Cobalt redox mediators donate directly to PSI in vitro. The initial results assessing the ability of these cobalt complexes to directly donate to photo-oxidized P700⁺ PSI was assessed over a timescale of 2.5 s. When no donor was present, no recovery of photo-oxidation was seen and a long-lived P700⁺ PSI signal was seen. All complexes were present at 10 mM concentration.

	Di-methoxy ClO4 Co#1	Di-methoxy PF6 Co#2	Di-tert-butyl ClO4 Co#3	Di-tert-butyl PF6 Co#4
k obs (s−1)	0.014	0.028	4.0 × 10−5	4.6 × 10−5