A time-resolved electron paramagnetic resonance study of the photoexcited triplet state of free-base porphycene

1998 ◽  
Vol 95 (5) ◽  
pp. 1013-1019 ◽  
Author(s):  
C.W. M. Kay ◽  
K. Mobius
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Triplet State ◽  
Electron Paramagnetic Resonance Study ◽  
Free Base ◽  
Paramagnetic Resonance ◽  
Time Resolved ◽  
Electron Paramagnetic

Energy transfer and structure determination of porphyrin dimers linked via a phenylenebisvinylene bridge: A time-resolved triplet electron paramagnetic resonance study

2002 ◽  
Vol 06 (09) ◽  
pp. 578-592 ◽  
Author(s):  
Eli Stavitski ◽  
Tamar Galili ◽  
Haim Levanon ◽  
Anthony K. Burrell ◽  
David L. Officer ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Energy Transfer ◽  
Electron Paramagnetic Resonance Study ◽  
Free Base ◽  
Paramagnetic Resonance ◽  
Time Resolved ◽  
Line Shape Analysis ◽  
Electron Paramagnetic ◽  
Porphyrin Dimers

The photoexcited triplet state in a series of homo and hetero dimers was examined by time resolved electron paramagnetic resonance (TREPR) spectroscopy. The systems studied here consist of free-base tetraxylylporphyrin ( H 2 TXP ) and Zn (II) tetraxylylporphyrin ( ZnTXP ) and held together covalently by phenylenebisvinylene bridge at different positions. Experiments were carried out on the dimers, dissolved in an isotropic matrix (toluene), and in an anisotropic matrix of a liquid crystal (LC). Analysis of the results demonstrates that the dimers exhibit different geometries, depending on the linkage. Specifically, the triplet line shape analysis indicates that the para-dimers have a planar structure, the meta-dimers reveal the existence of two structural conformers, i.e. planar and slightly bent, while the ortho-dimers are characterized by the strongly bent molecular structure. The dimers exhibit efficient intramolecular singlet energy transfer (EnT) from ZnTXP to H 2 TXP subunit. On the other hand, EnT in all hetero dimers studied here is incomplete and some contribution from ZnTXP subunit is present in all triplet spectra. Thus, the efficiency of the EnT in the present systems is determined by properties of the connecting spacer, and does not depend on specific conformation and geometry of the molecule.

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