Table 1.
Computed C–C bond length difference (Δr), and relative free energies (ΔGrel) between the C2h and D2h structures of TtB-s-indacene at the B3LYP, M06–2X, ωB97X-D, and M11/6–311+G(d,p) levels.
| Level | HF[a] (%) |
PG[b] | Δr[c] (Å) |
ΔErel (kcal/mol) |
δ H8[d] (ppm) |
δ H2[d] (ppm) |
|---|---|---|---|---|---|---|
| B3LYP | 20 |
C
2h
D 2h |
– 0 |
– 0.00 |
– 6.20 |
– 4.60 |
| M06–2X | 54 |
C
2h
D 2h |
0.066 0 |
0.00 0.30 |
6.62 6.32 |
4.97 4.60 |
| ωB97X-D | SR:22 LR:100 ω:0.20 |
C
2h
D 2h |
0.069 0 |
0.00 0.57 |
6.59 6.26 |
4.93 4.53 |
| M11 | SR:42.8 LR:100 ω:0.25 |
C
2h
D 2h |
0.086 0 |
0.00 1.80 |
6.81 6.40 |
5.20 4.67 |
| X-ray[e] | – | D 2h | 0.001 | – | 6.61 | 4.70 |
[a]
Short range (SR) and long range (LR) percentages of HF exchange.
[b]
Point Group.
[c]
Δr is the difference between the two C–C bond lengths of the central six-membered ring connected to C4/C8.
[d]
Proton chemical shifts were computed at B97–2/6–311+G(d,p) using the computed chemical shielding for hydrogen in benzene as a reference.
[e]
Based on X-ray crystal structure at 100 K (reference [4]). All ring C–C bonds and the four C–Ct-butyl bonds were fixed to reported X-ray data, all other parameters were optimized at M11/6–311+G(d,p).