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Double-pillared cobalt Pacman complexes: synthesis, structures and oxygen reduction catalysis
Aline M J Devoille1, Jason B Love
1EaStCHEM School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh, UK EH9 3JJ.
Dalton Transactions (Cambridge, England : 2003)
|October 27, 2011
Summary
Researchers synthesized and characterized novel binuclear cobalt complexes using a Schiff-base pyrrole macrocycle. These complexes show promising catalytic activity for the oxygen reduction reaction, converting dioxygen to water efficiently.
Area of Science:
- Inorganic Chemistry
- Catalysis
- Electrochemistry
Background:
- Schiff-base macrocycles are important ligands in coordination chemistry.
- Cobalt complexes are investigated for their catalytic properties.
- Oxygen reduction reaction (ORR) is crucial for energy conversion technologies.
Purpose of the Study:
- To synthesize and structurally characterize new binuclear cobalt complexes with a double-pillared cofacial Schiff-base pyrrole macrocycle.
- To evaluate the catalytic activity of these complexes in the oxygen reduction reaction.
- To compare their efficacy with existing Schiff-base analogues.
Main Methods:
- Salt-elimination method for complex synthesis.
- Nuclear Magnetic Resonance (NMR) spectroscopy for solution structure determination.
- X-ray crystallography for solid-state structure elucidation.
- Spectroscopic techniques to study reactivity with dioxygen.
Main Results:
- A new binuclear cobalt complex, [Co(2)(L)], was synthesized and characterized.
- The complex exhibits a cofacial structure in solution and solid state.
- Reversible reaction with dioxygen to form a paramagnetic complex was observed.
- A new aqua-hydroxy double salt, [Co(2)(μ-H(3)O(2))(py)(2)(L)][BF(4)], was characterized.
- The complex catalyzed the selective four-electron reduction of dioxygen to water in acidified benzonitrile.
- Significantly improved catalytic efficacy compared to o-phenylene Schiff-base analogues was demonstrated.
Conclusions:
- The synthesized binuclear cobalt complex is an effective catalyst for the oxygen reduction reaction.
- The Schiff-base pyrrole macrocycle facilitates efficient four-electron reduction of dioxygen to water.
- This class of complexes offers a promising alternative for ORR catalysis.
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