Taxonomy of Chemical Bondings: Opportunities and Challenges

Abstract

The concept of the chemical bond is fundamental to chemistry, governing atomic interactions that define all known matter. Despite this central role, the classification and most convenient naming of chemical bonds remain subjects of debate due to the diverse theoretical models and experimental observations. Modelings from quantum mechanical calculations and heuristic principles from experimental observations offer valuable and complementary insights, but sometimes the match and coalescence of these different approaches into a common terminology is not immediate. This paper describes a hierarchical categorization of noncovalent interactions based on the electrophilic atom involved, aligning with IUPAC definitions of hydrogen bonding (HB), halogen bonding (HaB), chalcogen bonding (ChB), and pnictogen bonding (PnB). The resulting taxonomy may avoid some ambiguities that arise from naming interactions based on single chemical/physical features. The proposed categorization that moves from more general and comprehensive terms to more specific and descriptive terms may ensure clarity, comprehensiveness, consistency with periodic trends, and invariancy over evolving understanding of the chemical bonds so that findings can be communicated and stored effectively via both human and machine based protocols.