Table 3. Bond Angles and Relative Energies of DFT Optimized Structures of SION-32, SION-33, and SION-34 Simulated with All Probable Protonation Schemesa.
| C6–N1–C2 (deg) | C2–N3–C4 (deg) | C5–N7–C8 (deg) | ΔE (kcal/mol) | |
|---|---|---|---|---|
| SION-32, N1-protonated | 123.50 | 113.97 | 15.44 (N3) | |
| SION-32, N3-protonated | 120.74 | 117.03 | ||
| SION-33, N1-protonated | 123.21 | 102.32 | 12.90 (N7) | |
| SION-33, N7-protonated | 119.55 | 107.84 | ||
| SION-34, N1-protonated | 124.45 | 114.46 | 13.29 (N1) | |
| SION-34, N3-protonated | 120.96 | 117.52 |
a
The energetically favored site of N protonation is given in each ΔE column entry in parentheses.