Journal
CHEMICAL SCIENCE
Volume 3, Issue 1, Pages 257-269Publisher
ROYAL SOC CHEMISTRY
DOI: 10.1039/c1sc00614b
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Funding
- Australian Research Council [DP0208776]
- Ministry of Education, Culture, Sports, Science and Technology, Japan [20108010, 23750014]
- KOSEF/MEST through WCU [R31-2008-000-10010-0]
- Grants-in-Aid for Scientific Research [20108010, 23750014, 20108001] Funding Source: KAKEN
- Australian Research Council [DP0208776] Funding Source: Australian Research Council
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The exceptionally long lived charge separation previously observed in a b,b'-pyrrolic-fused ferrocene-porphyrin-fullerene triad (lifetime 630 mu s) and related porphyrin-fullerene dyad (lifetime 260 mu s) is attributed to the production of triplet charge-separated states. Such molecular excited-state spin polarization maintained over distances of up to 23 angstrom is unprecedented and offers many technological applications. Electronic absorption and emission spectra, femtosecond and nanosecond time-resolved transient absorption spectra, and cyclic voltammograms of two triads and four dyads are measured and analyzed to yield rate constants, donor-acceptor couplings, free-energy changes, and reorganization energies for charge-separation and charge-recombination processes. Production of long-lived intramolecular triplet states is confirmed by electron-paramagnetic resonance spectra at 77-223 K, as is retention of spin polarization in p-conjugated ferrocenium ions. The observed rate constants were either first predicted (singlet manifold) or later confirmed (triplet manifold) by a priori semiclassical kinetics calculations for all conceivable photochemical processes, parameterized using density-functional theory and complete-active-space self-consistent-field calculations. Identified are both a ps-timescale process attributed to singlet recombination and a mu s-timescale process attributed to triplet recombination.
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