Acid Comparison Essay

2008

A PROTEIN-APPENDED ROTAXANE
BY

HAYTHIM HASSANEIN
SUPERVISOR PALL THORDARSON

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Contents

Certificate of Orignality .............................................................................................................. i Abstract ...................................................................................................................................... ii Acknowledgements ................................................................................................................... iii Table of Contents ....................................................................................................................... 2 1. Introduction ............................................................................................................................
Macrocycle shuttling process occurs either through electrochemical oxidation of the benzidine residue or protonation of the basic nitrogens on this station. Both of these methods rely on the repulsive electrostatic interactions between the positively charged axial component and the post-switching cationic nature of the benzidine station (Figure 5.4). Deuterated trifluoroacetic acid (d-TFA) was added in the solution which resulted in the protonation of the benzidine residue and shuttling of macrocycle in to the biphenol station of the Rotaxane. This was supported by NOESY 1H NMR that showed a shift in the peaks in retrospect to Rotaxane solution containing CD3CN (Figure 5.5). Addition of deuterated pyridine (d5-pyridine) neutralised the d-TFA and hence oxidiation of the benzidine residue occurred and the macrocycle had shuttled back to bind to the residue in its favourable conclusions obtained from the 1H NMR spectroscopic studies are supported by room-temperature ultraviolet/visible spectroscopy state (Figure
The focus of these chemically synthesised systems centres the selfFigure 5.8 – Structure of the CAEN Teramc system with the rotaxane monolayer embedded between two electrodes

assembly of nano-scale components. Literature has been reported on the use of rotaxanes in these CAEN

models called the Teramac25. The Teramac system consists of a rotaxane monolayer embedded between two perpendicularly oriented electrodes. Synthesis of this system was via step-wise deposition on a silicon substrate. The rotaxane monolayer was deposited through the Langmuir-Blodgett apparatus. The rotaxane structure is composed of two bipyridinium units with bis-paraphenylene-34-crown-10 macrocycle rings. Reduction and oxidation processes controlled the switching properties of the Termac system and characterisation of any signal produced by the rotaxane monolayer was via normalised density of state plots (NDOS). Tunnelling and biasing was observed in the rotaxane junction after the system was exposed to oxidation processes. AND and OR gate simulations were commenced on these rotaxane monolayer systems which demonstrate application in futuristic computational technologies. One major disadvantage of this system was whether the rotaxane monolayer could survive the deposition of the top electrode.