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The Balancing Act of Stabilising High Oxidation States of Copper And The Balancing Act of Stabilising High Oxidation States of Copper and Nickel with Redox Non-Innocent Ligands containing Thiosemicarbazone and Dithiocarbazate Schiff Bases Jessica Kate Bilyj Bachelor of Science (Hons) 0000-0002-8664-5023 A thesis submitted for the degree of Doctor of Philosophy at The University of Queensland in 2020 School of Chemistry and Molecular Biosciences Abstract The use of N,S chelating ligands such as thiosemicarbazides and dithiocarbazates provides an excellent environment to complex transition metals in a variety of oxidation states. Ligands of this sort initially prompted research in the medical field for their anti-cancer activity. However, it was later realised their ability to complex metals for use in other applications was far more extensive. Complexes of Cu(III) and Ni(III) are rare (compared to Cu(II) and Ni(II)) and are not often isolated as stable entities, but have been proposed as transient intermediates in some reactions. The general requirements for stabilising high oxidation states stem from the nature of the donor atoms, the degree of electron delocalisation, the size of the chelate rings, the use of electron donating groups and the formal charge on the ligand to balance the high charge of the metal ion. Combining the -diketone acetylacetone with 2 equivalents of the relevant thiosemicarbazide or dithiocarbazate produces a tetradentate N2S2 ligand that is suitable for stabilising high oxidation states according to the above specifications. These two families, acetylacetone bis(thiosemicarbazone) and acetylacetone bis(dithiocarbazate) Schiff bases, were investigated here in complex with Cu and Ni. The Ni(II) coordination chemistry with the acetylacetone bis(thiosemicarbazone) ligands was studied and two linkage isomers were observed to form; a symmetric and an asymmetric species, in the absence of oxygen. Exposure to air led to the symmetric Ni(II) isomer undergoing ligand oxidation with a ketone group installed on the acetylacetone backbone. The explanation for this phenomenon was linked with the redox-activity of the ligand. The Cu(II) coordination chemistry found only symmetric coordination of the acetylacetone bis(thiosemicarbazone) ligands and again ligand oxidation to the ketone derivative was seen. In this case a Cu(II) intermediate (most likely bearing a ligand centred radical) was identified using a combination of spectroelectrochemistry, voltammetry and time-resolved UV-Vis spectroscopy. The findings were extended to investigating the copper and nickel complexes of the analogous benzoylacetone bis(thiosemicarbazones) to explore the mix of electron donating and electron withdrawing features on the acetylacetone moiety, along with the presence of a bulky substituent to see if this directed the coordination or reactivity of the complex. 3 Finally, investigating acetylacetone bis(dithiocarbazate) Schiff base complexes of nickel and copper revealed a major effect upon exchanging the non-coordinating terminal nitrogen of a thiosemicarbazone with a sulfur of a dithiocarbazate. In this case, both Cu(III) and Ni(III) complexes were isolated and structurally characterised. This produced surprisingly significant differences that may be the key to understanding why high oxidation states are more often seen with ligands of acetylacetone bis(dithiocarbazate) Schiff bases than acetylacetone bis(thiosemicarbazones). 4 Declaration by Author This thesis is composed of my original work, and contains no material previously published or written by another person except where due reference has been made in the text. I have clearly stated the contribution by others to jointly-authored works that I have included in my thesis. I have clearly stated the contribution of others to my thesis as a whole, including statistical assistance, survey design, data analysis, significant technical procedures, professional editorial advice, financial support and any other original research work used or reported in my thesis. The content of my thesis is the result of work I have carried out since the commencement of my higher degree by research candidature and does not include a substantial part of work that has been submitted to qualify for the award of any other degree or diploma in any university or other tertiary institution. I have clearly stated which parts of my thesis, if any, have been submitted to qualify for another award. I acknowledge that an electronic copy of my thesis must be lodged with the University Library and, subject to the policy and procedures of The University of Queensland, the thesis be made available for research and study in accordance with the Copyright Act 1968 unless a period of embargo has been approved by the Dean of the Graduate School. I acknowledge that copyright of all material contained in my thesis resides with the copyright holder(s) of that material. Where appropriate I have obtained copyright permission from the copyright holder to reproduce material in this thesis and have sought permission from co- authors for any jointly authored works included in the thesis. 5 Publications included in this Thesis 1. Jessica K. Bilyj, Mark J. Riley, and Paul. V. Bernhardt, Isomerism and Reactivity of Nickel(II) Acetylacetone Bis(thiosemicarbazone) Complexes, Dalton Transactions, 2018, 47 (6), 2018-2030 2. Jessica K. Bilyj, Jeffery R. Harmer, and Paul. V. Bernhardt, Formation and Reactivity of Copper Acetylacetone Bis(thiosemicarbazone) Complexes, European Journal of Inorganic Chemistry, 2018, 43, 4731 – 4741 3. Jessica K. Bilyj, Nicole V. Silajew, Graeme R. Hanson, Jeffery R. Harmer, and Paul. V. Bernhardt, Trivalent Copper Stabilised by Acetylacetone Dithiocarbazate Schiff Base Ligands: Structural, Spectroscopic and Electrochemical Properties, Dalton Transactions, 2019, 48 (41), 15501-15514 The following publication has been incorporated as Chapter 2. 1. 1. Jessica K. Bilyj, Mark J. Riley, and Paul. V. Bernhardt, Isomerism and Reactivity of Nickel(II) Acetylacetone Bis(thiosemicarbazone) Complexes, Dalton Transactions, 2018, 47 (6), 2018-2030 Contributor Statement of contribution % Jessica Bilyj writing of text 70 proof-reading and editing 15 experimental undertakings 70 computational calculations 80 preparation of figures 80 initial concept 50 Mark Riley writing of text 10 proof-reading and editing 15 supervision, guidance 10 experimental undertakings 0 computational calculations 20 preparation of figures 10 initial concept 0 Paul Bernhardt writing of text 10 Bernhardt proof-reading and editing 70 supervision, guidance 90 computational calculations 0 preparation of figures 10 initial concept 50 6 The following publication has been incorporated as Chapter 3. 2. Jessica K. Bilyj, Jeffrey R. Harmer, and Paul. V. Bernhardt, Formation and Reactivity of Copper Acetylacetone Bis(thiosemicarbazone) Complexes, European Journal of Inorganic Chemistry, 2018, 43, 4731 – 4741 Contributor Statement of contribution % Jessica Bilyj writing of text 85 proof-reading and editing 20 experimental undertakings 90 computational calculations 0 preparation of figures 80 initial concept 50 Jeffrey Harmer writing of text 5 proof-reading and editing 5 supervision, guidance 5 experimental undertakings 10 computational calculations 50 preparation of figures 0 initial concept 0 Paul Bernhardt writing of text 10 proof-reading and editing 75 supervision, guidance 95 computational calculations 50 preparation of figures 20 initial concept 50 7 The following publication has been incorporated as Chapter 7. 3. Jessica K. Bilyj, Nicole V. Silajew, Graeme R. Hanson, Jeffrey R. Harmer, and Paul. V. Bernhardt, Trivalent Copper Stabilised by Acetylacetone Dithiocarbazate Schiff Base Ligands: Structural, Spectroscopic and Electrochemical Properties, Dalton Transactions, 2019, 48 (41), 15501-15514 Contributor Statement of contribution % Jessica Bilyj writing of text 80 proof-reading and editing 20 experimental undertakings 75 computational calculations 0 preparation of figures 80 initial concept 10 Nicole Silajew writing of text 0 proof-reading and editing 0 experimental undertakings 15 computational calculations 10 preparation of figures 10 initial concept 10 Jeffrey Harmer writing of text 5 proof-reading and editing 5 supervision, guidance 5 experimental undertakings 5 computational calculations 20 preparation of figures 0 initial concept 0 Graeme Hanson writing of text 5 proof-reading and editing 0 supervision, guidance 5 experimental undertakings 5 computational calculations 20 preparation of figures 0 initial concept 0 Paul Bernhardt writing of text 10 proof-reading and editing 75 supervision, guidance 90 computational calculations 50 preparation of figures 20 initial concept 80 8 Submitted Manuscripts included in this Thesis No manuscripts submitted for publication. Other Publications during Candidature 1. Paul V. Bernhardt, Jessica K. Bilyj, Victor Brosius, Dmitry Chernyshov, Robert J. Deeth, Marco Foscato, Vidar R. Jensen, Nicole Mertes, Mark J. Riley and Karl W. Tornroos, Spin Crossover in a Hexaamineiron(II) Complex: Experimental Confirmation of a Computational Prediction, Chemistry A European Journal, 2018, 24 (20), 5082-5085 2. Marcelo M. Pedroso, Christopher Selleck, Jessica Bilyj, Jeffrey R. Harmer, Lawrence R. Gahan, Nataša Mitić, Alistair J. Standish, David L. Tierney, James A. Larrabee and Gerhard Schenk, Reaction Mechanism of the Metallohydrolase CpsB from Streptococcus pneumonia, a Promising Target for Novel Antimicrobial Agents, Dalton Transactions, 2017, 46 (39), 13194-13201 3. Tenuun Bayaraa, Julia
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