Studies of redox potentials and reactions with molecular oxygen of a series of 4Fe-4s complexes attached to a 36-membered macrocycle show that all three electron transfer processes, 1 -/2-, 2-/3-, and 3-/4-, are reversible for the cyclic aryl-substituted clusters, and that half-wave potentials for alkyl derivatives with hydrophobic macrocycles showed largely positive shifts of the 1 -/2-couples as given in high-potential iron-sulphur proteins as well as a stabilising effect of the cores towards molecular oxygen.

Catalytic formation of oxygen from water was observed in the photosensitized reaction by trisbipyridineruthenium(II) using manganese dioxide as a redox catalyst and pentaammine chlorocobalt(III) as an electron acceptor in acidic solution. The β- and “activated” materials are found to be the most efficient and specific redox catalysts, and a 230% of O2 yield based on MnO2 is obtained.

Cyclodextrin inclusion complexes of viologens with hydrophobic tails increased the stability of the pyridinium moiety of the viologen to hydrogenation, which resulted in up to five times higher efficiency in terms of hydrogen produced per viologen consumed.

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