A Quantum Mechanical Study on Identifying Reliable Descriptors to Evaluate the Strength of <scp>HOCl</scp> Complexes

ABSTRACT A theoretical investigation at MP2 = full/aug‐cc‐pVTZ level has been carried out on the hydrogen and halogen bonded complexes of the HOCl molecule with various Lewis bases (N‐, S‐, and O‐bases), aiming to identify a suitable descriptor for evaluating the bond strength in a generalized manner. A total of 24 halogen and hydrogen bonded complexes formed between the HOCl molecule and different electron donors have been investigated. The binding strength of these complexes was analyzed in relation to several descriptors, including proton affinity (PA), negative electrostatic potential ( V s,min ), electron density ρ ( r c ) at the bond critical point (BCP), charge transfer (CT), and hyperconjugation energy. Among these, the electron density emerged as the most reliable descriptor, showing a strong correlation with the binding strength across all the studied complexes, followed by hyperconjugation energy. In contrast, other parameters exhibited good correlations only when evaluated for specific bases but failed to maintain consistency across all types of complexes. These correlations not only contribute to a better understanding of the nature of hydrogen and halogen bonds with the HOCl molecule but also offer an effective approach for predicting their relative strengths, particularly in scenarios where both types of interactions coexist and compete with each other.