Wspólnotowy Serwis Informacyjny Badan i Rozwoju - CORDIS

Develop methods for assembling ordered catenane and rotaxane arrays

The surface science results entail to a great extent the formation of ordered arrays. We continued our study of ordered monolayers and multilayer films of fumaric rotaxane on metal substrates grown by sublimation in ultra high vacuum and characterized by XPS and HREELS, in view of validating the structural models developed from theoretical calculations.

We could demonstrate that the adsorption properties of fumaric rotaxane are similar on Au and Ag, i.e. the molecule chemisorbs through interaction of three amide functions with the substrate. However, the absence of a surface component in the O1s XPS spectrum of fumaric rotaxane/Ag(111) and the presence of such a component for fumaric rotaxane/Au(111) clearly confirmed the weaker interaction with Ag compared to Au as deduced from the theoretical calculation.

Moreover we were able to show that it was the macrocycle which was responsible for the order in the monolayers. In fact, thread monolayers were not ordered, macrocycle monolayers showed the highest degree of order and fumaric rotaxane/Au(111) showed the best order at coverages slightly below monolayer but were still well ordered when the monolayer was reached. STM studies of these surfaces in ultra high vacuum did not give good results because the molecules interacted very strongly with the scanning tip and were displaced at room temperature during the scan.

However, STM studies in tetradecane macrocycle monolayers on Au(111) prepared ex situ by sublimation in ultra high vacuum, gave very interesting results: it was possible to generate an ordered layer also by adsorption in an electric field. In fact, we found that the molecules desorbed from the gold surface when the tetradecane drop was deposited so that only the clean gold surface was seen by STM but with time they re-adsorbed under the influence of the electric field between the tip and the surface.

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University of Edinburgh
Forbes Chair of Organic Chemistry West Main's Road
EH9 3JJ Edinburgh
United Kingdom
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