HETERONUCLEAR DIPOLAR DECOUPLING IN THE NMR STUDIES OF MOLECULES IN SOLID AND LIQUID-CRYSTALLINE STATES USING A PHASE-WIGGLED SWF-TPPM SEQUENCE
CYRIL AUGUSTINE *
Department of Chemistry, St. Berchmans College Campus, Mahatma Gandhi University, 686101, Kerala, India
*Author to whom correspondence should be addressed.
Abstract
The phase-wiggled two-pulse phase modulation or PW-TPPM, a recently formulated scheme functions effectively for heteronuclear dipolar decoupling in nuclear magnetic resonance of static solid samples [R. Fu, Chem. Phys. Lett. 483, 147, 2009]. In PW-TPPM, the two pulses within each TPPM element have different alternating phase angles and thus these elements become phase-wiggled. In this communication, a modified PW-TPPM scheme is presented, generated by varying pulse durations of the parent PW-TPPM in a way similar to SWf-TPPM (Swept-frequency two-pulse phase modulation) decoupling sequence. The rationale was to find the impact of the tangential variations in pulse durations on the efficiency of PW-TPPM decoupling scheme. The performance of the newly formed sequence, termed as PWSWf-TPPM, is studied in liquid crystals and rotating solids.
Keywords: NMR of liquid crystals, NMR of solids, 13C-1H dipolar decoupling, PW-TPPM, SWf-TPPM, SPINAL-64, PWSWf-TPPM