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RESEARCH NOTE: TRIPLET RADICAL ION PAIR STATE OF THE Zn‐PORPHYRIN‐VIOLOGEN DYAD AS A MAGNETIC FIELD SENSITIVE PROBE OF PHASE TRANSITIONS IN SMALL UNILAMELLAR VESICLES
Author(s) -
Shafirovich Vladimir Ya.,
Batova Elena E.,
Levin Peter P.
Publication year - 1992
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1992.tb04265.x
Subject(s) - viologen , porphyrin , vesicle , photochemistry , chemistry , ion , dyad , chemical physics , field (mathematics) , membrane , physics , organic chemistry , biochemistry , mathematics , acoustics , pure mathematics
— The magnetic field effect on the recombination kinetics of the triplet radical ion pair state (RIPS) of the Zn‐porphyrin‐viologen dyad (P‐Ph‐Vi 2+ ) in the small unilamellar vesicles (SUV) of d, l ‐dipalmitoyl‐α‐phosphatidylcholine has been studied by the nanosecond laser flash photolysis technique at 5–60°C. The increase in temperature from 25 to 40°C enhances the rate constant ( k r ) of the RIPS recombination in zero magnetic field from 0.9 × 10 6 to 1.6 × 10 6 s ‐1 while k , is temperature insensitive at 5–25 and 40–60°C. The typical break in the k r temperature dependence is observed in the temperature range of the phase transition of the SUV bilayers from the solid to the fluid state. The k r value in a strong magnetic field ( B = 0.24 T) is equal to 2.7 × 10 5 s ‐1 it is independent of temperature at 5–60°C. The shape of the magnetic field dependence of k r is unaffected by the phase transition of the SUV bilayers and is characterized by the existence of an initial plateau of k r at B = 0 to 0.5 mT.