2 research outputs found
Bottom-Up Synthesis of Multiply Fused Pd<sup>II</sup> Anthriporphyrinoids
Anthriporphyrinoid and its dimeric homologues were synthesized
by Suzuki–Miyaura coupling and subsequent oxidation. Both porphyrinoids
were smoothly converted to their PdII complexes and were
further decorated by Suzuki–Miyaura coupling with thiophene
derivatives and subsequent oxidative fusion reaction to provide multiply
fused compounds. Most PdII anthriporphyrinoids have been
structurally well characterized to be planar for monomeric and helically
twisted for dimeric species. The dimeric anthriporphyrinoids show
paratropic ring currents due to their global antiaromatic networks,
the extent of which increases with an increase of conjugated network.
Multiply fused dimeric anthriporphyrinoids show helical structures,
fully reversible six redox potentials, small HOMO–LUMO gaps,
and absorption tails reaching in the near-infrared region, suggesting
the high potential of this approach to explore molecular graphene.
Optical separations of the dimeric helical species were accomplished,
and racemization barrier heights were determined
Overpotential-Induced Introduction of Oxygen Vacancy in La<sub>0.67</sub>Sr<sub>0.33</sub>MnO<sub>3</sub> Surface and Its Impact on Oxygen Reduction Reaction Catalytic Activity in Alkaline Solution
Oxygen reduction reaction (ORR) catalytic
activity of La<sub>0.67</sub>Sr<sub>0.33</sub>MnO<sub>3</sub> epitaxial
thin films was investigated
in a KOH solution by using a rotating-disk electrode. We found that
while the films exhibit ORR current, the current is not limited by
oxygen transport resulting from the film electrode rotation and shows
the large hysteresis against the potential sweep direction. This behavior
is in stark contrast to the oxygen reduction reaction activity of
an electrode ink made from LSMO bulk powder, whose ORR current is
oxygen-transport limited. <i>In situ</i> synchrotron X-ray
absorption spectroscopy also reveals that the valence state of Mn
in the LSMO film surface is lowered under the reducing atmosphere
caused by the overpotential. This indicates the overpotential-induced
introduction of oxygen vacancies in the film surface. We also show
that the ORR current of the LSMO films exposed to the reducing atmosphere
is lowered than that of the original surface. These results indicate
that the ORR catalytic activity of LSMO surfaces is strongly influenced
by oxygen vacancies