Understanding light-driven H₂ evolution through the electronic tuning of aminopyridine cobalt complexes

Area of Science:

• Coordination Chemistry
• Catalysis
• Materials Science

Background:

• Cobalt complexes are investigated for catalytic applications.
• Ligand design is crucial for tuning metal center properties and catalytic activity.

Purpose of the Study:

• To synthesize and characterize a new family of cobalt complexes.
• To investigate the effect of ligand electronic tuning on water reduction catalysis.
• To elucidate the mechanism of cobalt-intermediate formation during catalysis.

Main Methods:

• Synthesis of cobalt complexes with varying pyridine substituents.
• UV-Vis spectroscopy, luminescence quenching, and Transient Absorption Spectroscopy (TAS).
• Kinetic isotopic experiments and Density Functional Theory (DFT) calculations.

Main Results:

• A series of [CoII(OTf)2(Y,XPyMe-tacn)] complexes were synthesized.
• Electron-withdrawing pyridine moieties enhanced catalytic activity by 20-fold.
• Direct observation of CoI intermediates formed from photogenerated IrIII species.

Conclusions:

• Ligand electronic properties significantly impact cobalt complex catalysis.
• The study provides insights into the mechanism of water reduction catalysis by cobalt complexes.
• Understanding intermediate formation is key to optimizing catalytic efficiency.