Evaluating Shielding-Based Ring-Current Models by Using the Gauge-Including Magnetically Induced Current Method.

Magnetically induced current densities and integrated ring-current strength susceptibilities have been calculated at the density functional theory (DFT) level for a test set consisting of 17 ring-shaped molecules using the gauge-including magnetically induced current (GIMIC) method. Reliable values for the ring-current strengths have been obtained by performing numerical integration of the current-density susceptibility passing a cut plane perpendicularly to the molecular ring. The current densities and ring current strengths were calculated at the DFT level using the B3LYP functional and def2-TZVP basis sets. Current densities and ring-current strengths have also been calculated at the Hartree-Fock self-consistent field (HF-SCF) level using Dunning's aug-cc-pVTZ basis sets, which allow a direct comparison with ring-current strengths that have previously been estimated using ring-current models based on magnetic shielding calculations. Current density calculations at both levels of theory show that the magnetic shielding based ring-current models are not a very accurate means to estimate the magnetically induced ring current strengths, whereas they provide qualitatively the correct aromaticity trends for the studied molecules. [ABSTRACT FROM AUTHOR]