Table 1. Spectral properties of the APM-ethanethiol adduct in solvents of increasing polarity.
| Solvent | Extinction coefficient (ε) M-1·cm-1 | Excitation maximum, nm (λexc) | Emission maximum, nm (λem) | Quantum yield* (Qf) | Lifetime†, ns (τ) | Stokes shift‡, cm-1 (nm) |
|---|---|---|---|---|---|---|
| Toluene | — | 521 | 580 | 0.10 | 0.43, 1.72 a2/a1 = 0.082 | -2,986 (95) |
| Dioxane | — | 523 | 583 | 0.17 | 1.47 | -2,972 (94) |
| Ethyl acetate | 47,000 | 526 | 596 | 0.49 | 2.31 | -2,892 (94) |
| Tetrahydrofuran | — | 535 | 602 | 0.44 | 2.20 | -2,810 (92) |
| Acetone | 51,000 | 540 | 609 | 0.91 | 4.24 | -2,727 (91) |
| CH3CN | 47,000 | 553 | 614 | 0.78 | 3.53 | -2,627 (90) |
| DMSO | 48,000 | 563 | 630 | 0.45 | 2.05 | -2,546 (92) |
| EtOH | 52,000 | 565 | 621 | 0.59 | 2.14 | -2,191 (78) |
| MeOH | — | 572 | 622 | 0.34 | 1.58 | -2,152 (77) |
| H2O | — | 598 | 633 | 0.05 | 0.41, 2.01 a2/a1 = 0.67 | -1,858 (72) |
*
Fluorescence quantum yields determined relative to sulforhodamine 101 in EtOH (16).
†
a2/a1 is the amplitude ratio of decay rates for solvents with lifetimes fit by two exponentials.
‡
Stokes shift calculated as difference in average frequency, v̄em - v̄exc, with equivalent wavelength values given in parentheses.