Given these findings, we turned to NMR spectroscopy studies to probe the conformations of these NHC-CDIs in solution. F NMR measurements of 1 and 9 revealed that 1 displayed a broad line shape (ΔV = 362 Hz, compared to 9, ΔV = 92 Hz) which is consistent with the high fluxionality of the N-C6F5 aryl rings in 1. Variable temperature F NMR of 1 suggested that this fluxionality decreased upon cooling to -25 °C where the broad singlet resolved into a doublet (ΔV = 180 Hz). These findings were consistent with the earlier computations of the isomerization of 1 and the corresponding low barrier of interconversion (ca. 14 kcal/mol). UV-vis spectra also displayed significant differences between 1 and 9, wherein an absorbance band (lmax = 471 nm) of 1 was observed in MeCN that was not present in 9 (Figure and SI Figure ). Time-dependent-DFT calculations suggested that this additional band in the spectrum of 1 corresponds to a charge transfer state resulting from electron transfer from the CDI p system to the NHC p system, which is most consistent with the (E/E) isomer (Figure and SI Figure ). These transitions for the E/Z and Z/Z isomers are computed to be blue-shifted.