In these contexts, NHC-CDI isomerization could serve as a powerful tool for tuning structure and reactivity. For example, access to the nucleophilic amidate nitrogens of NHC-CDIs may be optimized in the E/E isomer relative to the sterically encumbered E/Z and Z/Z isomers. To date, however, there are no reports of NHC-CDI adducts that adopt a preferred E/E conformation in the absence of metal coordination. Therefore, we set out to understand what molecular features of NHC-CDIs may enable the predictive design of Z/Z, E/Z, and E/E isomers, which would provide full access to the conformational space available to this unique class of molecules. We performed computational studies of previously reported NHC-CDI adducts to understand the key criteria responsible for conformer stability. A survey of the Cambridge Structural Database yielded 22 distinct NHC-CDI adducts, 13 of which did not contain metals (see SI Computational Details). None of the 13 structures without metals were isolated in the E/E conformation (SI Figure ). Geometric optimizations of the 13 X-ray structures were performed, followed by constrained potential energy scans and relaxations to determine the relative energies of conformers and barriers to their interconversion. The library of experimental NHC-CDI crystal structures was supplemented with 15 theoretical NHC-CDIs to afford a systematic investigation into the steric and electronic factors of NHC-CDI conformer stability (Figures ). These computational investigations showed that steric repulsion between the NHC and CDI N-substituents significantly destabilized the E/E isomer compared to the Z/Z or E/Z isomers (Figure , example E/E = 10.3 kcal/mol vs Z/Z = 0 kcal/mol), a likely explanation for the dearth of E/E isomers reported to date. Next, we set out to identify interactions that could stabilize the E/E conformation (Figure ). Due to the proximity of the N-aryl substituents of the NHC and CDI in the E/E isomer, we hypothesized that N-aryl motifs that could engage in p-stacking or hydrogen bonding may stabilize this conformation (see SI Figure ). From a series of computed structures (Figure and SI Figures ), we identified an electron-rich NHC (bis-3,4,5-trimethoxyl benzene, A) and an electron-deficient CDI (bis-pentafluoro benzene, B) that formed a candidate (E/E)NHC-CDI adduct 1. This adduct exhibited p-stacking interactions that favored the E/E conformer, with the E/Z and Z/Z conformers being 2.9 kcal/mol and 4.4 kcal/mol higher in energy, respectively. Transition state calculations revealed low barriers (ca. 14 kcal/mol) for interconversion between these conformers, which would allow for all isomers to be accessed at room temperature (SI Figure ).