Marczak Renata, Wielopolski Mateusz, Gayathri S Shankara, Guldi Dirk M, Matsuo Yutaka, Matsuo Keiko, Tahara Kazukuni, Nakamura Eiichi
Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 3, 91058 Erlangen, Germany.
J Am Chem Soc. 2008 Dec 3;130(48):16207-15. doi: 10.1021/ja8013902.
Quantum chemical calculations and various photophysical techniques, ranging from steady-state absorption and steady-state as well as time-resolved fluorescence to femtosecond pump-probe experiments, were employed to examine ground- and excited-state interactions in a set of novel double-decker buckyferrocenes (i.e., Fe(2)(C(60)Me(10))Cp(2)): C(2v) and D(5d) isomers. When compared to the individual reference systems, the intimate fullerene/ferrocene contacts reflect appreciable ground-state interactions, namely, substantial redistribution of charge density between the two electron donors (i.e., ferrocenes) and the electron acceptor (i.e., fullerene). Furthermore, an intervalence charge-transfer transition (i.e., ferrocene-ferrocenium interaction) was established, but only in the C(2v) isomer. The first insight into the electron donor-acceptor interactions came from inspecting the fullerene-centered fluorescence. Relative to the reference compounds that contain no ferrocene, which exhibit quantum yields of up to 0.1, and knowing that the fluorescence of the investigated double-decker type conjugates is quenched to 10(-3), transient absorption measurements prove unequivocally the rapid formation of the radical ion-pair states as the dominant products of excited-state deactivation in the double-decker buckyferrocenes. Despite these products having much higher lying radical ion-pair states relative to the corresponding single-decker buckyferrocene, their lifetimes, which vary between 12 and 39 ps, are slightly shorter.
