New series of intramolecularly coordinated diaryltellurium compounds. Rational synthesis of the diarylhydroxytelluronium triflate [(8-Me 2NC 10H 6) 2Te(OH)](O 3SCF 3)

The reaction of 8-dimethylaminonaphthyllithium etherate with the tellurium(II) bis(dithiocarbamate) Te(S₂CNEt₂)₂ provided the diaryltelluride (8-Me₂NC₁₀H₆)₂Te (1). The oxidation of 1 with an excess of H₂O₂ did not afford the expected diaryltellurium(IV) oxide (8-Me₂NC₁₀H₆)₂TeO (2), but the diaryltellurium(VI) dioxide (8-Me₂NC₁₀H₆)₂TeO₂ (3). The preparation of 2 was achieved by the comproportionation reaction of 1 and 3. The protonation of 2 using triflic acid gave rise to the formation of diarylhydroxytelluronium triflate [(8-Me₂NC₁₀H₆)₂Te(OH)](O₃SCF₃) (4), which features the protonated diaryltellurium oxide [(8-Me₂NC₁₀H₆)₂Te(OH)]+ (4a). Compounds 1, 3·H₂O·H₂O₂, 3·2H₂O, and 4 were characterized by X-ray crystallography. The experimentally obtained molecular structures were compared to those calculated for 1–3, 4a, and (8-Me₂NC₁₀H₆)₂Te(OH)₂ (5) as well as the related diphenyltellurium compounds Ph₂Te (6), Ph₂TeO (7), Ph₂TeO₂ (8), [Ph₂Te(OH)]+ (9a), and Ph₂Te(OH)₂ (10) at the DFT/B3PW91 level of theory.

Electronic structure of the azide group in 3′-Azido-3′- deoxythymidine (AZT) compared to small azide compounds

Theoretical calculations for some structural and electronic properties of the azide moiety in the nucleoside reverse transcriptase (RT) inhibitor 3′-azido-3′- deoxythymidine (AZT) are reported. These properties, which include geometrical properties in three dimensional space, Hirshfeld charges, electrostatic potential (MEP), vibrational frequencies, and core and valence ionization spectra, are employed to study how the azide group is affected by the presence of a larger fragment. For this purpose, two small but important organic azides, hydrazoic acid and methyl azide, are also considered. The general features of trans Cs configuration for RNNN fragments[1] is distorted in the large AZT bio-molecule. Hirshfeld charge analysis shows charges are reallocated more evenly on azide when the donor group R is not a single atom. Infrared and photoelectron spectra reveal different aspects of the compounds. In conclusion, the electronic structural properties of the compounds depend on the specific property, the local structure and chemical environment of a species.

π-Selective stationary phases: (II) Adsorption behaviour of substituted aromatic compounds on n-alkyl-phenyl stationary phases

The frontal analysis method was used to measure the adsorption isotherms of phenol, 4-chlorophenol, p-cresol, 4-methoxyphenol and caffeine on a series of columns packed with home-made alkyl-phenyl bonded silica particles. These ligands consist of a phenyl ring tethered to the silica support via a carbon chain of length ranging from 0 to 4 atoms. The adsorption isotherm models that fit best to the data account for solute–solute interactions that are likely caused by π–π interactions occurring between aromatic compounds and the phenyl group of the ligand. These interactions are the dominant factor responsible for the separation of low molecular weight aromatic compounds on these phenyl-type stationary phases. The saturation capacities depend on whether the spacer of the ligands have an even or an odd number of carbon atoms, with the even alkyl chain lengths having a greater saturation capacity than the odd alkyl chain lengths. The trends in the adsorption equilibrium constant are also significantly different for the even and the odd chain length ligands.