Physical Chemistry Chemical Physics, 2006, 8, 1994 - 1999
Quadrupolar coupling selective cross-polarization in solid state NMR
A new strategy is presented for achieving selective heteronuclear polarization transfers from half-integer quadrupolar spins in magic-angle spinning (MAS) NMR. By combining cross-polarization with a recently introduced RAPT pulse sequence that selectively excites the signal of a half-integer quadrupolar nucleus based on its quadrupolar coupling constant magnitude, we demonstrate that hetero-nuclei in its close proximity may be selectively excited. Selective 23Na 1H polarization transfers are demonstrated in Na2MoO4·2H2O, Na2HPO4·2H2O and a mixture of NaHCO3 and Na2HPO4·2H2O.