The effect of substituent rotation on aromatic quadrupole moments

Abstract

We recently reported substituent constants for the accurate prediction of molecular quadrupole moments of mono-, di-, tri- and tetra-substituted aromatics. Four of the substituents in the study, –OH, –NO2, –NH2, and –CH3, were polyatomic and for these groups the substituent constants only hold for the lowest energy, or near-lowest energy, geometries. Herein, we report a computational investigation of the effect of rotation of –OH, –NO2, –NH2, and –CH3 groups on the aromatic quadrupole moment, Θzz. As expected, rotation of these substituents significantly affects the aromatic Θzz value; however, the affects are clearly periodic. Additionally, we have modified the methods to best employ our substituent constants.