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Molecularly resolved studies of the reactions of amines with Cu(110) surfaces

Edwards, Dyfan. 2006. Molecularly resolved studies of the reactions of amines with Cu(110) surfaces. PhD Thesis, Cardiff University.

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Abstract

The interaction of with clean, partially oxidised and fully oxidised Cu(110) surfaces has been studied by XPS and STM at room temperature and is compared to the reactions of 2-tertbutylaniline. Limited dissociation occurs at clean Cu(110), but at a partially oxidised surface, a chemisorbed phenylimide ((C6I I>N(a)) product is formed, together with water which desorbs. The phenyl imide forms three different (4 ()W 4 (A (4 0) domains, described by, and unit meshes. A coadsorption y2 2) y- 2) 2) of aniline and dioxygen in a 300:1 mixture results two structures, described by (3) f3 and unit meshes. In both cases, the maximum surface l-i V U V concentration predicted by STM is half that actually determined by quantification of the XPS peaks. Pi-stacking of the phenyl rings is proposed to account for this discrepancy. 2-tertbutylaniline adsorbs at partially oxidised Cu(l 10) surfaces, forming a moderately ordered p(2x2) structure. The maximum surface coverage predicted by STM is in agreement with the actual maximum surface concentration of 2.5 x 1014cm'2. The interaction of dimethylamine with clean, partially oxidised and fully oxidised Cu(110) surface at room temperature has been studied by STM and XPS. Reaction with partially oxidised Cu(110) causes reconstruction of the chemisorbed oxygen islands from the well know p(2xl)-0(a) structure to a (3x1) phase. The expanded oxygen islands desorb as water and structures orientated in the <110> direction, assigned to (CH3)2N, form in their place. The structures are stable for several minutes, after which they desorb, possibly as CIl3NCH2(g) via a P-elimination reaction. Reaction with a complete O(a) monolayer results in limited dimethylamine adsorption. Dimethylamine does not react with clean Cu(110) at room temperature. The reaction of ethylamine with clean, partially oxidized and fully oxidized Cu(110) has been studied by STM and XPS at room temperature and is compared with the reactions of diaminoethane and 2,2,2-trifluoroethylamine. Kthylamine reacts with partially oxidized Cu(110) causing expansion of the oxygen islands from p(2xl) to (3x1) structures. After a period of several minutes, the expanded oxygen islands desorb as water, leaving a clean surface. Kthylamine reacts with a full O(a) monolayer without any reconstruction, causing desorption of all surface oxygen and resulting in a clean surface. It is proposed that the ethylamine desorbs as CM3CI INI I via a p-elimination reaction. Diaminoethane reacts with partially oxidized Cu(110) in the exact same manner as ethylamine. At partially oxidized Cu(110), 2,2,2- trifluorethylamine causes desorption of all chcmisorbcd oxygen without causing any reconstruction of the oxygen islands. A clean surface is left at the end of the reaction. A full O(a) monolayer is inert to 2,2,2-trifluorethylamine. The interaction of 4,4-diaminobenzophenone, (I bNCV ICO, with clean Cu(110) surfaces has been investigated by STM and XPS at room temperature. Sub-monolayer coverages give rise to three distinct, highly ordered structures. The first can be described using by a unit mesh. 1 he others are based around a pair of (7) (7) molecules, forming and lattices. Above a monolayer, order breaks down.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Chemistry
Subjects: Q Science > QD Chemistry
ISBN: 9781303208744
Date of First Compliant Deposit: 30 March 2016
Last Modified: 31 Jan 2020 09:04
URI: http://orca-mwe.cf.ac.uk/id/eprint/56193

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