Electron Transport across Vesicle Bilayers Sensitized by Pyrenes: Design and Syntheses of Unsymmetrically Substituted Bifunctional Pyrenes Acting as Excellent Sensitizers

Yoshida, Asako; Harada, Akitomo; Mizushima, Tadashi; Murata, Shigeru

doi:10.1246/cl.2003.68

Cited by 10 publications

(2 citation statements)

References 7 publications

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“…7, 8 In the course of our studies on pyrene-sensitized photoreactions, 9 we found that pyrene derivatives embedded into the bilayers of phosphatidylcholine (PC) vesicles photochemically induce transport of electrons from ascorbate (Asc − ) entrapped into the inner waterpool to MV 2+ dissolved in the outer aqueous solution without any additional components acting as electron carriers. 10 The free-energy change for the total redox reaction of our electron transfer system is estimated to be +12.7 kcal mol −1 . 11,12 Thus, although the pyrenes employed in our experiments unfortunately do not absorb visible light (>400 nm), this system satisfies the other three criteria mentioned above.…”

Section: Introductionmentioning

confidence: 92%

Pyrene-sensitized electron transport across vesicle bilayers: dependence of transport efficiency on pyrene substituents

et al. 2006

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Endoergic electron transport across vesicle bilayers from ascorbate (Asc-) in the inner waterpool to methylviologen (MV2+) in the outer aqueous solution was driven by the irradiation of pyrene derivatives embedded in the vesicle bilayers. The initial rate of MV2+ reduction is dependent on the substituent group of the pyrenyl ring; a hydrophilic functional group linked with the pyrenyl ring by a short methylene chain acts as a sensitizer for the electron transport. Mechanistic studies using (1-pyrenyl)alkanoic acids (1a-c) as sensitizers suggest that the electron transport is mainly initiated by the reductive quenching of the singlet excited state of the pyrene by Asc- and proceeds by a mechanism involving electron exchange between the pyrenes located at the inner and outer interface across the vesicle bilayer. We designed and synthesized novel unsymmetrically substituted pyrenes having both a hydrophilic group linked by a short methylene chain and a hydrophobic long alkyl group (5a-c), which acted as excellent sensitizers for the electron transport across vesicle bilayers.

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Section: Introductionmentioning

confidence: 92%

Pyrene-sensitized electron transport across vesicle bilayers: dependence of transport efficiency on pyrene substituents

et al. 2006

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“…In the course of our studies on artificial photosynthesis using pyrene derivatives as chromophores, , we have investigated the aggregation behaviors of amphiphilic pyrenes in water and their usefulness for artificial light-harvesting systems. Pyrenes have several merits as chromophores for studies on artificial photosynthesis: large extinction coefficients in the near-ultraviolet region, relatively long lifetime of their singlet excited state, intense fluorescence that is sensitive to their surroundings, and ease of preparation of a wide variety of their derivatives.…”

Section: Introductionmentioning

confidence: 99%

Aggregation of Amphiphilic Pyranines in Water: Facile Micelle Formation in the Presence of Methylviologen

Sasaki

Murata

2008

Langmuir

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Four amphiphilic pyranines in which the acidic hydrogen of pyranine was replaced by an octyl, dodecyl, hexadecyl, and eicosyl group, POCn (n ) 8, 12, 16, and 20), were prepared, and their spectroscopic properties and aggregation behaviors in water were investigated. The critical micelle concentration (cmc) of the amphiphilic pyranines was found to be relatively large even in POC20 having a long hydrophobic alkyl chain (ca. 3 × 10 -3 M). 1 H NMR studies revealed that POC16 and POC20 exist in the compact structure with the pyranine nucleus wrapped with a long methylene chain in water. As in the case of parent pyranine, the addition of methylviologen (MV 2+ ) to an aqueous solution of POCn resulted in the absorption spectral change and efficient quenching of POCn fluorescence. In the case of POC8 and POC12, these spectral changes induced by the MV 2+ addition were thoroughly explained in terms of the formation of the electrostatic complex POCn/MV 2+ with a complexation constant of ∼3 × 10 4 M -1 . On the other hand, an unexpectedly large dependence of the absorption spectral change, as well as fluorescence quenching, on the total concentration of MV 2+ was observed in POC16 and POC20. The Stern-Volmer plot for quenching of the fluorescence of POC16 and POC20 gave a curve deviating largely upward from a straight line. The plot was successfully analyzed by the equation induced by assuming the aggregate formation of the complex POCn/MV 2+ , which revealed the considerably small cmc values of the complexes, 3.6 × 10 -7 and 3.6 × 10 -8 M for POC16/MV 2+ and POC20/MV 2+ , respectively. Experimental evidence in support of the aggregate formation was obtained by 1 H NMR and dynamic light scattering studies.

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