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The seasonal variation in essential oils from leaves of Vitex gardneriana Schauer was studied. Analysis of the chemical composition showed the presence of 3 monoterpenes, 2 non-oxygenated (α-pinene and β-pinene) and 1 oxygenated (eucalyptol), and 24 sesquiterpenes, 21 non-oxygenated and 3 oxygenated. The main compound, 6.9-guaiadiene, presented the highest concentrations in October (30.15%), January (28.86%) and February (22.73%); cis-calamenene had the highest concentrations in December (35.62%), April (34.92%), November (34.63%) and March (33.57%); and caryophyllene oxide possessed the highest concentrations in September (16.68%), January (15.06%) and August (14.39%). Additionally, essential oils extracted in January (LC50 78.3 μg/mL), March (LC50 44.1 μg/mL), April (LC50 47.9 μg/mL), May (LC50 28.0 μg/mL), July (LC50 43.5 μg/mL), August (LC50 62.0 μg/mL) and December (LC50 84.3 μg/mL) exhibited significant larvicidal activity against third instar larvae of Aedes aegypti.

In the present study, a systematic investigation on vibrational properties of captopril (C9H15NO3S) single crystal under pressure is presented. At first, it is used density functional theory calculation in order to furnish the assignment of the normal modes as observed through Raman spectroscopy. In the second part of the paper, it is shown the Raman spectra of captopril for several pressures up to 6.7 GPa in the spectral range from 50 to 3300 cm−1. The study indicates that the captopril molecules assumes the trans conformation in all pressure range investigated. The modes appearing in the low wavenumber region of the spectrum suggest the crystal undergoes a phase transition between 2 and 3 GPa. Additionally, a softening of the C O bond of both amide and carboxylic group is observed up to approximately 2.7 GPa and after this pressure a stiffiness is noted. Finally, is verified a disorder associated with the CH group during compression.

Chalcones are important intermediates in the biosynthesis of biologically active compounds such as flavonoids and their derivatives. In this paper, a new chalcone 2E-1-(2ʹ-Hydroxy-3ʹ,4ʹ,6ʹ-trimethoxyphenyl)-3-(phenyl)-prop-2-en-1-one (HYTPHENYL) was synthesized by the condensation reaction of Claisen-Schmidt in basic medium between the 2-hydroxy-3,4,6-trimethoxyacetophenone (HTMCX) and benzaldehyde. The molecular structure of this chalcone was determined by Nuclear Magnetic Resonance, and characterized by infrared and Raman spectroscopy, at room temperature. Its electrochemical behavior was also evaluated. Vibrational wavenumber and wavevector have been predicted using the Density Functional Theory (DFT) calculations and their normal modes were analyzed in terms of the potential energy distribution (PED). Furthermore, DFT calculations were carried out to obtain the molecular orbitals and the electrostatic surface map. Electronic absorption spectrum of HYTPHENYL was measured and compared with that obtained for the HTMCX compound. Additionally, analysis of the antimicrobial activity and antibiotic resistance modulation was carried out to evaluate the antibacterial potential of the HYTPHENYL chalcone.

In this paper the isolation of 2-Hydroxy-3,4,6-trimethoxyacetophenone (C11O5H14) from the stem bark of Croton anisodontus Mull. Arg. (Euphorbiaceae) is presented and its structure is characterized using Nuclear Magnetic Resonance and single crystal X-ray diffraction. The crystalline structure of this natural compound, which presents potential antimicrobial activity, was determined at 100 K and 298 K. Additionally, the vibrational properties were characterized through infrared and Raman spectroscopy at room temperature in the spectral regions 400 cm−1 to 4000 cm−1 and 25 cm−1 to 4000 cm−1, respectively. Vibrational wavenumber and wavevector have been predicted using the Density Functional Theory calculations with the hybrid functional B3LYP and the basis set 6–31 G(d,p). Furthermore, the description of the normal modes was furnished in terms of the Potential Energy Distribution. Hirshfeld surface analysis is presented in order to investigate the interactions between the molecules in the crystals. Density Functional Theory calculations were carried out in order to obtain the molecular orbitals and other quantum chemical parameters. Experimental and theoretical UV absorption spectra of 2-Hydroxy-3,4,6-trimethoxyacetophenone are also evaluated from time-dependent density functional theory with the purpose to analyze the energies of the most important molecular orbitals and the transitions modes for this compound. Finally, the electrostatic surface potential map was also constructed to display the charge density distribution and the sites of chemical reactivity.

Essential oils are aroma compounds extracted from plants with pharmacology and mecial uses, being also utilized as perfumes, cosmetics and for flavoring foods. In this work, Fourier Transform-Raman and Attenuated Total Reflection-infrared spectra of essential oils from Plectranthus amboinicus Lour. Spreng (Labiateae) and Vanillosmopsis arborea Baker (Asteraceae) were investigated at room temperature. The analysis of the vibrational spectra of the major constituents performed on the basis of density functional theory (DFT) calculations allowed us to assign the normal modes of these essential oils. Our analyses show that vibrational spectra of these essential oils in the spectral region of lower wavenumber (

The chalcone compound (2 E )-1-(4-aminophenyl)-3-phenyl-prop-2-en-1-one of chemical formula C 15 H 13 NO was synthesized and structurally characterized using Nuclear Magnetic Resonance (NMR). The spectroscopy investigation has been carried out by Fourier Transform Raman (FT-Raman), Fourier Transform infrared (FT-IR) and Density Functional Theory (DFT) calculations. The FT-IR and FT-Raman spectra of polycrystalline samples were recorded at room temperature in the regions 400 cm −1 to 4000 cm −1 and 40 cm −1 to 4000 cm −1 , respectively. DFT calculation was performed with the objective to assign the normal modes of the material. A comparison with experimental spectra allowed us to assign all the normal modes of this material. The description of the normal modes was done both considering the potential energy distribution (PED) and on the basis of previous studies of vibrational spectroscopy of other chalcone substances.

This study reports a temperature-dependent Raman scattering and X-ray diffraction study of K2Mo2O7·H2O. The high-temperature Raman scattering analysis shows that the material remains structurally stable, with triclinic symmetry, in a temperature range from 300 to 413 K and undergoes a structural phase transition between 413 and 418 K. This phase transition is most likely connected with the dehydration process of K2Mo2O7·H2O. The temperature-dependent X-ray diffraction patterns are measured from 30 to 573 K. The results show that the discovered phase transition occurs between 419 and 433 K, in good agreement with the Raman scattering results. According to the Raman data, with increasing temperature, the dehydrated crystal of K2Mo2O7 undergoes a new phase transformation at 603 K and melts at ~843 K. Principal component and hierarchical cluster analyses are performed based on the treatment of the raw spectral data to infer the phase transformations occurring in the material. Assignments of the Raman modes for the K2Mo2O7 system at ambient conditions are studied through first-principles calculations based on density functional perturbation theory. These calculations are applied to understand the electronic properties, including the band structure and the associated projected density of states, of K2Mo2O7 under the local density approximation.

Captopril is a drug widely used in hypertension treatment. This molecule has two isomeric forms (cis and trans) according to the dihedral angle ω (O4C18N5C15). In the present study, we theoretically rotated the dihedral angle in steps of 5° in the range of -180° to 180°, using the DFT calculation with the functional B3LYP and the basis set 6–31G++(d, p) both in a gaseous environment and in an aqueous solution. In each environment, we were able to find a minimum energy structures, calculate the energy of the frontier orbitals (HOMO and LUMO) for the captopril in the gas phase and in aqueous solution, as well as calculate their vibrational spectra. When analyzing the HOMO and LUMO orbitals, all conformations presented HOMO around the sulfur atom. LUMO, on the other hand, presented a higher concentration around the aromatic ring and the carboxyl group, mainly in aqueous solution. Although trans conformers have a larger energy gap, the cis conformers showed a better reactive index. The cis and trans conformers showed similar MEP. In addition, the Raman and infrared spectroscopy proved to be an excellent technique to identify the isomeric form of the captopril molecule, observing the stretching modes of the carbonyl groups. The geometry and surfaces of the molecular potentials provide support for identifying the formation of the hydrogen bond.

In the present study, the natural product named 15,16-epoxy-4-hydroxy-labda-13(16),14-dien-3,12-dione (C 20 H 28 O 4 ), a labdane-type diterpene was isolated from the stems of Croton jacobinensis for the first time. This new compound was characterized by infrared and Raman spectroscopy combined with Density Functional Theory calculation. Additionally, the antimicrobial and modulatory antibiotic activities of the compound towards Escherichia coli and Pseudomonas aeruginosa strains were assessed. The labdane diterpene demonstrated a modulatory effect when combined with the antibiotics assayed against both bacteria. A synergistic effect against Escherichia coli can be observed when the compound is associated with gentamicin, reducing the concentration of this antibiotic that is required to inhibit bacterial growth. Other synergistic effects can be observed with gentamicin and cephalothin antibiotics against P. aeruginosa .

A new derivative of Meldrum's acid 5-((5-chloropyridin-2-ylamino)methylene)-2,2-dimethyl-1,3-dioxane-4,6-dione (CYMM) of molecular formula C12H11ClN2O4 was synthesized and structurally characterized using single crystal X-ray diffraction technique. The vibrational properties of the crystal were studied by Fourier Transform infrared (FT-IR), Fourier Transform Raman (FT-Raman) techniques and theoretical calculations of quantum chemistry using Density functional theory (DFT) and Density functional perturbation theory (DFPT). A comparison with experimental spectra allowed the assignment of all the normal modes. The descriptions of the normal modes were carried by means of potential energy distribution (PED). Additionally, analysis of the antimicrobial activity and antibiotic resistance modulatory activity was carried out to evaluate the antibacterial potential of the CYMM.

Flavonoids are secondary metabolites of plants which perform various functions. One subclass of flavonoid is auronol that can present immunostimulating activity. In this work Fourier-Transform Infrared with Attenuated Total Reflectance (FTIR-ATR) and Fourier-Transform Raman (FT-Raman) spectra of an auronol, derriobtusone A (C18H12O4), were obtained at room temperature. Theoretical calculations using Density Functional Theory (DFT) were performed in order to assign the normal modes and to interpret the spectra of the derriobtusone A molecule. The FTIR-ATR and FT-Raman spectra of the crystal, were recorded at room temperature in the regions 600 cm−1 to 4000 cm−1 and 40 cm−1 to 4000 cm−1, respectively. The normal modes of vibrations were obtained using Density Functional Theory with B3LYP functional and 6-31G+ (d,p) basis set. The calculated frequencies are in good agreement with those obtained experimentally. Detailed assignments of the normal modes present in both the Fourier-Transform infrared and the Fourier-Transform Raman spectra of the crystal are given.

Schiff base N,N′-bis(salicylidene)-1,2-phenylenediamine, salophen, is a substance that presents synergism when combined with amikacin against Staphylococcus aureus and Escherichia coli . Measurements of temperature dependence of the Raman spectra of salophen combined with thermal analysis investigations are presented. The room temperature crystalline structure seems to be stable up to the temperature where the phase transition from solid to liquid (433–443 K) is observed. The Raman spectra in the temperature range 433–443 K were observed to be characterized by the loss of external vibrational modes, in accordance with thermal analysis curves. According to thermogravimetric analysis, salophen shows a weight loss variation in the temperature range 300–453 K corresponding to 5% loss in weight, which is attributed to dehydration and materials melting temperature. The enthalpy (ΔH) obtained from the integration of the differential scanning calorimetry peak at melting (T m = 438 K) and decomposition temperature (T d = 484 K) is founded to be – 91 J/g and 239 J/g, respectively. Finally, it was carried out biological assays to evaluate the antibacterial potential of the salophen.

In this work results on vibrational properties of an organic substance that is used in popular medicine, the diterpene kaurane rel-(1S, 4aS, 7S,8aS)-7-(vinyl)-tetradecahydro-1,4a-dimethylphenanthrene-7,8a-carbolactone-1-carboxylic acid (C 20 H 28 O 4 ), extracted from Croton argyrophylloides , is presented. This plant is considered endemic in the Northeast of Brazil, and the diterpene is only one among several substances with potential pharmaceutical application. Fourier Transform Raman spectroscopy and Fourier Transform infrared spectroscopy were utilized in order to obtain the vibrational normal modes of the substance. Additionally, ab initio calculations by density functional theory with the B3LYP functional and calculations of potential energy distribution, performed to assign the bands observed by both spectroscopies, are shown. Finally, studies performed with Raman spectroscopy at low temperatures between 20 and 300 K, in order to investigate evidence of a possible phase transition, are presented.

Chalcones and their derivatives have been widely studied at research institutions and industries, in order to verify their biological properties against various diseases. In this work, it was carry out the synthesis of chalcones (E)-3-(furan-2-yl) -1- (2‑hydroxy-3,4,6-trimethoxyphenyl) prop‑2-en-1-one (HYTFURFURAL) and (E) -1- (2‑hydroxy-3,4-dimethoxyphenyl) -3-(thiophen-2-yl) prop‑2-en-1-one (HYTTHIOPHENE) by Claisen-Schmidt aldolic condensation reaction. The molecular structures of these new heteroaryl chalcones have been elucidated and characterized by 1H and 13C Nuclear Magnetic Resonance, Fourier transform Raman (FT-Raman), Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR), and Ultraviolet-Visible (UV–Vis) spectroscopy. Calculations using the Functional Density Theory (DFT) were performed to predict the vibrational wavenumbers and to obtain the HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) molecular orbitals, and starting from them, the quantum descriptors: vertical ionization energy (I), vertical electron affinity (A), chemical potential (μ), electronegativity (χ), global hardness (η), and electrophilicity index (ω). Antimicrobial and modulatory antibiotic activities of these chalones were also investigated. The mechanism of the NorA and MepA efflux pump inhibition was also studied by means of molecular docking. The HYTFURFURAL and HYTTHIOPHENE chalcones did not present intrinsic activity against the tested bacterial strains; however, they were able to potentiate the activity of norfloxacin against the SA1199B (NorA) strain, as well as the activity of ciprofloxacin against the K2068 (MepA) strain. These results indicate that the HYTFURFURAL and HYTTHIOPHENE chalcones are promising compounds as adjuvants to the norfloxacin and ciprofloxacin antibiotics in the treatment of infections caused by S. aureus.

The vibrational, optical, electrochemical and thermal properties of Meldrum acid derivative 5-aminomethylene 5 - [(2-hydroxyanilino) methylidene] -2,2-dimethyl-1,3-dioxane-4,6-dione (HYM) were investigated combining Infrared and Raman spectroscopy at room temperature assisted by DFT calculations, UV–vis spectroscopy assisted by TD-DFT calculations, cyclic voltammetry and thermal analysis. The B3LYP / 6−311++G(d, p) calculations led to the identification of the minimums on the potential energy surfaces of the molecule, from these calculations the most stable conformer in relation to the dihedral angle C8-N1-C7-C4 was predicted at 360°. Comparison between experimental and theoretical vibrational spectra provides an accurate understanding of the fundamental vibrational modes and leads to a better interpretation of experimental Raman and infrared spectra. The vibrational mode assignment given in terms of potential energy distribution analysis (PED) leads us to a broader interpretation of the vibrational spectra of the investigated material. The UV–vis spectrum of the compound was recorded in the region between 200 and 450 nm and the HOMO and LUMO electronic properties were calculated by TD- DFT. The gap energy calculated from the difference between the HOMO and LUMO orbitals was obtained with a value of 4.52 eV. The HYM is thermally stable up to 142 °C based on data obtained from TG-DTA analysis.

The polymorphism is a characteristic of several active principles, and can affect the bioavailability of a drug. Among the drugs used in the treatment of heart diseases, captopril is one of the most widely used in the world. Despite the knowledge of vibrational properties of captopril under high temperature and under high pressure, a lack of information impedes the understanding of the substance in the crystal form at low temperatures. In this research, we investigated the vibrational properties of captopril crystals under cryogenic conditions in the 300–8 K interval using Raman spectroscopy. By observing the behavior of the inter- and intra-molecular vibrations it was possible to infer that the captopril molecules suffered a rearranging into the unit cell due slight orientational changes mainly involving C H⋯O hydrogen bonds. The phenomenon occurs in a large temperature range. However, the observed changes do not suggest the occurrence of a structural phase transition and the Raman spectra indicate that the trans conformation is recorded down to the lowest temperature available in the experiments.

We report here the analysis of vibrational properties of the ZnMoO4 by using theoretical and experimental approaches, well as results of high pressure experiments in this system. The analysis of the lattice dynamics calculations through the classical rigid ion model, was applied to determine the mode assignment in the triclinic phase of the ZnMoO4. Additionally, the experimental high-pressure Raman spectra of the ZnMoO4 were carried out from 0 GPa up to 6.83 GPa to shed light on the structural stability of this system. The pressure-dependent studies showed that this crystal undergoes a first order phase transition at around 1.05 GPa. The Raman spectrum analysis of the new phase shows a significant change in the number of modes for the spectral range of 20–1000 cm−1. The instability of this phase occurs due to the decrease of the Mo O bond lengths in the high-pressure phase, connected with tilting and/or rotations of the MoO4 tetrahedra leading to a disorder at the MoO4 sites. The second and third phase transformations were observed, respectively, at about 2.9 GPa and 4.77 GPa, with strong evidences, in the Raman spectra, of crystal symmetry change. The principal component analysis (PCA) and the hierarchical cluster analysis (HCA) were used in order to infer the intervals of pressure where the different phases do exist. Discussion about the number of non equivalent sites for Mo ions and the kind of coordination for molybdenum atoms is also furnished.

The chemical composition, vibrational spectroscopy and DFT studies of the essential oils from Lippia sidoides constituents were performed in this study. The harvesting time periods greatly affect the yields of the essential oil extracted from the leaves of the Lippia sidoides plant material. The chemical composition of the essential oil by gas chromatography coupled to mass spectrometry (GC MS) showed thymol as the main constituent of the essential oil. Through Fourier transform Raman (FT-Raman) and Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy measurements exhibited a good agreement of the thymol component from the essential oil and the polycrystalline thymol. The Density Functional Theory (DFT) calculations were performed over the molecular structure of the thymol and predicted its Raman and infrared spectra. A good correlation between the experimental spectra of the essential oil and the thymol was observed. Complete assignments of the normal modes were presented for both Raman and infrared spectra of the thymol.

In the present study, the chalcone (2E)-1-(3′-methoxy-4′-hydroxyphenyl)-3-(3-nitrophenyl)prop-2-en-1-one (C16H13NO5, hereafter named AVMNB) was synthesized and structurally characterized using the 1H and 13C NMR technique and GC-MS. The vibrational and electrochemical properties of the AVMNB chalcone and its antibacterial activity against multi-resistant strains of Escherichia coli 06 and Staphylococcus aureus 10 were evaluated. The FT-Raman, ATR-FTIR, and UV-VIS spectra of the polycrystalline samples were recorded at room temperature. Quantum chemistry theoretical calculations were used to obtain information about the normal vibration modes, and the electronic transitions and the quantum chemical parameters expected for this chalcone. The pharmacokinetics properties were also estimated using the SwissADME platform. The AVMNB chalcone displayed antibacterial activity against multi-resistant strains of Staphylococcus aureus 10 and Escherichia coli 06 when associated with the ciprofloxacin and gentamicin antibiotics, respectively, indicating that this compound may contribute to the control of antibacterial resistance.

This report presents the results of experimental and theoretical Raman and infrared vibrational spectroscopic studies on the triclinic phase of zinc molybdate α-ZnMoO4 polycrystals. The assignments of the Raman and infrared modes were predicted using first-principle calculation through density functional perturbation theory (DFPT). Additionally, a theoretical study of the electronic properties of ZnMoO4 in relation to both the band structure and the associated projected density of states (PDOS) was performed by using first-principle calculations under the local density approximation (LDA). The ZnMoO4 presents an indirect band-gap from the gamma point on the valence band to the Y point on the conduction band. The calculated electronic gap is in line with the well-known trend of DFT-LDA underestimation of band gap, confirming that the ZnMoO4 crystal is a semiconductor compound with an indirect band-gap of about 3.35 eV.

The vibrational properties of the dipeptide l -leucyl- l -leucine hydrate were investigated through Raman and infrared spectroscopy. With the aid of first principle calculations using the density functional theory, the assignment of the vibrational modes from the material was furnished. In addition, the behavior of the crystal under high pressure was investigated using Raman spectroscopy (~8 GPa) and synchrotron X-ray diffraction (~26 GPa). The results show significant changes in both the X-ray diffractogram and the Raman spectra, suggesting that l -leucyl- l -leucine hydrate undergoes a phase transition between 2.3 and 2.9 GPa. Finally, for pressures above 16 GPa the broadening of X-ray peaks suggests a disorder in the crystal lattice induced by high-pressure effects.

In the present study, the natural product sonderianin diterpene (C 21 H 26 O 4 ), a diterpenoid isolated from Croton blanchetianus , with potential application in the drug industry, was characterized by nuclear magnetic resonance, infrared and Raman spectroscopy. Vibrational spectra were supported by Density Functional Theory calculations. Infrared and Raman spectra of sonderianin were recorded at ambient temperature in the regions from 400 cm −1 to 3600 cm −1 and from 40 cm −1 to 3500 cm −1 , respectively. DFT calculations with the hybrid functional B3LYP and the basis set 6–31 G(d,p) were performed with the purpose of obtaining information on the structural and vibrational properties of this organic compound. A comparison with experimental spectra allowed us to assign all of the normal modes of the crystal. The assignment of the normal modes was carried out by means of potential energy distribution.

N,N′-bis(salicylidene)-1,2-phenylenediamine, also known as Salophen, is a Schiff base which crystallizes in monoclinic structure and space group P21/c, with four molecules per unit cell. It has been intensely studied in last decades because of its excellent properties with many potential applications. In the present study, the structural and vibrational properties of the Salophen were investigated combining scanning electronic microscopy (SEM), Raman, infrared, nuclear magnetic resonance (NMR) spectroscopy as experimental techniques and theoretical calculation based on density functional theory (DFT). The interpretation of the vibrational modes was carried out by means of potential energy distribution (PED). The theoretical results are in good agreement with experimental ones.

In this study, the structural and vibrational properties of Meldrum’s acid derivative 5-(5-Ethyl-1,3,4-thiadiazol-2-ylamino)methylene-2,2-dimethyl-1,3-dioxane-4,6-dione, C11H13N3O4S were studied combining experimental techniques such as Raman and FT-IR spectroscopy and density functional theory (DFT) calculations. The Raman and FT-IR spectra were recorded at room conditions in the regions from 80 to 3400 cm−1 and 400 to 4000 cm−1, respectively. Vibrational wavenumbers were predicted using DFT calculations with the hybrid functional B3LYP and basis set 6-31G(d,p). A comparison between experimental and theoretical data is provided for the Raman and FT-IR spectra. The descriptions of the normal modes were carried by means of potential energy distribution (PED).

In this study, we coordinate the Schiff base 4-{[(1E)-(2-Hydroxyphenyl)methylidene]amino}-1,5-dimethyl-2-phenyl-1,2 dihydro-3H-pyrazol-3-one, C18H17N3O2 with zinc ions to form a new coordination compound with chemical formula C36H36N6O4Zn. This is the first effort to determine the vibrational properties of the C36H36N6O4Zn using infrared and Raman spectroscopy combined with Density functional based methods (DFT). The vibrational modes analyses were performed based on Potential Energy Distribution (PED). A comparison of theoretical and experimental spectra allowed us to assign most of the normal modes of the crystal and interpreted the experimental findings. According to our results, the zinc ions coordinated with two imine nitrogens and two pyrazolone oxygens.

The use of films or membranes to treat cutaneous lesions has become a standard therapeutic procedure in the last two decades. For this reason, many polymeric materials such as chitosan, collagen, alginate, and gelatin, have been investigated to better understand their physical, chemical and biological properties. This study addresses the preparation, structural and spectroscopic characterization of chitosan membranes, chitosan with glycerol and chitosan with glycerol plus allantoin as the active principle, using Scanning Electron Microscopy (SEM), X-Ray diffraction (XRD), Differential Scanning Calorimetry (DSC), Raman and Infrared spectroscopy techniques. The insertion of the active principle allantoin in the polymer matrix was also observed using the techniques mentioned above. The results from this study showed that the chitosan membranes containing the active principle allantoin in the polymer matrix present adequate characteristics for the use in medicine as a biodegradable drug vehicle.

This work reports a theoretical and experimental study on the electronic and vibrational properties of Bi2(MoO4)3. First-principle calculations were applied to increase the understanding on the properties of the chemical composition through the energy bands. The conduction band minimum (CBM) is found at the high symmetric Γ-point, while the valence-band maximum (VBM) is located between the Z and the Γ-points. Therefore, these facts confirm that the Bi2(MoO4)3 crystal is a semiconductor compound with an indirect band-gap of about 2.1 eV. Moreover, lattice dynamic properties were calculated using density functional perturbation theory (DFPT) in order to assign the experimental Raman bands. In addition, we performed temperature-dependent Raman spectroscopic studies in the Bi2(MoO4)3 crystals to obtain information on structural changes induced by effects of the temperature change. From the changes observed in the Raman spectra phase transitions at ∼ 668 and 833 K were inferred, with the last one possibly related to the disorder due to the heating process.

Triterpenoids comprise an important class of compounds presenting a wide range of biologically important properties. Acetyl aleutitolic acid (AAA) is a triterpenoid isolated from Croton zehntneri , with molecular formula C 32 H 50 O 4 . Its structure has been characterized by NMR spectroscopy, however, there are no papers available regarding its vibrational properties. The Fourier-Transform Infrared with Attenuated Total Reflectance and Fourier-Transform Raman spectra, together with Density Functional Theory calculations of AAA are reported. Vibrational spectra were recorded at 300 K in the regions 600 cm −1 to 4000 cm −1 and 40 cm −1 to 4000 cm −1 , for IR and Raman, respectively. Vibrational wavenumbers were predicted using Density Functional Theory calculations with the hybrid functional B3LYP and the basis set 6-31 G(d,p). A complete assignment of vibrational modes is given.

In this work the Fourier transform infrared and the Raman spectra of bis( L -hisidinato)nickel(II) monohydrate were recorded at room temperature. Optimized geometry and vibrational frequencies were obtained by means of Density Functional Theory (DFT). Experimental and theoretical vibrational spectra were compared and a complete analysis of the modes was done in terms of the Potential Energy Distribution (PED).

In this work we present a study of the vibrational spectra of 2,2-dimethyl-5-(4H-1,2,4-triazol-4-ylaminomethylene)-1,3-dioxane-4,6-dione monohydrate, C 9 H 10 N 4 O 4 ⋅H 2 O. The FT-IR and FT-Raman spectra of the crystal were recorded at room temperature in the regions 400–4000 cm −1 and 50–4000 cm −1 , respectively. Vibrational wavenumbers and wave vector were predicted using density functional theory calculations with the B3LYP functional and 6-31G(d,p) basis set. The descriptions of the normal modes were made after considering the Potential Energy Distribution (PED). A comparison with experimental spectra allowed us to assign all of the normal modes of the crystal.

This research reports a pressure dependent Raman study of the sorbic acid between 0.0 and 10.0GPa. The unpolarized Raman spectra were measured in the spectral range of 20-3000cm-1. The high-pressure Raman scattering study of the sorbic acid showed that it underwent a gradual, disordering process. At the room temperature and at the ambient pressure conditions, the crystal structure of the sorbic acid belongs to the monoclinic system with a C2/c (C2h6) space group. The pressure increase induced a higher disorder in the monoclinic unit cell, since a single bending mode, and only very broad stretching Raman modes are present at pressure of ~10GPa. Upon pressure release the high-pressure phase transforms directly into the ambient-pressure phase. The presence of the internal vibrational modes is a guarantee that the molecular structure is maintained. Beyond this, the presence of external modes shows that the crystal has a memory to reverse the process and suggest that the crystal, which was in high disorder (broad Raman bands), does not suffer decomposition in the crystalline structure. The DFT calculations for the sorbic acid were performed in order to understand the vibrational properties. The theoretical study showed that the volume of the unit cell and beta angle decrease significatively when passing from the 0.0GPa to 8.0GPa. The decreases in the volume and beta angle of this particular unit cell were supposed to induce the larger increase in the bandwidths of the observed bands, pointing to some disorder in the monoclinic phase.

In the present study, the natural product 3-Methoxyquercetin, a flavonoid with potential antiviral activity, was characterized through infrared and Raman spectroscopies combined with Density Functional Theory calculation. The flavonoid was extracted from Strychnos pseudoquina St. Hil (Loganiaceae) by chromatographic techniques. The optimized molecular structure and calculated vibrational spectra were performed by B3LYP/6-31G (d,p) basis set. The optimized structure was compared with X-ray diffraction data of other flavonoids compounds, and the theoretical data are in good agreement with experimental ones. Fourier transform–Raman and –infrared spectra, as well as the assignment of the normal modes are also presented.

The Schiff base 4-{[(1E)-(2-Hydroxyphenyl)methylidene]amino}-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one (C 18 H 17 N 3 O 2 ) is a synthetic compound with a variety of scientific and technological applications, such as clinic, analytic and pharmacologic. In this work FT-Raman spectrum and FT-infrared spectrum of C 18 H 17 N 3 O 2 were investigated at 300 K. Vibrational wavenumber and wave vector have been predicted using Density Functional Theory (B3LYP) calculations with the 6-31 G(d,p) basis set. The description of the normal modes was performed by means of the potential energy distribution. A comparison with experiment allowed us to assign most of the normal modes of the crystal.

The Fourier transform infrared and Fourier transform Raman spectra of xanthoxyline crystals are reported, along with ab initio computations of the vibrational spectrum of the xanthoxyline molecule. The infrared and Raman spectra were recorded at 300 K in the 400- to 4,000- and 40- to 4,000-cm−1 intervals, respectively. The vibrational wave numbers and wave vectors were obtained from a density functional computation with the 6-31 G(d,p) basis set and the B3LYP approximation to the exchange correlation functional. Comparison with the theoretical results allows assignment of normal modes to the prominent features of the recorded spectra.

Raman spectra of l -alanine, l -threonine and taurine amino acids crystals under high-pressure conditions at room temperature were investigated in a diamond anvil cell in order to observe the behavior of the torsional mode of NH 3 unit. It was observed for l -threonine and taurine crystals that increasing pressure produces an increase in the wave number of the band associated to the torsional vibration of ammonium group, while for l -alanine crystal a decrease in the wave number is observed. The anomalous behavior of l -alanine is explained in terms of the length and geometry of the hydrogen bonds within the crystalline structure: due to a short average length the effect of pressure is to deform the hydrogen bond, while for l -threonine and taurine, pressure approximates the N and O atoms in the N–H⋯O intermolecular bond.

Seselin, C14H12O3, is a coumarin which crystallizes in a monoclinic structure P21/b(C2h5) with four molecules per unit cell. In a Fourier-transform Raman spectroscopic study performed at room temperature, several normal modes were observed. Vibrational wavenumber and wave vector calculations using density functional theory were compared with experiment, which allowed the assignment of a number of normal modes of the crystal. Temperature-dependent Raman spectra were recorded between 10 and 300 K. No anomalies were observed in the phonon spectra, indicating that the monoclinic structure remains stable. Copyright © 2007 John Wiley & Sons, Ltd.

Fatty acids are substances found in most living beings in nature. Here we report the effect of the low temperature in the vibrational and structural properties of the C form of palmitic acid, a fatty acid with 16 carbon atoms. The Raman spectra were obtained in the temperature interval from 300 to 18K in the spectral range between 30 and 3100 cm(-1). The assignment of the duly observed bands was done based on the density functional theory. On cooling, the main changes observed in the lattice mode region of the Raman spectra were interpreted as a conformational modification undergone by the palmitic acid molecules in the unit cell. The X-ray diffraction measurements were obtained from 290 to 80K showing a slight modification in the lattice parameters at about 210K. Differential scanning calorimetry (DSC) measurements were recorded between 150 and 300K and no enthalpic anomaly in the DSC thermogram was observed. These techniques provided strong evidence of the conformational change in the molecules of palmitic acid at low temperatures.

Brillouin spectroscopy was used to study the phase transitions of LiK 0.80 (NH 4 ) 0.20 SO 4 mixed crystals in the temperature range 10–300 K. The relevant elastic stiffness coefficients were evaluated at room temperature. The quasi-longitudinal γ 16 and the quasi-transverse γ 17 mode frequencies were measured in the above temperature range. From their frequency vs. temperature curve, three different phase transitions were determined. Two of the four phases presented by the crystal were found to be ferroelastic. The observed phases are tentatively assigned through a comparison with the phase transitions undergone by LiKSO 4 and LiK 0.96 (NH 4 ) 0.04 SO 4 crystals. An anomalous behavior of the Brillouin linewidth near the 260 K phase transition was observed.

In this work we present a study of the vibrational spectra of 4,5,6,8,9-pentachloropyrimido-[1,2-a][1,8]naphthyridin-10-one, C 11 H 2 Cl 5 N 3 O, a substance belonging to the important pharmacological class of 1,8-naphthyridine derivatives. The Fourier transform infrared and the Fourier transform Raman spectra of the crystal were recorded at room temperature in the regions 400–4000 and 50–4000 cm −1 , respectively. Vibrational wavenumbers were predicted using Density Functional Theory calculations with the B3LYP functional on 6-31G(d,p) and 6-311++G(d,p) basis sets. The descriptions of the normal modes were made after calculating the potential energy distribution. Additionally, potential reaction sites were evaluated through Mulliken population and Frontier Orbital analysis.

This work reports a temperature-dependent vibrational spectroscopic study of the sorbic acid (C6H8O2), as well as the mode assignment at ambient conditions, based on the density functional theory. Temperature-dependent vibrational properties have been performed in polycrystalline sorbic acid through both Raman and infrared spectroscopy in the 20–300 K and 80–300 K temperature ranges, respectively. These studies present the occurrence of some modifications in the Raman spectra that could be interpreted as a low temperature phase transition undergone by sorbic acid from the monoclinic phase to an unknown phase with conformational change of the molecules in the unit cell.

Raman spectra of LiK0.8(NH4)0.2SO4 were obtained as a function of applied pressure. The measurements were carried out using a microscope to focus the light into a spot size of 2 µm, in order to avoid probing a multi-domain sample. With increasing pressure, many of the Raman peaks are shifted towards higher wavenumbers. At certain pressures the number of peaks changes and the ˜ν vs P plots are discontinuous. These effects occurring at P = 0.9 and 2.5 GPa were interpreted as structural phase transitions. The pressure coefficients are given for modes derived from the pure E2 and A(LO) symmetries of α-phase. Copyright © 2001 John Wiley & Sons, Ltd.

Raman spectra of ${(\mathrm{AlN})}_{8\ensuremath{-}\ensuremath{\delta}}/({\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{N}{)}_{\ensuremath{\delta}}/{(\mathrm{GaN})}_{8\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}/({\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{N}{)}_{\ensuremath{\delta}}$ superlattices with interface thickness varying between $\ensuremath{\delta}=0$ and $\ensuremath{\delta}=3$ are calculated. The influence of the nonabrupt interface related broadening is described in the complete range of scattering, with special attention to the modes giving stronger contribution to the Raman intensity. It is shown that the dispersion of folded acoustic phonons does not change appreciably with the interface smoothing. For $\ensuremath{\delta}=0$ the Raman spectra display new peaks due to the enhancement of some confined optic modes.

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T19:01:27Z No. of bitstreams: 1 S0103-97332009000100012.pdf: 249754 bytes, checksum: 9915c64ac233ca4a4b457907a79841a8 (MD5) Made available in DSpace on 2013-08-22T19:01:27Z (GMT). No. of bitstreams: 1 S0103-97332009000100012.pdf: 249754 bytes, checksum: 9915c64ac233ca4a4b457907a79841a8 (MD5) Previous issue date: 2009-03-01 Made available in DSpace on 2013-09-30T20:01:28Z (GMT). No. of bitstreams: 2 S0103-97332009000100012.pdf: 249754 bytes, checksum: 9915c64ac233ca4a4b457907a79841a8 (MD5) S0103-97332009000100012.pdf.txt: 27844 bytes, checksum: 42a96ad199aac25818f3619e382b2c39 (MD5) Previous issue date: 2009-03-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T15:15:44Z No. of bitstreams: 2 S0103-97332009000100012.pdf: 249754 bytes, checksum: 9915c64ac233ca4a4b457907a79841a8 (MD5) S0103-97332009000100012.pdf.txt: 27844 bytes, checksum: 42a96ad199aac25818f3619e382b2c39 (MD5) Made available in DSpace on 2014-05-20T15:15:44Z (GMT). No. of bitstreams: 2 S0103-97332009000100012.pdf: 249754 bytes, checksum: 9915c64ac233ca4a4b457907a79841a8 (MD5) S0103-97332009000100012.pdf.txt: 27844 bytes, checksum: 42a96ad199aac25818f3619e382b2c39 (MD5) Previous issue date: 2009-03-01 Pilocarpine is a natural substance with potential application in the treatment of several diseases. In this work Fourier Transform (FT)-Raman spectrum and the Fourier Transform infra red (FT-IR) spectrum of pilocarpine hydrochloride C11H17N2O2+.Cl- were investigated at 300 K. Vibrational wavenumber and wave vector have been predicted using density functional theory (B3LYP) calculations with the 6-31 G(d,p) basis set. A comparison with experiment allowed us to assign most of the normal modes of the crystal. Universidade Federal do Mato Grosso Instituto de Física Universidade Federal do Ceará (UFC) Departamento de Física Universidade Regional do Cariri Dep. Ciências Físicas e Biológicas Universidade Estadual do Ceará Universidade Federal do Ceará (UFC) Dep. Química Orgânica e Inorgânica Universidade Federal do Ceará (UFC) Departamento de Farmácia Universidade Estadual de São Paulo Faculdade de Ciências