Spectroscopic studies of formation and decay of triplet exciplexes. Evidence for a limited role of charge-transfer interactions in a nonpolar solvent

Roy, Juganta K.; Carroll, Felix A.; Whitten, David G.

doi:10.1021/ja00827a017

Cited by 53 publications

(16 citation statements)

References 4 publications

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“…The product of the quenching can be properly called an "exciplex" in both cases but it is clear that formation of the exciplex in the cases where the "redox state" lies well above the triplet in energy must involve other than exclusively charge transfer interactions. 49 Although we have observed such behavior with metalloporphyrins and a variety of acceptors, the results do not seem a property of porphyrins alone since quenching of the anthracene triplet by the same acceptors leads to similar results.~,, so…”

Section: B Electron Transfer Quenching and Exciplex Formationmentioning

confidence: 72%

Photochemistry of porphyrins and their metal complexes in solution and organized media

Whitten

1978

Reviews of Chemical Intermediates

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Section: B Electron Transfer Quenching and Exciplex Formationmentioning

confidence: 72%

Photochemistry of porphyrins and their metal complexes in solution and organized media

Whitten

1978

Reviews of Chemical Intermediates

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“…The formation of such triplet exciplexes in nonpolar solvent has been reported during the quenching of the triplet states of metalloporphryrins by various quinones in toluene. 6,7,[36][37][38][39] Thus, the formation of 3 [C 70 (dÀ) -MOEP (d+) ]* could provide a possible explanation for the near diffusion-controlled triplet quenching rate constant of 3 -MOEP (d+) ]* into the solvent-separated ionpair (SSIP) or into free ion radicals in solution. In the region of toluene-rich content (toluene > 75%), a transient triplet state absorption spectrum was observed, from which the k q values were obtained in a manner similar to that in toluene.…”

Section: Resultsmentioning

confidence: 99%

Photoinduced electron transfer between metal octaethylporphyrins and fullerenes (C60/C70) studied by laser flash photolysis: electron-mediating and hole-shifting cycles

El‐Khouly¹,

Araki²,

Fujitsuka³

et al. 2002

Phys. Chem. Chem. Phys.

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Electron transfer (ET) processes of fullerenes (C 60 /C 70 ) with metal octaethylporphyrins (MOEP) in a polar solvent have been investigated by a nanosecond laser photolysis technique in the visible/near-IR regions. By the selective excitation of C 60 /C 70 using OPO laser light it has been proved that electron transfer takes place from the ground states MOEP to the triplet excited states 3 C 60 */ 3 C 70 *. By selective excitation of MOEP the electron transfer processes via 3 MOEP* to C 60 /C 70 were also confirmed. In nonpolar toluene the lifetimes of 3 C 60 */ 3 C 70 * decreased in the presence of MOEP without evidence for electron and/or energy transfer processes. On adding benzonitrile to toluene the ion-radical formation was increased, suggesting that the triplet exciplexes 3 [MOEP (d+) -C 60 (dÀ) /C 70 (dÀ)]* would be dominant prior to the ion-pair formation in a less-polar solvent. On addition of a viologen dication the electron of the anion radicals of C 60 /C 70 transfers to the viologen dication yielding the viologen radical cation. In the system MOEP-C 60 /C 70 -aromatic amine (DTQH), as a second donor having lower oxidation potential than MOEP, the hole shift from the radical cation of MOEP to the aromatic amine was observed. These observations proved that the photosensitized electron-transfer/electron-mediating and photosensitized electron-transfer/hole-shift cycles have been confirmed by the transient absorption spectral method.

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“…Quinones are known to be effective quenchers of porphyrin triplet states, interacting by electron exchange or transfer (Pileni and Gratzel, 1980;Nahor et al, 1981;Lindsey et al, 1983) or by the formation of exciplexes (Roy et al, 1974). Barboy and Feitelson have recorded the reaction of AQS with Zn porphyrin (Barboy and Feitelson, 1986) or with Zn-PP-myoglobin (Barboy and Feitelson, 1987).…”

Section: Excited Triplet State Reaction With Quinonementioning

confidence: 99%

Reactions of excited triplet states of metal substituted myoglobin with dioxygen and quinone

Papp¹,

Vanderkooi²,

Owen³

et al. 1990

Biophysical Journal

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The triplet state absorption and phosphorescence of Zn and Pd derivatives of myoglobin were compared. Both metal derivatives exhibit long triplet state lifetimes at room temperature, but whereas the Pd derivative showed exponential decay and an isosbestic point in the transient absorption spectra, the decay of the Zn derivative was nonsingle exponential and the transient absorption spectra showed evidence of more than one excited state species. No difference was seen in triplet quenching by oxygen for either derivative, indicating that differences in the polypeptide chain between the two derivatives are not large enough to affect oxygen penetrability. Quenching was also observed by anthraquinone sulfonate. In this case, the possibility of long-range transfer by an exchange mechanism is considered.

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Spectroscopic studies of formation and decay of triplet exciplexes. Evidence for a limited role of charge-transfer interactions in a nonpolar solvent

Cited by 53 publications

References 4 publications

Photochemistry of porphyrins and their metal complexes in solution and organized media

Photochemistry of porphyrins and their metal complexes in solution and organized media

Photoinduced electron transfer between metal octaethylporphyrins and fullerenes (C60/C70) studied by laser flash photolysis: electron-mediating and hole-shifting cycles

Reactions of excited triplet states of metal substituted myoglobin with dioxygen and quinone

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