Electron transfer in porphyrin—quinone cyclophanes

Heitele, H.; Pöllinger, F.; Kremer, K.; Michel‐Beyerle, M. E.; Futscher, Michael; Voit, G.; Weiser, Jürgen; Staab, Heinz A.

doi:10.1016/0009-2614(92)90021-e

Cited by 61 publications

(37 citation statements)

References 38 publications

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“…The fluorescence decay kinetics of the systems studied here (Table 1) follows the qualitative picture developed in ref 15. Briefly, we distinguish three different regimes with (a) monoexponential decay with a characteristic time constant comparable to the unquenched porphyrin moiety ( 7 = 11-13 ns in the free-base porphyrins, 1.3-1.6 ns in the Zn-porphyrins), (b) strongly quenched biexponential fluorescence decay, and (c) very short-lived fluorescence on the order of 1 ps.…”

Section: Resultsmentioning

confidence: 97%

Energy Gap and Temperature Dependence of Photoinduced Electron Transfer in Porphyrin-Quinone Cyclophanes

Heitele¹,

Poellinger²,

Haeberle³

et al. 1994

J. Phys. Chem.

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We have investigated intramolecular photoinduced charge separation and recombination in a series of cyclophanebridged porphyrinquinone systems by means of time−resolved fluorescence decay measurements. Rates of charge separation have been determined as a function of the free energy change of the reaction, of the polarity of the solvent, and of the temperature. In some systems a long−lived fluorescence is observed which is attributed to a thermal repopulation of the initially excited state from the charge transfer state. This delayed fluorescence allows the calculation of the rate of recombination in these cases. The observation of delayed fluorescence for a particular donor−acceptor compound in some solvent serves as a reference for the reaction free energy of the respective charge separation (AG, N 0 eV). The free energy change in other systems is estimated by correcting for differences in the redox potentials of the respective porphyrins and quinones. Electronic couplings and reorganization energies are determined by globally fitting standard rate expressions as a function of the free energy change to the experimental rate data. Three different kinds of fits are performed by (a) using both charge separation and recombination within the nonadiabatic approximation, (b) allowing for Landau−Zener adiabaticity corrections, and (c) fitting rates of charge separation (in the normal region) only. A particular focus lies in the specific effects imposed by the compact structure of the porphyrin−uinone cyclophanes. It is shown that electron transfer in these systems is nonadiabatic and dominated by intramolecular reorganization whereas the influence of the surrounding solvent is minimized by the close packing of electron donor and accepto

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Section: Resultsmentioning

confidence: 97%

Energy Gap and Temperature Dependence of Photoinduced Electron Transfer in Porphyrin-Quinone Cyclophanes

Heitele¹,

Poellinger²,

Haeberle³

et al. 1994

J. Phys. Chem.

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“…Benzoquinone is a well-known substance for quenching the excited states of transition-metal complexes via energy transfer [25,26]; Cr(bpy) 3 3+* quenched by phenol has also been reported by Pizzocaro et al [27]. Therefore, the inhibition effect of GA in this system can be proposed as being the result of an energy transfer reaction between freshly electrogenerated Ru(bpy) 3 2+* and o-benzoquinone derivatives.…”

Section: Mechanism Of the Ecl Inhibitionmentioning

confidence: 83%

Flow injection analysis of gallic acid with inhibited electrochemiluminescence detection

Lin

Yongqiang

et al. 2004

Analytical and Bioanalytical Chemistry

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A flow injection (FI)-electrochemiluminescent (ECL) method has been developed for the determination of gallic acid, based on an inhibition effect on the Ru(bpy)(3)(2+)/tri- n-propylamine (TPrA) ECL system in pH 8.0 phosphate buffer solution. The method is simple and convenient with a determination limit of 9.0x10(-9) mol/L and a dynamic concentration range of 2x10(-8)-2x10(-5) mol/L. The relative standard deviation (RSD) was 1.0% for 1.0x10(-6) mol/L gallic acid ( n=11). It was successfully applied to the determination of gallic acid in Chinese proprietary medicine-Jianming Yanhou Pian. The inhibition mechanism proposed for the quenching effect of the gallic acid on the Ru(bpy)(3)(2+)/TPrA ECL system was the interaction of electrogenerated Ru(bpy)(3)(2+*) and o-benzoquinone derivative at the electrode surface. The ECL emission spectra and UV-visible absorption spectra were applied to confirm the mechanism.

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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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Electron transfer in porphyrin—quinone cyclophanes

Cited by 61 publications

References 38 publications

Energy Gap and Temperature Dependence of Photoinduced Electron Transfer in Porphyrin-Quinone Cyclophanes

Energy Gap and Temperature Dependence of Photoinduced Electron Transfer in Porphyrin-Quinone Cyclophanes

Flow injection analysis of gallic acid with inhibited electrochemiluminescence detection

The Gold Porphyrin First Excited Singlet State¶

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