Toy Models Reveal Intrinsic Biases in NICS : Insights to Verify NICS Interpretations

ABSTRACT The nucleus‐independent chemical shift (NICS) as an aromaticity index rests on the premise that the NICS value can be interpreted to infer those aspects of a system's current‐density susceptibility () that are relevant to magnetic aromaticity. While the shielding density acts as an intermediary in the inferential relation between NICS and , the complexity of shielding‐density patterns in molecular systems hinders the extraction of generalizable insights. To address the complexity associated with molecular systems, toy models are introduced that isolate inherent features of the NICS– relationship and separate intrinsic NICS behavior from aromaticity. NICS is found to provide an inherently biased reflection of , resulting in artifacts that could be misinterpreted to yield conclusions that conflict with the magnetic aromaticity criterion. This work establishes a foundation for using toy models to obtain the insight needed to verify NICS interpretations with respect to the underlying in molecular systems.