Selective Activation of Chalcogen Bonding: An Efficient Structuring Tool toward Crystal Engineering Strategies

Area of Science:

• Crystal Engineering
• Supramolecular Chemistry
• Materials Science

Background:

• Chalcogen bonding (ChB) is an emerging noncovalent interaction analogous to halogen bonding (XB).
• Despite its potential, ChB faces challenges in predictability and synthetic accessibility, particularly for heavier chalcogens (Se, Te).
• Existing limitations hinder the widespread application of ChB in crystal engineering and materials design.

Purpose of the Study:

• To enhance the strength and predictability of ChB interactions.
• To explore novel ChB donors based on divalent selenium and tellurium systems.
• To demonstrate the utility of ChB in crystal engineering, focusing on anionic networks and topochemical reactions.

Main Methods:

• Design and synthesis of novel ChB donors with dissymmetrical σ-holes using electron-withdrawing groups.
• Cocrystallization studies with halide and bipyridine acceptors.
• Investigation of ChB-driven topochemical reactions, including [2+2] cycloadditions and polydiacetylene formation.

Main Results:

• Developed new organic selenocyanates, alkynyl chalcogenides, and o-carborane derivatives as effective ChB donors.
• Demonstrated the ability of these compounds to strongly chelate halides and organize reactive molecules.
• Achieved predictable ChB interactions comparable in strength to XB, enabling controlled solid-state reactions.

Conclusions:

• Dissymmetrization of σ-holes in divalent chalcogen systems significantly enhances ChB strength and predictability.
• This approach unlocks new possibilities for ChB in crystal engineering, anionic network formation, and topochemical transformations.
• The selective activation concept is broadly applicable to other σ-hole interactions for controlled molecular assembly.