Tuning two-electron transfer in terpyridine-based platinum(ii) pincer complexes.

Area of Science:

• Inorganic Chemistry
• Electrochemistry
• Coordination Chemistry

Background:

• Achieving reversible multi-electron transfer in metal complexes requires managing significant coordination geometry changes.
• Ligand design is key to stabilizing metal centers in different oxidation states.

Purpose of the Study:

• To synthesize and characterize platinum(II) complexes featuring pip2NCN- pincer and terpyridine ligands.
• To investigate the electrochemical properties, specifically multi-electron transfer, of these novel platinum complexes.
• To explore how ligand substituents influence the redox behavior and stability of the complexes.

Main Methods:

• Synthesis of platinum(II) complexes with varying pincer (Z-pip2NCN-) and terpyridine (R-tpy) ligands.
• Characterization using 1H NMR spectroscopy to determine ligand coordination modes.
• Electrochemical analysis, including cyclic voltammetry, to study oxidation and reduction potentials.

Main Results:

• The Z-pip2NCN- ligand acts as a monodentate ligand, while the R-terpyridyl ligand is tridentate.
• Platinum(II) complexes undergo a two-electron oxidation, stabilized by the pincer ligand's flanking groups.
• Two distinct platinum-centered reductions were observed, with tunable potentials based on ligand substituents.
• An oxidation-to-reduction electron ratio (n_ox/n_red) close to 1.8 was estimated, supporting two-electron transfer.

Conclusions:

• Pip2NCN- pincer and terpyridine ligands effectively support square planar Pt(II) and octahedral Pt(IV) geometries for reversible electron transfer.
• Ligand substitution provides a means to tune the redox potentials of platinum complexes over a significant range.
• These findings offer a pathway for designing electrocatalysts and redox-active materials with tailored electrochemical properties.