SBA-15 mesoporous silica has been functionalized with aminopropyl groups through a simple co-condensation approach of tetraethyl orthosilicate (TEOS) and (3-aminopropyl)triethoxysilane (APTES) using amphiphilic block copolymers under acidic conditions. The organic-modified SBA-15 materials have hexagonal crystallographic order, pore diameter up to 60 A, and the content of aminopropyl groups up to 2.3 mmol g(-1). The influences of TEOS prehydrolysis period and APTES concentration on the crystallographic order, pore size, surface area, and pore volume were examined. TEOS prehydrolysis prior to the addition of APTES was found essential to obtain well-ordered mesoporous materials with amino functionality. The amount of APTES incorporated in the silica framework increased with the APTES concentration in the synthesis gel, while the ordering of the mesoporous structure gradually decreased. Analysis with TG, IR, and solid state NMR spectra demonstrated that the aminopropyl groups incorporated in SBA-15 were not decomposed during the preparation procedure and the surfactant P123 was fully removed through ethanol extraction. The modified SBA-15 was an excellent base catalyst in Knoevenagel and Michael addition reactions.

A quantitative NMR strategy is developed for the study of the network connectivity (intermediate range structure) and the cation distribution in the sodium aluminoborate glass system. The strategy is based on the analysis of rotational echo double resonance (REDOR) spectroscopy applied to the glasses and the crystalline model compounds Li 6 Al 2 (BO 3 ) 4 , NaBO 2 , and Na 2 B 4 O 7 . The heterodipolar multispin interaction between the quadrupolar spin systems 27 Al T 11 B and 23 Na T 11 B is analyzed in terms of approximate second moments, which are extracted from REDOR data measured at short dipolar evolution times. On the basis of 27 Al{ 11 B} and 11 B{ 27 Al}-REDOR results, the framework connectivity distribution is extracted and compared to statistical and preferential bonding distribution scenarios, respectively. The sodium aluminoborate system is characterized by a large degree of bonding regularity in the framework. Four-coordinated aluminum is preferentially linked to BO 3/2 and BO 2/2 Ounits and vice versa, while linking between two four-coordinate units is disfavored, as expected on the basis of bond valence considerations. In glasses with low aluminum contents and/or high sodium contents, there is a greater tendency toward a randomization of connectivities. Spatial correlations between the sodium nuclei and the boron atoms in the network are probed by complementary 23 Na{ 11 B}-and 11 B{ 23 Na}-REDOR experiments. The results reveal that both the three-and the four-coordinated boron species interact equally strongly with sodium cations, consistent with an overall homogeneous cation distribution.

The utility of heteronuclear double-resonance NMR methods involving the quadrupolar nuclei 11 B and 27 Al is demonstrated for probing the intermediate-range order in aluminoborate glasses. Results from both rotational echo double resonance (REDOR) and heteronuclear cross-polarization magic angle spinning (CPMAS) studies are presented and discussed. While both techniques are strongly affected by the presence of large quadrupolar splittings, a working strategy is developed on the basis of which reliable structural interpretations are possible. Using this strategy, the effects of the cation type M on the structures of two basic glass compositions, 25MWithin each series having the same basic network composition, replacement of the modifier cation Na by Ca or Mg produces a large change in the speciation of framework aluminum ("cation effect"): while in the sodiumcontaining glass the overwhelming fraction of Al is present as tetrahedral AlO 4/2 sites, the calcium-and magnesium-containing glasses also possess larger fractions of five-and six-coordinated aluminum sites. 27 Al{ 11 B} REDOR results indicate that all of these aluminum environments interact equally strongly with the dominant BO 3/2 sites in both glasses. In addition, the reverse 11 B{ 27 Al} REDOR results reveal that the extent of the AlO 4/2 -BO 4/2 interaction in the network is highly dependent on the framework composition and on the M cation type. While sodium aluminoborate glasses reveal strong chemical ordering (avoidance of intertetrahedral linkages), the analogous Mg 2+ -based glasses tend toward a randomization of connectivities. Finally, twodimensional heteronuclear correlation spectra obtained via 11 B{ 27 Al} CPMAS suggest that AlO 5 and AlO 6 sites can provide a mechanism for stabilizing tetrahedral BO 4/2 units.

We demonstrate the possibility of recoupling chemical shift anisotropy (CSA) interactions in solid-state nuclear magnetic resonance (NMR) under high-speed magic-angle spinning (MAS) while retaining a static CSA powder pattern line shape and simultaneously attenuating homonuclear dipole–dipole interactions. CSA recoupling is accomplished by a rotation-synchronized radio-frequency pulse sequence with symmetry properties that permit static CSA line shapes to be obtained. We suggest a specific recoupling sequence, which we call ROCSA, for which the scaling factors for CSA and homonuclear dipole–dipole interactions are 0.272 and approximately 0.05, respectively. This sequence is suitable for high-speed C13 MAS NMR experiments on uniformly C13-labeled organic compounds, including biopolymers. We demonstrate the ROCSA sequence experimentally by measuring the C13 CSA patterns of the uniformly labeled, polycrystalline compounds L-alanine and N-acetyl-D,L-valine at MAS frequencies of 11 and 20 kHz. We also present experimental data for amyloid fibrils formed by a 15-residue fragment of the β-amyloid peptide associated with Alzheimer’s disease, in which four amino acid residues are uniformly labeled, demonstrating the applicability to biochemical systems of high molecular weight and significant complexity. Analysis of the CSA patterns in the amyloid fibril sample demonstrates the utility of ROCSA measurements as probes of peptide and protein conformation in noncrystalline solids.