We
report the independent role of isomerism of secondary sphere
substituents over their nature, a factor often overlooked in molecular
electrocatalysis pertaining to electrochemical sensing, by establishing
that isomerism redefines the electronic structure at the catalytic
reaction center via geometrical factors. UV–vis spectroscopy
and X-ray photoelectron spectroscopy suggest that a substituent’s
isomerism in molecular catalysts conjoins molecular planarity and
catalytic activation through competing field effects and resonance
effects. As a classical example, we demonstrate the influence of isomerism
of the −NO2 substituents for the electrocatalytic
multi electron oxidation of As(III), a potentially important electrochemical
pathway for water remediation and arsenic detection. The isomerism
dependent oxidative activation of catalytic center leads to a nonprecious
molecular catalyst capable for direct As(III) oxidation with an experimental
detection limit close to WHO guidelines. This work opens up an unusual
approach in analytical chemistry for developing various sensing platforms
for challenging chemical and electrochemical reactions.
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