Piecing it Together: An Additivity Scheme for Aromaticity using NICS-XY Scans.

Aromatic compounds are prevalent in both nature and man-made materials, yet their properties are still not fully understood and are therefore hard to predict. Herein, we introduce an additivity scheme for the prediction of the aromatic character of polycyclic aromatic hydrocarbons. Using a small set of building blocks and combination rules, we demonstrate the simple and intuitive construction of complete NICS-XY-scans for several test cases of one- and two-dimensional systems comprising six-membered rings. Partitioning the contribution of discrete building blocks provides insight into the aromatic character of these systems. The results obtained with this methodology provide a new perspective on the distribution of ring currents within polycyclic compounds and the effect of topology on the overall aromatic profile. The concept and strategy presented here are general and highly customizable. The scheme is easily applied to a wide range of interesting systems; it is especially beneficial for the investigation of large systems, as NICS-XY-scans are useful for their predictive utility with respect to optoelectronic and thermochemical properties.