In vitro antioxidant activity for 12 stannoxanes derived from Ph3SnCl (compounds 1-3), Ph2SnCl2 (compounds 4-6), Bu3SnCl (compounds 7-9), and Bu2SnCl2 (compounds 10-12), was assayed qualitatively by the chromatographic profile with 1,1-diphenyl-2-picrylhydrazil (DPPH) method and by two quantitative methods: the DPPH radical scavenging activity and Ferric-Reducing Antioxidant Power (FRAP) assays. The results were compared with those obtained with the starting materials 2-pyridine- carboxylic acid (I), 3-pyridinecarboxylic acid (II) and 4-pyridinecarboxylic acid (III), as well as with standard compounds, such as vitamin C and vitamin E, respectively. The in vitro antiradical activity with DPPH of diphenyltin derivative 5 showed a very similar behavior to vitamin C at a 20 μg/mL concentration, whereas according to the FRAP method, compound 8 was better. This difference is due to the mechanism of the antioxidant process. The Structure-Activity Relationships (SAR) for both methods is also reported.

The molecular structures of 5-methyl-1,3-dithia-5-aziniumpresent when the distances between hydridic and protic hydrogen atoms are shorter than 265 pm and angles for Bcyclohexane iodide, 5-chloroborane-5-methyl-1,3-dithia-5-azacyclohexane, 3,5-bis(borane)-3,5-dimethyl-1-thia-3,5-di-N-C bonds are smaller than 107.6(3)°. These interactions explain the conformation of the borane adducts in the solid azacyclohexane, and 1-borane-1,3,5-trimethyl-1,3,5-triazacyclohexane were determined by X-ray diffraction studies.state. Interactions between hydridic and protic hydrogen atoms are ed, [1c] but is important for comparison with the data of 3

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Keywords: 2-Aminobenzothiazole / Dibenzothiazolyltetraazathiapentalene / Electrophilic and nucleophilic sulfur atoms Reactions between CS 2 and the exocyclic amino groups of 2-aminobenzothiazoles gave series of molecules bearing thiourea, isothiourea, dithiocarbamate, dithiocarboimine, dimethyldithiocarbamate, methyldithiocarbamate, S-CH 3 and O-alkyl thiocarbamic ester, and guanidine groups. Preferred tautomers and conformers were determined. Most compounds present coordinative bonds between the endocyclic sulfur atom, which behaves as a Lewis acid, and oxygen, ni-

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Syntheses and structural study of the new compounds bis[2-(1H-benzimidazol-2-yl)phenyl]disulfide (1) and bis[2-(3H-benzimidazol-1-ium-2-yl)-phenyl]disulfide sulfate (2), and their corresponding bis-hydrogen sulfate (3), bis-dihydrogen-phosphate (4), bis-tetrafluoroborate (5) and bis-perchlorate (6), are reported. X-ray diffraction analyses of 2-6 and three pseudo-polymorphs of 1 have shown that the conformation of 1 is the result of sulfur weak N f S intramolecular interactions, where the sulfur atom is acting as a Lewis acid. Nitrogen protonation changes the elongated conformation of 1 into a folded conformation for 2-4 and a semifolded conformation in compounds 5 and 6 with the assistance of intramolecular π-π stacking and hydrogen bonds, which bridge the two halves of the molecules. All disulfides adopt chiral conformations in the solid state; the ensemble of these chiral conformations is racemic. They present polymeric arrays with multiple cooperative stabilizing intermolecular and intramolecular interactions like π-interactions, O f S, C(π) f S, N(π) f S, F f S, and H-bonds.