Table 2.
Irradiation wavelengths of the (E) isomers and photostationary state compositions for azothiophenes 4 a–l. For (Z)→(E) isomerization, all samples were irradiated at 305 nm.
|
Entry |
Compound |
(E)→(Z) irradiation wavelength [nm] |
(E)→(Z) PSS composition[a] [%] |
(Z)→(E) PSS composition[a] [%] |
||
|---|---|---|---|---|---|---|
|
|
|
|
(E) |
(Z) |
(E) |
(Z) |
|
1 |
4 b |
365 |
1 |
99 |
51 |
49 |
|
2 |
4 c |
385 |
6 |
94 |
64 |
36 |
|
3 |
4 d |
365 |
3 |
97 |
63 |
37 |
|
4 |
4 e |
365 |
2 |
98 |
59 |
41 |
|
5 |
4 f |
365 |
3 |
97 |
51 |
59 |
|
6 |
4 g |
365 |
<1 |
>99 |
57 |
43 |
|
7 |
4 h[ b] |
405 |
– |
– |
– |
– |
|
8 |
4 i [b] |
405 |
– |
– |
– |
– |
|
9 |
4 j |
385 |
5 |
95 |
59 |
41 |
|
10 |
4 k |
365 |
4 |
96 |
50 |
50 |
[a] Determined by HPLC at the corresponding isosbestic points of the spectra. [b] (Z) isomers could not be determined by HPLC analysis; the OMe‐substitution increases the overall basicity of these compounds facilitating the protonation by residual silanol groups of the column material leading to back‐switching.