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, 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 K_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. 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.