Evaluation of aromaticity: A new dissected NICS model based on canonical orbitals

Several methods to address aromaticity in terms of nucleus-independent chem. shifts (NICS) are compared. These include NICS at the ring center NICS(0), NICS 1 .ANG. above the ring plane NICS(1), arom. ring current shielding (ARCS), and dissected NICS, i.e. NICS calcd. from selected pi orbitals NICSpi, again in the ring plane and 1 .ANG. above. The methods are tested on the basis of d.-functional theory (DFT) and the individual gauge for local orbitals (IGLO) technique. Applications include simple org. rings (C4H4, C4H42+, C6H6, C5H5-, C7H7+) and transition metal carbonyl complexed mols. Fe(CO)3C4H4 and Cr(CO)3C6H6. [on SciFinder (R)]