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Self-assembled supramolecular ferrocene-fullerene dyads and triad: Formation and photoinduced electron transfer

Araki, Yasuyuki and Chitta, Raghu and Sandanayaka, Atula S. D. and Langenwalter, Kevin and Gadde, Suresh and Zandler, Melvin E. and Ito, Osamu and D'Souza, Francis (2008) Self-assembled supramolecular ferrocene-fullerene dyads and triad: Formation and photoinduced electron transfer. JOURNAL OF PHYSICAL CHEMISTRY C, 112 (6). pp. 2222-2229.

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Supramolecular ferrocene-fullerene constructs in which the donor, ferrocene linked to a benzo-18-crown-6 entity (Fc-crown), was self-assembled with the acceptor, fullerene bearing one or two alkyl ammonium ions (NH3+-C-60), yielding dyads or a triad, respectively. The newly formed conjugates were characterized by spectroscopic (fluorescence, electospray ionization-mass, and H-1 NMR) and electrochemical methods. The adopted crown ether-alkyl ammonium ion binding strategy resulting in stable donor-acceptor conjugates was also supported by the computational studies performed at the DFT B3LYP/3-21G(*) level in addition to the binding, constants obtained from fluorescence quenching studies. The experimentally calculated free-energy changes indicated exothermic light-induced charge-separation process. Accordingly, efficient photoinduced charge-separation processes were confirmed by the combination of the time-resolved fluorescence and nanosecond transient absorption spectral measurements. The rates of charge recombination were found to be 2-3 orders of magnitude lower, yielding radical ion-pairs, Fc(+)-crown/NH3+-C-60(center dot-) with lifetimes in the 10-240 ns range. Generally, by increasing the donor-acceptor distance, a decrease in both k(CS) and k(CR) was observed for the supramolecular ferrocene-fullerene dyads; that is, the lifetimes of Fc(+)-crown/NH3+-C-60(center dot-) changed from 10 to 165 ns. However, for the triad, involving two ferrocene donors of varying donor-acceptor distances, the k(CR) originating from the far-side located ferrocene was found to be 240 ns while the k(CR) from the near-side located ferrocene was faster than the time duration of the nanosecond laser pulse (6 ns).

Item Type:Article
Subjects:Physical Science > Nano objects
Material Science > Nanochemistry
ID Code:2833
Deposited By:Farnush Anwar
Deposited On:13 Jan 2009 13:17
Last Modified:13 Jan 2009 13:17

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