Relative stability (ΔE), vertical ionization potential (IPV), bond dissociation energy (BDE), dipole moment, and selected bond distances (r) of the global minimum amine-one and imine-ol tautomeric forms of compounds 1–9a.
| Property | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Amine-one | Imine-ol | Amine-one | Imine-ol | Amine-one | Imine-ol | Amine-one | Imine-ol | Amine-one | Imine-ol | Amine-one | Imine-ol | Amine-one | Imine-ol | Amine-one | Imine-ol | Amine-one | Imine-ol | |
| ΔEb | 0.0 (0.0) | 6.6 (6.0) | 0.0 (0.0) | 6.5 (6.0) | 0.0 (0.0) | 7.2 (6.5) | 0.0 (0.0) | 7.5 (6.8) | 0.0 (0.0) | 7.2 (6.5) | 0.0 (0.0) | 7.5 (6.6) | 0.0 (0.0) | 8.0 (7.0) | 0.0 (0.0) | 13.2 (11.9) | 0.0 (0.0) | 12.6 (11.3) |
| IPV | 163.4 | 164.2 | 161.7 | 162.8 | 158.0 | 159.1 | 156.1 | 156.7 | 162.4 | 163.0 | 160.3 | 165.0 | 158.6 | 160.2 | 154.5 | 161.1 | 156.8 | 165.4 |
| BDEb | 93.0 (83.8) | 86.4 (77.9) | 91.1 (82.0) | 84.6 (76.0) | 96.3 (87.1) | 89.1 (80.6) | 96.2 (86.9) | 88.7 (80.1) | 93.7 (84.7) | 86.6 (78.2) | 97.4 (88.1) | 89.9 (81.5) | 96.5 (87.5) | 88.5 (80.5) | 95.8 (87.1) | 82.6 (75.8) | 96.2 (87.1) | 83.6 (75.8) |
| Dipole | 5.88 | 1.38 | 5.84 | 1.69 | 6.50 | 2.85 | 7.72 | 4.11 | 5.39 | 1.73 | 6.48 | 2.92 | 7.63 | 3.81 | 11.22 | 5.33 | 6.99 | 3.94 |
| r N1N2 | 1.392 | 1.385 | 1.394 | 1.387 | 1.393 | 1.387 | 1.393 | 1.387 | 1.391 | 1.386 | 1.391 | 1.386 | 1.390 | 1.386 | 1.393 | 1.387 | 1.391 | 1.385 |
| r N2C3 | 1.304 | 1.318 | 1.305 | 1.318 | 1.305 | 1.318 | 1.305 | 1.318 | 1.305 | 1.318 | 1.305 | 1.318 | 1.305 | 1.318 | 1.304 | 1.317 | 1.304 | 1.317 |
| r C3C4 | 1.446 | 1.433 | 1.446 | 1.435 | 1.447 | 1.435 | 1.446 | 1.435 | 1.447 | 1.436 | 1.447 | 1.435 | 1.447 | 1.435 | 1.448 | 1.435 | 1.449 | 1.436 |
| r C4C5 | 1.460 | 1.403 | 1.460 | 1.404 | 1.461 | 1.405 | 1.460 | 1.405 | 1.460 | 1.407 | 1.460 | 1.407 | 1.461 | 1.407 | 1.464 | 1.406 | 1.464 | 1.407 |
| r C4C7 | 1.392 | 1.447 | 1.391 | 1.446 | 1.394 | 1.447 | 1.394 | 1.447 | 1.395 | 1.447 | 1.397 | 1.449 | 1.397 | 1.448 | 1.390 | 1.445 | 1.392 | 1.447 |
| r C5O6 | 1.244 | 1.321 | 1.245 | 1.322 | 1.245 | 1.320 | 1.245 | 1.319 | 1.247 | 1.318 | 1.246 | 1.317 | 1.245 | 1.315 | 1.243 | 1.319 | 1.244 | 1.317 |
| r C5N1 | 1.385 | 1.354 | 1.384 | 1.353 | 1.384 | 1.354 | 1.385 | 1.355 | 1.383 | 1.354 | 1.385 | 1.355 | 1.385 | 1.356 | 1.382 | 1.353 | 1.383 | 1.354 |
| r C7N8 | 1.350 | 1.304 | 1.350 | 1.305 | 1.348 | 1.303 | 1.347 | 1.305 | 1.350 | 1.307 | 1.348 | 1.305 | 1.348 | 1.306 | 1.353 | 1.305 | 1.352 | 1.304 |
| r O6H | — | 1.019 | — | 1.016 | — | 1.021 | — | 1.026 | — | 1.030 | — | 1.033 | — | 1.039 | — | 1.020 | — | 1.025 |
| r N8H | 1.031 | — | 1.033 | — | 1.032 | — | 1.032 | — | 1.034 | — | 1.033 | — | 1.032 | — | 1.033 | — | 1.035 | — |
| δ, Calcc | 11.90 | 14.17 | 12.09 | 14.02 | 12.46 | 14.47 | 12.53 | 14.89 | 12.13 | 15.21 | 12.36 | 15.38 | 12.26 | 15.65 | 12.82 | 14.35 | 12.69 | 14.62 |
| δ, Exptd | 12.59 | 12.13 | 12.81 | 12.89 | 12.58 | 12.75 | 12.85 | 12.79 | 13.22 | |||||||||
a
Calculated in the gas phase at the B3LYP/6-311++G(d,p) level. ΔE, IPV, and BDE in kcal mol−1, dipole moment in Debye, and r in Å. ΔE is the difference in energy between a given isomer and the amine-one tautomer. For parameters of the imine-one(I, II) tautomeric forms see ESI Table S1 and for properties calculated in chloroform, DMSO, and water for the amine-one and imine-ol forms see ESI Tables S2, S3 and S4, respectively.
b
ΔE and BDE corrected for ZPE are reported in brackets.
c
Calculated chemical shifts (in ppm) for H at O6 (imine-ol) and N8 (amine-one).
d
Data from ref. 21.