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RESEARCH PRODUCT

Discrete supramolecular donor-acceptor complexes

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The renewed interest in noncovalently associating electroactive molecules arises in part from the quest for new organic materials that convert solar energy into electrical/ chemical equivalents. In this context, the formation of charge-separated states is a key prerequisite. Charge-transfer events triggered by light have been studied in supramolecular donor–acceptor systems based on hydrogen bonds and coordinative metal bonds. Although many of the most widely utilized electroactive fragments feature large pconjugated surfaces, to date the use of p–p aromatic interactions has mainly been limited to the construction of semi-infinite ensembles of chromophores either to achieve charge transport—with the known example of charge transfer through DNA bases—or to increase the efficiency of light absorption. Detailed studies on charge-transfer interactions in discrete supramolecular systems held together by p–p aromatic interactions are surprisingly scarce. Recently, we succeeded in the realization of donor–acceptor supramolecules based on the recognition of the convex exterior of C60 by the concave surface of p-extended tetrathiafulvalene derivatives. Numerous incentives, especially in the context of constructing more efficient optoelectronic devices, are offered by these C60/exTTF materials. Herein we describe the physicochemical characterization of the supramolecular donor–acceptor p complexes and provide a theoretical description of the underlying host–guest interactions. The meta and para tweezers (MTW and PTW, respectively) share a straightforward design, in which two 2-[9-(1,3dithiol-2-ylidene)anthracen-10(9H)-ylidene]-1,3-dithiole (exTTF) units are connected through isophthalic or terephthalic diester spacers, respectively (Scheme 1). MTW and