DIPOLAR DEPHASING BETWEEN QUADRUPOLAR AND SPIN-1/2 NUCLEI - REDOR AND TEDOR NMR EXPERIMENTS ON VPI-5

In this work we examine the use of dipolar-dephasing magic-angle spinning NMR to study mixed pairs of quadrupolar and spin-1/2 nuclei in solids. Dipolar connectivities are examined in both directions between the Al-27(I=5/2) and P-31(I=1/2) spins in the very large pore aluminophosphate VPI-5, which is considered representative of a range of inorganic framework materials. Rotational-echo double-resonance (REDOR) and transferred-echo double-resonance (TEDOR) experiments are demonstrated, as well as a two-dimensional extension of the TEDOR experiment. These experiments restore the heteronuclear dipolar coupling under MAS conditions via a train of radiofrequency pulses, thereby providing information about connectivities and distances between coupled nuclei in these inorganic solids.