Estimating order parameters by MQNMR

The total spectral width of any MQ spectrum is dominated by the values of the dipolar couplings in the spin system. The dipolar couplings in turn are a function of the order parameters and the internuclear distances (Eq. (3)). The iterative analysis of most spectra of aligned molecules typically begins with a trial geometry then by trial and error assessing possible molecular ordering to provide a visual match to spectral features. Model compounds 

Field et al.62 developed a general procedure to estimate the Saupe order parameters for spin systems aligned in liquid crystal media by iteratively fitting the experimental and simulated spectral widths of the high-order multiple quantum spectra. 

For the 8-spin system of indene (1 ), aligned in liquid crystalline solution, the observed spectral widths of the 5Q, 6Q and 7Q spectra were measured at 30428, 23185 and 14940 Hz, respectively (Fig. 17). 

---