The Non-Covalent Interactions index: From biology to chemical reactivity and solid-state

ABSTRACT

The Non-Covalent Interaction (NCI) index has become a versatile tool for analyzing the presence and strength of localized and delocalized interactions in systems of interest to diverse areas such as biochemistry, reactivity, and solid state. Furthermore, it can be applied to promolecular, ab initio or even experimental electron densities, making it an even more flexible method. In this chapter, we demonstrate some of these NCI capacities by employing it in three representative cases (a) Interaction between the spike protein of some early variants of the SARS-CoV-2 virus with selected potential inhibitors. (b) The ring-opening metathesis polymerization of two norbornene derivatives, mediated by a ruthenium-alkylidene catalyst. (c) Effect of π-electron delocalization in the structural and electronic changes on the noncovalent interactions in two quinone crystals. These cases are illustrative of the application of NCI to study ligand-protein interactions, the interplay of inter and intramolecular forces in reaction pathways, and crystal packing, respectively. Moreover, we show the suitability of using different methods for obtaining the electron density in each example. © 2023 Elsevier Inc. All rights reserved.