Table 3.
Fluorescence properties of 1 in selected solvents: peak fluorescence emission wavelengths upon excitation at the enol, λemi,enol, and diketo, λemi,diketo, absorption peak; peak fluorescence excitation wavelengths with fluorescence recording at the enol emission peak, λexc,enol, and at 350 nm, λexc,diketo; fluorescence quantum yield of the enol tautomers, Φfluo,enol.
| Solvent | λemi,enol (nm) | λemi,diketo (nm) † | λexc,enol (nm) | λexc,diketo (nm) | Φfluo,enol |
|---|---|---|---|---|---|
| DCM | 426 | 403 | 326 (398) | 315 | 0.06 |
| DMF | 424 | 405 | 400 (325) | 280 (309) | 0.08 |
| DMSO | 428 | 403 | 400, 408 (322) | 293, 304 | 0.12 |
| EtOH | 447 | 413 | 401 (325) | 292 | 0.20 |
† reconstructed by subtraction of the out-of-peak excited fluorescence of the enol tautomers, see text for detailed procedure.