Cyclometalated Osmium-Amine Electronic Communication through the p-Oligophenylene Wire

Area of Science:

• Organometallic Chemistry
• Supramolecular Chemistry
• Electrochemistry

Background:

• Bis-tridentate cyclometalated osmium complexes are valuable for studying electron transfer.
• Redox-active triarylamine substituents enable electrochemical investigations.
• Molecular wires, such as p-oligophenylenes, are used to control electronic communication.

Purpose of the Study:

• To synthesize and characterize novel osmium complexes with varying p-oligophenylene wire lengths.
• To investigate the electronic communication between the osmium center and the triarylamine substituent.
• To compare the electronic coupling in osmium complexes with previously studied ruthenium analogues.

Main Methods:

• Synthesis of bis-tridentate cyclometalated osmium complexes.
• X-ray crystallography for structural determination of key complexes.
• Electrochemical studies (cyclic voltammetry) to analyze redox behavior.
• Combined experimental and theoretical (DFT) calculations for electronic structure analysis.

Main Results:

• Two consecutive anodic redox couples were observed between +0.1 and +0.9 V vs Ag/AgCl.
• Potential splitting ranged from 300-390 mV, indicating significant electronic interaction.
• Electron delocalization was observed for short wires, while localization occurred on osmium for longer wires.
• Electronic coupling parameter (Vab) showed a distance-dependent decay slope of -0.19 Å(-1).

Conclusions:

• The length of the p-oligophenylene wire significantly influences electron delocalization in osmium-amine systems.
• Osmium complexes exhibit a steeper electronic coupling decay compared to analogous ruthenium systems.
• Long-range-corrected DFT functionals (UCAM-B3LYP) provide more accurate results for these osmium complexes.