A review on the recent advances of six classes of organic photocatalysts with respect to photophysical and redox properties.

In this report, the synthesis and characterization of two bis-cyclometalated iridium(III) complexes are presented. Singlecrystal X-ray diffraction shows that [Ir(ppy) 2 (4,4′-bis-(diethylphosphonomethyl)-2,2′-bipyridine)]PF 6 adopts a pseudooctahedral geometry. The complexes have an absorption feature in the near-visible−UV region and emit green light with excited-state lifetimes in hundreds of nanoseconds. The redox properties of these complexes show reversible behavior for both oxidative and reductive events. [Ir(ppy) 2 (4,4′-bis(phosphonomethyl)-2,2′-bipyridine)]PF 6 readily binds to metal oxide supports, like nanostructured Sn IV -doped In 2 O 3 and TiO 2 , while still retaining reversible redox chemistry. When incorporated as the photoanode in dye-sensitized solar cells, the devices exhibit open-circuit voltages of >1 V, which is a testament to their strength of these iridium(III) complexes as photochemical oxidants.

In order to design a series of photoredox compounds with a broad range of reactivity, eosin Y, a xanthene derivative, was chosen as a precursor to synthesize a new series of organic photocatalysts. The synthesis and characterization of these four new organic photocatalysts was undertaken. Redox potentials of this series of photocatalysts varied by 110 mV, which shows that these catalysts can be tuned for specific reactions. The measured fluorescence quantum yields ranged from 0.33 to 0.65 which outperform most transition metal photocatalysts. The excited state lifetimes (ns) of the new photocatalysts are comparable to those of the parent complex, but the λ max value for absorption was red-shifted into the green light region of the solar spectrum. Despite the absorbance shift to lower energy wavelengths, the new photocatalysts were more potent reductants compared to the parent complex and were able to undergo oxidative quenching and promote the photocatalytic enol arylation reaction.

Unprecedented one-step C=C bond cleavage leading to opening of the π-bowl, that could provide access to carbon-rich structures with previously inaccessible topologies, is reported; highlighting the possibility to implement drastically...