Improved double-quantum NMR correlation spectroscopy of dipolar-coupled quadrupolar spins

Symmetry-based homonuclear ZQ dipolar recoupling sequences sandwiched between central transition selective π/2-pulses are used to excite central transition double-quantum coherences between half-integer quadrupolar nuclei undergoing magic-angle spinning. Using 2Q-1Q correlation protocols, all 27Al-27Al connectivities are established over 6 Å in the aluminophosphate AlPO-CJ19 and a chlorite mineral.