Low Potential CO 2 Reduction by Inert Fe(II)-Macrobicyclic Complex: A New Concept of Cavity Assisted CO 2 Activation.

The advantage of a pre-organized π-cavity of Fe(II) complex of a newly developed macrobicycle cryptand is explored for CO ₂ reduction by overcoming the problem of high overpotential associated with the inert nature of the cryptate. Thus, a bipyridine-centered tritopic macrobicycle having a molecular π-cavity capable of forming Fe(II) complex as well as potential for CO ₂ encapsulation is synthesized. The inert Fe(II)-cryptate shows much lower potential in cyclic voltammetry than the Fe(II)-tris-dimethylbipyridine (Fe-MBP) core. Interestingly, this cryptate shows electrochemical CO ₂ reduction at a considerably lower potential than the Fe-MBP inert core. Therefore, this study represents that a well-structured π-cavity may generate a new series of molecular catalysts for the CO ₂ reduction reaction (CO ₂ RR), even with the inert metal complexes.
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