Multidentate halogen bond acceptors: from fluorides to iodides. Anticooperativity in halogen-bonded clusters

Area of Science:

• Supramolecular Chemistry
• Chemical Crystallography
• Computational Chemistry

Background:

• Halogen bonding is a key non-covalent interaction.
• Halide anions can function as halogen bond acceptors.
• Understanding the factors influencing halogen bond strength and geometry is crucial.

Purpose of the Study:

• To investigate the occurrence frequency of halide anions as halogen bond acceptors of varying denticity.
• To computationally assess the impact of halide acceptor denticity on interaction energy and its nature.
• To analyze non-additivity in halogen-bonded systems.

Main Methods:

• Survey of the Cambridge Structural Database.
• Statistical analysis of crystallographic data.
• Computational studies using model halogen-bonded complexes.
• Canonical energy decomposition analysis (canonical EDA).

Main Results:

• Most studied motifs (C-I)n⋯Y− exhibit n ≤ 4 halogen bond donors.
• Fluoride anions show no motifs with more than four ligands in crystal structures.
• Canonical EDA reveals trends in interaction energy and components with increasing donor number.
• Identified factors differentiating a theoretical adduct (F3C-I)5⋯F− from analogous complexes.

Conclusions:

• Halide acceptor denticity is limited in known crystal structures.
• Computational analysis provides insights into interaction energy changes with increasing denticity.
• Non-additivity of interactions in model systems was studied and its source identified.