DFT investigation of the influence of Jahn-Teller distortion on the aromaticity in square-planar arsenic and antimony clusters

Density functional theory (DFT) calculations were performed to investigate aromaticity of tetra atomic metalloid clusters, As-4(2-) and Sb-4(2-). The careful analysis of nuclear independent chemical shifts (NICS) revealed strong sigma antiaromatic and week pi aromatic character of investigated species. This unexpected behavior is explained through the analysis of antagonistic paratropic and diatropic contributions, and with detailed adaptive natural density partitioning (AdNDP) analysis. Furthermore, we investigated aromatic/antiaromatic behavior of Jahn-Teller (JT) active species As-4(-) and Sb-4(-). NICS parameters have been scanned along the Intrinsic Distortion Path (IDP) showing strong antiaromaticity which decreases with increasing deviation from D-4h to D-2h symmetry