Not All That Has a Negative NICS Is Aromatic: The Case of the H-Bonded Cyclic Trimer of HF

Abstract

In this work, we used the induced magnetic field (Bind) to study the degree of aromaticity of the planar (HF)3 ring. The induced magnetic field analysis shows that the degree of electron delocalization in the hydrogen-bonded cyclic trimer of HF is very low. This result is in agreement with those obtained using GIMIC and is opposite to the Rehaman’s suggestion. Our results demonstrate a clear limitation of the NICS index when a strong anisotropy is exhibited and suggest that the NICS values should be used carefully to discuss aromaticity in systems without an important pz-orbital overlap that produces the π clouds. In view of the fact that the NICS index is extensively used by computationally and theoretically oriented experimental chemists, this is an important warning.