From being an aesthetic molecular object to a building block for the construction of molecular machines, catenane and related mechanically interlocked molecules (MIMs) continue to attract immense interest in many...
A [2]catenane switch that the intramolecular pyrene excimer emission can be controlled by orthogonal cation binding and solvent polarity change in various amplitudes and dynamic ranges is reported.
Efficient
O2 reduction reaction (ORR) for selective
H2O generation enables advanced fuel cell technology. Nonprecious
metal catalysts are viable and attractive alternatives to state-of-the-art
Pt-based materials that are expensive. Cu complexes inspired by Cu-containing
O2 reduction enzymes in nature are yet to reach their desired
ORR catalytic performance. Here, the concept of mechanical interlocking
is introduced to the ligand architecture to enforce dynamic spatial
restriction on the Cu coordination site. Interlocked catenane ligands
could govern O2 binding mode, promote electron transfer,
and facilitate product elimination. Our results show that ligand interlocking
as a catenane steers the ORR selectivity to H2O as the
major product via the 4e– pathway, rivaling the
selectivity of Pt, and boosts the onset potential by 130 mV, the mass
activity by 1.8 times, and the turnover frequency by 1.5 fold as compared
to the noninterlocked counterpart. Our Cu catenane complex represents
one of the first examples to take advantage of mechanical interlocking
to afford electrocatalysts with enhanced activity and selectivity.
The mechanistic insights gained through this integrated experimental
and theoretical study are envisioned to be valuable not just to the
area of ORR energy catalysis but also with broad implications on interlocked
metal complexes that are of critical importance to the general fields
in redox reactions involving proton-coupled electron transfer steps.
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