Ultrafast Photoinduced Electron Transfer in Rigid Porphyrin-Quinone Dyads

Macpherson, Alisdair N.; Liddell, Paul A.; Lin, Su; Noss, Lori; Seely, G. R.; DeGraziano, Janice M.; Moore, Ana L.; Moore, Thomas A.; Gust, Devens

doi:10.1021/ja00132a021

Cited by 87 publications

(81 citation statements)

References 9 publications

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“…As an example, the evolution of the time-resolved spectra of 1 in toluene, Et 2 O, and THF in a 3000 ps temporal window is reported in Figure 10. The broad absorption band with a maximum at 640 nm is unambiguously attributable to the porphyrin radical cation, in agreement with a large number of literature reports, [4,39,40] which suggests that the extent of charge transfer [41] is virtually complete in solvents of any polarity. The lifetime values of the electron-transfer products as a function of solvent polarity, which were obtained by ground-state recovery traces (Figure 10), follow the decreasing trend observed for the luminescence decays (Table 6).…”

Section: Transient Absorption Spectrasupporting

confidence: 89%

Photophysical and Electrochemical Properties of meso,meso‐Linked Oligoporphyrin Rods with Appended Fullerene Terminals

et al. 2005

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The electrochemical and photophysical properties of molecular architectures consisting of oligomeric meso,meso-linked oligoporphyrin rods linked at both extremities to methanofullerene moieties are presented in comparison to those of model systems. Cyclic voltammetry data evidence the presence of a strong intramolecular electronic coupling along the porphyrin oligomers that varies slightly with their length. This interaction affects the redox potentials of both fullerene and porphyrin moieties. The electronic coupling between the two chromophores is confirmed by comparing the redox potentials of porphyrin arrays before and after attachment of the carbon sphere. Electronic absorption, fluorescence, and phosphorescence spectra of the porphyrin oligomers in toluene are reported, which provide the energy of the lowest singlet and triplet electronic excited states. In the fullerene-porphyrin conjugates, ground-state charge-transfer (CT) interactions are evidenced by low-energy absorption features above 750 nm. These systems also exhibit near-infrared (NIR) CT luminescence in toluene with lifetimes shorter than 1000 ps. On increasing the solvent polarity (from toluene to Et2O and THF), CT emissions become progressively weaker, red-shifted, and shorter lived, which reflects the energy-gap law and Marcus inverted region effects. Luminescence is not detected in benzonitrile. Picosecond transient absorption spectroscopy of the porphyrin-fullerene conjugates allows detection of the porphyrin cation as a clear fingerprint for electron transfer. The rate of charge recombination is in agreement with CT luminescence lifetimes, which confirms the occurrence of NIR radiative back-electron transfer.

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Section: Transient Absorption Spectrasupporting

confidence: 89%

Photophysical and Electrochemical Properties of meso,meso‐Linked Oligoporphyrin Rods with Appended Fullerene Terminals

et al. 2005

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“…However, this is not necessarily the case. For example, photoinduced electron transfer with comparable time constants has been observed in several porphyrin–quinone dyad systems (22–34). In addition, singlet–singlet energy transfer from carotenoid polyenes to chlorophylls and porphyrins in both natural photosynthetic and synthetic model systems can occur on the subpicosecond time scale (35–41).…”

Section: Discussionmentioning

confidence: 95%

The Gold Porphyrin First Excited Singlet State¶

Andréasson¹,

Kodis²,

Lin³

et al. 2007

Photochemistry and Photobiology

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Gold porphyrins are often used as electron‐accepting chromophores in artificial photosynthetic constructs. Because of the heavy atom effect, the gold porphyrin first‐excited singlet state undergoes rapid intersystem crossing to form the triplet state. The lowest triplet state can undergo a reduction by electron donation from a nearby porphyrin or another moiety. In addition, it can be involved in triplet–triplet energy transfer interactions with other chromophores. In contrast, little has been known about the short‐lived singlet excited state. In this work, ultrafast time‐resolved absorption spectroscopy has been used to investigate the singlet excited state of Au(III) 5,15‐bis(3,5‐di‐t‐butylphenyl)‐2,8,12,18,‐tetraethyl‐3,7,13,17‐tetramethylporphyrin in ethanol solution. The excited singlet state is found to form with the laser pulse and decay with a time constant of 240 fs to give the triplet state. The triplet returns to the ground state with a lifetime of 400 ps. The lifetime of the singlet state is comparable with the time constants for energy and photoinduced electron transfer in some model and natural photosynthetic systems. Thus, it is kinetically competent to take part in such processes in suitably designed supermolecular systems.

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“…A similar approach, as used in ref. [13] porphyrinϪquinone diads are investigated in which a naphthoquinone is attached by a bicyclic bridge to the meso and β positions (positions 5 and 7, Figure 2) of a porphyrin. In ref.…”

Section: Discussion Of Literature Examplesmentioning

confidence: 99%

The Role of the Electronic Structure of the Porphyrin as Viewed by EPR/ENDOR Methods in the Efficiency of Biomimetic Model Compounds for Photosynthesis

Huber

2001

Eur. J. Org. Chem.

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A project to investigate the parameters that determine the efficiency of biomimetic porphyrin quinone model compounds for photosynthesis is described. It should aid in understanding the origin of the high efficiency of energy conversion in the light‐induced charge separation in photosynthesis. Specifically, the contribution of the electronic matrix element to the electron transfer (ET) rates is addressed. Targeting the electronic structure of the ET components, EPR (electron paramagnetic resonance) and ENDOR (electron nuclear double resonance) spectroscopy were performed on the appropriate radical derivatives of the porphyrins and quinones to determine MO coefficients. Together with semiempirical MO methods, these coefficients were used to obtain information on the frontier orbitals of the donor and acceptor moieties, the porphyrins, and quinones of the model compounds. The porphyrin frontier orbitals (HOMO and LUMO) have been implicated in the balance of ET rates for charge separation and charge recombination, which is related to the efficiency. A model is presented to correlate the substitution pattern of the porphyrin with the efficiency of the model compound. In particular, the effect of porphyrin substitution, including the covalent link to an acceptor, and the comparison of porphyrins with chlorins and chlorophylls are addressed. The model allows for a quantification of these effects in some cases. Differences in the frontier orbital structure suggest that the [5,10,15,20 tetraaryl(alkyl)porphyrinato]metal complexes are sufficiently different from chlorophylls to be nonideal model compounds. These results are related to recent publications, and possible improvements of experimental and theory approaches are addressed.

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Ultrafast Photoinduced Electron Transfer in Rigid Porphyrin-Quinone Dyads

Cited by 87 publications

References 9 publications

Photophysical and Electrochemical Properties of meso,meso‐Linked Oligoporphyrin Rods with Appended Fullerene Terminals

Photophysical and Electrochemical Properties of meso,meso‐Linked Oligoporphyrin Rods with Appended Fullerene Terminals

The Gold Porphyrin First Excited Singlet State¶

The Role of the Electronic Structure of the Porphyrin as Viewed by EPR/ENDOR Methods in the Efficiency of Biomimetic Model Compounds for Photosynthesis

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