Evaluating iron diimines: ion-pairing, lability and the reduced state
David Schilter1, Umberto Terranova2, Caden B Summers1
1Department of Chemistry and Biochemistry, Texas State University, San Marcos, TX 78666, USA. schilter@txstate.edu.
Physical Chemistry Chemical Physics : PCCP
|March 31, 2025
Summary
Tris(diimine)iron(II) complexes show varying stability and redox properties in the gas phase. Their ligand field strength influences thermal stability and collision cross-sections, impacting their potential in photoredox catalysis.
Area of Science:
- Inorganic Chemistry
- Physical Chemistry
- Computational Chemistry
Background:
- Tris(diimine)iron(II) complexes are promising photosensitizers.
- Their small ligand fields lead to lability and unique redox properties.
Purpose of the Study:
- To investigate the gas-phase stability and redox behavior of [Fe(N^N)3]2+ dications.
- To understand the influence of diimine ligands on complex properties.
Main Methods:
- Mass spectrometry and density-functional theory (DFT) were employed.
- Collision-induced dissociation (CID) and ion-mobility spectrometry (IMS) were used to study stability and collision cross-sections.
- Redox potentials were calculated and correlated with experimental reduction reactions.
Main Results:
- Tetraarylborates are poor ligands, requiring ligand dissociation for ion pair dissociation.
- Dications exhibit contrasting thermal stabilities, with [Fe(bipy(t-Bu)2)3]2+ being the most stable.
- Collision cross-sections vary, with [Fe(bipy(t-Bu)2)3]2+ being the largest.
- Monocation stability follows a similar trend to dication stability, suggesting effective stabilization of both charge states.
Conclusions:
- The π-donor and -acceptor properties of diimine ligands are crucial for stabilizing both dication and radical monocation states.
- These findings are relevant for the application of iron complexes in photoredox catalysis.
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