Supramolecular Covalence in Bifurcated Chalcogen Bonding

Area of Science:

• Supramolecular Chemistry
• Inorganic Chemistry
• Computational Chemistry

Background:

• Supramolecular interactions are typically classified as noncovalent.
• Recent evidence suggests many such interactions have a substantial covalent component.
• Chalcogen bonding is a key type of interaction involving elements from the chalcogen group.

Purpose of the Study:

• To investigate the nature of bifurcated chalcogen bonding in [MX6]2-:YX2 systems.
• To determine the factors governing binding energies and covalent character in these interactions.
• To explore the role of substituents in modulating supramolecular interactions.

Main Methods:

• Theoretical calculations were employed, including quantum chemical topology and localized molecular orbital analysis.
• Systematic variation of metal (M), chalcogen (Y), and halide (X) substituents.
• Analysis of electrostatic contributions versus substituent effects on binding energies.

Main Results:

• Electrostatic parameters were insufficient to predict binding energy trends.
• Lewis basicity of halide substituents on the chalcogen atom was found to be the primary driver of binding energy.
• A strong correlation between substituent effects, binding energy, and the covalent character of the chalcogen bond was observed.

Conclusions:

• Chalcogen bonding in these systems exhibits significant covalent character, termed 'supramolecular covalence'.
• Orbital interactions and electron sharing are key features of this bonding.
• Substituent effects, particularly Lewis basicity, are crucial for understanding and tuning supramolecular interactions.