VisualizingNMR-shielding effect infullerene-ZnPcaggregates: Characteristic patterns ofZnP-basedhosts and encapsulation nature fromDFTcalculations

The formation of supramolecular aggregates incorporating C(60)fullerenes can be followed and characterized by nuclear magnetic resonance (NMR) measurements. Here, we unravel the particular patterns provided by zinc-porphyrin (ZnP)-bridged dimers, where the aromatic character of each ZnP unit leads to an enhanced shielding region for the closest fullerene atoms, denoting a slight shielding effect for the equatorial atoms. The nature of the stabilization is discussed and compared to a single ZnP-C(60)aggregate and a ZnP-dimer (ZnP2-C-60) model, with a significant contribution from noncovalent pi-pi interactions, allowing us to address the role of bridging chains. The experimental(13)C-NMR spectrum of C(60)in a bridged ZnP dimer shows a single peak owing to the constant tumbling inside the host, which averages the different groups of carbon atoms. The calculations in a static scenario reveal information concerning the local chemical environment underlying the observed shift in relation to isolated C-60. We expect that the current approach can be useful to rationalize and predict the origin of the NMR shift upon the formation of host-guest aggregates involving small and large host species.

Automated summary

The formation of supramolecular aggregates incorporating C(60) fullerenes was studied using nuclear magnetic resonance (NMR) measurements and the shielding effect and stabilization properties of zinc-porphyrin (ZnP)-bridged dimers were discussed. Experimental(13)C-NMR spectra showed a single peak for C(60) in a bridged ZnP dimer due to constant tumbling inside the host, providing insights into the observed shift in the local chemical environment compared to isolated C-60. This approach has the potential to rationalize and predict NMR shifts in host-guest aggregates involving small and large host species.