Photoelectron transfer between a magnesium-free-base porphyrin heterodimer and duroquinone. Selective excitation and time-resolved EPR studies

Journal Article · Thu Dec 16 04:00:00 EST 1993 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100152a026· OSTI ID:5042286

Levanon, H; Regev, A; Galili, T; Hugerat, M; Fajer, J ^[1]; Chang, C K ^[2]

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1. Hebrew Univ., Jerusalem (Israel)
2. Michigan State Univ., East Lansing, MI (United States)

The photoexcited triplet state of a cofacial heterodimer, [Mg-H[sub 2]], comprised of Mg and H[sub 2] porphyrins, and photoinduced electron transfer (ET) between the heterodimer and duroquinone in 1:1 mixture of CH[sub 2]Cl[sub 2] ethanol were studied by selective laser excitation combined with time-resolved CW or with pulsed EPR spectroscopies. ET originates from the photoexcited triplet or triplet radical pair states. Upon photoexcitation of the Mg subunit (580 nm), a noticeable delay time of approximately 20 ns in ET is observed, whereas with photoexcitation of the H[sub 2] part (620 nm), no delay time in ET is noticed. The dependence of ET upon excitation wavelength is interpreted in terms of the formation and participation of a charge-transfer state that is operative at 205 K. The delay time is attributed to an intradimer ET that produces the triplet radical pair state [sup 3][Mg[sup [sm bullet]+]-H[sub 2][sup [sm bullet][minus]]]. Photoexcitation at 620 nm results in ET via the lower-lying triplet of H[sub 2] without involvement of the charge-transfer state. 35 refs., 9 figs., 3 tabs.

• DOE Contract Number: AC02-76CH00016
• OSTI ID: 5042286
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 97:50; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140505 -- Solar Energy Conversion-- Photochemical
Photobiological
& Thermochemical Conversion-- (1980-)
36 MATERIALS SCIENCE
360606 -- Other Materials-- Physical Properties-- (1992-)
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ABSORPTION SPECTRA
CARBOXYLIC ACIDS
CHARGE TRANSPORT
CHEMICAL REACTIONS
CONVERSION
DIMERS
ELECTROMAGNETIC RADIATION
ELECTRON SPIN RESONANCE
ELECTRON TRANSFER
ENERGY CONVERSION
ENERGY LEVELS
EXCITED STATES
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
LASER RADIATION
MAGNETIC RESONANCE
MULTIPLETS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOSYNTHESIS
PHOTOSYNTHETIC REACTION CENTERS
PORPHYRINS
RADIATION EFFECTS
RADIATIONS
RESOLUTION
RESONANCE
SOLAR ENERGY CONVERSION
SPECTRA
SYNTHESIS
TIME RESOLUTION
TIMING PROPERTIES
TRIPLETS