Femtosecond relaxation processes from upper excited states of tetrakis(N-methyl-4-pyridyl)porphyrins studied by transient absorption spectroscopy

Enescu, Mironel; Steenkeste, Karine; Tfibel, F.; Fontaine‐Aupart, Marie‐Pierre

doi:10.1039/b207421d

Cited by 61 publications

(85 citation statements)

References 30 publications

(41 reference statements)

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“…Its lifetime is observed as a rise time after Soret excitation in the

S_{1}^{hot}

population (see below). The measured lifetime agrees with previously reported results for free base porphyrins in solution, 9,24 as well as gas phase measurements. 29,30 The ultrafast relaxation from S 2 to S 1 indicates relaxation through a conical intersection.…”

Section: Resultssupporting

confidence: 91%

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Electronic state dependence of heterogeneous electron transfer: injection from the S₁ and S₂ state of phlorin into TiO₂

Nieto-Pescador

Abraham

Pistner

et al. 2015

Phys. Chem. Chem. Phys.

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Ultrafast time-resolved measurements were performed on a novel pentafluorophenyl substituted 5,5-dimethyl phlorin derivative in solution and when attached to TiO2 colloidal films. The complex excited state dynamics of this porphyrinoid after S1 and S2 excitation was compared at different wavelengths and can be assigned to several subsequent relaxation mechanisms. The difference between excited state dynamics in the free molecule and when attached to an electron accepting electrode was measured. For both cases the dynamics was compared after excitation to the S1 and the S2 state. For the free molecule in solution an intermediate relaxation step was identified and assigned to a buckling motion of the tetrapyrrole ring. On the electrode, heterogeneous electron transfer (HET) times from both states were very similar and around 50 fs. Surprisingly, the large difference in the density of acceptor states that are resonant with the respective donor level of the molecule does not significantly influence HET dynamics. This result indicates that HET proceeds into intermediate transition states that are different from steady state surface states obtained from experiments or computations. The density of states (DOS) of these transient acceptor states appears not to be directly related to the corresponding surface or bulk DOS.

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“…Its lifetime is observed as a rise time after Soret excitation in the

S_{1}^{hot}

Section: Resultssupporting

confidence: 91%

“…This time constant is similar to those assigned to vibrational cooling processes within the Q bands of other porphyrins. 9,24 …”

Section: Resultsmentioning

confidence: 99%

Electronic state dependence of heterogeneous electron transfer: injection from the S₁ and S₂ state of phlorin into TiO₂

Nieto-Pescador

Abraham

Pistner

et al. 2015

Phys. Chem. Chem. Phys.

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“…19 This result indicates that the lifetime of the excited electronic state associated to the Soret transition is too short to be resolved in our measurements (<80 fs), as was already observed for the free chromophore. 28 Thus, the lifetimes presently measured correspond either to a vibrational evolution into the S 1 state manifold and/or to another fast process possibly involving a low-lying intermediate charge-transfer state (see Discussion).…”

Section: Resultsmentioning

confidence: 64%

Ultrafast Guanine Oxidation by Photoexcited Cationic Porphyrins Intercalated into DNA

et al. 2004

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The photophysical and photochemical properties of a cationic porphyrin [bis(arginyl)porphyrin (BAP)] complexed to [poly(dG-dC)] 2 and [poly(dA-dT)] 2 have been investigated and compared to those of free BAP in aqueous solution. A drastic enhancement of the quantum yield of nonradiative deactivation of the lowest excited singlet state of BAP is observed upon intercalation between GC base pairs in [poly(dG-dC)] 2 but not upon complexation with [poly(dA-dT)] 2 . Both picosecond time-resolved fluorescence and femtosecond transient absorption measurements give evidence for the occurrence of an ultrafast direct electron transfer (k g 1.25 × 10 13 s -1 ) from guanine to the lowest excited singlet state of BAP followed by an efficient back electron transfer (k ) 8.3 × 10 12 s -1 ). A classical nonadiabatic Marcus model for this reverse electron transfer explains the experimental observations which allow one to estimate the electronic coupling energy (230 cm -1 ) involved for BAP-[poly(dG-dC)] 2 complexes.

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“…In our experiments, the overall spectral similarities between the 4 ps and the 200 ps component spectrum suggest that the 4 ps process is due to an S 1 → S n transition. The 4-ps process should therefore be related to vibrational relaxation and the solvent-induced vibrational energy redistribution of the initially excited S 1 state, a relaxation process characteristic for porphyrins [84,85,96,97]. The long-lifetime component that persists for times far beyond the 360-ps window of our measurements, is obviously associated with the nanosecond decay from the fully equilibrated S 1 population as recently observed in fluorescence lifetime measurements on PChla [98].…”

Section: Protochlorophyllide Amentioning

confidence: 74%

Femtosecond time‐resolved spectroscopy on biological photoreceptor chromophores

Schmitt¹,

Dietzek

Hermann

et al. 2007

Laser & Photonics Reviews

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This paper reviews our results on femtosecond timeresolved spectroscopy (transient absorption, transient-grating and fluorescence spectroscopy) to study the photophysics and photochemistry of the two very important biological photoreceptor chromophores phycocyanobilin (PCB) and protochlorophyllide a (PChla). The compound PCB serves as a model chromophore for the photoreceptor phytochrome. By means of transient-grating spectroscopy where the excitation wavelength was varied over the spectral region of the S0 → S1-absorption the ultrafast processes were studied upon excitation with varying excess energy delivered to the system. On the basis of the results obtained, both the rate of the photoreaction in PCB and the rate of the decay of different excited-state species via different decay channels depend on the excitation wavelength. Furthermore, transient absorption experiments illuminating the excited-state dynamics of PChla, a porphyrin-like compound and, as substrate of the NADPH/protochlorophyllide oxidoreductase (POR), a precursor of the chlorophyll biosynthesis are presented. In addition to pump-energy-dependent measurements performed with PChla dissolved in methanol, the excited-state dynamics of PChla was interrogated in different solvents that were chosen to mimic different environmental conditions. In addition to the femtosecond time-resolved absorption experiments the picosecond time-resolved fluorescence of the system was studied. The transient absorption and time-resolved fluorescence data allow suggesting a detailed model for the excited-state relaxation of PChla describing the excited-state processes in terms of The model suggested to account for the excited-state relaxation processes in protochlorophyllide a upon photoexcitation is presented a branching of the initially excited state population into a reactive and nonreactive path. Thus, the excited-state potential energy surface exhibits two distinct S1 and Sx minima separated from the Franck-Condon region along two most likely orthogonal reaction coordinates. Finally, the model derived is related to models suggested to account for the reduction of PChla to chlorophyllide a within the natural enzymatic environment of POR.

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Femtosecond relaxation processes from upper excited states of tetrakis(N-methyl-4-pyridyl)porphyrins studied by transient absorption spectroscopy

Cited by 61 publications

References 30 publications

Electronic state dependence of heterogeneous electron transfer: injection from the S₁ and S₂ state of phlorin into TiO₂

Electronic state dependence of heterogeneous electron transfer: injection from the S₁ and S₂ state of phlorin into TiO₂

Ultrafast Guanine Oxidation by Photoexcited Cationic Porphyrins Intercalated into DNA

Femtosecond time‐resolved spectroscopy on biological photoreceptor chromophores

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Femtosecond relaxation processes from upper excited states of tetrakis(N-methyl-4-pyridyl)porphyrins studied by transient absorption spectroscopy

Cited by 61 publications

References 30 publications

Electronic state dependence of heterogeneous electron transfer: injection from the S1 and S2 state of phlorin into TiO2

Electronic state dependence of heterogeneous electron transfer: injection from the S1 and S2 state of phlorin into TiO2

Ultrafast Guanine Oxidation by Photoexcited Cationic Porphyrins Intercalated into DNA

Femtosecond time‐resolved spectroscopy on biological photoreceptor chromophores

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Product

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Electronic state dependence of heterogeneous electron transfer: injection from the S₁ and S₂ state of phlorin into TiO₂

Electronic state dependence of heterogeneous electron transfer: injection from the S₁ and S₂ state of phlorin into TiO₂