Structural and Motional Features of a Layered Sodium Hydrous Silicate as Revealed by Solid State NMR

Abstract

An approach for the investigation of layered alkali metal polysilicate hydrous materials is presented by choosing complementary multinuclear NMR methodologies. New insights into the structural and motional features of magadiite, a layered sodium silicate hydrate, have been gained using 1H, 2H, 29Si and 23Na one- and two-dimensional NMR experiments. Complementary 1H MAS single- and double-quantum studies have proven to be powerful tools in a clear recognition of the nature of hydrous species involved in hydrogen bonding. 1H and 2H MAS experiments permitted us to determine the extent of the mobility of water molecules and provided corroborating evidences of an intralayer, strongly hydrogen bonded character of silanol groups. On the basis of a novel strategy in the analysis of the cross polarization dynamics, it appeared that magadiite contains two types of structurally different Q(3) tetrahedra, as well as two types of sodium ions. The strategy applied in this work might be useful to obtain structural and motional information in the related layered alkali metal silicates, as well as in other classes of nanoporous materials.

Determining the geometry of strongly hydrogen-bonded silanols in a layered hydrous silicate by solid-state nuclear magnetic resonance

“…[1][2][3][4] The final goal of these investigations is to design new materials with specific properties such as selective adsorption and catalytic activity. [6][7][8][9][10][11][12][13] Hydrated sodium silicates are of rapidly growing industrial interest due to their high ion-or proton-exchange properties and new applications in catalysis and in the synthesis of composite mesoporous materials. Hydrogen bonds are the most important of all directional intermolecular interactions and play a central role in determining molecular conformation and aggregation, as well as the function and dynamics of a great number of systems in diverse areas ranging from inorganic to biological chemistry.…”

Convenient conversion of crystalline layered silicate octosilicate into RWR-type zeolite by acetic acid intercalation

“…From this consideration, the shortest O-O distance between the silanol groups on both sides of the interlayer was calculated to be ca. 2.5 Å ; the interlayer space would probably be retained by the formation of hydrogen bonding between the silanol groups, 18,19 resulting in the generation of a pseudo micropore structure. Although a shift in the resonance lines corresponding to Q 3 and Q 4 was observed in the 29 Si MAS-NMR spectrum of Ac-octosilicate ( Fig.…”

The Tautomeric Forms of Cyameluric Acid Derivatives

“…The signals at 4.3/4.7 ppm and 6.9 ppm are typical for H 2 O molecules embedded in a hydrogen-bonding network. [47][48][49] The splitting of the resonances for compound 5 demonstrates the existence of hydrogen bonds, which differ significantly in their strength. This as well as the intensity ratio of these signals at d 14.2 and 11.1 ppm of 1:3 corresponds very well to the crystal structure (see below), where one short hydrogen bond (1.84 for O7···H14) and three relatively long hydrogen bonds (2 1.93 und 1 1.97 ) are observed.…”