Photophysics and halide quenching of a cationic metalloporphyrin in water

In this work, the steady state S 0 –S 1 and S 0 –S 2 absorption and emission behaviour of the water-soluble tetrakis( N -methyl-4-pyridyl)porphyrin zinc( ii ) tetrachloride (ZnTMPyP) in media of constant and high ionic strength, both with and without iodide ions as a fluorescence quencher, was measu...

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Veröffentlicht in:Photochemical & photobiological sciences 2013-06, Vol.12 (6), p.1079-1085
Hauptverfasser: Ponce, Concepcion P., Steer, Ronald P., Paige, Matthew F.
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Sprache:eng
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Zusammenfassung:In this work, the steady state S 0 –S 1 and S 0 –S 2 absorption and emission behaviour of the water-soluble tetrakis( N -methyl-4-pyridyl)porphyrin zinc( ii ) tetrachloride (ZnTMPyP) in media of constant and high ionic strength, both with and without iodide ions as a fluorescence quencher, was measured. The quenching of the ZnTMPyP S 1 state by iodide ions proceeds primarily through diffusion-limited interaction in an encounter pair but the formation of a loose association between the ZnTMPyP S 1 state and iodide ions also provides a minor quenching pathway. The ZnTMPyP S 2 state was quenched minimally by iodide, likely through an electron transfer mechanism at an average donor–acceptor distance of ~0.7 nm. The results presented here highlight the notion that significant iodide quenching of the ZnTMPyP S 1 state can be a source of inefficiencies in porphyrin-based dye-sensitized solar cells. The minimal quenching of the S 2 state indicates that no significant loss of efficiency will be introduced by using iodide as component of the electrolyte system in upconversion by triplet–triplet annihilation (UC-TTA) enhanced solar cells.
ISSN:1474-905X
1474-9092
DOI:10.1039/c3pp50022e