Complexation and electronic communication between corannulene-based buckybowls and a curved truxene-TTF donor

The association behavior of an electron-donating, bowl-shaped, truxene-based tetrathiafulvalene (truxTTF) with two corannulene-based fullerene fragments, C₃₂H₁₂ and C₃₈H₁₄, 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 logK_a=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. Timedependent 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 C₃₂H₁₂ or C₃₈H₁₄ and their supramolecular associates with truxTTF. In the case of truxTTF·C₃₈H₁₄, photoexcitation yields the charge-separated state truxTTFC⁺·C₃₈H₁₄·-with a lifetime of approximately 160 ps.