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Issue 1, 2012
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Long-lived long-distance photochemically induced spin-polarized charge separation in β,β′-pyrrolic fused ferrocene-porphyrin-fullerene systems

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Abstract

The exceptionally long lived charge separation previously observed in a β,β′-pyrrolic-fused ferrocene-porphyrin-fullerene triad (lifetime 630 μs) and related porphyrin-fullerene dyad (lifetime 260 μs) is attributed to the production of triplet charge-separated states. Such molecular excited-state spin polarization maintained over distances of up to 23 Å 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 π-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 μs-timescale process attributed to triplet recombination.

Graphical abstract: Long-lived long-distance photochemically induced spin-polarized charge separation in β,β′-pyrrolic fused ferrocene-porphyrin-fullerene systems

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Publication details

The article was received on 26 Aug 2011, accepted on 20 Sep 2011 and first published on 12 Oct 2011


Article type: Edge Article
DOI: 10.1039/C1SC00614B
Citation: Chem. Sci., 2012,3, 257-269
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    Long-lived long-distance photochemically induced spin-polarized charge separation in β,β′-pyrrolic fused ferrocene-porphyrin-fullerene systems

    S. Lee, A. G. Larsen, K. Ohkubo, Z. Cai, J. R. Reimers, S. Fukuzumi and M. J. Crossley, Chem. Sci., 2012, 3, 257
    DOI: 10.1039/C1SC00614B

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