Table 1. Important Photophysical Parameters of 1a, 1b, and 1c.
| compound | solvent/host | S1 (eV)a | T1 (eV)b | ΔEST (eV)f | PF lifetime (ns)c | DF lifetime (μs)c | kf (×107 s–1)d | kISC (×106 s–1)d | krISC (×105 s–1)d |
|---|---|---|---|---|---|---|---|---|---|
| 1a | DCM | 2.68 | –0.13 | 21 | 3.6 | 2.6 | 16 | 4.5 | |
| o-DCB | 2.75 | –0.06 | 23 | 2.0 | 3.72 | 4.0 | 5.4 | ||
| Zeonex | 3.00 | 2.81 | 0.19 | 6.0 | 3.3 × 103e | ||||
| neat | 3.11 | 0.30 | 7.0 | 1.6 and 62e | |||||
| 1b | DCM | 2.65 | –0.13 | 24 | 5.0 | 2.0 | 21 | 4.3 | |
| o-DCB | 2.75 | –0.03 | 23 | 3.4 | 3.3 | 5.2 | 2.9 | ||
| Zeonex | 2.98 | 2.78 | 0.20 | 7.3 | 2.4 × 103e | ||||
| neat | 3.10 | 0.32 | 11 | 19 and 83e | |||||
| 1c | DCM | 2.85 | 0.02 | 21 | 15 | 4.0 | 1.0 | 0.6 | |
| o-DCB | 2.95 | 0.12 | 17 | 5.8 | 4.9 | 1.2 | 1.4 | ||
| Zeonex | 3.13 | 2.83 | 0.30 | 4.4 | 12 × 103e | ||||
| neat | 3.05 | 0.22 | 7.3 | 3.5 and 197e |
a
Determined from photoluminescence onset in different host/film environments.
b
Determined from phosphorescence onset in Zeonex (80 K, 10 ms delay after pulsed excitation).
c
Determined from amplitude weighted averages of double exponential fit components or individual component lifetimes for highly nonexponential neat film decays (fits in the SI, Figures S49–S57).
d
Determined from kinetic fitting of PF and DF by the previously reported TADF model.49
e
DF emission included a significant room-temperature phosphorescence (RTP) component, precluding extraction of rISC rates through kinetic fitting.
f
S1 – T1, values < 0 indicate that the singlet state (CT character) lies below the phosphorescent and TADF-active triplet state (LE character) (see ref (44)).