jo0c00072_si_001.pdf (4.29 MB)
Octapodal Corannulene Porphyrin-Based Assemblies: Allosteric Behavior in Fullerene Hosting
journal contribution
posted on 2020-03-18, 18:34 authored by Sergio Ferrero, Héctor Barbero, Daniel Miguel, Raúl García-Rodríguez, Celedonio M. ÁlvarezAn
octapodal corannulene-based supramolecular system has been prepared
by introducing eight corannulene moieties in a porphyrin scaffold.
Despite the potential of this double picket fence porphyrin for double-tweezer
behavior, NMR titrations show exclusive formation of 1:1 adducts.
The system exhibits very strong affinity for C60 and C70 (K1 = (2.71 ± 0.08) ×
104 and (2.13 ± 0.1) × 105 M–1, respectively), presenting selectivity for the latter. Density functional
theory (DFT) calculations indicate that, in addition to the four corannulene
units, the relatively flexible porphyrin tether actively participates
in the recognition process, resulting in a strong synergistic effect.
This leads to a very strong interaction with C60, which
in turn also induces a large structural change on the other face (second
potential binding site), leading to a negative allosteric effect.
We also introduced Zn2+ in the porphyrin core in an attempt
to modulate its flexibility. The resulting metalloporphyrin also displayed
single-tweezer behavior, albeit with slightly smaller binding constants
for C60 and C70, suggesting that the effect
of the coordination of fullerene to one face of our supramolecular
platform was still transmitted to the other face, leading to the deactivation
of the second potential binding site.