TY - JOUR
T1 - Local Environment of Superoxide Radical Formed on the TiO2 Surface Produced From Ti(OiPr)4 Exposed to H2O2
AU - Samoilova, Rimma I.
AU - Dikanov, Sergei A.
N1 - Funding Information:
This work was supported by Grant DE-FG02-08ER15960 (S.A.D.) from the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Sciences, U.S. Department of Energy. The authors are grateful to Dr. Andrei Astashkin (University of Arizona) for help in the preliminary simulations of orientation-selective pulsed ENDOR spectra and very useful discussions. This article is dedicated to Professors Klaus Möbius and Kev M. Salikhov on the occasion of their 85th anniversary. Both of them have done outstanding contributions in the science of magnetic resonance. The authors of this article had the privilege of professional communications with Professor Salikhov as well as friendly discussions at the “coffee club” in the laboratory of Professor Yu. D. Tsvetkov during many years of his and our work in V. V. Voevodsky Institute of Chemical Kinetics and Combustion (Novosibirsk). Later we have always been receiving encouraging support and help from Kev Minullinovich at multiple stages of his multifaceted career.
Funding Information:
This work was supported by Grant DE-FG02-08ER15960 (S.A.D.) from the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Sciences, U.S. Department of Energy. The authors are grateful to Dr. Andrei Astashkin (University of Arizona) for help in the preliminary simulations of orientation-selective pulsed ENDOR spectra and very useful discussions. This article is dedicated to Professors Klaus Möbius and Kev M. Salikhov on the occasion of their 85th anniversary. Both of them have done outstanding contributions in the science of magnetic resonance. The authors of this article had the privilege of professional communications with Professor Salikhov as well as friendly discussions at the “coffee club” in the laboratory of Professor Yu. D. Tsvetkov during many years of his and our work in V. V. Voevodsky Institute of Chemical Kinetics and Combustion (Novosibirsk). Later we have always been receiving encouraging support and help from Kev Minullinovich at multiple stages of his multifaceted career.
Publisher Copyright:
© 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.
PY - 2022/9
Y1 - 2022/9
N2 - A selective heterogeneous catalyst with the superoxide anion O2•− stable at room temperature, generated by treating Ti(OR)4 (R = iPr, nBu) with H2O2, was previously reported and used for the oxidation of organic compounds. It was proposed that exceptional stability of the O2•− is resulted from its stabilization near Ti+4 cation on the TiO2 surface with the participation of water molecules and/or OH groups. In this article, we performed high-resolution pulsed EPR study on the O2•− in this catalyst with the aim to obtain quantitative information about its interactions with the surrounding molecules. Our data has shown that the O2•− is involved in weak hyperfine interactions with protons in the nearest environment, which do not exceed a value of 2 MHz. It corresponds to an Os…H distance of ≥ 3 Å that excludes the formation of hydrogen bonds. The analysis of possible structures of O2•− adsorption on TiO2 surface taking into account our results and lack of radical mobility at room temperature previously observed in EPR spectra led us to suggest that the O2•− is stabilized in the form of superoxo bridge coordinated with two titanium atoms.
AB - A selective heterogeneous catalyst with the superoxide anion O2•− stable at room temperature, generated by treating Ti(OR)4 (R = iPr, nBu) with H2O2, was previously reported and used for the oxidation of organic compounds. It was proposed that exceptional stability of the O2•− is resulted from its stabilization near Ti+4 cation on the TiO2 surface with the participation of water molecules and/or OH groups. In this article, we performed high-resolution pulsed EPR study on the O2•− in this catalyst with the aim to obtain quantitative information about its interactions with the surrounding molecules. Our data has shown that the O2•− is involved in weak hyperfine interactions with protons in the nearest environment, which do not exceed a value of 2 MHz. It corresponds to an Os…H distance of ≥ 3 Å that excludes the formation of hydrogen bonds. The analysis of possible structures of O2•− adsorption on TiO2 surface taking into account our results and lack of radical mobility at room temperature previously observed in EPR spectra led us to suggest that the O2•− is stabilized in the form of superoxo bridge coordinated with two titanium atoms.
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U2 - 10.1007/s00723-021-01424-0
DO - 10.1007/s00723-021-01424-0
M3 - Article
AN - SCOPUS:85115108041
VL - 53
SP - 1089
EP - 1104
JO - Applied Magnetic Resonance
JF - Applied Magnetic Resonance
SN - 0937-9347
IS - 7-9
ER -