Fig. 2: Cage escape quantum yields and excited-state quenching kinetics.
From: Cage escape governs photoredox reaction rates and quantum yields
a, Transient absorption decays of the reference complex [Ru(bpy)3]2+ (12 µM in aerated H2O) at 455 nm and the [Ru(bpz)3]2+ (12 µM)–TAA-OMe (2 mM) pair in aerated CH3CN at 293 K at 717 nm under 422 nm excitation. Both solutions have identical absorbance at 422 nm (Supplementary Fig. 55a). The concentrations of the 3MLCT-excited [Ru(bpy)3]2+ and TAA-OMe·+ formed in this experiment were 3.14 and 1.82 ± 0.06 μM, respectively. b, Transient absorption decays of the reference complex [Ru(bpy)3]2+ (12 µM in aerated H2O) at 455 nm and the [Cr(dqp)2]3+ (30 µM)–TAA-OMe (2 mM) pair in aerated CH3CN at 293 K at 717 nm under 416 nm excitation. Both solutions have identical absorbance at 416 nm (Supplementary Fig. 56a). The concentrations of the 3MLCT-excited [Ru(bpy)3]2+ and TAA-OMe·+ were 1.56 and 0.20 ± 0.02 μM, respectively. In a and b, the relative concentrations of the photoproducts were derived from the measured ΔOD values at 455 nm for the reference (3MLCT-excited [Ru(bpy)3]2+) and at 717 nm for the donor–acceptor pairs (TAA-OMe·+), as well as the respective Δε values at the relevant observation wavelengths (Δε455 = −10,100 M−1 cm−1 for [Ru(bpy)3]2+ (ref. 33) and Δε717 = 32,600 ± 300 M−1 cm−1 for TAA-OMe·+). This analysis yielded ФCE values of 58 ± 2% for the [Ru(bpz)3]2+–TAA-OMe pair and 13 ± 1% for the [Cr(dqp)2]3+–TAA-OMe pair in CH3CN at room temperature, as marked by the dashed horizontal lines. c, Quenching rate constants (kq) for photoinduced electron transfer from the individual donors 1–12 to [Ru(bpz)3]2+ and [Cr(dqp)2]3+ plotted as a function of the reaction free energy (ΔGET). The halide-substituted donors are marked by the ellipsoids. d, Cage escape quantum yields (ФCE) obtained with [Ru(bpz)3]2+ and [Cr(dqp)2]3+ for the electron donors 1–12.
