Entropically driven self-assembly of a strained hexanuclear indium metal-organic macrocycle and its behavior in...

Area of Science:

• Coordination Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Metal-organic macrocycles are complex structures with diverse applications.
• Understanding self-assembly processes is key to designing novel materials.
• Indium(III) coordination chemistry offers unique properties for macrocycle formation.

Purpose of the Study:

• To synthesize and characterize a novel hexanuclear indium metal-organic macrocycle (In-MOM).
• To investigate the self-assembly principles governing the formation of strained macrocycles.
• To explore the stability and dissociation behavior of the synthesized In-MOM.

Main Methods:

• Self-assembly reaction between N-cyclopentanoylaminobenzoylhydrazide (H(4)L(4)) and In(III) nitrate hydrate in methanol.
• Structural characterization of the resulting hexanuclear In-MOM.
• Solubility studies in different solvents (acetonitrile and dimethylsulfoxide).

Main Results:

• Formation of a D(3)-symmetric, strained hexanuclear indium metal-organic macrocycle, [In(III)(6)(H(2)L(4))(6)(NO(3))(x)(solvent)(6-x)](NO(3))(6-x).
• The macrocycle formation is entropically favored over enthalpically favored octanuclear structures due to indium's coordination preferences and ligand flexibility.
• The In-MOM exhibits stability in acetonitrile but partial dissociation in dimethylsulfoxide, leading to new indium species.

Conclusions:

• The study demonstrates the successful synthesis of a unique strained hexanuclear indium macrocycle.
• Thermodynamic factors (entropy) play a crucial role in the formation of these strained supramolecular structures.
• The solvent-dependent stability of the In-MOM highlights the dynamic nature of metal-organic assemblies.