University of Groningen
Mechanisms in non-heme iron oxidation catalysis
Chen, Juan
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Publication date: 2018
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Chen, J. (2018). Mechanisms in non-heme iron oxidation catalysis: Photochemistry and hydrogen peroxide activation. University of Groningen.
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The work described in this thesis was carried out at the Molecular Inorganic Chemistry department of the Stratingh Institute for Chemistry, University of Groningen, The Netherlands.
The work reported in this thesis was supported financially by the Chinese Scholarship Council.
Printed by: Ipskamp Drukkers, Enschede, The Netherlands Cover design: Chaoyan Li
ISBN: 978-94-034-0731-9 (printed version) ISBN: 978-94-034-0730-2 (electronic version)
MECHANISMS IN NON-HEME
IRON OXIDATION CATALYSIS
Photochemistry and hydrogen peroxide activation
PhD thesis
to obtain the degree of PhD at the
University of Groningen
on the authority of the
Rector Magnificus Prof. E. Sterken
and in accordance with
the decision by the College of Deans.
This thesis will be defended in public on
Friday 15 June 2018 at 12.45 hours
by
Juan Chen
born on 27 January 1989
Supervisors
Prof. W.R. Browne
Prof. E. Otten
Assessment committee
Prof. A.J. Minnaard
Prof. R.J.M. Klein Gebbink
Prof. R.J. Deeth
Table of Contents
CHAPTER 1 ... 1
Photochemistry of Iron complexes ... 1
1.1 Introduction ... 2
1.2 Electronic structures and spin states ... 3
1.3 Photochemistry of iron complexes ... 5
1.3.1 Photo assisted Fenton Reactions ... 5
1.3.2 Photo induced ligand degradation - decarboxylation ... 5
1.3.3 Photo-induced releasing of small molecules ... 8
1.3.4 Potential anticancer metallodrugs – photocytotoxicity of iron complexes ... 12
1.3.5 Photochemistry of iron complex in catalytic oxidation reaction ... 17
1.4 Photochemistry of non-heme iron complexes and an overview of the thesis ... 26
1.5 References ... 27
CHAPTER 2 ... 33
Direct photochemical activation of non-heme Fe(IV)=O complexes ... 33
2.1 Introduction ... 34
2.2 Results and Discussion... 34
2.3 Conclusions ... 44
2.4 Experimental section ... 45
2.5 Acknowledgements ... 46
2.6 References ... 46
CHAPTER 3 ... 49
A non-heme iron photocatalyst for light driven aerobic oxidation of methanol ... 49
3.1 Introduction ... 50
3.2 Results and Discussion... 51
3.3 Conclusion ... 61
3.4 Experimental section ... 62
3.5 Acknowledgements ... 62
3.6 References ... 62
CHAPTER 4 ... 65
Selective Photo-Induced Oxidation with O2 of a Non-Heme Iron(III) Complex to a Bis(imine-pyridyl)iron (II) Complex... 65
4.1 Introduction ... 66
4.2 Results and Discussion... 67
4.4 Experimental section ... 78
4.5 Acknowledgements ... 79
4.6 References ... 79
CHAPTER 5 ... 81
Heterolytic O-O bond cleavage in a N5 coordinated non-heme iron(II) complex and the role of comproportionation in the direct generation of oxoiron(IV) ... 81
5.1 Introduction ... 82
5.2 Results and Discussion ... 83
5.2.1 Reaction of 1 with near sub-stoichiometric H2O2 ... 84
5.2.2 Reaction of 1 with near sub-stoichiometric H2O2 at -30 oC ... 89
5.2.3 Thermodynamic considerations ... 92 5.3 Conclusions ... 93 5.4 Experimental section ... 93 5.5 Acknowledgements ... 93 5.6 References ... 93 CHAPTER 6 ... 95
H2O2 Oxidation by FeIII-OOH Intermediates and its Impact on Catalytic Efficiency ... 95
6.1 Introduction ... 96
6.2 Results and Discussion ... 97
6.2.1 Reaction of 1 with stoichiometric H2O2 and homolysis of O-O bond of [(N4Py)FeIII -OOH]2+ ... 97
6.2.2 Disproportionation of H2O2 by 1 in methanol ... 99
6.2.3 Regeneration of FeIII-OOH and O2 evolution ... 101
6.2.4 Reaction of [(N4Py)FeIV=O]2+ (4) with methanol and H2O2 ... 103
6.2.5 Mechanistic considerations ... 105
6.2.6 DFT calculations ... 106
6.2.7 Competition between the oxidation of methanol and H2O2 disproportionation catalyzed by 2a ... 109 6.3 Conclusions ... 110 6.4 Experimental section ... 111 6.5 Acknowledgements ... 111 6.6 References ... 111 Appendix A ... 115
General Description of Techniques and Measurements ... 115
A.1 Physical methods ... 116
A.3 Estimation of photochemical quantum yield. ... 117
A.4 References ... 118
Summary ... 119
Overview and Future Perspective ... 123
Samenvatting ... 127
Acknowledgements... 133
