Table 1.
Computational studies on solvents on ITI photo-isomerization
| Z-isomer | |||||
|---|---|---|---|---|---|
| Solvent (εr) | λmax,Z (nm) | Transition | |||
| exp. | calc. | ππ*/nπ* | θ1(C1-C2-N4-C5)/θ2(C2-N4-C5-C6) | ΔμES-GS,Z(D) | |
| Cyclohexane (2.02) | 416 | 373 |
S0→S2 0.61/0.18 |
179.8/49.8 | 1.77 |
| Toluene (2.37) | 430 | 374 |
S0→S2 0.61/0.20 |
179.8/50.2 | 1.86 |
| CHCl3 (4.71) | 435 | 378 |
S0→S2 0.61/0.20 |
180.0/51.4 | 2.26 |
| MeOH (32.61) | 429 | 398 |
S0→S1 0.58/0.34 |
−179.8/54.1 | 1.55 |
| DMSO (46.83) | 432 | 379 |
S0→S2 0.61/0.24 |
180.0/54.1 | 2.82 |
| E-isomer | |||||
|---|---|---|---|---|---|
| Solvent (εr) | λmax,E (nm) | Transition | |||
| exp. | calc. | ππ*/nπ* | θ1(C1-C2-N4-C5)/θ2(C2-N4-C5-C6) | ΔμES-GS,E(D) | |
| Cyclohexane (2.02) | 517, 554 | 520 |
S0→S1 0.55/0.31 |
9.5/60.6 | −2.85 |
| Toluene (2.37) | 510, 551 | 519 |
S0→S1 0.55/0.31 |
9.5/61.7 | −2.96 |
| CHCl3 (4.71) | 506, 549, | 513 |
S0→S1 0.55/0.31 |
9.3/62.9 | −3.48 |
| MeOH (32.61) | 515, 552 | 505 |
S0→S1 0.54/0.30 |
9.3/66.0 | −4.17 |
| DMSO (46.83) | 514, 553 | 503 |
S0→S1 0.55/0.31 |
9.0/66.9 | −4.05 |
| Transition state | |||||||
|---|---|---|---|---|---|---|---|
| Solvent (εr) | Δλmax (nm) | t1/2 (ms) | (kcal/mol) | ||||
| exp. | calc. | exp. | exp. | calc. | θ1(C1-C2-N4-C5)/θ2(C2-N4-C5-C6) | μGS,TS(D) | |
| Gas phase (1.00) | – | – | – | – | NA (13.2) | NA (0.0/0.0) | NA (1.20) |
| Cyclohexane (2.02) | 101, 138 | 147 | 9.5 ± 0.4 | 14.1 | 12.8 (12.8) | 0.0/90.4 (−0.1/0.1) | 3.85 (1.30) |
| Toluene (2.37) | 80, 121 | 145 | 12.4 ± 0.9 | 14.2 | 12.7 (12.9) | 0.0/90.4 (−0.1/0.1) | 3.97 (1.33) |
| CHCl3 (4.71) | 71, 114 | 135 | 16.9 ± 1.2 | 14.4 | 13.3 (13.7) | 0.0/90.4 (−0.1/0.1) | 4.44 (1.52) |
| MeOH (32.61) | 86, 123 | 107 | 18.5 ± 1.4 | 14.4 | 14.4 (NA) | 0.0/87.5 (NA) | 5.25 (NA) |
| DMSO (46.83) | 82, 121 | 124 | 23.3 ± 2.0 | 14.6 | 13.5 (NA) | 0.0/90.2 (NA) | 4.92 (NA) |
Solvatochromic shifts of λmax for the Z (Top) and E (Middle) isomers of ITI 1a. Experimental λmax,E values are obtained from TA that show two absorption maxima which are both reported and the maximum, of which the one with the highest absorption is highlighted in bold. Theoretical λmax values and the difference of GS and ES dipole moments (ΔμES-GS) were obtained at the SMD-TD-M06-2X/6-311++G(2df,2p) level using the SMD-M06-2X/6-31+G(d) geometries, from which also twisting angles θ1 and θ2 were derived (see Fig. 2a). Bottom: Thermal relaxation of ITI 1a. Experimental half-lives were calculated from ms TA. The GS dipole moments for the transition state (μGS,TS) were obtained at the SMD-M06-2X/6-31+G(d) level, at which also the twisting angles θ1 and θ2 as well as the activation barriers for thermal relaxation were derived (see Fig. 2a). The data in parentheses refer to a planar TS structure