Table 2.
Spectroscopic properties of 1-3 and substituted diaza[6]helicenes 4 – 15 in acetonitrile.
| Cpd. | Substituents: positions | λabs (nm) | ε (103 M‐1 cm‐1) | λem (nm) | ϕfl (%) | τ (ns) | kR (106 s‐1)[a] | kNR (106 s‐1)[b] | |
|---|---|---|---|---|---|---|---|---|---|
| 1 | - | 562 | 15.5 | 595 | 12[c] | 9[e] | 4.0 | 30.0 | 220 |
| 2 | - | 562 | 10.7 | 614 | 22[c] | 19[e] | 6.8 | 32.3 | 115 |
| 3 | - | 614 | 14.7 | 658 | 31[c] | 20[d] | 9.8 | 31.6 | 70.4 |
| 4 | NO2: 8,10 | 560 | 18.2 | 591 | 46[c] | 50[e] | 10.9 | 42.2 | 49.5 |
| 5 | Cl: 8,10 | 630 | 14.4 | 690 | 13[c] | 8[d] | 6.1 | 31.3 | 143 |
| 6 | Br: 8,10 | 622 | 10.5 | 678 | 6.5[c] | 4[d] | 3.0 | 21.7 | 312 |
| 7 | I: 8 | 620 | 13.4 | 675 | 2.6[c] | 1.5[d] | 1.0 | 26.0 | 974 |
| 8 | Ph: 8,10 | 642 | 9.8 | 711 | 1.6[d] | 2.0 | 8.0 | 492 | |
| 9 | p-anisyl: 8,10 | 657 | 8.9 | 755 | <1[d] | 0.3[f] | 6.7 | 3330 | |
| 10 | PhC≡C: 8,10 | 650 | 8.3 | 740 | <1[d] | 0.6[f] | 5.0 | 1660 | |
| 11 | NH2: 8,10 | 731 | 1.9 | - | - | - | - | - | |
| 12 | NMe2: 8,10 | 724 | 4.6 | - | - | - | - | - | |
| 13 | CN: 5,13 | 682 | 8.2 | 731 | 1.0[d] | 0.7[f] | 14.3 | 1410 | |
| 14 | NHPr: 5 | 582 | 22.9 | 619 | 70[c] | 12.3 | 56.9 | 24.4 | |
| 15 | NHPr: 5, Br: 8,10 | 598 | 27.4 | 645 | 5.0[c] | 5.0[d] | 0.9[f] | 55.6 | 1060 |
[a]
kR=ϕ/τ.
[b]
kNR=(1- ϕ)/τ.
[c]
Relative to cresyl violet (MeOH, ϕfl = 54%).
[d]
Relative to oxazine 725 (EtOH, ϕfl = 11%).
[e]
Relative to sulforhodamine 101 (EtOH, ϕfl = 95%).
[f]
Fluorescence lifetimes measured by fluorescence upconversion technique. All the fluorescence decays were fitted as mono exponential functions. Lifetimes are given with an error of +/- 0.1 ns for the TCSPC data and +/- 0.3 ps for the upconversion data.