Abstract
Zinc-meso-tetrasulfonatophenyl-porphyrin (ZnTPPS4-) spontaneously forms a complex with methyl viologen (MV2+) in aqueous solutions. Both the free porphyrin and its complex with viologen were studied by pump-probe spectroscopy. Excitation in the porphyrin Soret band with a short laser pulse (fwhm = 200 fs) populated the upper excited-state S2, and the subsequent processes were followed by the transient absorbance changes involved. For the free ZnTPPS,4- the transient absorption spectrum of the upper excited-state S2 was different from that of the lowest excited-state S1. The S2 to S1 internal conversion could therefore be followed, and a S2 lifetime of 1.3 ± 0.2 ps was determined. In the ZnTPPS4--MV2+ complex, excitation in the Soret band produced spectral changes attributed to the charge separated state ZnTPPS3--MV+, with a rate limited by the laser pulse (rate constant >5 × 1012 s-1). This suggests that the photoinduced electron transfer from the excited porphyrin to the methyl viologen occurred directly from the S2 state of the porphyrin, before internal conversion to S1. The reverse electron transfer that followed regenerated the ground state reactants with a rate constant (1.3 ± 0.2) × 1012 s-1.
| Original language | English |
|---|---|
| Pages (from-to) | 3258-3262 |
| Number of pages | 5 |
| Journal | Journal of Physical Chemistry B |
| Volume | 103 |
| Issue number | 16 |
| Publication status | Published - 1999 |
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- Physical and Theoretical Chemistry
Cite this
Photoinduced electron transfer reactions in a porphyrin-viologen complex : Observation of S2 to S1 relaxation and electron transfer from the S2 state. / Andersson, Mikael; Davidsson, Jan; Hammarström, Leif; Korppi-Tommola, Jouko; Peltola, Timo.
In: Journal of Physical Chemistry B, Vol. 103, No. 16, 1999, p. 3258-3262.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Photoinduced electron transfer reactions in a porphyrin-viologen complex
T2 - Observation of S2 to S1 relaxation and electron transfer from the S2 state
AU - Andersson, Mikael
AU - Davidsson, Jan
AU - Hammarström, Leif
AU - Korppi-Tommola, Jouko
AU - Peltola, Timo
PY - 1999
Y1 - 1999
N2 - Zinc-meso-tetrasulfonatophenyl-porphyrin (ZnTPPS4-) spontaneously forms a complex with methyl viologen (MV2+) in aqueous solutions. Both the free porphyrin and its complex with viologen were studied by pump-probe spectroscopy. Excitation in the porphyrin Soret band with a short laser pulse (fwhm = 200 fs) populated the upper excited-state S2, and the subsequent processes were followed by the transient absorbance changes involved. For the free ZnTPPS,4- the transient absorption spectrum of the upper excited-state S2 was different from that of the lowest excited-state S1. The S2 to S1 internal conversion could therefore be followed, and a S2 lifetime of 1.3 ± 0.2 ps was determined. In the ZnTPPS4--MV2+ complex, excitation in the Soret band produced spectral changes attributed to the charge separated state ZnTPPS3--MV+, with a rate limited by the laser pulse (rate constant >5 × 1012 s-1). This suggests that the photoinduced electron transfer from the excited porphyrin to the methyl viologen occurred directly from the S2 state of the porphyrin, before internal conversion to S1. The reverse electron transfer that followed regenerated the ground state reactants with a rate constant (1.3 ± 0.2) × 1012 s-1.
AB - Zinc-meso-tetrasulfonatophenyl-porphyrin (ZnTPPS4-) spontaneously forms a complex with methyl viologen (MV2+) in aqueous solutions. Both the free porphyrin and its complex with viologen were studied by pump-probe spectroscopy. Excitation in the porphyrin Soret band with a short laser pulse (fwhm = 200 fs) populated the upper excited-state S2, and the subsequent processes were followed by the transient absorbance changes involved. For the free ZnTPPS,4- the transient absorption spectrum of the upper excited-state S2 was different from that of the lowest excited-state S1. The S2 to S1 internal conversion could therefore be followed, and a S2 lifetime of 1.3 ± 0.2 ps was determined. In the ZnTPPS4--MV2+ complex, excitation in the Soret band produced spectral changes attributed to the charge separated state ZnTPPS3--MV+, with a rate limited by the laser pulse (rate constant >5 × 1012 s-1). This suggests that the photoinduced electron transfer from the excited porphyrin to the methyl viologen occurred directly from the S2 state of the porphyrin, before internal conversion to S1. The reverse electron transfer that followed regenerated the ground state reactants with a rate constant (1.3 ± 0.2) × 1012 s-1.
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M3 - Article
VL - 103
SP - 3258
EP - 3262
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
SN - 1520-6106
IS - 16
ER -