Suppression of Spinning Sidebands

Where there is a combination of different sites, each of which produces a significant number of sidebands, simplification of the spectrum by removal of the spinning sidebands would be extremely helpful. Dixon (1982) introduced the concept of breaking up the rotation period into intervals separated by 180° pulses. The phase of each spin is inverted by the pulses and the total phase accumulated by each spin can be calculated. Then for all the sidebands to be removed, the sum of the phase for spins contributing to the spinning sidebands needs to vanish, independent of the orientation of the particular crystallite. The basic TOSS sequence has been developed to compensate for imperfections by extension of the applied phase cycles and by paying careful 

---

The CP step is an essential building block for pulse sequences in solid-state NMR. The easiest ID experiments that are routinely used for characterization of organic, organometallic and hybrid solids are total suppression of spinning sidebands (TOSS), nonquatemary suppression, and so on. 

The pulse sequence used most often for this purpose is the TOSS sequence (total suppression of spinning sidebands. Fig. 3.3.9) [Dixl, Gril]. Before the start of data acquisition at r = ts the spin system is prepared by four 180° pulses at well-defined times... 

Fig. 3.3.9 TOSS preparation in MAS NMR for suppression of spinning sidebands. The 180 TOSS pulses are not equally spaced in practice.

H. Geen, G. Bodenhausen, Pure absorption-mode chemical exchange nuclear magnetic resonance spectroscopy with suppression of spinning sidebands in a slowly rotating solid, J. Chem. Phys. 97 (1992) 2928. 

Fig. 8 Schematic diagrams for the following pulse sequences (A) single pulse excitation/magic-angle spinning, (B) total suppression of sidebands, and (C) delayed decoupling, or dipolar dephasing.

Abbreviations BCC. body centered cubic DOS. density of states ESR. electron spin resonance HX.AI S, extended X-ray absorption fine structure F CC. face centered cubic (a crystal structure). FID, free induction decay FT, Fourier transform FWHM, full width at half maximum HCP, hexagonal close packed HOMO, highest occupied molecular orbital IR, Infrared or infrared spectroscopy LDOS, local density of states LUMO, lowest unoccupied molecular orbital MAS. magic angle spinning NMR. nuclear magnetic resonance PVP. poly(vinyl pyrrolidone) RF. Radiofrequency RT, room temperature SEDOR, spin echo double resonance Sf, sedor fraction SMSI, strong metal-support interaction TEM. transmission electron microscopy TOSS, total suppression of sidebands. 

Fig. 1 SSNMR spectra of ibuprofen, 75.6 MHz. (A) Bloch decay experiment (single pulse), no decoupling, static, 240-sec pulse delay, 100 scans, 400-min experiment time. (B) Same as (A) but with decoupling ( 60 kHz). (C) Same as (B) but with 5-kHz MAS. (D) Cross-polarization experiment, with H decoupling ( 60 kHz), 5-kHz MAS, 1.5-msec contact time, 3-sec pulse delay, 100 scans, 5-min experiment time. (E) Same as (D) with the TOSS pulse sequence applied to suppress spinning sidebands. Note Asterisk ( ) denotes spinning sidebands sharp ( ) denotes spectrometer background artifact.

Fig. 6 CPMAS NMR spectra of (A) bupivacaine-fb (5% wt/wt) in lipospheres (95% wt/wt) (B) lipospheres (C) difference spectrum of (A) minus (B) (D) bupivacaine-fb. Asterisks ( ) denote spinning sidebands incompletely suppressed by the TOSS sequence. (From Ref. l)...

---