Hydrogen Bond Dynamics in Solid Triphenylsilanol

Abstract

Dynamic properties of the hydroxyl groups in a selectively deuterated polycrystalline sample of triphenylsilanol (Ph3SiOD) have been studied using variable-temperature solid-state 2H NMR spectroscopy. The crystal structure of triphenylsilanol contains eight crystallographically independent molecules, which are arranged in two tetrameric building units. Within each of these tetrameric units, the four silicon atoms are arranged in the form of a slightly distorted square, with the O atoms of the four hydroxyl groups involved in O−H···O hydrogen bonding. The temperature dependence of the quadrupole echo 2H NMR line shape in the temperature range 213−358 K and 2H NMR spin−lattice relaxation time measurements at 368 K demonstrate that the hydrogen-bonding arrangement is dynamic. From the 2H NMR line-shape analysis, the dynamic process is interpreted as interconversion between “clockwise” and “anticlockwise” hydrogen-bonding arrangements within each tetrameric unit, via a two-site jump motion of each hydroxyl de...