Table 2. Photophysical data of 1a–6a, 1b–4b and L1–L4 a .
| UV/Vis absorption, λ max/nm (103 ε/M–1 cm–1) | Emission |
|||||||
| Medium | λ F/nm | λ Ph/nm | τ PF b /ns | τ DF c /μs | τ phos/μs | Φ em d | ||
| 1a | 265 (14.1), 275 (14.6), 305 (9.3), 311 (9.8), 319 (12.4), 379 (6.9) | CH2Cl2 298 K | 467 | — | 12.0 | 11.9 | — | 0.91 |
| Glassy 77 K | 442 | 630, 688 e | n.d. f | 109 e | ||||
| Solid 298 K | 504 | — | 5.3 | — | ||||
| Solid 77 K | 492 | — | 11.6 | — | ||||
| 2a | 271 (13.9), 316 (3.2), 331 (3.2), 410 (40.0), 423 (3.7, br) | CH2Cl2 298 K | 466 | 596, 652 e | 2.7 | 4.6 | n.d. f | 0.70 |
| 11.8 g | 13.6 g | |||||||
| Glassy 77 K | 460, 481 | 596, 653 e | 243 e | 203 e | ||||
| Solid 298 K | 405 (weak), 480 (sh), 515 (max) | 598, 652 (sh) e | 15.0 e | 24.6 e | ||||
| Solid 77 K | 409 (weak), 487 (max), 517 (sh) | 597, 654(sh) e | 9.4 e | 12.0 e | ||||
| 3a | 283 (12.2), 333 (5.6), 350 (11.3), 380 (23.8), 397 (25.5) | CH2Cl2 298 K | 441 | 613, 670 e | 2.8 | 2.6, 12.5 | n.d. f | 0.78 |
| 31.5 g | 61.9 g | |||||||
| Glassy 77 K | 418, 439, 462 (sh) | 569, 609, 666 e | n.d. f | 530 e | ||||
| Solid 298 K | 403 (sh), 503 | 610, 668 e | 29.1 | 64.9 e | ||||
| Solid 77 K | 404 (sh), 504 | 627, 680 e | 35.1 | 92.3 e | ||||
| 4a | 280 (13.5), 325 (4.5), 412 (10.1), 553 (40.2) | CH2Cl2 298 K | 593 | — | 0.8 | — | — | 0.04 |
| 5a | 266 (18.6), 279 (15.8), 294 (12.5), 305 (11.2), 311 (10.1), 319 (12.7), 371 (7.1) | CH2Cl2 298 K | 456 | — | 11.0 | 6.8 | — | 0.90 |
| 6a | 259 (18.3), 280 (17.5), 298 (7.8), 305 (10.7), 311 (11.4), 319 (14.2), 383 (8.3) | CH2Cl2 298 K | 476 | — | 14.0 | 7.4 | — | 0.84 |
| 1b | 283 (20.4), 310 (24.1), 318 (26.8), 369 (13.0), 381 (13.8) | CH2Cl2 298 K | 461 h | 630, 671 (sh) | 13.8 h | — | 104 | 0.003 i |
| Glassy 77 K | 610, 668 | n.d. f | ||||||
| 2b | 312 (13.9), 406 (35.9, br), 432 (40.7) | CH2Cl2 298 K | 473 h | 592, 642 (sh) | 9.0 h | — | 124 | 0.01 i |
| Glassy 77 K | 585, 605, 643 | 1200 | ||||||
| Solid 298 K | 530, 601, 660 | 1.4 | ||||||
| 3b | 312 (12.7), 325 (11.9), 379 (26.6), 395 (29.5) | CH2Cl2 298 K | 459 h | 603, 659 (sh) | 5.2 h | — | 205 | 0.04 i |
| Glassy 77 K | 598, 614 (sh), 652 | 2200 | ||||||
| 4b | 312 (12.1), 320 (12.0), 366 (7.6), 384 (9.6), 401 (10.7), 515 (24.0, br), 546 (41.7) | CH2Cl2 298 K | 583 | — | 2.1 | — | — | 0.13 |
| L1 | 303 (8.7), 309 (9.7), 316 (11.9), 341 (4.1) | CH2Cl2 298 K | 412 | — | 1.0 | — | — | 0.07 |
| L2 | 260 (15.9), 326 (4.7), 405 (24.0, br), 417 (24.7) | CH2Cl2 298 K | 455 | — | 3.6 | — | — | 0.94 |
| L3 | 333 (14.6), 350 (22.4), 367 (20.6) | CH2Cl2 298 K | 378, 398, 419 (sh) | — | 0.5 | — | — | 0.11 |
| L4 | 321 (3.9, br), 376 (5.3, br), 486 (14.8, sh), 517 (45.4) | CH2Cl2 298 K | 533 | — | 6.4 | — | — | 0.83 |
a Data were obtained from steady-state measurements with degassed CH2Cl2 solutions (2 × 10–5 M) unless specified. Measurements with glassy solutions were performed in EtOH/MeOH (4 : 1) mixture at 77 K.
b Emission lifetimes of prompt fluorescence (τ PF) were determined by time-correlated single photon counting (TCSPC) measurement.
c Emission lifetimes of delayed fluorescence (τ DF) were obtained from fitting the decay of the time-resolved emission (TRE) as a mono-exponential decay in the delay time range of 0–40 ns and 1–46 μs, respectively. Measurements were performed in degassed CH2Cl2 (5 × 10–5 M) solutions.
d Emission quantum yields (Φ em) were obtained using quinine sulfate in degassed 0.5 M H2SO4 (Φ = 0.546) as the standard unless specified. Φ em measured in steady state is the overall emission quantum yield, i.e. Φ em = Φ PF + Φ DF for 1a–3a and 5a–6a.
e Obtained from time-resolved emission spectra.
f Emission lifetime was not determined (n.d.) due to weak emission signal.
g Determined from time-resolved emission spectra in degassed CH2Cl2 (1 × 10–5 M) solutions.
h Determined from fs-TRF spectra.
i Emission quantum yields (Φ em) were obtained using [Ru(bpy)3][PF6]2 in degassed acetonitrile as the standard (Φ = 0.062).