4 research outputs found
Rational Design of Mononuclear Iron Porphyrins for Facile and Selective 4e<sup>–</sup>/4H<sup>+</sup> O<sub>2</sub> Reduction: Activation of O–O Bond by 2nd Sphere Hydrogen Bonding
Facile and selective
4e<sup>–</sup>/4H<sup>+</sup> electrochemical
reduction of O<sub>2</sub> to H<sub>2</sub>O in aqueous medium has
been a sought-after goal for several decades. Elegant but synthetically
demanding cytochrome c oxidase mimics have demonstrated selective
4e<sup>–</sup>/4H<sup>+</sup> electrochemical O<sub>2</sub> reduction to H<sub>2</sub>O is possible with rate constants as fast
as 10<sup>5</sup> M<sup>–1</sup> s<sup>–1</sup> under
heterogeneous conditions in aqueous media. Over the past few years,
in situ mechanistic investigations on iron porphyrin complexes adsorbed
on electrodes have revealed that the rate and selectivity of this
multielectron and multiproton process is governed by the reactivity
of a ferric hydroperoxide intermediate. The barrier of Oî—¸O
bond cleavage determines the overall rate of O<sub>2</sub> reduction
and the site of protonation determines the selectivity. In this report,
a series of mononuclear iron porphyrin complexes are rationally designed
to achieve efficient Oî—¸O bond activation and site-selective
proton transfer to effect facile and selective electrochemical reduction
of O<sub>2</sub> to water. Indeed, these crystallographically characterized
complexes accomplish facile and selective reduction of O<sub>2</sub> with rate constants >10<sup>7</sup> M<sup>–1</sup> s<sup>–1</sup> while retaining >95% selectivity when adsorbed
on
electrode surfaces (EPG) in water. These oxygen reduction reaction
rate constants are 2 orders of magnitude faster than all known heme/Cu
complexes and these complexes retain >90% selectivity even under
rate
determining electron transfer conditions that generally can only be
achieved by installing additional redox active groups in the catalyst
Rational Design of Mononuclear Iron Porphyrins for Facile and Selective 4e<sup>–</sup>/4H<sup>+</sup> O<sub>2</sub> Reduction: Activation of O–O Bond by 2nd Sphere Hydrogen Bonding
Facile and selective
4e<sup>–</sup>/4H<sup>+</sup> electrochemical
reduction of O<sub>2</sub> to H<sub>2</sub>O in aqueous medium has
been a sought-after goal for several decades. Elegant but synthetically
demanding cytochrome c oxidase mimics have demonstrated selective
4e<sup>–</sup>/4H<sup>+</sup> electrochemical O<sub>2</sub> reduction to H<sub>2</sub>O is possible with rate constants as fast
as 10<sup>5</sup> M<sup>–1</sup> s<sup>–1</sup> under
heterogeneous conditions in aqueous media. Over the past few years,
in situ mechanistic investigations on iron porphyrin complexes adsorbed
on electrodes have revealed that the rate and selectivity of this
multielectron and multiproton process is governed by the reactivity
of a ferric hydroperoxide intermediate. The barrier of Oî—¸O
bond cleavage determines the overall rate of O<sub>2</sub> reduction
and the site of protonation determines the selectivity. In this report,
a series of mononuclear iron porphyrin complexes are rationally designed
to achieve efficient Oî—¸O bond activation and site-selective
proton transfer to effect facile and selective electrochemical reduction
of O<sub>2</sub> to water. Indeed, these crystallographically characterized
complexes accomplish facile and selective reduction of O<sub>2</sub> with rate constants >10<sup>7</sup> M<sup>–1</sup> s<sup>–1</sup> while retaining >95% selectivity when adsorbed
on
electrode surfaces (EPG) in water. These oxygen reduction reaction
rate constants are 2 orders of magnitude faster than all known heme/Cu
complexes and these complexes retain >90% selectivity even under
rate
determining electron transfer conditions that generally can only be
achieved by installing additional redox active groups in the catalyst
Rational Design of Mononuclear Iron Porphyrins for Facile and Selective 4e<sup>–</sup>/4H<sup>+</sup> O<sub>2</sub> Reduction: Activation of O–O Bond by 2nd Sphere Hydrogen Bonding
Facile and selective
4e<sup>–</sup>/4H<sup>+</sup> electrochemical
reduction of O<sub>2</sub> to H<sub>2</sub>O in aqueous medium has
been a sought-after goal for several decades. Elegant but synthetically
demanding cytochrome c oxidase mimics have demonstrated selective
4e<sup>–</sup>/4H<sup>+</sup> electrochemical O<sub>2</sub> reduction to H<sub>2</sub>O is possible with rate constants as fast
as 10<sup>5</sup> M<sup>–1</sup> s<sup>–1</sup> under
heterogeneous conditions in aqueous media. Over the past few years,
in situ mechanistic investigations on iron porphyrin complexes adsorbed
on electrodes have revealed that the rate and selectivity of this
multielectron and multiproton process is governed by the reactivity
of a ferric hydroperoxide intermediate. The barrier of Oî—¸O
bond cleavage determines the overall rate of O<sub>2</sub> reduction
and the site of protonation determines the selectivity. In this report,
a series of mononuclear iron porphyrin complexes are rationally designed
to achieve efficient Oî—¸O bond activation and site-selective
proton transfer to effect facile and selective electrochemical reduction
of O<sub>2</sub> to water. Indeed, these crystallographically characterized
complexes accomplish facile and selective reduction of O<sub>2</sub> with rate constants >10<sup>7</sup> M<sup>–1</sup> s<sup>–1</sup> while retaining >95% selectivity when adsorbed
on
electrode surfaces (EPG) in water. These oxygen reduction reaction
rate constants are 2 orders of magnitude faster than all known heme/Cu
complexes and these complexes retain >90% selectivity even under
rate
determining electron transfer conditions that generally can only be
achieved by installing additional redox active groups in the catalyst
Rational Design of Mononuclear Iron Porphyrins for Facile and Selective 4e<sup>–</sup>/4H<sup>+</sup> O<sub>2</sub> Reduction: Activation of O–O Bond by 2nd Sphere Hydrogen Bonding
Facile and selective
4e<sup>–</sup>/4H<sup>+</sup> electrochemical
reduction of O<sub>2</sub> to H<sub>2</sub>O in aqueous medium has
been a sought-after goal for several decades. Elegant but synthetically
demanding cytochrome c oxidase mimics have demonstrated selective
4e<sup>–</sup>/4H<sup>+</sup> electrochemical O<sub>2</sub> reduction to H<sub>2</sub>O is possible with rate constants as fast
as 10<sup>5</sup> M<sup>–1</sup> s<sup>–1</sup> under
heterogeneous conditions in aqueous media. Over the past few years,
in situ mechanistic investigations on iron porphyrin complexes adsorbed
on electrodes have revealed that the rate and selectivity of this
multielectron and multiproton process is governed by the reactivity
of a ferric hydroperoxide intermediate. The barrier of Oî—¸O
bond cleavage determines the overall rate of O<sub>2</sub> reduction
and the site of protonation determines the selectivity. In this report,
a series of mononuclear iron porphyrin complexes are rationally designed
to achieve efficient Oî—¸O bond activation and site-selective
proton transfer to effect facile and selective electrochemical reduction
of O<sub>2</sub> to water. Indeed, these crystallographically characterized
complexes accomplish facile and selective reduction of O<sub>2</sub> with rate constants >10<sup>7</sup> M<sup>–1</sup> s<sup>–1</sup> while retaining >95% selectivity when adsorbed
on
electrode surfaces (EPG) in water. These oxygen reduction reaction
rate constants are 2 orders of magnitude faster than all known heme/Cu
complexes and these complexes retain >90% selectivity even under
rate
determining electron transfer conditions that generally can only be
achieved by installing additional redox active groups in the catalyst