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Time-resolved Photophysical Characterization of Triplet-harvesting Organic Compounds at an Oxygen-free Environment Using an iCCD Camera
Published on: December 27, 2018
Photoexcited triplet state properties of brominated and nonbrominated Ga(III)-corroles as studied by time-resolved
Linn Wagnert1, Roy Rubin, Alexander Berg
1Department of Physical Chemistry, Hebrew University of Jerusalem, Jerusalem 91904, Israel.
Abstract:
The effect of the corrole macrocycle bromination on its photoexcited triplet state parameters was examined in a comparison study of brominated and nonbrominated Ga(III) 5,10,15-tris(pentafluorophenyl)corroles, employing X-band (9.5 GHz) time-resolved electron paramagnetic resonance (TREPR) spectroscopy. It is demonstrated that the spectrum of the brominated Ga-corrole is characterized by an opposite polarization pattern and a larger zero-field splitting (ZFS) parameter |D|, compared to nonbrominated Ga-corrole. With the assignment of a negative sign for the ZFS parameter D, the dominant intersystem crossing (ISC) pathways are evaluated. Spectral line shape analysis reveals that in the brominated Ga-corrole,the out-of-plane triplet sublevel is overpopulated (A(Z) > A(X), A(Y)), while in nonbrominated Ga-corrole, the in-plane triplet sublevels are preferentially populated (A(X), A(Y) ≫ A(Z)). The differences in the photophysical properties of the corroles are attributed to the heavy atom effect upon corrole skeleton bromination, which enhances the spin-orbit coupling strength in the brominated complex, thus affecting its ISC and ZFS parameters.
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