Density functional calculations of the anisotropic effects of borazine and 1,3,2,4-diazadiboretidine.

On the basis of the nucleus-independent chemical shift (NICS) concept, the anisotropic effects of two inorganic rings, namely, borazine and planar 1,3,2,4-diazadiboretidine, are quantitatively calculated and visualized as isochemical shielding surfaces (ICSSs). Dissection of magnetic shielding values along the three Cartesian axes into contributions from σ and π bonds by the natural chemical shielding-natural bond orbital (NCS-NBO) method revealed that their appearance is not a simple reflection of the extent of (anti)aromaticity.