Photoexcited triplet state properties of brominated and nonbrominated Ga(III)-corroles as studied by time-resolved electron paramagnetic resonance.

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(pentafluotophenyl)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 vertical bar D vertical bar, 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) >> Az) 1 he differences in the photophysical properties of the col roles 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