Tuning Electron Delocalization and Transfer Rates in Mixed-Valent Ru3O Complexes through "Push-Pull" Effects

Area of Science:

• Inorganic Chemistry
• Coordination Chemistry
• Electron Transfer Studies

Background:

• Oxo-centered triruthenium clusters are versatile platforms for studying electron transfer.
• Tuning electronic properties through ancillary ligands is crucial for controlling reactivity.
• Understanding electron transfer mechanisms is fundamental in catalysis and molecular electronics.

Purpose of the Study:

• To investigate electron transfer rates in a series of oxo-centered triruthenium clusters.
• To correlate electron self-exchange rates with structural and electronic modifications of ancillary ligands.
• To elucidate the factors governing electron transfer in these multinuclear complexes.

Main Methods:

• Synthesis of [Ru3(OAc)6(μ3-O)(CO)(L)(pep)] clusters with varying ancillary ligands (L = cpy, py, dmap).
• Determination of electron self-exchange rate constants for the 0/- couple using 1H NMR line broadening experiments.
• Analysis of 1H NMR contact shifts to probe electronic effects of ancillary ligands on the pep ligand.

Main Results:

• Electron self-exchange rate constants ranged from 4.3 to 9.2 (× 10^7 M^-1 s^-1) in ACN-d3.
• Faster self-exchange rates correlated with increased electron-donating character of the ancillary pyridine ligand (dmap > py > cpy).
• Observed trends were attributed to increased orbital overlap and push-pull electronic modulation.

Conclusions:

• Ancillary ligand substituents significantly influence electron transfer rates in triruthenium clusters.
• Electron-donating ligands enhance self-exchange rates by promoting greater orbital overlap.
• NMR contact shift data support the electronic modulation effects of ancillary ligands.