| ¹H NMR (400 MHz, D₂O) |
δ = 8.13 (d, J = 7.2 Hz, 3H), 8.06 (d, J = 8.3 Hz, 3H), 7.80 (td, J = 7.9, 1.6 Hz, 3H), 7.57 (d, J = 5.6 Hz, 3H), 7.03 (t, J = 6.6 Hz, 3H), 6.53 (d, J = 11.7 Hz, 3H) |
| UV–vis absorption in Ar-saturated water |
Absorption up to ~470 nm |
| Room-temperature phosphorescence |
Emission maximum: 493 nm; triplet energy: 2.76 eV, determined from the high-energy edge where the emission intensity was 10 % of the emission maximum |
| Emission lifetime in Ar-saturated water |
2.1 µs at room temperature; independent of pH; 1.7 µs at 60 °C |
| Emission lifetime in air-saturated water |
547 ns; addition of 0.1 M Na₂SO₃ drastically elongated the lifetime, almost restoring the value obtained under Ar saturation |
| Emission lifetime under hydrogen-generation conditions |
2.1 µs before irradiation; 330 ns after 3 h of irradiation |
| Transient absorption of the ³MLCT state |
Broad absorption band between 400 and 550 nm |
| Two-pump transient absorption (405 and 515 nm, 10 ns inter-pulse delay) |
A new signal was assigned to hydrated electrons and oxidized IrFsppy; it remained largely constant up to 4 ns, with an early decay of ~210 ps to about 80 % of the initial value |
| Two-pump transient absorption, second-pump wavelength dependence (343 nm first pump, 450–1000 nm second pump, 10 ns separation) |
Wavelengths from 600 to 1000 nm did not trigger hydrated-electron formation; below ~600 nm the hydrated-electron signal increased rapidly and peaked at ~485 nm before decreasing |
| Photoionization quantum yield initiated by the green laser pulse |
4.5 % |
| Hydrated-electron lifetime (35 µM IrFsppy, 0.15 M NaH₂PO₄, strongly alkaline solution, pH ~12) |
2.3 µs in the absence of protons |
| Hydrated-electron quenching by protons, Stern–Volmer rate constant |
kq = 1.8 × 10¹⁰ M⁻¹ s⁻¹ |
| Transient absorption of oxidized IrFsppy |
Pronounced ground-state bleach in the UVA region and a broad absorption band centered at 600 nm; the spectrum agreed with the spectroelectrochemical spectrum of one-electron-oxidized IrFsppy |
| Cyclic voltammetry (aqueous 0.1 M Na₂HPO₄/NaH₂PO₄, pH 7, 0.5 V s⁻¹, Ar, 22 °C), oxidation potential |
E₁/₂ = 0.89 V vs. SCE |
| Transient absorption with Na₂SO₃ (0.1 M, pH 4.7) |
The whole oxidized-IrFsppy spectrum returned to baseline within 75 µs |
| Regeneration by Na₂SO₃ at pH 4.7, apparent rate constant |
1.6 × 10⁶ M⁻¹ s⁻¹ |
| Regeneration by SO₃²⁻ at pH 4.7, estimated rate constant |
5.0 × 10⁸ M⁻¹ s⁻¹, assuming HSO₃⁻ is inactive |
| UV–vis, emission, transient-absorption, spectroelectrochemical, cyclic-voltammetry and ¹H NMR spectra |
Image data were not transcribed |