Table 1.
Selected second order donor → acceptor interaction energies (E(2) in kcal/mol) computed (B3LYP/6–311++G(d,p)) for the four conformers of the studied compounds.
| Donor →acceptor interaction | syn-syn | syn-anti | anti-syn | anti-anti |
|---|---|---|---|---|
| lpσ(S1)→ σ∗(C7 = N1) | 6.51 | 6.43 | - | - |
| lpσ(S1)→ σ∗(C7–O1) | - | - | 5.34 | 5.29 |
| lpπ(S1)→ π∗(C7 = N1) | 29.09 | 29.11 | 27.73 | 27.39 |
| lpσ(O1)→ σ∗(C7 = N1) | 4.75 | 4.77 | 4.38 | 4.40 |
| lpπ(O1)→ π∗(C7 = N1) | 33.84 | 34.05 | 32.47 | 32.70 |
| lp(N1)→ σ∗(C7–O1) | 12.80 | 13.23 | 14.05 | 14.00 |
| lpπ(O2)→ π∗(C9 = O3) | 47.86 | 48.35 | 47.72 | 48.91 |
| lpπ(O1)→ π∗(C=C) | 22.05 | 21.96 | 21.27 | 21.27 |
| lp(O3)→ σ∗(S1–C7) | 0.89 | - | - | - |