Noble gas bonds facilitate anion⋯anion supramolecular assemblies: insights from CSD and DFT analysis

Abstract

Noble gas bonding (NgB) is a noncovalent interaction where noble gases, such as xenon or krypton, function as Lewis acids. These interactions arise from regions of positive electrostatic potential, known as σ-holes or π-holes, which form on the noble gas atom and interact with electron-rich sites, such as lone pairs or anions. Although recently discovered, NgBs have demonstrated considerable potential in supramolecular chemistry, with their strength—especially in the case of heavier noble gases like xenon—comparable to that of hydrogen bonds. Anion⋯anion interactions, which are typically hindered by electrostatic repulsion, can occur through attractive forces like σ-hole and π-hole interactions. While these interactions are increasingly observed in biological and synthetic systems, particularly in solid-state and polar environments, their stabilization via NgBs remains largely unexplored. In this study, we present a computational and experimental analysis of noble gas bonds (NgBs) facilitating anion⋯anion interactions, emphasizing the unique role of xenon as a σ-hole donor. Through a combination of Cambridge Structural Database (CSD) inspection and density functional theory (DFT) calculations, we reveal the novel contribution of NgBs in dispersing electrostatic charge, allowing for the stabilization of anion⋯anion dimers. Our findings suggest that, while the concept of counterion-mediated anion⋯anion attraction is well known, the use of noble gas bonding offers a distinct and previously unexplored mechanism for enabling such interactions. These results open new possibilities for designing supramolecular assemblies with unconventional bonding motifs.