Unexpected change in charge transfer behavior in a cobalt(II) porphyrin-fullerene conjugate that stabilizes radical ion pair states
Sutton L, Scheloske M, Pirner K, Hirsch A, Guldi DM, Gisselbrecht JP (2004)
Publication Type: Journal article, Original article
Publication year: 2004
Journal
Original Authors: Sutton L.R., Scheloske M., Pirner K.S., Hirsch A., Guldi D.M., Gisselbrecht J.-P.
Publisher: American Chemical Society
Book Volume: 126
Pages Range: 10370-10381
Journal Issue: 33
DOI: 10.1021/ja048983d
Abstract
Two cobalt(II) porphyrin-C malonate-linked conjugates, the mono-connected Co1 and the bis-connected trans-2 isomer Co3, have been synthesized for the first time either by direct cyclopropanation with the precursor malonate Co4 or by metalation of the bisadduct H3. For the investigation of the interaction between the porphyrin donor and fullerene acceptor within these dyads, electrochemical and photophysical investigations have been carried out. Compared to Zn3 and trans-2 bisadduct 7, the first reduction of the fullerene moiety within Co3 becomes easier (40 mV in dichloromethane and 20 mV in benzonitrile), indicating significant interactions between the π-system of the fullerene and the d-orbitals of the central Co atom. Compared to the Co complexes 9, Co4, and Co1, the first oxidation of Co3 is considerably shifted to more positive potentials, if benzonitrile instead of dichloromethane is used as solvent. At the same time, the oxidation is no longer centered on the Co(II) center but on the porphyrin macrocycle, as corroborated by spectroelectrochemistry. A similar solvent dependence was observed in transient absorption spectroscopic measurements. In toluene, benzonitrile and anisole photoinduced electron transfer within Co3 leads to the formation of a charge-separated state Co(II)P-C with a lifetime of 560 ± 20 ns in benzonitrile, whereas in other solvents such as THF, nitrobenzene, ortho-diclorobenzene, and tert-butylbenzene the formation of a Co(III)P-C as transient was detected, which is, however, short-lived (860 ± 40 ps in THF) and exhibits charge recombination dynamics that are in the Marcus inverted region. Particularly important is the fact that the electronic coupling (V) in Co(III)P-C is 18 cm substantially smaller than the V value of 313 cm in ZnP-C60.
Authors with CRIS profile
Andreas Hirsch
Lehrstuhl für Organische Chemie II
Dirk Michael Guldi
Lehrstuhl für Physikalische Chemie I
Involved external institutions
France (FR)How to cite
APA:
Sutton, L., Scheloske, M., Pirner, K., Hirsch, A., Guldi, D.M., & Gisselbrecht, J.-P. (2004). Unexpected change in charge transfer behavior in a cobalt(II) porphyrin-fullerene conjugate that stabilizes radical ion pair states. Journal of the American Chemical Society, 126(33), 10370-10381. https://doi.org/10.1021/ja048983d
MLA:
Sutton, Liam, et al. "Unexpected change in charge transfer behavior in a cobalt(II) porphyrin-fullerene conjugate that stabilizes radical ion pair states." Journal of the American Chemical Society 126.33 (2004): 10370-10381.
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