Understanding the kinetics and energetics of interfacial electron transfer in molecular systems is crucial for the development of a broad array of technologies, including photovoltaics, solar fuel systems and energy storage. The Marcus formulation for electron transfer relates the thermodynamic driving force and reorganization energy for charge transfer between a given donor/acceptor pair to the kinetics and yield of electron transfer. Here we investigated the influence of the thermodynamic driving force for photoinduced electron transfer (PET) between single-walled carbon nanotubes (SWCNTs) and fullerene derivatives by employing time-resolved microwave conductivity as a sensitive probe of interfacial exciton dissociation. For the first time, we observed the Marcus inverted region (in which driving force exceeds reorganization energy) and quantified the reorganization energy for PET for a model SWCNT/acceptor system. The small reorganization energies (about 130 meV, most of which probably arises from the fullerene acceptors) are beneficial in minimizing energy loss in photoconversion schemes.

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The sequential addition of CN(-) or CH3(-) and electrophiles to three perfluoroalkylfullerenes (PFAFs), C(s)-C70(CF3)8, C1-C70(CF3)10, and C(s)-p-C60(CF3)2, was carried out to determine the most reactive individual fullerene C atoms (as opposed to the most reactive C=C bonds, which has previously been studied). Each PFAF reacted with CH3(-) or CN(-) to generate metastable PFAF(CN)(-) or PFAF(CH3)2(2-) species with high regioselectivity (i.e., one or two predominant isomers). They were treated with electrophiles E(+) to generate PFAF(CN)(E) or PFAF(CH3)2(E)2 derivatives, also with high regioselectivity (E(+)=CN(+), CH3(+), or H(+)). All of the predominant products, characterized by mass spectrometry and (19)F NMR spectroscopy, are new compounds. Some could be purified by HPLC to give single isomers. Two of them, C70(CF3)8(CN)2 and C70(CF3)10(CH3)2(CN)2, were characterized by single-crystal X-ray diffraction. DFT calculations were used to propose whether a particular reaction is under kinetic or thermodynamic control.

Six new poly(trifluoromethyl)azulenes prepared in a single high-temperature reaction exhibit strong electron accepting properties in the gas phase and in solution and demonstrate the propensity to form regular π-stacked columns in donor-acceptor crystals when mixed with pyrene as a donor.