Outer sphere perturbation of delocalized mixed-valence complexes

Area of Science:

• Coordination Chemistry
• Materials Science
• Spectroscopy

Background:

• Ruthenium polypyridyl complexes are widely studied for their photophysical and electrochemical properties.
• Bridging ligands offer pathways for electronic communication between metal centers.

Purpose of the Study:

• To synthesize and characterize novel ruthenium complexes featuring bridging azodi(phenylcyanamide) (adpc) and 1,4-dicyanamidebenzene (dicyd) ligands.
• To investigate the electronic structure, mixed-valence properties, and metal-metal coupling in these complexes.

Main Methods:

• Synthesis and characterization of dinuclear ruthenium complexes.
• Infrared (IR) and Near-Infrared (NIR) spectroscopy.
• Visible spectroelectrochemistry and cyclic voltammetry.
• X-ray crystallography for structural determination.

Main Results:

• The crystal structure of [[Ru(ttp)(bpy)](2)(micro-adpc)][PF(6)](2).6DMF revealed a planar bridging adpc ligand with anti-configured cyanamide groups.
• IR and comproportionation data confirmed delocalized mixed-valence states.
• Spectroscopic analysis predicted multiple metal-to-metal-to-metal charge transfer (MMCT) transitions.
• Solvent dependence of the MMCT band energy was observed, attributed to solvent interactions with the bridging ligand.

Conclusions:

• The synthesized ruthenium complexes exhibit delocalized mixed-valence character.
• Metal-metal coupling is influenced by the bridging ligand's electronic properties and solvent interactions.
• The study provides insights into superexchange pathways in polynuclear metal complexes.