Chemically Induced Nuclear Spin Polarization in Photo-Initiated Radical Ion Reactions

Roth, Heinz D.

doi:10.1007/978-94-010-1265-2_4

Cited by 15 publications

(7 citation statements)

References 55 publications

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“…Our results strongly suggest the intermediate formation of a radical ion pair as the signal intensity increased with solvent polarity (Roth, 1977). The effects were also reduced as the FC concentration was increased from M to 5 x M and they even faded out when it exceeded 5 x M .…”

Section: -M O P Without Any Substratesupporting

confidence: 50%

“…The effects were also reduced as the FC concentration was increased from M to 5 x M and they even faded out when it exceeded 5 x M . Such decay of the CIDNP signal could be correlated with the increasing rate of the electron exchange between an ion radical and its parent molecule (Roth, 1977). Consequently the effects would result from the formation of both semi-oxidized and semi-reduced species of the FC, such as clearly established with other photosensitizers: methylene blue, eosin or thionine (Koizumi et al, 1978):…”

Section: -M O P Without Any Substratementioning

confidence: 99%

“…A progressive line-broadening was observed on the FC H-4 signal during irradiation. This phenomenon is generally ascribed to degenerate electron exchange between an ion radical and its diamagnetic precursor and could account for an electron transfer reaction (Roth, 1977).…”

Section: A Monofunctional Case: 3-cpsmentioning

confidence: 99%

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Photo‐cidnp as a Tool for the Study of the Reactivity of Photosensitizing Drugs: The Furocoumarins

Marko

Vermeersch

Febvay-Garot

et al. 1988

Photochem & Photobiology

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Abstract— Several monofunctional and bifunctional furocoumarin derivatives were studied by means of the photo‐CIDNP technique. Nuclear spin polarizations were observed on some of these derivatives when irradiated in acetonitrile solutions. The likely occurrence of both semi‐reduced and semi‐oxidized species of the FC in the reaction scheme is discussed. When N‐acetyltyrosine was added to the solution, CIDNP effects were observed on both reactants. They arose from a highly reversible pathway, as no photoproduct was polarized. On the FC part, the stronger effects were always observed on the 3,4 pyrone double bond suggesting that it must possess the highest spin density in the reaction intermediate. According to previous studies, the latter should be the FC anion or neutral radical. For the amino‐acid moiety, the intensity of the polarizations was strongly dependent on the nature of the FC. This allowed the classification of the FC into three groups (zero, weak and strong intensities). As compared with their photobiological reactivity, this classification seemed to be related to the usual mono‐ and bifunctional distinction. This is the second example showing that photo‐CIDNP could be used as a preliminary test for the study of the photosensitizing drug properties.

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Section: -M O P Without Any Substratesupporting

confidence: 50%

Section: -M O P Without Any Substratementioning

confidence: 99%

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Photo‐cidnp as a Tool for the Study of the Reactivity of Photosensitizing Drugs: The Furocoumarins

Marko

Vermeersch

Febvay-Garot

et al. 1988

Photochem & Photobiology

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“…That static magnetic fields may act on photochemical reactions was discovered by magnetic resonance spectroscopists who observed anomalous intensities (absorptive or emissive) of NMR (Bargon, Fischer & Johnsen, 1967; see for reviews Kaptein, 1975;Roth, 1977) and ESR lines (Fessenden & Schuler, 1963). Somewhat later it was established that also the yield of products of photochemical reactions as monitored by optical spectroscopy may be affected by a strong magnetic field (Michel-Beyerle et al 1976;Schulten et al 1976).…”

Section: The Reaction Centre Tripletmentioning

confidence: 99%

Magnetic field effects on photosynthetic reactions

1981

Quart. Rev. Biophys.

174

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When light impinges on photosynthetic material – a plant leaf, an alga or a photosynthetic bacterium – it is absorbed by an array of lightcollecting pigments. Through resonant energy transfer the absorbed quantum of light is transported to a trap, the reaction centre. Within such a trap, a specialized (bacterio)chlorophyll complex is able to eject from its excited state an electron. This electron is ‘captured’ by an adjacent acceptor, which in turn donates the electron to a second acceptor, and so on. Thus, light energy is converted into chemical energy which is ultimately used in the metabolic processes of the cell.

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“…Furthermore radical ion pair formation can also be related with line-broadening phenomena. The latter are ascribed to electron exchange between a radical ion and its diamagnetic precursor (Roth, 1977;Closs and Sitzmann, 1981). Our results show that the broadening was strongly pH-dependent and became preponderant in basic media.…”

Section: Porphyrins In the Absence Of Any Substratementioning

confidence: 72%

Photo‐cidnp Evidence for Charge‐transfer Interaction Between Synthetic Water‐soluble Porphyrins and Guanine*

Nouën

Marko

Vermeersch

et al. 1989

Photochem & Photobiology

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Photoreactions of aqueous solutions of synthetic water‐soluble porphyrins were studied by the 1H and 13C CIDNP technique. Strong polarizations, which were very sensitive to the presence of added acid, were observed on the cationic porphyrins (TMePyPH2‐TAPPH2) when irradiated through continuous UV‐visible light. They resulted from the reverse electron transfer between the semi‐oxidized and the semi‐reduced species of the derivative. When the experiments were carried out in the presence of nucleobases, guanine (and its derivatives) was the only residue that was polarized. This is thoroughly interpreted in terms of a reversible electron transfer reaction leading to guanine photooxidation by the porphyrin excited triplet state. It was shown to be drastically pH‐dependent and was correlated to the redox potential of the porphyrin. It was not affected by the incident wavelength. The reaction proceeded through the intermediate formation of the correlated radical‐ion pair: porphyrin radical anion‐guanine radical cation. This study suggested that a Type I (free radical) reaction could be one of the primary processes in DNA photosensitization by porphyrins.

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Chemically Induced Nuclear Spin Polarization in Photo-Initiated Radical Ion Reactions

Cited by 15 publications

References 55 publications

Photo‐cidnp as a Tool for the Study of the Reactivity of Photosensitizing Drugs: The Furocoumarins

Photo‐cidnp as a Tool for the Study of the Reactivity of Photosensitizing Drugs: The Furocoumarins

Magnetic field effects on photosynthetic reactions

Photo‐cidnp Evidence for Charge‐transfer Interaction Between Synthetic Water‐soluble Porphyrins and Guanine*

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