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Song HE, Kirmaier C, Diers JR, et al. Energy- and hole-transfer dynamics in oxidized porphyrin dyads. J Phys Chem B. 2009;113(1):54-63doi: 10.1021/jp8060637.
Song, H. E., Kirmaier, C., Diers, J. R., Lindsey, J. S., Bocian, D. F., & Holten, D. (2009). Energy- and hole-transfer dynamics in oxidized porphyrin dyads. The journal of physical chemistry. B, 113(1), 54-63. https://doi.org/10.1021/jp8060637
Song, Hee-eun, et al. "Energy- and hole-transfer dynamics in oxidized porphyrin dyads." The journal of physical chemistry. B vol. 113,1 (2009): 54-63. doi: https://doi.org/10.1021/jp8060637
Song HE, Kirmaier C, Diers JR, Lindsey JS, Bocian DF, Holten D. Energy- and hole-transfer dynamics in oxidized porphyrin dyads. J Phys Chem B. 2009 Jan 08;113(1):54-63. doi: 10.1021/jp8060637. PMID: 19067561.
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J Phys Chem B. 2009 Jan 08;113(1):54-63. doi: 10.1021/jp8060637.

Energy- and hole-transfer dynamics in oxidized porphyrin dyads.

The journal of physical chemistry. B

Hee-eun Song, Christine Kirmaier, James R Diers, Jonathan S Lindsey, David F Bocian, Dewey Holten

Affiliations

  1. Department of Chemistry, Washington University, St. Louis, Missouri 63130-4889, USA.

PMID: 19067561 DOI: 10.1021/jp8060637

Abstract

The mechanisms and dynamics of quenching of a photoexcited free base porphyrin (Fb*) covalently linked to a nearby oxidized zinc porphyrin (Zn(+)) have been investigated in a set of five dyads using time-resolved absorption spectroscopy. The dyads include porphyrins joined at the meso-positions by a diphenylethyne linker or a diarylethyne linker with 2,6-dimethyl substitution on either one or both of the aryl rings. Another dyad is linked at the beta-pyrrole positions of the porphyrins via a diphenylethyne linker. The type of linker and attachment site modulate the interporphyrin through-bond electronic coupling via steric hindrance (porphyrin-linker orbital overlap) and attachment motif (porphyrin electron density at the connection site). For each ZnFb dyad, the zinc porphyrin is selectively electrochemically oxidized (to produce Zn(+)Fb), the free base porphyrin is selectively excited with a 130 fs flash (to produce Zn(+)Fb*), and the subsequent dynamics monitored. The Zn(+)Fb* excited state has a lifetime of approximately 3 to approximately 30 ps (depending on the linker steric hindrance and attachment site) and decays by parallel excited-state energy- and hole-transfer pathways. The relative yields of the two channels depend on a number of factors including the linker-mediated through-bond electronic coupling and a modest (< or =20%) Forster through-space contribution for the energy-transfer route. One product of Zn(+)Fb* decay is the metastable ground-state ZnFb(+), which decays to the Zn(+)Fb preflash state by ground-state hole transfer with a linker-dependent rate constant of (20 ps)(-1) to (150 ps)(-1). Collectively, these results provide a detailed understanding of the mechanism and dynamics of quenching of excited porphyrins by nearby oxidized sites, as well as the dynamics of ground-state hole transfer between nonequivalent porphyrins (Zn and Fb). The findings also lay the foundation for the study of ground-state hole transfer between identical porphyrins (e.g., Zn/Zn, Fb/Fb) in larger multiporphyrin arrays wherein a hole is selectively placed via electrochemical oxidation.

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