Rate constants (k) and efficiencies (η) for the individual elementary processes illustrated in Fig. 2; abbreviations as defined in the text. All values for de-aerated DMF at 20 °C.

Step no.	Description of step	k/M−1 s−1	η a
1	TTET from fac-[Ir(ppy)3] to tBuPy	2.1 × 109	0.91
1b	Reductive quenching of fac-[Ir(ppy)3] by DMA	1.1 × 104	0.003
1c	Oxidative quenching of fac-[Ir(ppy)3] by substrate 1	9.8 × 105	0.05
2	TTA-UC of tBuPy	1.1 × 1010	0.99b
2b	Reductive quenching of 3*tBuPy by DMA	<1.0 × 103	<0.05
3	Reductive quenching of 1*tBuPy by DMA	4.8 × 109	0.99
3b	Oxidative quenching of 1*tBuPy by substrate 1	6.4 × 107	0.31
4	Electron transfer from tBuPy˙− to substrate 1	1.1 × 109	0.99

^aEfficiencies estimated based on the initial concentrations of fac-[Ir(ppy)₃], ^tBuPy, DMA and substrate 1 in the photocatalytic reactions of Section 2.6.

^bA concentration of 0.027 mM is assumed for ^3*tBuPy on the basis of 10% photoexcited fac-[Ir(ppy)₃] and TTET with 90% efficiency. Further details are given in Section 2.11 of the ESI.