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Photochemistry and Photophysics of Coordination Compounds

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196 S. Campagna et al.<br />

gave the predicted increase <strong>of</strong> Voc <strong>of</strong> 200 mV, which was in agreement<br />

with the obtained value (180 mV) [422]. It is interesting that an increase<br />

<strong>of</strong> the lifetime <strong>of</strong> the interfacial charge-separated state TiO2(e – )–Ru(II)–<br />

PTZ + has a direct influence on the overall efficiency <strong>of</strong> the cell. A similar<br />

approach inspired the design <strong>of</strong> the supramolecular species 74, basedon<br />

the “red dye” N3 sensitizer. Optical excitation <strong>of</strong> a nanocrystalline TiO2<br />

film dye coated with such a species showed a long-lived charge-separated<br />

state [423].<br />

8<br />

Miscellanea<br />

The fields that have been recently powered by Ru photochemistry are much<br />

more than those reported in some detail in this article. A few <strong>of</strong> those that are<br />

not discussed above will be briefly mentioned.<br />

Ru(II)-based chromophores have been linked to a plethora <strong>of</strong> receptor<br />

species, like calixarenes, crowns, <strong>and</strong> azacrowns, essentially for sensing<br />

purposes [280, 424, 425]. Ru(II) chromophores have also been embedded in<br />

oxygen-permeating polymers to yield luminescent sensors for molecular oxygen<br />

determination in atmosphere [426–429]. New systems have been designed<br />

<strong>and</strong> studied for obtaining OLED materials. In this regard, a dinuclear<br />

Ru complex has been used in conjunction with an organic luminophore to<br />

generate two-color electroluminescence [430].<br />

Multichromophoric species made <strong>of</strong> Ru(II) chromophores interfaced with<br />

organic aromatics having suitable triplet-state levels have been studied to extend<br />

the lifetime <strong>of</strong> the MLCT excited state by a sort <strong>of</strong> delayed luminescence<br />

involving intercomponent energy transfer, with the organic triplet states used<br />

as excited-state energy storage systems [431–440, 442]. A few such species are<br />

compounds 75 (which is the first reported example <strong>of</strong> such a behavior [431]),<br />

76 [437], <strong>and</strong> 77 [435]. Compound 77 is one <strong>of</strong> the species featuring the most<br />

outst<strong>and</strong>ing behavior: its emission in fluid solution at room temperature<br />

(with maximum at about 600 nm) has lifetimes ranging from 43 µs (acetone<br />

solution) to 61 µs (acetonitrile)to115 µs (DMSO solution) [435]. With<br />

the aim <strong>of</strong> increasing the excited-state lifetime as well as the luminescence

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