10a-(4-Biphenyl)-10b-methyl-10a,10b-dihydropyrene: a conformational study and ring current effect

A dithiacyclophane was employed as a precursor to the title compound. A conformational study of the dithiacyclophane revealed a unique phenomenon in its terphenyl unit: one ring is rigidly held, the other terminal ring undergoes free rotation and the central ring exhibits restricted mobility. The aromatic protons of the biphenyl unit are all shielded by the dihydropyrene unit and well resolved in the 1H NMR spectrum, consistent with a ring current effect extended to eight conjugated carbon atoms away from the molecular plane of dihydropyrene.