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Visualizing NMR ‐shielding effect in fullerene‐ZnPc aggregates: Characteristic patterns of ZnP‐based hosts and encapsulation nature from DFT calculations
Author(s) -
MacLeod Carey Desmond,
RodríguezKessler Peter L.,
MuñozCastro Alvaro
Publication year - 2021
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.26500
Subject(s) - chemistry , dimer , porphyrin , supramolecular chemistry , fullerene , electromagnetic shielding , proton nmr , crystallography , electron paramagnetic resonance , molecule , stereochemistry , photochemistry , nuclear magnetic resonance , materials science , organic chemistry , crystal structure , physics , composite material
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 ZnPC 60 aggregate and a ZnP‐dimer (ZnP 2 C 60 ) model, with a significant contribution from noncovalent ππ 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.