Fig. 3.

Structural models and nitrogen chemical shifts of the imidazole-imidazolium dimer. The models are optimized without restraint (B) and with the restraint of the 2L0J backbone (C1 and C1′) or 3LBW backbone (C2). Intramolecular and intermolecular hydrogen bonds are indicated by dashed lines. The chemical shifts shown follow the convention of Fig. 2. For C1, the dependence of the electronic energy on the inter-ring angle (sampled by varying the χ₂ torsion angle of the left ring) is also shown.