have been used to elucidate the physico-chemical and liquid crystalline properties of the system. [ABSTRACT FROM AUTHOR]

Post-combustion carbon capture using membranes is a key approach to control CO 2 emissions from power plants using fossil fuels. The minor contaminants, such as SO 2 and O 2 , may influence the long-term membrane performance. With the presence of SO 2 in the feed gas, SO 2 could preferably react with amine carriers and hinder the permeation of CO 2 in the amine-containing facilitated transport membranes. Possible amine degradation and competitive reactions would reduce membrane performance with real flue gas. With SO 2 concentrations of 0.7–5 ppm, two amine-containing facilitated transport membranes were tested at 57 and 102 °C, respectively. Unstable membrane performance was observed at 102 °C for the membrane containing Lupamin® as fixed-site carrier and potassium glycinate (K-Gly) as mobile carrier in the presence of SO 2 . On the contrary, two membranes containing polyvinylamine (PVAm) as fixed-site carrier and amino acid salts as mobile carriers showed stable separation performance in the presence of 1–3 ppm SO 2 at 57 °C. Therefore, the operating temperature plays a significant role in the membrane stabilities in the presence of SO 2 . In addition, the infrared (IR) spectra of the membrane components exposed to SO 2 with respect to exposure time were collected. It was found that the amines reacted with SO 2 to form sulfite products irreversibly at 102 °C. The spectral results were consistent with the observed membrane separation performance. The stable membrane performances of the facilitated transport membranes at 57 °C with SO 2 at ppm levels indicate the applicability of the developed amine-containing membranes for use in CO 2 capture from real flue gas. [ABSTRACT FROM AUTHOR]

In this work, the title molecule, 7-Methyl-3-[(3-methyl-3-mesityl-cyclobutyl]-5-phenyl-5 H -thiazolo[3,2-α]pyrimidine-6-carboxylic acid ethyl ester (C 30 H 34 N 2 O 2 S 1 ), was synthesized and characterized by FT-IR spectroscopy and single crystal X-ray diffraction. The compound crystallizes in the triclinic space group P 2 1 / c . with Z = 4, a = 14.1988(6), b = 19.0893(5), c = 10.1325(4) Å, V = 2674.56(17) A 3 . The optimized structure parameters of the studied molecule was determined theoretically using HF/6-31G(d) and B3LYP/6-31G(d) methods for ground state, and compared with previously reported experimental findings. The calculated harmonic vibrational frequencies are scaled and they are compared with experimental frequencies obtained by FT-IR spectra. The electronic properties, such as HOMO and LUMO energies, and molecular electrostatic potential (MEP) are also performed. [ABSTRACT FROM AUTHOR]

FTIR spectroscopy is a powerful method to analyse materials and especially fiber structure. This technique is largely used to obtain quick information on the fiber composition and to detect possible transformations after physical and chemical treatments. Unlike other techniques, FTIR is a quick method which demands a reduced amount of fibers. Furthermore, it is a non destructive method especially for Attenuated Total Reflectance (ATR), and Near Infrared (NIR) spectroscopy which are nowadays widely used. In this work, FTIR spectrum of agave fiber has been thoroughly investigated. Because of its complexity, the spectrum was separated into two regions: CH and hydrogen bond stretching (>2500 cm −1 ) and “fingerprint” region (<2000 cm −1 ). A detailed study of intermolecular and intramolecular chains was made. Infrared ratios (Lateral Order Index, Total Crystallinity Index, and Hydrogen Bond Intensity) were used to study the crystallinity and the degree of regularity of agave fiber. [ABSTRACT FROM AUTHOR]

ATR-FTIR spectroscopy in the combination with chemometrics has been practiced over the past decades. Works presented in numerous disciplines provide ample empirical evidence in support for the coupling relationship. However, Data Pre-processing (DP) which constitutes the first step in chemometric analysis pipelines, is seldom given reasonable attentions. The aim of this paper is two-fold: (a) to review contemporary DP practice strategy by ATR-FTIR user, and (b) to critically discuss the rationales that could have been nurturing such practices. In the first part, basic concepts of chemometrics and ATR-FTIR spectroscopy are described. Then, the status quo of DP practice strategy is outlined and critically discussed on whether the contemporary practice has been malpractice or best practice. Finally, rationales that could have possibly contributed to some of the malpractices are discussed. [ABSTRACT FROM AUTHOR]

Sulfur mustard (SM) is one of the most dangerous chemical compounds used against humans, mostly at war conditions but also in terrorist attacks. Even though the sulfur mustard has been synthesized over a hundred years ago, some of its molecular properties are not yet resolved. We investigate the structural flexibility of the SM molecule in the gas phase by Car–Parrinello molecular dynamics simulations. Thorough conformation analysis of 81 different SM configurations using density functional theory is performed to analyze the behavior of the system at finite temperature. The conformational diversity is analyzed with respect to the formation of intramolecular blue-shifting C H⋯S and C H⋯Cl hydrogen bonds. Molecular dynamics simulations indicate that all structural rearrangements between SM local minima are realized either in direct or non-direct way, including the intermediate structure in the last case. We study the lifetime of the SM conformers and perform the population analysis. Additionally, we provide the anharmonic dynamical finite temperature IR spectrum from the Fourier Transform of the dipole moment autocorrelation function to mimic the missing experimental IR spectrum. [ABSTRACT FROM AUTHOR]

Microwave dielectric ceramics with excellent properties and low sintering temperatures are pursued saving energy and cofiring with metal electrodes (especially Ag, Cu). Herein, a low-firing Na 2 CaTi 2 Ge 3 O 12 garnet was fabricated via a simple solid-state method. XRD, SEM, Raman spectrum, and dielectric characterization were used to reveal the influence of sintering temperature on crystal structure and dielectric properties. A single-phase Na 2 CaTi 2 Ge 3 O 12 ceramic densified at 960 °C has the optimized dielectric properties with ε r = 15.3 ± 0.2, Q × f = 55,900 ± 2000 GHz, and τ f = −15.7 ± 0.5 ppm/°C. The infrared (IR) spectrum was applied to estimate the intrinsic contribution of lattice vibration to microwave dielectric properties. The anti-reductive feature of Na 2 CaTi 2 Ge 3 O 12 ceramic was evaluated via sintering at a reducing atmosphere while cofiring with Cu electrodes. The good chemical compatibility with Ag and Cu electrodes manifests the potential prospect of Na 2 CaTi 2 Ge 3 O 12 ceramic in the low-temperature co-fired ceramic (LTCC) application. • Single-phase sample Na 2 CaTi 2 Ge 3 O 12 with excellent microwave dielectric properties were obtained at 960 ℃. • The intrinsic dielectric properties were estimated by fitting IR spectra. • Na 2 CaTi 2 Ge 3 O 12 ceramic is chemically compatible with both metal Ag and Cu. • The anti-reduction feature is evaluated while sintering in the argon atmosphere. [ABSTRACT FROM AUTHOR]

In present letter, based on density functional theory plus dispersion (DFT-D) and a self-consistent charge density-functional tight-binding (SCC-DFTB) method, the structural and electronic properties are reported, and the phase transition are investigated by analyzing its thermodynamics properties and IR spectrum of RDX. The anisotropy of α- and γ-RDX were discussed at 0–10 GPa. By fitting the third-order Birch–Murnaghan equation of states, the bulk modulus and its pressure derivative of RDX were determined. The α-RDX phase is found stable at ambient condition, however, under pressures, both the values of lattice constants a , b , c and the Δ E vdw at around 4 GPa show abrupt changes which indicate a structural transition occurred. By analyzing the linear compressibility of a , b , c axes at 0–8 GPa, one clearly see that the molecules in α-RDX phase underwent rotations and translational motion to their position in the γ-RDX phase at about 4 GPa, which validates the α–γ phase transition. The IR spectra of α-form and γ-form RDX was calculated by analyzing the trajectory of molecules motion, which also show the phase transition from the spectra changes. Employing the quasi-harmonic Debye model, the enthalpy and specific heat were investigated at various pressures of both phases. The condition of equal enthalpies in both phases also indicates the phase transition of α-form to γ-form at around 4 GPa. The variation of specific heat with temperature approaches to the classical Dulong–Petit's law at high temperature, while at low-temperature it obeys the Debye's T 3 law. [ABSTRACT FROM AUTHOR]

The chemical characteristics of degraded beeswax in the wax treated volumes of the annals of King Sejong in the Joseon Dynasty of Korea were investigated and compared with a standard beeswax sample. The oxidation index of the artificially thermally aged beeswax was similar to that of the beeswax in the waxed volumes of the annals of King Sejong. The beeswax in the waxed volumes had gradually degraded in molecular weight over about 400 years. Two low molecules free fatty acid (tetradecanoic acid and lauric acid) were detected in the beeswaxes on the Annals of King Sejong and artificially aged beeswax. These fatty acids should be generated from ester compound of the beeswax by oxidative and hydrolytic degradation. Therefore, it can be concluded that the beeswax in the waxed volume of King Sejong should be oxidized and hydrolyzed gradually for a long time progressed. [ABSTRACT FROM AUTHOR]

Electrochemical oxidation of copper and aluminium using alternating current of industrial frequency results in the formation of non-equilibrium products. Their transformations during the ageing in sodium chloride solutions of different concentrations have been considered. According to X-Ray diffraction confirmed by TG/DSC/DTG analysis, irrespective of solution concentration, the ageing products consist of aluminium oxyhydroxide (boehmite, AlOOH), copper-aluminium carbonate hydroxide hydrate (Cu–Al/LDH) and copper chloride hydroxide (Cu 2 (OH) 3 Cl). The increase of the solution concentration leads to Cu 2 (OH) 3 Cl formation and makes difficulties for metal oxide carbonization to Cu–Al/LDH. Ageing in highly diluted solution contributes not only to Cu–Al/LDH formation but also boehmite hydration that is verified by IR-spectra. The pore structure characteristics have been also discussed. They do not significantly depend on phase composition and vary in ranges of 161.2–172.6 m 2 /g (specific surface areas), 0.459–0.535 cm 2 /g (total pore volumes). Pore size distributions reveal that a pore structure is predominantly formed by pore with the sizes from 3 to 22 nm; 3.6 nm is the size of pores with the largest pore volume. [ABSTRACT FROM AUTHOR]

The polarization modulation infrared reflection–absorption spectra of collagen adsorbed on a titania surface and quantum chemical calculations are used to describe components of the amide I mode to the protein structure at a sub-molecular level. In this study, imino acid rich and poor fragments, representing the entire collagen molecule, are taken into account. The amide I mode of the collagen triple helix is composed of three absorption bands which involve: (i) (∼1690 cm −1 ) the C O stretching modes at unhydrated groups, (ii) (1655–1673 cm −1 ) the C O stretching at carbonyl groups at imino acids and glycine forming intramolecular hydrogen bonds with H atoms at both NH 2 and, unusual for proteins, CH 2 groups at glycine at a neighbouring chain and (iii) (∼1640 cm −1 ) the C O stretching at carbonyl groups forming hydrogen bonds between two, often charged, amino acids as well as hydrogen bonds to water along the entire helix. The IR spectrum of films prepared from diluted solutions ( c < 50 μg ml −1 ) corresponds to solution spectra indicating that native collagen molecules interact with water adsorbed on the titania surface. In films prepared from solutions ( c ⩾ 50 μg ml −1 ) collagen multilayers are formed. The amide I mode is blue-shifted by 18 cm −1 , indicating that intramolecular hydrogen bonds at imino acid rich fragments are weakened. Simultaneous red-shift of the amide A mode implies that the strength of hydrogen bonds at the imino acid poor fragments increases. Theoretically predicted distortion of the collagen structure upon adsorption on the titania surface is experimentally confirmed. [ABSTRACT FROM AUTHOR]

Infrared absorption of the H2O stretching modes around 3400cm−1 is commonly used to detect the presence of H2O inside SiO2. Obtaining the exact concentration of water remains difficult since the molar absorption coefficient (ε) is not known. In this work ε is determined for H2O absorbed in sub-atmospheric chemical vapor deposited SiO2 and compared to liquid water. By integration over the whole absorption band width, ε is found to be 7.64±1.08×104 M−1 cm−2. When considering peak absorption at the absorption band maximum only, the value is ε =139.5±11.8M−1 cm−1 which is significantly lower than the literature value of liquid water for which ε =231.66±0.05M−1 cm−1. This difference is attributed to the absence of hydrogen bridges between H2O molecules, evidenced by the featureless absorption spectrum of H2O inside SiO2. [ABSTRACT FROM AUTHOR]

Abstract: The canonical and zwitterionic conformers of gaseous dipeptide arginylglycine, ArgGly, were thoroughly researched. A large number of trial structures were generated by considering all combinations of internal single bond rotamers of three ArgGly tautomers. The structures were successively optimized with the methods of PM3, HF/3-21G*, BHandHLYP/6-31G* and BHandHLYP/6-31+G**. The conformational energies were finally calculated by the approaches of DFT/BHandHLYP, DFT/B3LYP, DFT/B97D and MP2 using the basis set of 6-311++G (2df,2p). The results of the four methods are quite different on various aspects. However, all the computational approaches find that the most stable structure of ArgGly is zwitterionic. The properties of the low energy conformers such as the rotational constants, dipole moments, vertical ionization energies, temperature dependent conformational distributions and IR spectra are analyzed. These data should be helpful for understanding the experiments as well as for the differentiation of the four theoretical approaches by the experiments. [Copyright &y& Elsevier]

Abstract: A crystal structure redetermination of the L-tryptophan picrate crystal previously studied by Ishida et al. (Chem. Pharm. Bull. 41 (1993) 433–438) showed that it comprises L-tryptophan L-tryptophanium dimeric cation, one picrate anion and picric acid. The O⋯O distance of the O–H⋯O hydrogen bond in the dimeric cation is equal to 2.470(6)Å. The infrared spectrum of the crystal was registered and analyzed. The infrared spectrum of the crystals contains a broad absorption band centered at ca. 1170cm−1, which is assigned to the stretching vibration of the O–H bond. [Copyright &y& Elsevier]

Abstract: The FTIR spectrum of symmetrical derivative of the tetraoxa[8]circulene, named para-dinaphthyleno-2,3,10,11-tetraundecyldiphenylenotetrafuran (p-2B2N4R, R= n-C11H23) has been recorded and interpreted using density functional theory (DFT) calculations for the model compounds p-2B2N4R (R=H, C2H5). The unsubstituted tetraoxa[8]circulene, namely para-dinaphthylenodiphenylenotetrafuran (p-2B2N) and para-dinaphthyleno-2,3,10,11-tetraethyldiphenylenotetrafuran (p-2B2N4R, R=C2H5) belong to the D 2h and D 2 symmetry point groups, respectively. The equilibrium molecular geometry, harmonic vibrational frequencies and infrared intensities have been calculated utilizing the DFT/B3LYP method with the 6–31G(d) basis set using the symmetry constraints. Comparison of the calculated vibrational spectra with the experimental data provides a reliable assignment of the observed bands in the FTIR spectra. The results of quantum-chemical calculations provide a complete interpretation of vibrational modes based on a good agreement with all details of the experimental spectra. [Copyright &y& Elsevier]

Abstract: 4-Methoxy 4-nitrostilbene (MONS), a new organic nonlinear optical material has been synthesized. Based on the solubility data good quality single crystal with dimensions up to 38×11×3mm3 has been grown by slow evaporation method using ethyl methyl ketone (MEK) as a solvent. Powder XRD confirms the crystalline property and also the diffraction planes have been indexed. The lattice parameters for the grown MONS crystals were determined by using single crystal X-ray diffraction analysis and it reveals that the crystal lattice system is triclinic. The crystalline perfection of the grown crystals has been analysed by high resolution X-ray diffraction (HRXRD) rocking curve measurements. Fourier transform infrared (FTIR) spectrum for powdered MONS sample confirms the functional groups present in the grown crystal. The UV–vis absorption spectrum has been recorded in the range of 190–1100nm and the cut off wavelength 499nm has been determined. The optical constants of MONS have been determined through UV–vis–NIR spectroscopy. The MONS crystals were further subjected to other characterizations. i.e., 1H NMR, TG/DTA, photoluminescence and microhardness test. The Kurtz and Perry powder technique confirms the NLO property of the grown crystal and the SHG efficiency of MONS was found to be 1.55× greater than that of KDP crystal. [Copyright &y& Elsevier]

Abstract: Li3NaBaB6O12 was synthesized by high temperature solution method. It crystallizes in trigonal space group (No. 148) with lattice constants a = 9.462(9) Å, c = 18.71(3) Å, Z = 6. The crystal structure of Li3NaBaB6O12 is a three-dimensional (3D) network composed of the isolated twelve-membered cyclic B12O24 groups interconnected by NaO6, LiO4 and BaO9 polyhedra. Functional groups in the sample were identified by IR spectrum. Li3NaBaB6O12 exhibits a short UV cutoff edge below 190 nm. Band structures and density of states were calculated. [Copyright &y& Elsevier]

Abstract: Density functional theory (DFT) calculations, atom in molecules (AIM) theory, natural bond orbital (NBO) analysis and infrared (IR) spectroscopy were performed to investigate the interactions between water molecules and ionic liquid 1-ethyl-3-methylimidazolium acetate ([emim]Ac). It was found that [emim]Ac interacts with water molecules mainly via H-bonds, and the anionic part of [emim]Ac plays a major role in the interaction with H2O. The energies of H-bonds were estimated from spectral shifts of hydroxy antisymmetric stretching vibration. Moreover, the experimental results also indicated that hydroxy of water mainly interacts with the COO− of [emim]Ac. Further studies indicated that the intensity of hydroxy stretching vibrations tend to be stronger with the increase of the concentration of water. In addition, the frequency of hydroxy stretching vibrations showed clearly red-shift, and the COO− vibrational frequency gradually shifted to the lower wavenumber region, which were indicative of extended hydrogen bonded network. [Copyright &y& Elsevier]

Abstract: The adsorption and photocatalytic decomposition under UV irradiation of dimethyl sulfide ((CH3)2S: DMS) on synthetic colloidal calcium hydroxyapatite (Ca10(PO4)6(OH)2: Hap) particles were examined by in vacuo IR measurements. The adsorption isotherms of DMS on Hap exhibited the Langmuir type. The saturated adsorbed amount of DMS was increased with increasing the outgassing temperature of Hap, showing a maximum of 2.4molecules/nm2 at 250°C. Similar tendency could be observed for change in area intensity of surface P-OH bands of Hap estimated from in vacuo IR measurements against outgassing temperature. By adsorption of DMS, the surface P-OH bands of Hap weakened while the CH bands due to DMS appeared. These results revealed that the DMS was adsorbed on surface P-OH groups of Hap. When the UV light was irradiated to the DMS-adsorbed Hap, the surface P-OH bands revived and the CH bands weakened. This fact strongly indicated the photocatalytic decomposition of DMS took place on surface P-OH groups of Hap, which was thought to be due to the formation of surface P-OH radicals by UV irradiation. [Copyright &y& Elsevier]

Abstract: Combined experimental and theoretical studies have been performed on the structure and vibrational spectra (IR and Raman spectra including far region) of 2-quinolinecarboxaldehyde. Hartree–Fock (HF) and density functional B3LYP calculations have been employed with the 6-311++G(d,p) basis set for investigating the structural and spectroscopic properties of two possible aldehyde rotamers of 2-quinolinecarboxaldehyde. When the O atom of the aldehyde is farther away than the nitrogen atom of the quinoline, 2-quinolinecarboxaldehyde has the lowest possible energy, and thus is in its ground state. The computed vibrational frequencies of this lowest energy rotamer agree also slightly better than those of the higher energy rotamer with the experimental frequencies after the computed frequencies are scaled. [Copyright &y& Elsevier]

Abstract: The infrared bar-spectrum of a single ammonia molecule encapsulated in nano-cage C60 fullerene molecule is modeled using the site inclusion model successfully applied to analyze spectra of CO2 isotopologues isolated in rare gas matrix. Calculations show that NH3 can rotate freely on a sphere of radius 0.184Å around the site center of the nano-cage and spin freely about its C3 symmetry axis. In the static field inside the cage degenerate ν 3 and ν 4 vibrational modes are blue shifted and split. When dynamic coupling with translational motion is considered, the spectral signature of the ν 2 mode is modified with a higher hindering barrier (2451cm−1), an effective reduced mass (6.569gmol−1) and a longer tunneling time (55594ps) for the fundamental level compared to gas-phase values (2047cm−1), (2.563gmol−1) and (20.85ps). As a result this mode is red shifted. Moreover, simulation shows that the changes in the bar-spectrum of the latter mode can be used to probe the temperature of the surrounding media in which fullerene is observed. [Copyright &y& Elsevier]

Abstract: First mixed-ligand polyoxometalate complex of neptunium, K10.5H0.5[Np(BW11O39)(W5O18)]·15H2O, has been synthesized. Its structure has been determined using X-ray diffractometry and confirmed by electron and IR absorption spectroscopy. The structure consists of [Np(BW11O39)(W5O18)]11− anions, potassium cations and water molecules. The overall symmetry of the [Np(BW11O39)(W5O18)]11− anion can be approximated as C s . Two tetradentate ligands, [W5O18]6− and [BW11O39]9−, are connected to an Np atom through lacunary O atoms, so that a square antiprismatic surrounding of Np is formed. [Copyright &y& Elsevier]

Abstract: The single crystals of Li2Cu5(PO4)4 have been grown in the Li2CO3–H3BO3 borate fluxes. Li2Cu5(PO4)4 crystallizes in the centrosymmetric triclinic space group P-1 with a = 6.03580(10) Å, b = 9.2211(2) Å, c = 11.4138(2) Å, α = 75.5750(10)°, β = 80.2540(10)°, γ= 74.1590(10)°, Z = 2. The three-dimensional framework is built up of LiO5, CuO4, Cu/LiO5 polyhedra and isolated PO4 tetrahedra. The IR spectrum and UV–Vis–NIR diffuse reflectance spectrum of Li2Cu5(PO4)4 have been studied. [Copyright &y& Elsevier]

Abstract: Geometries of silica rings in SBA-15 mesoporous molecular sieve were investigated by the density functional theory (DFT). The stable conformations of model clusters with monocyclic and bicyclic silica rings were obtained. By comparing the calculated values of Si–O bond length and O–Si–O, Si–O–Si bond angles with the experimental data of amorphous silica, we found that all monocyclic rings are not the reasonable model to represent the structure of SBA-15 mesoporous molecular sieve. After having investigated the bicyclic model clusters theoretically, we inferred that 5-, 6- and 7-membered rings should be the main structural elements in the SBA-15 framework. Among the model clusters employed in this study the model 5–6-s was proved to be the best one for the SBA-15 molecular sieve. A comparison between the calculated IR frequencies of the model clusters and the measured values of SBA-15 further verified that the bicyclic model clusters employed here are reasonable and the model 5–6-s is the most suitable model cluster for the SBA-15 mesoporous molecular sieve. [ABSTRACT FROM AUTHOR]

Abstract: Geometrical structures and corresponding vibrational spectra of neutral Au n () clusters are investigated by density-functional theory. We found their far-infrared spectra are distinctively structure-dependent, providing an efficient way to identify their structures. A new ground-state Au23 bulk-fragment isomer is found, exhibiting also some specific low-frequency far-infrared peaks for cage-like structure. [ABSTRACT FROM AUTHOR]

Three kinds of polymer hollow fiber membranes--polyethersulphone (PES), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN)--were used for recycling of used lubricating oil. The efficiency of membrane separation was characterized by means of the membrane rejection and the physical and chemical properties of the oils. The separation and analytical methods, for example, Fourier Transform Infrared (FTIR), UV-visible absorption spectra, column chromatography; etc. were employed to illustrate the separation mechanism and the potential structures of used lubricant oil so as to assess the differences between the used lubricating oil and the permeate. Results show that the membrane process can not only remove metal particles and dusts from waste lubricant oil, but also improve its liquidity and flash point. Further, the ultrafiltration membrane (PAN) has higher rejection than microfiltration membranes (PES and PVDF). The results of FT-IR and UV absorption spectra show that waste lubricant oil has almost 90% long chain saturated hydrocarbons, which are originally from the base oil. The middle polarity compositions may be lactones, esters, aldehydes, ketones, carboxylic acids, which may come from the oxidation of base oil and additives during the use of lubricating oil. Moreover, the molecules of the retentate contain aromatic rings as the basic unit in structure. The conjugated aromatic rings in the unit are mainly composed of two rings and three rings, whose connections are "linear order", namely cata-condensed. Overall, it will provide much more reference data for optimizing the regeneration processes of used lubricant oil. [ABSTRACT FROM AUTHOR]

• In this paper, with aim of creating curvature in monolayer flat phosphorene, the optical properties of monolayer phosphorene nanotubes in IR range has been investigated and then the SPR label free sensor based on phosphorene-graphene nanotubes is proposed. • Creating a curvature in monolayer flat phosphorene leads to enhancement in absorption (40%), and this leads to transferring absorption spectrum from mid IR to THZ range. • Phosphorene-graphene nanotubes in the vicinity of silver noble metal and in interaction with the electromagnetic wave generate a strong plasmons which is localized in phosphorene. The generated plasmons suggest these nanotubes as a good sensor due to their sensitivity to surrounding environment. • Optimization of geometric parameters and the properties of two-dimensional materials was performed in the proposed sensor. It is showed that this sensor has the good ability to detect gasses or biomolecules in the refractive index range from 1 to 1.6. • The best quality factor reported to be 818 for the refractive index 1.2 and the best sensitivity was 1040 for refractive index 1.2. • The ability of sensing biomolecules such as Deionization water, MDCK, whole blood and glucose has been investigated by means of this sensor. • Nanotubes, in comparison to flat phosphorene, show higher anisotropic effects. Because of anisotropic properties of phosphorene, in this paper, the effect of curvature on phosphorene is investigated by designing phosphorene nanotubes in the IR range. It was observed that creating curvature in the phosphorene monolayer would increase the absorption rate. By designing a SPR biosensor based on phosphorene nanotubes, the sensitivity of this sensor to environmental factors was investigated. The results revealed that phosphorene nanotubes showed good ability to identify materials with a refractive index in the range of 1 to 1.6, with an accuracy of 0.005. Eventually, the sensing ability of this sensor for some biomolecules such as water, MDCK, and blood was examined, and the quality factor of the proposed sensor for identifing these biomolcules was repored to be 753.8, 816.6, and 784.6 respectively. One of the most important results of comparing nanotubes with flat phosphorene was that the former proved to have a greater anisotropic effect. [ABSTRACT FROM AUTHOR]

Abstract: It is claimed that some recent N-glycosyl sulfonamides exhibit important biological activity. In particular, the title sulfonamide shows activity against lung carcinoma. It has been obtained elsewhere as an anomeric mixture, in which the α form predominates. The 1H and 13C NMR spectra were also recorded. Present calculations carried out in the framework of the density functional theory, show that the β anomer form should be thermodynamically more stable than the α one. The relative stability could be associated in principle to some particular intramolecular hydrogen bonds. As those results are in contrast with experimental findings, they suggest that the synthesis of the title compound takes place under kinetic control mainly. The IR spectrum of the title N-glycosyl sulfonamide is recorded in the present work and theoretical calculations are performed to aid in the assignment of both the NMR and IR spectra. [Copyright &y& Elsevier]

Abstract: Electrode potential of 6-(2,3-dihydro-1,3-dioxo-2-phenyl-1H-inden-2-yl)-2,3-dihydroxybenzaldehyde (DPDB) in methanol have been calculated theoretically. For the achievement of this task, the density functional theory (B3LYP/6-31G(d)) was employed with the inclusion of the entropic and thermochemical corrections to yield the free energies of the redox reactions. The electrode potential was also obtained experimentally by means of an electrochemical technique (cyclic voltammetry). The geometric parameters, the vibrational frequency values and the UV spectrum of DPDB and 2-(2,3-dihydro-1,3-dioxo-2-phenyl-1H-inden-2-yl)-5,6-dioxocyclohexa-1,3-dienecarbaldehyde (DPDD is the oxidized form of DPDB), were computed using the same methods. The calculated IR spectrum of DPDB, used for the assignment of the IR frequencies, was observed in the experimental FT-IR spectrum. The correlation between the theoretical and experimental DPDB vibrational frequencies was 0.996. This agreement mutually verified the accuracy of the experimental method and the validity of the applied mathematical model. [Copyright &y& Elsevier]

Abstract: A new semiorganic nonlinear optical bis (thiourea) cadmium zinc chloride (BTCZC) crystal has been synthesized. BTCZC single crystals were grown from aqueous solution by slow evaporation technique. The solubility of BTCZC has been determined for various temperatures. Single crystal X-ray diffraction (XRD) study has been carried out to identify the lattice parameters. Fourier transform infrared (FTIR) studies confirm the various functional groups present in the grown crystal. The transmission and absorption spectra of this crystal show that the lower cut off wavelength lies at 260nm. The thermal analyses confirmed that the crystal is stable upto 201°C. The nonlinear optical (NLO) property of the grown crystal has been confirmed by Kurtz-powder second harmonic generation (SHG) test. [Copyright &y& Elsevier]

Abstract: The vibrational properties of cyclohexene-2-ethanamine molecule are studied by both theoretically and experimentally. The theoretical calculations are performed using density functional perturbation theory (DFPT) based on plane wave pseudopotential method while the experimental technique is infrared (IR) spectroscopy. We also present the results of theoretical calculation of STM images for electron density of the cyclohexene-2-ethanamine. Our results also show that DFPT can be applied to the molecular systems in GGA approximation by comparing experimental and other commercial theoretical methods. [Copyright &y& Elsevier]

Abstract: Infrared vibrational spectrum of 11αH-dihydrozaluzanin E has been measured at room temperature and it was analyzed theoretically by means of ab initio calculations. The conformational space of the compound has been scanned using molecular dynamics and complemented with functional density calculations that optimize the geometry of the lowest-energy conformers of each species as obtained in the simulations. The vibrational frequencies were assigned using functional density calculations. The Molecular Electrostatic Potential Map (MEP) was obtained and analyzed. Coupling constants were calculated at ab initio level and by means of the Karplus-Calculator method and via the MestRe-J Program, chemical shifts were also calculated at ab initio level and all the results were compared with respect to experimental data. Conclusions are reported on the stereochemistry of the molecule. [Copyright &y& Elsevier]

Abstract: 2,5-Diamino-3,6-dichloro-1,4-benzoquinone has been synthesized by modifying the procedure reported in literature. Its IR spectrum has been recorded in the solid phase in the range 4000–400cm−1. Ab initio calculations have been performed using Gaussian ’03 program to compute optimized geometry, harmonic vibrational frequencies along with intensities in IR and Raman spectra and atomic charges at RHF/6-31+G*, B3LYP/6-31+G* and B3LYP/6-311++G** levels. To make vibrational analysis Gaussian View software was used. The optimized molecular structure is found to possess C 2h point group symmetry. The observed IR frequencies have been assigned to different modes taking C 2h molecular symmetry with the help of pictorial view of normal modes. From the magnitude of the observed frequencies corresponding to the NH2 stretching motions an indication of H-bonding is noticed. From geometrical parameters of the molecule it appears that two parallel sets of conjugated strands are formed in this molecule providing a route to conduct charges. The N–H bonds facing towards chlorine atoms are found to be shorter than those facing towards oxygen atoms indicating the presence of H-bonding between hydrogen atom of an NH2 group and carbonyl (quinoid) oxygen atom. [Copyright &y& Elsevier]

Abstract: Quantum-chemical calculations on two isomers of molecule C24H16 in which two hexaprismanes are linked by four carbon–carbon single bonds have been performed using density functional theory (DFT) method. The geometric structures, vibrational frequencies, and vertical ionization energy as well as vertical electron affinity of isomer I and isomer II have been obtained at the B3LYP/6-31G∗∗ level of theory. Meanwhile, the present paper has also computed the enthalpies of formation and strain energies for two isomers so as to evaluate their stability from a thermodynamic point of view. [Copyright &y& Elsevier]

Abstract: DFT (B3LYP/6-31G(d) and B3PW91/6-31G(d)) calculations were performed for (E)-3-(4,5-dihydroxy-2-tosylphenyl) acrylic acid (DTA). The calculated IR spectrum of DTA and (2E)-3-(3,4-dioxo-6-tosylcyclohexa-1,5-dienyl) acrylic acid (DTDA) were used for the assignment of IR frequencies. Correlation between theoretical and experimental vibrational frequencies of DTA molecule was 0.994. DTA has two geometric structures, cis and trans. Since the cis structure of caffeic is unstable, it can not be found in nature, but in this research, its electrode potential have been calculated theoretically. Electrode potential of DTA solution obtained by cyclic voltammetry on the surface of a glassy-carbon electrode is 0.328V. The electrode potentials were also calculated using the energies of solvation and the sum of electronic and thermal free energies of the species. The observed and calculated changes in the reduction potential of DTA differ from those of the reference compound caffeic acid by just 0.010 and 0.016V for B3LYP and B3PW91, respectively, providing a method by which the reduction potentials of related molecules can be predicted very accurately. [Copyright &y& Elsevier]