Quantum-chemical simulation of solid-state NMR spectra: the example of a molecular tweezer host-guest complex

A systematic quantum-chemical study of the convergence of proton NMR shieldings with the size of solid-state fragments is presented for a host-guest system. The largest system computed at Hartree-Fock and density-functional theory levels comprises a full first shell of complexes surrounding a central unit within an X-ray based structure and a total of 1196 atoms and 13,260 basis functions. While the influence of methodological aspects can be considered to be converged within the error bars of experiment and theory, the deviation of one of the protons provides evidence for the possibility of a dynamic rotation process of the guest within the host complex.