Figure 4
1H (500 MHz)–13C HETCOR MAS (12.5 kHz) spectra of the DI–PM cocrystal recorded using FSLG 1H homonuclear decoupling (Bielecki et al., 1989 ) in t1 with a CP transfer duration of (a) 100 µs, (b) 500 µs and (c) 1 ms. The spectrum in part (a) is repeated from Fig. 3 (c). 104 transients were co-added for each of (b) 128 or (c) 90 t1 FIDs using a recycle delay of (b) 6 or (c) 5.5 s, corresponding to a total experimental time of (b) 22 or (c) 14 h. The scaling factor in F1 was determined to be (a) and (b) 1.80 or (c) 1.73. The base contour level is at (a) 20, (b) 13 and (c) 25% of the maximum peak height. Red crosses correspond to GIPAW-calculated 1H and 13C chemical shifts (see Table 2 ) for (a) one-bond C—H bonds and (b) and (c) C⋯H proximities between (b) 1.2 and 2.2 Å, and (c) 2.2 and 3.0 Å. |