Multidimensional description of the aromaticity in planar five-membered NSNS ring systems.

The effect of the ring-closing fragment on the aromaticity of planar five-membered rings containing an NSNS fragment is investigated systematically. The influence of changing the group or period number of the ring-closing atom is studied as well as the effect of a substituent on this ring-closing element. Two sets of four five-membered ring systems were investigated. To reach a multidimensional description of the aromaticity, a robust set of geometrical, magnetic and energetic aromaticity criteria were combined. pi-Electron populations based on the stockholder scheme were calculated and lead to a quantity that correlates to the other aromaticity criteria. A third set of molecules was introduced to verify the conclusions.