Jump to main content
Jump to site search

Issue 10, 2015
Previous Article Next Article

Water oxidation catalysed by iron complex of N,N′-dimethyl-2,11-diaza[3,3](2,6)pyridinophane. Spectroscopy of iron–oxo intermediates and density functional theory calculations

Author affiliations

Abstract

The macrocyclic [FeIII(L1)Cl2]+ (1, L1 = N,N′-dimethyl-2,11-diaza[3,3](2,6)pyridinophane) complex is an active catalyst for the oxidation of water to oxygen using [NH4]2[CeIV(NO3)6] (CAN), NaIO4, or Oxone as the oxidant. The mechanism of 1-catalysed water oxidation was examined by spectroscopic methods and by 18O-labelling experiments, revealing that FeIV[double bond, length as m-dash]O and/or FeV[double bond, length as m-dash]O species are likely to be involved in the reaction. The redox behaviour of 1 and these high-valent Fe[double bond, length as m-dash]O species of L1 has been examined by both cyclic voltammetry and density functional theory (DFT) calculations. In aqueous solutions, the cyclic voltammograms of 1 at different pH show a pH-dependent reversible couple (E1/2 = +0.46 V vs. SCE at pH 1) and an irreversible anodic wave (Epa = +1.18 V vs. SCE at pH 1) assigned to the FeIII/FeII couple and the FeIII to FeIV oxidation, respectively. DFT calculations showed that the E value of the half reaction involving [FeV(L1)(O)(OH)]2+/[FeIV(L1)(O)(OH2)]2+ is +1.42 V vs. SCE at pH 1. Using CAN as the oxidant at pH 1, the formation of an FeIV[double bond, length as m-dash]O reaction intermediate was suggested by ESI-MS and UV-vis absorption spectroscopic measurements, and the rate of oxygen evolution was linearly dependent on the concentrations of both 1 and CAN. Using NaIO4 or Oxone as the oxidant at pH 1, the rate of oxygen evolution was linearly dependent on the concentration of 1, and a reactive FeV[double bond, length as m-dash]O species with formula [FeV(L1)(O)2]+ generated by oxidation with NaIO4 or Oxone was suggested by ESI-MS measurements. DFT calculations revealed that [FeV(L1)(O)2]+ is capable of oxidizing water to oxygen with a reaction barrier of 15.7 kcal mol−1.

Graphical abstract: Water oxidation catalysed by iron complex of N,N′-dimethyl-2,11-diaza[3,3](2,6)pyridinophane. Spectroscopy of iron–oxo intermediates and density functional theory calculations

Back to tab navigation

Supplementary files

Article information


Submitted
08 May 2015
Accepted
23 Jun 2015
First published
22 Jul 2015

This article is Open Access
All publication charges for this article have been paid for by the Royal Society of Chemistry

Chem. Sci., 2015,6, 5891-5903
Article type
Edge Article

Water oxidation catalysed by iron complex of N,N′-dimethyl-2,11-diaza[3,3](2,6)pyridinophane. Spectroscopy of iron–oxo intermediates and density functional theory calculations

W. To, T. Wai-Shan Chow, C. Tse, X. Guan, J. Huang and C. Che, Chem. Sci., 2015, 6, 5891
DOI: 10.1039/C5SC01680K

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. Material from this article can be used in other publications provided that the correct acknowledgement is given with the reproduced material.

Reproduced material should be attributed as follows:

  • For reproduction of material from NJC:
    [Original citation] - Published by The Royal Society of Chemistry (RSC) on behalf of the Centre National de la Recherche Scientifique (CNRS) and the RSC.
  • For reproduction of material from PCCP:
    [Original citation] - Published by the PCCP Owner Societies.
  • For reproduction of material from PPS:
    [Original citation] - Published by The Royal Society of Chemistry (RSC) on behalf of the European Society for Photobiology, the European Photochemistry Association, and RSC.
  • For reproduction of material from all other RSC journals:
    [Original citation] - Published by The Royal Society of Chemistry.

Information about reproducing material from RSC articles with different licences is available on our Permission Requests page.


Social activity

Search articles by author

Spotlight

Advertisements