A complete vibrational study on a potential environmental toxicant agent, the 3,3',4,4'-tetrachloroazobenzene combining the FTIR, FTRaman, UV-Visible and NMR spectroscopies with DFT calculations.

In this study 3,3',4,4'-tetrachloroazobenzene (TCAB) was prepared and then characterized by infrared, Raman, multidimensional nuclear magnetic resonance (NMR) and ultraviolet-visible spectroscopies. The density functional theory (DFT) together with the 6-31G(*) and 6-311++G(**) basis sets were used to study the structures and vibrational properties of the two cis and trans isomers of TCAB. The harmonic vibrational wavenumbers for the optimized geometries were calculated at the same theory levels. A complete assignment of all the observed bands in the vibrational spectra of TCAB was performed combining the DFT calculations with the scaled quantum mechanical force field (SQMFF) methodology. The molecular electrostatic potentials, atomic charges, bond orders and frontier orbitals for the two isomers of TCAB were compared and analyzed. The comparison of the theoretical ultraviolet-visible spectrum with the corresponding experimental demonstrates a good concordance while the calculated (1)H and (13)C chemicals shifts are in good conformity with the corresponding experimental NMR spectra of TCAB in solution. The npp(*) transitions for both forms were studied by natural bond orbital (NBO) while the topological properties were calculated by employing Bader's Atoms in the Molecules (AIM) theory. This study shows that the cis and trans isomers exhibit different structural and vibrational properties and absorption bands.

On the interaction of vanadium species with the monoisoamyl ester of meso-2,3-dimercaptosuccinic acid.

The interaction of the VO2+ cation with the monoisoamyl ester of meso-2,3-dimercaptosuccinic acid (MiADMSA) was investigated by electron absorption spectroscopy in aqueous solutions at different pH values. The spectral behavior, complemented with a spectrophotometric titration, shows the generation of a [VO(MiADMSA)2](4-) complex in which the oxocation interacts with two pairs of deprotonated -SH groups of the ester. Besides, MiADMSA rapidly reduces VO3(-) to VO2+, which might be chelated by an excess of the ester, and also produces relatively rapid reduction of V2O5 suspensions at pH = 6.5. The results of this study suggest that MiADMSA might be a potentially useful detoxification agent for vanadium.

Potential antitumoral properties of a new copper complex with santonic acid.

A new copper(II) complex of santonic acid [Cu(2)(sant)(4)(H(2)O)(2)].2(1/2)H(2)O has been prepared and characterized by electronic, vibrational, EPR spectral studies, and stability determinations in solution. The presence of two antiferrromagnetically coupled copper centers in the solid state was detected by EPR. The dinuclear Cu(II) complex crystallizes in the tetragonal P4(3)2(1)2 space group, with a=b=14.498(3), c=64.07(1)A. Biological studies indicate that the complex displays interesting potential antitumoral actions.

Synthesis, characterization and biological activity of oxovanadium (IV) complexes with cyclic polyalcohols.

Oxovanadium (IV) complexes of the cyclic polyols conduritol C (cond) and myo-inositol (inos) of stoichiometry Na(2)[VO(cond)(2)].2H(2)O and Na(2)[VO(inos)(2)].H(2)O were obtained in aqueous alkaline solutions. They were characterized by infrared and UV-Vis spectroscopies, thermoanalytical (thermogravimetric and differential thermal analysis) data and magnetic susceptibility measurements. The biological activities of the complexes on the proliferation, differentiation and glucose consumption were tested on osteoblast-like cells in culture. Conduritol C and myo-inositol did not produce any effect on these parameters. Normal and tumoral cell proliferation was inhibited about (ca.40-60%) by the two oxovanadium (IV) complexes in concentrations as low as 100microM. The complexes were also inhibitory on cell differentiation (ca. 70-80%) while they stimulate glucose consumption. Comparisons of these effects with those of the oxovanadium (IV) cation, under the same experimental conditions, were also performed.

(-)-Parasantonic acid and its enol lactone, (+)-parasantonide: observation of the rare acid-to-acid catemeric hydrogen-bonding mode in a gamma,epsilon-diketocarboxylic acid.

The title diketo acid, (-)-alpha,3a,7-trimethyl-5,8-dioxo-1,4-ethanoperhydropentalene-1-acetic acid, C(15)H(20)O(4), is shown to aggregate in the solid state as acid-to-acid hydrogen-bonded catemers, whose chains follow 2(1) screw axes from each carboxyl H atom to the C=O group of a neighboring carboxyl group [O.O = 2.672 (4) A and O.H-O = 173 degrees ]. Two parallel counterdirectional screw-related single-strand hydrogen-bonded chains pass through the cell in the a direction. Two intermolecular C=O.H-C close contacts are present in this compound. Both this diketo acid and its enol lactone, (+)-parasantonide [systematic name: (-)-alpha,3a,7-trimethyl-5-oxo-1,4-ethenoperhydropentalene-1,8-carbolactone], C(15)H(18)O(3), have an R configuration at the methylated chiral center adjacent to the carboxyl group, unlike the precursor from which they are derived, viz. (-)-santonic acid.