Are the Most Stable Fused Heterobicycles the Most Aromatic?

Abstract

The authors' answer to the question in the title is: No, the most stable positional isomers of the isoelectronic heteroatom analogues (1 and 2) of the pentalene dianion are not the most aromatic. Their arguments are based on the geometric and magnetic criteria (computed magnetic susceptibilities and anisotropies, 1H NMR chemical shifts and nucleus-independent chemical shifts).