Ipsocentric and allocentric methods of mapping induced current density

摘要

Distributed-origin strategies for calculating magnetic response in terms of locally paramagnetic (DZ) or diamagnetic (PZ) induced currents are compared in pure and in modified forms that push the origin towards nearby nuclei (DZ2, PZ2). For visualisation of ring-currents, ipsocentric DZ has practical and conceptual advantages, with interpretation in terms of well-defined orbital contributions, whereas for nuclear shieldings allocentric PZ2 has greater accuracy. Maps are presented for diatropic, paratropic and localised systems: benzene, planarised cyclooctatetraene, borazine, clamped benzenes. All variants give indistinguishable pi-maps, but differ in the a plane, near heavy nuclei. Mixed ipsocentric-mapping/allocentric-property-calculation combines efficiency and insight into magnetic aromaticity. (C) 2004 Elsevier B.V. All rights reserved.