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Homolytic Cleavage of Molecular Oxygen by Manganese Porphyrins Supported on Ag(111)

Murphy, Barry E.; Krasnikov, Sergey A.; Sergeeva, Natalia N.; Cafolla, Attilio A.; Preobrajenski, Alexei LU ; Chaika, Alexander N.; Luebben, Olaf and Shvets, Igor V. (2014) In ACS Nano 8(5). p.5190-5198
Abstract
Oxygen binding and cleavage are important for both molecular recognition and catalysis. Mn-based porphyrins in particular are used as catalysts for the epoxidation of alkenes, and in this study the homolytic cleavage of O-2 by a surface-supported monolayer of Mn porphyrins on Ag(111) is demonstrated by scanning tunneling microscopy, X-ray absorption, and X-ray photoemission. As deposited, {5,10,15,20-tetraphenylporphyrinato}Mn(III)CI(MnCITPP) adopts a saddle conformation with the average plane of its macrocyde parallel to the substrate and the axial CI ligand pointing upward, away from the substrate. The adsorption of MnCITPP on Ag(111) Is accompanied by a reduction of the Mn oxidation state from Mn(III) to Mn(II) due to charge transfer... (More)
Oxygen binding and cleavage are important for both molecular recognition and catalysis. Mn-based porphyrins in particular are used as catalysts for the epoxidation of alkenes, and in this study the homolytic cleavage of O-2 by a surface-supported monolayer of Mn porphyrins on Ag(111) is demonstrated by scanning tunneling microscopy, X-ray absorption, and X-ray photoemission. As deposited, {5,10,15,20-tetraphenylporphyrinato}Mn(III)CI(MnCITPP) adopts a saddle conformation with the average plane of its macrocyde parallel to the substrate and the axial CI ligand pointing upward, away from the substrate. The adsorption of MnCITPP on Ag(111) Is accompanied by a reduction of the Mn oxidation state from Mn(III) to Mn(II) due to charge transfer between the substrate and the molecule. Annealing the Mn(II)CITPP monolayer up to 510 K causes the chlorine ligands to desorb from the porphyrins while leaving the monolayer intact. The Mn(II)TPP is stabilized by the surface acting as an axial ligand for the metal center. Exposure of the Mn(11)TPP/Ag(111) system to molecular oxygen results in the dissociation of O-2 and forms pairs of Mn(111)OTPP molecules on the surface. Annealing at 445 K reduces the Mn(111)OTPP complex back to Mn(II)TPP/Ag(111). The activation energies for Cl and 0 removal were found to be 0.35 +/- 0.02 eV and 0.26 +/- 0.03 eV, respectively. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
porphyrins, axial ligand, self-assembly, scanning tunneling microscopy, X-ray absorption, X-ray photoemission
in
ACS Nano
volume
8
issue
5
pages
5190 - 5198
publisher
The American Chemical Society
external identifiers
  • wos:000336640600111
  • scopus:84901649625
ISSN
1936-086X
DOI
10.1021/nn501240j
language
English
LU publication?
yes
id
c2b679e9-e92b-42d7-b32b-66d89f51ab63 (old id 4558462)
date added to LUP
2014-07-17 12:09:52
date last changed
2017-08-27 03:45:20
@article{c2b679e9-e92b-42d7-b32b-66d89f51ab63,
  abstract     = {Oxygen binding and cleavage are important for both molecular recognition and catalysis. Mn-based porphyrins in particular are used as catalysts for the epoxidation of alkenes, and in this study the homolytic cleavage of O-2 by a surface-supported monolayer of Mn porphyrins on Ag(111) is demonstrated by scanning tunneling microscopy, X-ray absorption, and X-ray photoemission. As deposited, {5,10,15,20-tetraphenylporphyrinato}Mn(III)CI(MnCITPP) adopts a saddle conformation with the average plane of its macrocyde parallel to the substrate and the axial CI ligand pointing upward, away from the substrate. The adsorption of MnCITPP on Ag(111) Is accompanied by a reduction of the Mn oxidation state from Mn(III) to Mn(II) due to charge transfer between the substrate and the molecule. Annealing the Mn(II)CITPP monolayer up to 510 K causes the chlorine ligands to desorb from the porphyrins while leaving the monolayer intact. The Mn(II)TPP is stabilized by the surface acting as an axial ligand for the metal center. Exposure of the Mn(11)TPP/Ag(111) system to molecular oxygen results in the dissociation of O-2 and forms pairs of Mn(111)OTPP molecules on the surface. Annealing at 445 K reduces the Mn(111)OTPP complex back to Mn(II)TPP/Ag(111). The activation energies for Cl and 0 removal were found to be 0.35 +/- 0.02 eV and 0.26 +/- 0.03 eV, respectively.},
  author       = {Murphy, Barry E. and Krasnikov, Sergey A. and Sergeeva, Natalia N. and Cafolla, Attilio A. and Preobrajenski, Alexei and Chaika, Alexander N. and Luebben, Olaf and Shvets, Igor V.},
  issn         = {1936-086X},
  keyword      = {porphyrins,axial ligand,self-assembly,scanning tunneling microscopy,X-ray absorption,X-ray photoemission},
  language     = {eng},
  number       = {5},
  pages        = {5190--5198},
  publisher    = {The American Chemical Society},
  series       = {ACS Nano},
  title        = {Homolytic Cleavage of Molecular Oxygen by Manganese Porphyrins Supported on Ag(111)},
  url          = {http://dx.doi.org/10.1021/nn501240j},
  volume       = {8},
  year         = {2014},
}