On the Validity of Atomic Charges as Reactivity Descriptors: Bridging Conceptual Density Functional Theory With Information‐Theoretic Approach in Transition‐Metal Catalysis

ABSTRACT

Atomic charges are widely used as intuitive measures of chemical reactivity, yet their theoretical validity as quantitative descriptors remains unclear. In this work, we examine the relationship between global reactivity indices from conceptual density functional theory (CDFT) and local atomic charges derived from the information‐theoretic approach (ITA), using NO _x intermediates coordinated to Mn ⁴⁺ centers involved in the selective catalytic reduction of NO _x as a model system. Strong linear correlations are observed between Hirshfeld charges on oxygen atoms and CDFT descriptors, including electron affinity and electrophilicity index, demonstrating that atomic charges can quantitatively represent electrophilicity and nucleophilicity at true reaction centers. Benchmark analysis further shows that Hirshfeld charge uniquely preserves this equivalence among common charge schemes. In contrast, charges on nitrogen atoms exhibit volcano‐type relationships with CDFT reactivity indices, indicating a breakdown of descriptor validity when an atomic site is not directly involved in the reaction. Analysis of electronic structure properties reveals that this apparent scaling originates from the underlying Mn 3d states, rather than the intrinsic reactivity of the nitrogen site. These results establish a clear criterion for the validity of atomic charges as reactivity descriptors and provide a density‐based framework bridging CDFT and ITA for understanding and designing transition‐metal catalytic systems.