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Title: Linking Wheels for use in quantum information processing
Author: Carthy, Laura
ISNI:       0000 0004 2696 4131
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2010
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Heterometallic Cr7Ni-containing wheels have been identified as potential qubits for use in quantum information processing. The work described in this thesis details attempts to form a variety of multi-qubit systems for the purposes of better understanding the interactions occurring between the wheels and also forming potential 2-qubit quantum gates using redox/photo-active links. Mono-substituted wheels of type [Pr2NH2][Cr7MF8(O2CCMe3)15(L)], where L is acarboxylate with a pendant coordinating group, have been synthesised for use as bulky ligands in coordination chemistry with metal complexes. Various carboxylates have been substituted into the wheels and the products reacted with first row transition metal complexes in order to extend the series of linked-wheel systems. Many of these novel complexes have been characterised by X-ray crystallography, and in certain cases EPR studies have been undertaken to probe the strength of interactions occurring via different bridging units. The first well-established substituted wheel, [Pr2NH2][Cr7NiF8(O2CCMe3)15(O2CPy)] (Py= pyridine), has also been used in reactions with second and third row transition metal centres to show its ability to act as a ligand under more harsh conditions. In addition, the disubstituted product [Pr2NH2][Cr7NiF8(O2CCMe3)14(O2CPy)2] has been reacted with a copper complex in order to form a polymeric structure. Purple wheels of type [Cr7NiF3(O2CCMe3)15(EtGu)(H2O)] have been linked through a variety of extended organic molecules containing a minimum of two pendent pyridyl groups. Use of a ligand containing four pyridyl groups, 2,2´:4,4´´:4´,4´´´-quaterpyridyl(qpy) produced a three-wheel-containing system, creating an interesting modification of the wheel backbone not seen before. A series of transition metal complexes, containing qpy and its extended derivative bbpe, has been synthesised in order to form linked-wheel systems. While none of these systems has to date yielded a crystal structure, a significant amount of evidence has been collected to confirm successful formation of the desired products. UV-vis spectroscopic and electrochemical measurements show that these compounds are photo and/or redox-active,and preliminary luminescence studies indicate that the presence of the wheels quenches the emission from metal-to-ligand charge-transfer excited states. A series of mixed-wheel systems has been synthesised by reacting four different monosubstituted green wheels with four purple wheels (Cr7M, where M = Ni, Co, Mn or Zn). A total of fourteen novel systems has been formed, with two of the attempted reactions failing to occur. EPR studies on Cr7Ni-Cr7Ni linked systems show that the strongest interaction occurs when using isonicotinate as a link, with 4-pyridazinecarboxylate giving the weakest coupling. Studies have also been undertaken on Cr7Ni-Cr7Mn and Cr7Ni-Cr7Zn systems, with the former showing interactions and the latter showing none. Initial work to link wheels together indirectly via their templates was ultimately unsuccessful, but a variety of potential linker molecules were synthesised and are described.
Supervisor: Coe, Benjamin ; Winpenny, Richard Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Cr7Ni Wheels ; Redox activity ; Photoswitchability ; Transition Metals