Differentiating Ligand Tailoring and Cation Incorporation as Strategies for Tuning Heterobimetallic Cerium Complexes

Area of Science:

• Coordination Chemistry
• Lanthanide Chemistry
• Supramolecular Chemistry

Background:

• Tuning redox-active complexes with high coordination numbers using secondary cations is underexplored.
• Lanthanides, like cerium, often adopt high coordination numbers, making them ideal for such studies.

Purpose of the Study:

• Investigate the influence of steric bulk on secondary-cation-driven tuning of cerium complexes.
• Explore how cation binding affects structural and electrochemical properties.

Main Methods:

• Synthesis of a quasi-C3-symmetric cerium(III) complex with pendant benzyloxy groups.
• Electrochemical studies (e.g., cyclic voltammetry) and UV-visible spectroscopy.
• Analysis of cation binding affinities and coordination numbers.

Main Results:

• The cerium complex binds single Na+ or Ca2+ ions.
• Equilibrium binding affinity for Na+ was observed in acetonitrile, unlike tight binding in previous systems.
• Bulky benzyloxy groups modulated cation binding thermodynamics without preventing coordination number 8.
• The Ce(IV/III) reduction potential was tunable under equilibrium binding conditions.

Conclusions:

• Steric bulk on ligands can control secondary cation binding in lanthanide complexes.
• This control allows for tuning of electrochemical properties in heterobimetallic systems.
• The findings highlight the potential of structurally modulated complexes for tailored solution properties.