Vibrational assignments of cyclic dimers and inter-monomers of adenine relating FT-IR, FT-Raman and UV spectra with SQMFF and DFT calculations.

In this work, three different cyclic dimers and a tetramer of adenine taken from the experimental structure determined by X-ray diffraction have been studied by combination of experimental FT-IR, FT-Raman and UV-Visible spectra with hybrid B3LYP/6-311++G** and scaled quantum mechanical force field (SQMFF) calculations in order to perform the complete assignments of bands observed in the vibrational spectra. The characteristics of different N-H···N interactions of those three cyclic structures together with the group of IR bands observed between 2865 and 2599 cm have been elucidated considering the tetrameric structure. The cyclic dimers and the tetramer of adenine confirm that the bands observed between 2865 and 2599 cm are not due to N-H···N interactions but to bands of combination, as was previously suggested.

Behaviours of antiviral Oseltamivir in different media: DFT and SQMFF calculations.

The synthetic cyclohexenecarboxylate ester antiviral Oseltamivir (O) have been theoretically studied by B3LYP/6-311 +  + G** calculations to estimate its reactivity and behaviour in gas and aqueous media. The most stable structure obtained in above media is consistent with that reported experimental for Oseltamivir phosphate. The solvation energy value of (O) in aqueous media is between the predicted for antiviral Idoxuridine and Ribavirin.

Vibrational and structural study of onopordopicrin based on the FTIR spectrum and DFT calculations.

In the present work, the structural and vibrational properties of the sesquiterpene lactone onopordopicrin (OP) were studied by using infrared spectroscopy and density functional theory (DFT) calculations together with the 6-31G(∗) basis set. The harmonic vibrational wavenumbers for the optimized geometry were calculated at the same level of theory. The complete assignment of the observed bands in the infrared spectrum was performed by combining the DFT calculations with Pulay's scaled quantum mechanical force field (SQMFF) methodology.

A complete assignment of the vibrational spectra of sucrose in aqueous medium based on the SQM methodology and SCRF calculations.

In the present study, a complete assignment of the vibrational spectra of sucrose in aqueous medium was performed combining Pulay's Scaled Quantum Mechanics Force Field (SQMFF) methodology with self-consistent reaction field (SCRF) calculations. Aqueous saturated solutions of sucrose and solutions at different molar concentrations of sucrose in water were completely characterized by infrared, HATR, and Raman spectroscopies. In accordance with reported data of the literature for sucrose, the theoretical structures of sucrose penta and sucrose dihydrate were also optimized in gas and aqueous solution phases by using the density functional theory (DFT) calculations.

Molecular structure of 4-hidroxy-3-(3-methyl-2-butenyl) acetophenone, a plant antifungal, by X-ray diffraction, DFT calculation, and NMR and FTIR spectroscopy.

The molecular structure of two mixed and closely related conformers of the title compound, C13H16O2, found in the solid with unequal occupancies has been determined by X-ray diffraction methods. The substance crystallizes in the monoclinic Pca2(1) space group with a=17.279(2), b=5.

A complete characterization of the vibrational spectra of sucrose.

We combined experimental vibrational spectroscopy (FTIR-Raman) and ab-initio calculations based on density functional theory (DFT) to predict the structural and vibrational properties of sucrose in solid phase. The structural properties of sucrose, such as the bond order, possible charge-transfer, and the topological properties of the glucopyran and glucofuran rings were studied by means of the Natural Bond Orbital (NBO) and Atoms in Molecules theory (AIM) investigation. For a complete assignment of the infrared and Raman spectra, the density functional theory (DFT) calculations were combined with Pulay's Scaled Quantum Mechanics Force Field (SQMFF) methodology in order to fit the theoretical frequency values to the experimental ones.

Structural study, coordinated normal analysis and vibrational spectra of 4-hydroxy-3-(3-methyl-2-butenyl)acetophenone.

Structural and vibrational properties of 4-hydroxy-3-(3-methyl-2-butenyl)acetophenone, isolated from Senecio nutans Sch. Bip. (Asteraceae) were studied by infrared and Raman spectroscopies in solid phase.

Experimental and theoretical vibrational investigation on the saccharinate ion in aqueous solution.

We combined experimental vibrational spectroscopy (FTIR-Raman) and ab-initio calculations based on the density functional theory (DFT) to predict the structural and vibrational properties of sodium saccharinate in the solid and aqueous solution phases. The structural properties for the saccharinate ion and its dimer, such as the bond order, possible charge-transfer and the topological properties for both rings in the two media were studied by means of the Natural Bond Orbital (NBO) and the Atoms in Molecules theory (AIM) investigation. For a complete assignment of the IR and Raman spectra, the density functional theory calculations were combined with Pulay's scaled quantum mechanics force field (SQMFF) methodology in order to fit the theoretical frequency values to the experimental ones.

Structural analysis, vibrational spectra and coordinated normal of 2R-(-)-6-hydroxytremetone.

We have studied and characterized the structural and vibrational properties of 2R-(-)-6-hydroxytremetone, isolated from Xenophyllum poposum (Phil.) by infrared and Raman spectroscopy in the solid phase. The density functional theory (DFT) method together with Pople's basis set show that two stable molecules for the compound have been theoretically determined in the gas phase and that both conformations are present in the solid phase, as was experimentally observed.

Phytotoxic activities of (2R)-6-hydroxytremetone.

Benzofurans are bioactive compounds isolated from the Asteraceae family. Benzofuran derivatives have been extensively studied because of their toxic effects on humans and animals. The phytotoxic activity of the benzofuran derivative (2R)-6-hydroxytremetone was studied on germination, seedling development, and cytotoxic and genotoxic effects on monocotyledoneous (onion and wheat) and dicotyledoneous (lettuce and tomato) species.