Controlling the Complexity and Interconversion Mechanisms in Self-Assembled [Fe₂ L₃ ]⁴⁺ Helicates and [Fe₄ L₆ ]⁸⁺...

Area of Science:

• Coordination chemistry
• Supramolecular chemistry
• Materials science

Background:

• Symmetric ligands are typically used in self-assembled coordination cages and metal-organic frameworks.
• Unsymmetric ligands offer potential for designing novel self-assembled structures with tunable properties.

Purpose of the Study:

• To explore the self-assembly of coordination structures using an unsymmetric ligand.
• To investigate the influence of ligand steric profile on the resulting structures and their dynamics.
• To characterize the formation of distinct helicate and cage architectures.

Main Methods:

• Synthesis and characterization of a novel unsymmetric ligand.
• Self-assembly experiments in solution.
• Spectroscopic and crystallographic analyses to determine structures.
• Thermodynamic and kinetic studies of interconversion processes.

Main Results:

• Successful preparation of two distinct self-assembled structures: a [Fe2L3]4+ helicate and a [Fe4L6]8+ cage.
• The cage structure is composed of 10 interconverting diastereomers and their enantiomers.
• The steric bulk of the unsymmetric ligand dictates the complexity, thermodynamics, and kinetics of the system's interconversion.

Conclusions:

• Unsymmetric ligands can lead to complex and diverse self-assembled coordination structures.
• Ligand design, specifically its steric profile, is a critical factor in controlling supramolecular assembly and dynamics.
• This work provides a new strategy for designing sophisticated coordination cages and helicates.