Table 1.
PSSs and energy differences (ΔG) between stable and metastable states and activation parameters (Gibbs free energy of activation (ΔG ≠), enthalpy of activation (ΔH ≠) and entropy of activation (ΔS ≠)) for THI and double bond isomerizations of macrocycles C8–22 and reference compound OMe. PSSs were determined by 1H NMR spectroscopy in toluene‐d 8 at −20 °C and are given as the amount of product formed in the indicated (photo)reactions. Energies were determined by 1H NMR spectroscopy in toluene‐d 8 (1 mM) and are reported for 20 °C in kcal mol−1. Activation parameters were determined by UV/Vis spectroscopy in octane (20 μM) and are reported for 20 °C. ΔH ≠ and ΔG ≠ are given in kcal mol−1; ΔS ≠ is given in cal K−1 mol−1.
|
|
PSS |
ΔG |
ΔG ≠ (ΔH ≠, ΔS ≠) |
|||||
|---|---|---|---|---|---|---|---|---|
|
|
(Zs→Em) |
(Es→Zm) |
(Em→Zs) |
(Em→Es) |
(Zm→Zs) |
(Em→Zs) |
(Em→Es) |
(Zm→Zs) |
|
|
|
|
|
|
|
|
|
|
|
C8 |
50±2 %[a] |
– |
≤ −2.0 |
– |
– |
18.8±0.2 (18.2, −2.16) |
– |
– |
|
C10 |
74±2 % |
– |
≤ −2.0 |
– |
– |
25.3±0.1 (26.3, 3.56) |
– |
– |
|
C12 |
81±2 % |
– |
≤ −2.0 |
– |
– |
29.0±0.1[c] (29.8, 2.22) |
– |
– |
|
C14 |
81±2 % |
– |
≤ −2.0 |
– |
– |
≥32[c,d] |
– |
– |
|
C16 |
83±2 % |
67±4 % |
– |
+0.9±0.1 |
≤ −2.0 |
– |
22.1±0.1 (14.1, −27.5) |
23.6±0.2[e] (19.9, −12.5) |
|
C18 |
80±2 % |
65±4 % |
– |
−0.5±0.1 |
≤ −2.0 |
– |
20.4±0.1 (18.1, −7.70) |
23.7±0.1 (19.9, −12.8) |
|
C20 |
81±2 % |
63±4 % |
– |
−1.0±0.1 |
≤ −2.0 |
– |
20.3±0.1 (17.3, −9.95) |
23.7±0.1 (19.3, −15.0) |
|
C22 |
80±2 % |
65±4 % |
– |
−1.4±0.1 |
≤ −2.0 |
– |
20.1±0.1 (18.6, −4.99) |
23.7±0.1 (19.5, −14.4) |
|
OMe |
78±2 %[b] |
70±4 % |
– |
≤ −2.0 |
≤ −2.0 |
– |
18.6±0.3 (15.7, −9.99) |
23.4±0.2 (19.5, −13.3) |
[a] PSS determined at −40 °C. [b] PSS determined at −46 °C. [c] Energy given at 110 °C. [d] Energy estimated from a single relaxation at 110 °C. [e] Activation parameters determined by NMR spectroscopy in toluene‐d 8.