Persulfurated Aromatic Compounds

Persulfurated arenes have been known for about 50 years but they were underexploited in chemistry in spite of facile, mild, and high-yielding syntheses. Their properties (redox potentials, UV/Vis absorption, conductivity, nonlinear optical properties, etc.) are mainly due to the aromaticity of the ring with sp2-hybridized carbon atoms and to the electronic contribution from numerous divalent sulfur ligands, which also stabilize negative or positive charges. The characteristic conformational patterns of the sulfur ligands often facilitate preorganization in supramolecular assemblies, with or without thiophilic metal cations, for designing redox sensors, ion-selective membranes, clathrates, organic conductors, nonlinear optical materials, liquid crystals, coordination polymers, and bioinorganic systems. A new class of supramolecules with various molecular shapes such as asterisks, chains, wheels, and windmills were reported.

27Al magic-angle spinning nuclear magnetic resonance satellite transition spectroscopy of glasses in the system K2O-Al2O3-SiO2

27Al magic-angle spinning nuclear magnetic resonance satellite transition spectroscopy at 78 MHz has been applied to determine (true) chemical shift and quadrupole coupling parameters of glasses in the system K2O-Al2O3-SiO2 with 60-80 mol% SiO2 and K2O concentrations between 0 and 24 mol%. The powdered crystalline aluminosilicates andalusite and sillimanite have also been examined. In the glasses, all Al appears to be tetrahedrally bound in the aluminosilicate network unless x = mol% K2O:mol% Al2O3 becomes extremely small. Upon decreasing x the distortion of the tetrahedral Al(OSi)4 units increases in steps, and possible explanations are discussed. Six-coordinated aluminum observed for x < 0.2 is connected with the occurrence of interstitial Al3+ ions which charge-compensate the AlO4 units in addition to K+.

Detection of multiple boron sites in glasses by 11B satellite transition nuclear magnetic resonance spectroscopy

The magic-angle spinning sidebands of the satellite transition (ST, m = +/- 3/2 <==> +/- 1/2) for 11B nuclear magnetic resonance (11B ST spectroscopy) have been used to detect multiple boron sites in Na2O-B2O3-SiO2 glasses. The experimental details and data analysis are described, how multiple BO4 and BO3 units can be distinguished using standard magic-angle spinning. For a 16Na2O-30B2O3-53.9SiO2 glass (0.1 MnO) two BO4 units with chemical shifts of -2.5 and 0 ppm were found which differ considerably in their quadrupole interaction. Besides this we found three different BO3 units with approximate chemical shifts of 17, 15, and 19 ppm. The results are compared with earlier measurements.