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Intramolecular photoinduced charge-separation and charge-recombination processes in a covalently connected C60-(spacer)-N,N-bis(biphenylyl)aniline (C60-spacer-BBA) dyad, in which the center-to-center distance of the electron acceptor and electron donor is 15 A, have been studied by time-resolved fluorescence and transient absorption methods. The observed low fluorescence intensity and the short fluorescence lifetime of the C60 moiety of the dyad in PhCN and THF indicate that charge separation takes place via the excited singlet state of the C60 moiety at a quite fast rate and a high efficiency. The nanosecond transient absorption spectra in PhCN and THF showed the broad absorption bands at 880 and 1100 nm, which were attributed to C60(*-)-spacer-BBA(*+). The charge-separated state decays with a lifetime of 330-360 ns in PhCN and THF at room temperature. From temperature dependence of the charge-recombination rate constants, the reorganization energy was evaluated to be 0.77-0.87 eV, which indicates that the charge-recombination process is in the inverted region of the Marcus parabola. With lowering temperature, the contribution of charge separation via the excited triplet state of the C60 moiety increases due to an increase in solvation of C60(*-)-spacer-BBA(*+).

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Oxidation O 0212Selective and Clean Oxidation of Alcohols with Benzimidazolium Fluorochromate (BIFC) under Solvent Free Conditions. -Benzimidazolium fluorochromate is shown to be an efficient oxidant for primary or secondary alcohols. The corresponding aldehydes or ketones are formed in high yields. -(SIVAMURUGAN, V.; RAJKUMAR, G. A.; ARABINDOO, B.; MURUGESAN*, V.; Indian J. Chem., Sect.

A rotaxane tethering both fullerene (C60) and ferrocene (Fc) moieties (abbreviated as (C60;Fc)rotax+) was synthesized in a good yield by the urethane end-capping of pseudorotaxane based on the crown ether-secondary amine motif. In (C60;Fc)rotax+, the C60 group serving as an electron acceptor is attached to the crown ether wheel, through which the axle with a Fc group acting as an electron donor on its end penetrates. The intrarotaxane photoinduced energy-transfer and electron-transfer processes between C60 and Fc in (C60;Fc)rotax+ have been investigated by time-resolved transient absorption and fluorescence measurements with changing solvent polarity. Nanosecond transient absorption measurements of the rotaxane demonstrated that the charge-separated state (C60*-;Fc*+)rotax+ is formed mainly via the excited triplet state of C60 in polar solvents. The lifetime of (C60*-;Fc*+)rotax+ was evaluated to be 20 ns in dimethylformamide (DMF) at room temperature. With lowing temperature, the lifetime of (C60*-;Fc*+)rotax+ extends to 270 ns in DMF at -65 degrees C, due to the structural changes leaving C60*- and Fc*+ at a relatively long distance in the low-temperature region.

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A [2]rotaxane was synthesized in a high yield from a dumbbell-shaped sec-ammonium salt having trityl thioether and 3,5-di-t-butylphenyl groups at the both ends and dibenzo-24-crown-8-ether, through the slipping, utilizing the reversible cleavage–rebondage of the trityl thioether linkage.