Chelatoaromaticity—existing: yes or no? An answer given by spatial magnetic properties (through space NMR shieldings—TSNMRS)

Abstract

The spatial magnetic properties (through space NMR shieldings—TSNMRS) of metal complexes (with ligands such as acetylacetone, 3-hydroxy-pyran(4)one) and “metallobenzenes” have been calculated by the GIAO perturbation method and visualized as Iso-Chemical-Shielding Surfaces (ICSS) of various sizes and directions. The TSNMRS values, thus obtained, can be successfully employed to quantify and visualize partial aromaticity of the metallocyclic ring by comparison with the spatial magnetic properties of the corresponding non-complexed ligands in comparable structural and electronic situations, and benzene, respectively. Because anisotropy/ring current effects in ¹H NMR spectra proved to be the molecular response property of TSNMRS, the results obtained concerning partial “chelatoaromaticity” are experimentally ensured.