Spectrum of the Month
September 1999
First Solid State Spectra in NMR Facility
Brian Pate and Ulli acquired the first solid state NMR spectra of the NMR facility. The top trace shows a carbon-13 spectrum of a Nickel porphyrin complex of the static sample. The spectra below were obtained by Magic Angle Spinning with varied speeds. Note how the lines at the isotropic shifts remain unchanged by the spinning frequency, while the spinning sidebands move. Clearly visible are the two lines around 150 ppm from the carbon-13 enriched sites in the ring. The doublet stems from inequivalent sites in the ring. In addition, several alkane resonances are identified between 10 and 40 ppm. The variation of spinning speeds was used to map out the powder patterns for each site. The observation of spinning sidebands of the doublet down to at least -40 ppm prove that the chemical shift powder patterns of the doublet extend beyond the alkane range probably down to -130ppm. The shoulder at 77ppm in the powder pattern of the static sample is identified to result from the resonance at 35ppm.
The knowledge of the chemical shift tensor components is now used to characterize the orientation of this material in its liquid crystalline phase.
Thank you, Brian
Spectrum