Hochauflösende Festkörper-NMR-Untersuchungen an Kieselsäuren. II. Hochauflösende 1H-Festkörper-NMR-Untersuchungen an polykristallinen Phyllokieselsäuren (H2Si2O5)x mit Hilfe von Vielimpulsverfahren bei tiefem und hohem Magnetfeld

Solid-State High Resolution N.M.R. Studies of Silicic Acids. II. Solid-State High Resolution ¹H N.M.R. Studies of Polycrystalline Phyllosilicic Acids (H₂Si₂O₅)_x by Using Combined Multiple Pulse Magic Angle Spinning Techniques at Low and High Magnetic Fields The α- and δ-phases of the phyllosilicic acid (H₂Si₂O₅)_x are studied by means of multiple pulse techniques (MREV8, BR24) and combined multiple pulse-magic angle spinning experiments at low (1.42 T) and high (6.35 T) magnetic fields. In addition to the main signal due to SiOH groups the NMR spectra of both samples show a small peak which can be assigned to water molecules. For the SiOH groups of both phases the anisotropy of the proton shielding tensors Δσ and the isotropic chemical shift values δ are obtained. According to the N.M.R. results a model for the hydrogen bonds is derived for the phyllosilicic acids. Compared with the α-phase, the SiOH groups in the δ-phase form weaker hydrogen bonds.