Is Gelation Behavior Predictable through a Crystal Engineering Approach? A Case Study in Four Similar Coordination...

Area of Science:

• Coordination Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Metallogelators self-assemble into extended networks, forming gels with potential applications.
• Understanding the factors governing self-assembly is crucial for controlling material properties.

Purpose of the Study:

• To investigate the gelation properties of terpyridine and dipyrazine-pyridine ligands with metal salts.
• To elucidate the driving forces behind the self-assembly of metallogelators.
• To understand the interplay between molecular structure, intermolecular interactions, and the resulting assembly behavior (gelation vs. crystallization).

Main Methods:

• Synthesis of novel dipyrazine-pyridine ligands and their metal complexes.
• Crystal structure analysis to scrutinize self-assembly mechanisms.
• Comparative study of gelation and crystallization behaviors.

Main Results:

• The dipyrazine-pyridine ligand derivatives form crystals through alternating molecular stacking, unlike the unidirectional stacking required for gel formation.
• A crystal engineering approach identified interactions favoring fiber network formation, crucial for both crystalline and gel states.
• A delicate balance between molecular shape and intermolecular interactions dictates whether gelation or crystallization occurs.

Conclusions:

• The observed gelation and crystallization phenomena are attributed to the subtle balance between molecular shape and intermolecular interactions.
• A direct link between molecular structure, assembly behavior, and intermolecular interactions was established.
• The study provides a deep understanding of the factors controlling solution, gelation, and crystallization in coordination compounds with minor molecular modifications.