Table 1 Properties of catalytic systems with 1 and different buffers.

Experimental conditions: 0.1 mM 1, 0.1 M buffer (1:1 HA/A or HB+/B), 0.1 M [n-Bu4N][BF4] in MeCN (~15 mM H2O), 1 atm O2. [DMF-H+], N,N′-dimethylformamidium triflate; TFAH, trifluoroacetic acid; [Lut-H+], lutidinium tetrafluoroborate; SalOH, salicylic acid; BzOH, benzoic acid; AcOH, acetic acid.

BufferpKa*E1/2 (V)ηeff (V)TOFmax (s−1)§log(TOFmax)
None−0.295
[DMF-H+]/DMF6.1−0.25*1.168.50.91
TFAH/TFA12.6−0.3490.883.20.51
[Lut-H+]/Lut14.1−0.23*0.680.07−1.17
SalOH/SalO16.7−0.5360.82121.08
BzOH/BzO21.5−0.6530.67631.80
AcOH/AcO23.5−0.6510.541702.23

*See the Supplementary Materials.

E1/2(FeIII/II) reduction potential (versus ferrocenium/ferrocene, under Ar, with 100 mM buffer).

‡From Eq. 2; ±0.02 V. §From FOWA.