Current density ipsocentric mappings

The criterion of ipsocentric ring current has been used to assess aromaticity in S-N heterocycles (and related inorganic ring systems). Current density maps indicate that the ten r-electron systems [SsNs], [S4N3] " and [S4N4] ", and the fourteen r-electron system [S5N5] " support diatropic k currents, reinforced by a circulations. 

Optimization at the restricted Hartree-Fock (RHF) and DFT (B3LYP) levels in the 6-31G basis set has also contributed to structural clarification of [l,2,5]thiadiazolo[3,4-f][l,2,5]thiadiazole 6 both approaches successfully predict that 6 ought to have planar equilibrium geometry. Direct a3 initio ipsocentric calculations of the total 7t-current density map for 6 permits classification as aromatic according to magnetic criteria. It exhibits a strong and uniform diatropic perimeter circulation, of comparable intensity to the parent monocycle 11 and similar to that of naphthalene <2004JA11202>. 

Fig. 5. Computed map of the 77 current density calculated in the ipsocentric approach for pentalene optimised at the RHF/6-31G level [14c]. Arrows show the projection of the current density induced by unit perpendicular magnetic field in the plane 1 bohr above the molecule. The clockwise sense indicates paramagnetic (anti-Lenz) circulation.

Fig. 2 7T current density maps computed at the ipsocentric RHF/6-31G level for clamped benzene and cyclooctatetraene systems. Benzene-based systems are shown on the left and COT-based systems on the right, with the three rows representing HC = CH clamps (7, (a) and 10, (b)), HB-BH clamps (8, (c) and 11, (d)) and HN-NH clamps (9, (e) and 12, (f)). Plotting conventions are as in Fig. 1. All systems are shown in planar geometries these are local optima for the HC = CH-clamped systems 7 and 10, but not for the others... 

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