The association behavior of an electron-donating, bowl-shaped, truxene-based tetrathiafulvalene (truxTTF) with two corannulene-based fullerene fragments, C32 H12 and C38 H14 , is investigated in several solvents. Formation of 1:1 complexes is followed by absorption titrations and complemented by density functional theory (DFT) calculations. The binding constants are in the range log Ka =2.9-3.5. DFT calculations reveal that the most stable arrangement is the conformation in which the 1,3-dithiole ring of truxTTF is placed inside the concave cavity of the corannulene derivative. This arrangement is confirmed experimentally by NMR measurements, and implies that a combination of π-π and CH-π interactions is the driving force for association. Time-dependent DFT calculations reproduce the experimental UV/Vis titrations and provide a detailed understanding of the spectral changes observed. Femtosecond transient absorption studies reveal the processes occurring after photoexcitation of either C32 H12 or C38 H14 and their supramolecular associates with truxTTF. In the case of truxTTF⋅C38 H14 , photoexcitation yields the charge-separated state truxTTF.+ ⋅C38 H14.- with a lifetime of approximately 160 ps.
Keywords: association constants; buckybowls; donor-acceptor systems; photoinduced charge transfer; supramolecular chemistry.
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