Claudio A. Téllez S

Density functional theory study of the Fourier transform infrared and Raman spectra of dichloro-bis(2,4-pentanedionate)tin(IV)

Fourier transform infrared and Fourier transform Raman spectra of dichloro-bis(2,4-pentanedionate)tin(IV) have been obtained. Density functional theory (DFT) BLYP calculations, have been carried out with the purpose of understanding the metal-ligand region spectra of this compound. Vibrational wavenumbers calculated by BLYP/6-31G* force fields are closed with the experimental results. The percentage of deviation of the bond lengths and bond angles gives a good picture of the normal modes, and serves as a basis for the assignment of the wavenumbers. The calculated geometrical parameters show slight differences compared with the experimental ones, and these differences can be explained by the different physical state of Sn(acac)2Cl2. The DFT-BLYP calculations assumed a free molecule in the gas phase. The experimental wavenumbers are obtained from the spectra of solid samples.

FT-infrared band analysis and temperature programmed dessorption for the Y, L and ferrierite zeolites.

With the aim to qualifying and quantifying the acidity of the Y, L and ferrierite zeolites, an infrared band analysis of pyridine adsorption and programmed temperature dessorption measurements were carried out to a set of nine samples of the Y, L and ferrierite zeolites. The infrared spectra before and after the pyridine adsorption process had revealed that the ferrierite zeolite shows, almost in the totality, Bronsted acid sites. The Y and L zeolites present, also, significative concentrations of Bronsted and Lewis acid sites. These facts allow to conclude that zeolite ferrierite is the strongest acid zeolite among these three types.

In vivo confocal Raman spectroscopy and molecular dynamics analysis of penetration of retinyl acetate into stratum corneum

OBJECTIVE The purpose of this study is to elucidate the behavior of retinyl acetate in penetrating human skin without the presence of enhancers by using confocal Raman spectroscopy and molecular dynamics simulation. METHODS In this study, in vivo confocal Raman spectroscopy was combined with molecular dynamics simulation to investigate the transdermal permeation of the aqueous suspension of retinyl acetate. RESULTS Permeation was measured after 30min, and retinyl acetate was found up to 20μm deep inside the stratum corneum. The delivery of retinyl acetate inside a skin membrane model was studied by molecular dynamics. The membrane model that was used represented normal young skin containing a lipid bilayer with 25% ceramide, 36% fatty acid, 30% cholesterol, and 6% cholesterol sulfate. CONCLUSION Spectroscopy data indicate that retinyl acetate permeates into the stratum corneum. Molecular dynamics data showed that retinyl acetate permeates in the membrane model and that their final location is deep inside the lipid bilayer. We showed, for the first time, a correlation between Raman permeation data and computational data.