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Light‐induced electron spin polarization in the ground state of water‐soluble copper porphyrins
Author(s) -
Rozenshtein Vladimir,
Berg Alexander,
Leva Haim,
Krueger Uwe,
Stehlik Dietmar,
Kandrashkin Yuri,
Van Der Est Art
Publication year - 2004
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1560/ff1q-02xd-q4vc-dhx0
Subject(s) - chemistry , photoexcitation , ground state , polarization (electrochemistry) , copper , electron paramagnetic resonance , spin polarization , spectral line , electron , atomic physics , molecular physics , excited state , nuclear magnetic resonance , physics , organic chemistry , quantum mechanics , astronomy
Light‐induced spin‐polarized transient EPR spectra are reported for several water‐soluble copper porphyrins. The spectra are assigned to the doublet ground state, with emissive spin polarization resulting from photoexcitation and subsequent electronic relaxation. In contrast to other systems for which polarization of a doublet ground state has been observed, the exchange interactions in the copper porphyrins are strong and the geometry is fixed. It is proposed that intersystem crossing from the photoexcited trip‐doublet to the trip‐quartet state can lead to net polarization of the spin system and that this polarization is maintained during electronic decay, possibly via charge‐transfer and exciplex states. The intensity of the observed spin polarization is essentially independent of the molecular orientation in the external field, but is strongly dependent on the nature of the charged peripheral groups. Possible reasons for this behavior are discussed.