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Metalloporphyrins, metallophthalocyanines, and analogs are known to act as efficient catalysts for the reduction of dioxygen in the presence of an acid in solution. Whether dioxygen is reduced to hydrogen peroxide (H2O2: two-electron reduced species of O2) or water (H2O: four-electron reduced species of O2) is changed depending on metals and ligands. This mini-review focuses on the catalytic production of hydrogen peroxide by a combination of 2e−O2 reduction and 2e−or 4e− H2O oxidation with the use of metalloporphyrins and metallophthalocyanines as photocatalysts. H2O2generated by the photocatalytic H2O oxidation with O2 can be used as a fuel in hydrogen peroxide fuel cells in which metalloporphyrins, metallophthalocyanines, and analogs are employed as the cathode catalysts. Metalloporphyrins are also employed as efficient electrocatalysts to exhibit significantly improved performance in a Zn-air battery that has a much higher energy density than that of lithium-ion batteries.

We report the synthesis, characterization, and electron-transfer (ET) oxidation reactivity of a chromium(V)–oxo TAML cation radical complex binding Sc3+ ion, {[CrV(O)(TAML•+)]-Sc3+}3+ (2-Sc). Its p...

Photocatalytic oxygenation of hexamethylbenzene occurs under visible-light irradiation of an O2-saturated acetonitrile solution containing a cobalt porphyrin complex CoII(TPP) (TPP2– = tetraphenylp...

The recent development of a functional model of photosystem II (PSII) has paved a new way to connect the PSII model with a functional model of photosystem I (PSI). However, PSI functional models have yet to be reported. We report herein the first potential functional model of PSI, in which plastoquinol (PQH

Photoirradiation of an acetonitrile solution containing p-benzoquinone derivatives (X-Q) as plastoquinone analogs, a nonheme iron(II) complex, [(N4Py)FeII]2+ (N4Py = N, N-bis(2-pyridylmethyl)- N-bis(2-pyridyl)methylamine), and H2O afforded the evolution of O2 and the formation of the corresponding hydroquinone derivatives (X-QH2) quantitatively. During the photodriven oxidation of water by X-Q, [(N4Py)FeII]2+ was oxidized by the excited state of X-Q to produce the iron(IV)-oxo complex ([(N4Py)FeIV(O)]2+) quantitatively. The concentration of [(N4Py)FeIV(O)]2+ remained virtually the same during the repeated cycles of photodriven oxidation of water by X-Q. [(N4Py)FeIV(O)]2+ was further oxidized by the excited state of X-Q to [(N4Py)FeV(O)]3+; this FeV-oxo species is proposed as an active oxidant that affects the water oxidation. The photocatalytic mechanism of the water oxidation by X-Q with [(N4Py)FeII]2+ was clarified by detecting intermediates using various spectroscopic techniques, such as transient absorption and electron paramagnetic resonance measurements. To the best of our knowledge, the present study reports the first example of a functional model of Photosystem II (PSII) using X-Q as plastoquinone analogs in the photocatalytic oxidation of water.