HETERO NUCLEAR DIPOLAR DECOUPLING IN THE NMR SPECTROSCOPY OF SOLIDS AND LIQUID CRYSTALS USING A SHORTER SWf-TPPM SEQUENCE WITH PHASE INCREMENTAL ALTERATION AND SUPERCYCLING

SWf-TPPM based decoupling sequences can be applied to remove heteronuclear spin interactions in liquid crystals and solids. Here we present a decoupling scheme for heteronuclear dipolar decoupling in anisotropic systems formulated by reducing the number of pulse pairs in the parent SWf-TPPM. The tangential sweep of pulse durations is maintained in the sequence with a phase incremental alteration followed by supercycling. The resulting decoupling scheme called PHINTAPT (Decoupling sequences with PHase angle INcrements and TAngential variation in Pulse Times) was compared with two commonly used decoupling sequences in solids and liquid-crystals namely, SPINAL-64 and SWf-TPPM by analyzing the intensities of various resonances in the proton decoupled 13C spectrum of U-13C-labelled tyrosine and the liquid crystal 4-n-pentyl-4’-cyanobiphenyl (5CB). The effectiveness of the decoupling scheme with respect to the experimental parameters such as RF field strength, MAS frequency and proton offset frequency is also studied.