Self-Assembled Supramolecular Ferrocene-Fullerene Dyads and Triad: Formation and Photoinduced Electron Transfer
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- 作者：Yasuyuki Araki ; Raghu Chitta ; Atula S. D. Sandanayaka ; Kevin Langenwalter ; Suresh Gadde ; Melvin E. Zandler ; Osamu Ito ; Francis D'Souza
- 刊名：Journal of Physical Chemistry C
- 出版年：2008
- 出版时间：February 14, 2008
- 年：2008
- 卷：112
- 期：6
- 页码：2222 - 2229
- 全文大小：459K
- 年卷期：v.112,no.6(February 14, 2008)
- ISSN：1932-7455
文摘
Supramolecular ferrocene-fullerene constructs in which the donor, ferrocene linked to a benzo-18-crown-6entity (Fc-crown), was self-assembled with the acceptor, fullerene bearing one or two alkyl ammonium ions(NH3+-C60), yielding dyads or a triad, respectively. The newly formed conjugates were characterized byspectroscopic (fluorescence, electospray ionization-mass, and 1H NMR) and electrochemical methods. Theadopted crown ether-alkyl ammonium ion binding strategy resulting in stable donor-acceptor conjugateswas also supported by the computational studies performed at the DFT B3LYP/3-21G(*) level in addition tothe 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 fluorescenceand nanosecond transient absorption spectral measurements. The rates of charge recombination were foundto be 2-3 orders of magnitude lower, yielding radical ion-pairs, Fc+-crown/NH3+-C60
- with lifetimes in the10-240 ns range. Generally, by increasing the donor-acceptor distance, a decrease in both kCS and kCR wasobserved for the supramolecular ferrocene-fullerene dyads; that is, the lifetimes of Fc+-crown/NH3+-C60-changed from 10 to 165 ns. However, for the triad, involving two ferrocene donors of varying donor-acceptor distances, the kCR originating from the far-side located ferrocene was found to be 240 ns while thekCR from the near-side located ferrocene was faster than the time duration of the nanosecond laser pulse (6ns).
- with lifetimes in the10-240 ns range. Generally, by increasing the donor-acceptor distance, a decrease in both kCS and kCR wasobserved for the supramolecular ferrocene-fullerene dyads; that is, the lifetimes of Fc+-crown/NH3+-C60-changed from 10 to 165 ns. However, for the triad, involving two ferrocene donors of varying donor-acceptor distances, the kCR originating from the far-side located ferrocene was found to be 240 ns while thekCR from the near-side located ferrocene was faster than the time duration of the nanosecond laser pulse (6ns).