Excitation relaxation of zinc and free-base porphyrin probed by femtosecond fluorescence spectroscopy

Akimoto, Seiji; Yamazaki, Tomoko; Yamazaki, Iwao; Osuka, Atsuhiro

doi:10.1016/s0009-2614(99)00688-0

Cited by 84 publications

(118 citation statements)

References 21 publications

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“…The three decay components obtained by global analysis may also be assigned to ultrafast energy migration between the porphyrins in the clusters and the decay processes correlate with vibration relaxation, internal conversion, and self-quenching. [21,33] In contrast, broad structureless transient absorption component spectra were obtained for (H 2 PC11C15MPP + C 60 ) m in the mixed solvent (Figure 10a). By taking into account the ultrafast porphyrin www.chemeurj.org fluorescence quenching by C 60 (< 100 fs), the porphyrin excited singlet state is quenched by C 60 to yield the charge-separated or the partial CT state of the porphyrin and C 60 molecules.…”

Section: Resultsmentioning

confidence: 98%

“…In the mixed solvent, two decay components with time constants of < 100 fs (82 %) and 2.4 ps (18 %) for (H 2 PC11C15MPP) m may result from ultrafast energy migration between the porphyrins in the clusters and the decay processes correlate with vibration relaxation, internal conversion, and self-quenching (Figure 9b). [21,33] Note that the fluorescence intensity of (H 2 PC11C15MPP + C 60 ) m ([H 2 P]:[C 60 ] = 1:6) in the mixed solvent is much lower than that of (H 2 PC11C15MPP) m in the same solvent. Similar ultrafast quenching was observed for (H 2 PC11MPP + C 60 ) m in the mixed solvent as well as for H 2 PC11MPP and C 60 in toluene relative to the reference systems without C 60 .…”

Section: Resultsmentioning

confidence: 99%

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Host–Guest Interactions in the Supramolecular Incorporation of Fullerenes into Tailored Holes on Porphyrin‐Modified Gold Nanoparticles in Molecular Photovoltaics

Imahori

Fujimoto

Kang

et al. 2005

Chemistry A European J

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Novel gold nanoparticles modified with a mixed self-assembled monolayer of porphyrin alkanethiol and short-chain alkanethiol were prepared (first step) to examine the size and shape effects of surface holes (host) on porphyrin-modified gold nanoparticles. The porphyrin-modified gold nanoparticles with a size of about 10 nm incorporated C60 molecules (guest) into the large, bucket-shaped holes, leading to the formation of a supramolecular complex of porphyrin-C60 composites (second step). Large composite clusters with a size of 200-400 nm were grown from the supramolecular complex of porphyrin-C60 composites in mixed solvents (third step) and deposited electrophoretically onto nanostructured SnO2 electrodes (fourth step). Differences in the porphyrin:C60 ratio were found to affect the structures and photoelectrochemical properties of the composite clusters in mixed solvents as well as on the SnO2 electrodes. The photoelectrochemical performance of a photoelectrochemical device consisting of SnO2 electrodes modified with the porphyrin-C60 composites was enhanced relative to a reference system with small, wedged-shaped surface holes on the gold nanoparticle. Time-resolved transient absorption spectroscopy with fluorescence lifetime measurements suggest the occurrence of ultrafast electron transfer from the porphyrin excited singlet states to C60 or the formation of a partial charge-transfer state in the composite clusters of supramolecular complexes formed between porphyrin and C60 leading to efficient photocurrent generation in the system. Elucidation of the relationship between host-guest interactions and photoelectrochemical function in the present system will provide valuable information on the design of molecular devices and machines including molecular photovoltaics.

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Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

Host–Guest Interactions in the Supramolecular Incorporation of Fullerenes into Tailored Holes on Porphyrin‐Modified Gold Nanoparticles in Molecular Photovoltaics

Imahori

Fujimoto

Kang

et al. 2005

Chemistry A European J

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“…By comparison with the estimated B lifetime, ≈ 40 ps, it has been concluded that, within the experimental error, all the tetraoxaporphyrin molecules excited into the B-state decay by internal conversion into the Q state. The transient absorption from the Q x ; Q y bands and the relaxation dynamics from the Soret band have been investigated in substituted porphyrins [309][310][311][312]. In tetraphenylporphyrin the internal conversions (B x , B y ) → Q y and Q y → Q x take place in less than 50 and 100 fs, respectively [310,311].…”

Section: Porphyrinsmentioning

confidence: 99%

“…The transient absorption from the Q x ; Q y bands and the relaxation dynamics from the Soret band have been investigated in substituted porphyrins [309][310][311][312]. In tetraphenylporphyrin the internal conversions (B x , B y ) → Q y and Q y → Q x take place in less than 50 and 100 fs, respectively [310,311]. Later, three decay channels are activated; (a) intramolecular vibrational redistribution by dephasing and elastic collision with the solvent with time constants 100-200 fs and 1.4 ps, (b) thermal equilibration by energy transfer to the solvent in the temporal range 10-20 ps and (c) intersystem crossing Q x → T 1 with time constant 12 ns.…”

Section: Porphyrinsmentioning

confidence: 99%

Structures of Annulenes and Model Annulene Systems in the Ground and Lowest Excited States

Gellini

Salvi

2010

Symmetry

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The paper introduces general considerations on structural properties of aromatic, antiaromatic and non-aromatic conjugated systems in terms of potential energy along bond length alternation and distortion coordinates, taking as examples benzene, cyclobutadiene and cyclooctatetraene. Pentalene, formally derived from cyclooctatetraene by cross linking, is also considered as a typical antiaromatic system. The main interest is concerned with [n]annulenes and model [n]annulene molecular systems, n ranging from 10 to 18. The rich variety of conformational and configurational isomers and of dynamical processes among them is described. Specific attention is devoted to bridged [10]-and [14]annulenes in the ground and lowest excited states as well as to s-indacene and biphenylene. Experimental data obtained from vibrational and electronic spectroscopies are discussed and compared with ab initio calculation results. Finally, porphyrin, tetraoxaporphyrin dication and diprotonated porphyrin are presented as annulene structures adopting planar/non-planar geometries depending on the steric hindrance in the inner macrocycle ring. Radiative and non-radiative relaxation processes from excited state levels have been observed by means of time-resolved fluorescence and femtosecond transient absorption spectroscopy. A short account is also given of porphycene, the structural isomer of porphyrin, and of porphycene properties.

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“…The reduced porphyrin macrocycle occurs in the pheophytins and, further complexed with magnesium, in the chlorophylls both of which are involved in light harvesting and the transformation of trapped sun light into stored chemical energy in the course of photosynthesis [74]. Because of this significance as biological reaction centers, but also because of their function as photosensitizers in photodynamic therapy and as catalysts in precision macromolecular synthesis [75,76], porphyrins have been the focus of a series of time-resolved spectroscopic investigations over the past years in order to gain a better insight into the internal excited-state dynamics [77][78][79][80][81][82][83][84][85]. For these studies a wide variety of time-resolved techniques has been used including transient absorption, nonlinear absorption, fluorescence and also four-wave-mixing spectroscopy.…”

Section: Protochlorophyllide Amentioning

confidence: 99%

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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Excitation relaxation of zinc and free-base porphyrin probed by femtosecond fluorescence spectroscopy

Cited by 84 publications

References 21 publications

Host–Guest Interactions in the Supramolecular Incorporation of Fullerenes into Tailored Holes on Porphyrin‐Modified Gold Nanoparticles in Molecular Photovoltaics

Host–Guest Interactions in the Supramolecular Incorporation of Fullerenes into Tailored Holes on Porphyrin‐Modified Gold Nanoparticles in Molecular Photovoltaics

Structures of Annulenes and Model Annulene Systems in the Ground and Lowest Excited States

Femtosecond time‐resolved spectroscopy on biological photoreceptor chromophores

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