Visualization of homoaromaticity in cations, neutral molecules and anions by spatial magnetic properties (through space NMR shieldings)-an 1H/13C NMR chemical shift study

Prototypes for homoaromaticity in cations, neutral molecules, and anions are theoretically studied at the MP2 level of theory. For the global minimum structures on the potential energy Surface both H-1/C-13 chemical shifts and spatial magnetic properties as through space NMR shieldings (TSNMRS) were calculated by the GIAO perturbation method. The TSNMRS are visualized as iso-chemical-shielding Surfaces (ICSS) of different sign and size. Coincident experimental and computed H-1/C-13 chemical shifts afforded the possibility to decide from the TSNMRSs at hand on both the existence and the size of homoaromaticity in the molecules studied. (C) 2009 Elsevier Ltd. All rights reserved.