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Title: Electrochemical properties of redox centres in coordination compounds and in gold nanocluster hybrids
Author: Cabo Fernández, Laura
ISNI:       0000 0004 2736 7523
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2011
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In the present work the properties of compounds that can display conformational switching and Coulomb blockade features as a result of electron transfer reactions have been investigated with a view to observing possible Negative Differential Resistance behaviour. This phenomenon is sometimes associated with oscillatory processes and could broaden the field of applications of nanoparticles such as for electronic devices and storage memories. Copper coordination compounds with macro cyclic ligands change their geometry from a distorted octahedral conformation, for Cu(II), to a tetrahedral geometry, for Cu(I), upon reduction of the metal centre. In the research described in this Thesis, copper was coordinated to tetradentante macrocycles with two types of donor sets, tetra-amine (i.e., N4) and macrocycles containing sulfur and nitrogen atoms (i.e., N2S2). It was found that increasing the cavity dimensions of the ligand, the copper(II) complexes were destabilised leading to a shift in the reduction potential to more positive values. The presence of tertiary amines and soft electron-donating atoms such as sulfur in the structure of the ligands favours the formation of Cu(I) intermediates in comparison with Cu(II) species. Rate constants for the electron transfer reactions and chemical steps for these reactions were estimated using computer simulations. Hexanethiolate gold clusters with an average core diameter of 1.8 nm and a calculated capacitance of 0.6 aF were synthesised using a two-phase method. These clusters presented Coulomb blockade responses due to Quantised Double-Layer charging (QDL) events in voltammetric studies. These nanoparticles were functionalised by a place-exchange reaction and terminal bromine groups were introduced by reaction with l l-bromo-l-undecanethiol. The clusters thus synthesised preserved the core single-charging events and served as precursors for the synthesis of hybrids with copper complexes via a nucleophilic substitution reaction. Place-exchange with 6-(ferrocenyl)-1-hexanethiol was also carried out to incorporate ferrocene centres on the cluster surface. Voltammetric measurements showed the redox response of the F c +/F c couple and the charging events of the gold core. A transition in the behaviour from single to multiple electron transfer response for the redox couple was observed as the number of ferrocene units per cluster was increased. For multiple electron transfer processes, a mechanism in which the core acts as a mediator has been proposed involving electron tunnelling through the chains linking the redox centre to the gold core.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available