Silicon‐29 nuclear magnetic resonance studies of aqueous silicate solutions. 8 spin–lattice relaxation times and mechanisms

The 29 Si spin–lattice relaxation times, T 1 ( 29 Si), of the various silicate anions present in high‐purity alkaline silicate solutions are reported. Regular silicate cages display the longest T 1 ( 29 Si) values and, in the case of the cubic octameric cage, an unexpectedly large nuclear Overhauser enhancement, indicating that, unlike the smaller silicate oligomers, the cubic octamer relaxes primarily via the ( 29 Si, 1 H) dipole‐dipole interaction. This phenomenon provides, inter alia , a simple diagnostic test for such cages.