Table 2.
Photophysical properties and pKa values of 6–14 and 22 in pH 7.0 PBS buffer and 1 M NaOH (given in parenthesis).
| Compound | Abs. λmax(nm) | ε (M−1 cm−1) | Fluor. λmax (nm) | Φb | pKa |
|---|---|---|---|---|---|
| 16 | 351 (384) | 24500 (22800) | 451 (482) | 0.30 (0.30) | 12.7 |
| 17 | 338 (380) | 18600 (18600) | 442 (462) | 0.01(0.03) | 12.8 |
| 18 | 324 (349) | 29800 (25700) | 455 (465) | 0.01(0.02) | 13.0 |
| 19 | 326 (358) | 29900(21300) | –a | –a | 12.9 |
| 20 | 365 (378) | 15000 (15500) | 457 (475) | 0.22(0.20) | 12.5 |
| 21 | 355 (380) | 15100 (16800) | 409 (443) | 0.03 (0.01) | 12.9 |
| 22 | 341 (363) | 19800 (23100) | 427 (452) | 0.02 (0.01) | >13.5 |
| 23 | 360 (373) | 29000 (21300) | 449 (474) | 0.25 (0.26) | 12.0 |
| 24 | 351 (373) | 17200 (19400) | 432 (454) | 0.07 (0.05) | 12.8 |
| 25 | 340 (357) | 20200 (23500) | 410 (449) | 0.02 (0.02) | >13.5 |
a
Fluorescence was not detectable for 19.
b
Quinine (Q = 0.55)15 and Anthracene (Q = 0.27)15, 16 were used as standards.