Title:	Viologen-nucleobase derivatives: building blocks for functional materials
Authors:	Ciobanu, Marius
Thesis advisor:	Prof. Dr. Uwe Beginn
Thesis referee:	Prof. Dr. Simona Asaftei
Abstract:	The main subject of this thesis is the synthesis and investigation of the properties and potential applications of a new class of hybrid compounds consisting of a rigid, electroactive 4,4’-bipyridinium core capped by nucleobase terminal groups with hydrogen bonding abilities. A new series of small molecules consisting in a 4,4’-bipyridinium unit carrying thymine or/and adenine as capping groups was synthetized. The synthesis strategy implied the regioselective alkylation of thymine and adenine bases respectively, followed by coupling of the alkylated precursors to 4,4’-bipyridine unit via Menschutkin reaction. Electrochemical, spectroelectrochemical and optical investigations revealed an intramolecular charge transfer (CT) relationship between nucleobases as donors and 4,4’-bipyridinium unit as acceptor which is accompanied by a change in color and a shift of the reduction potentials (approx. 60 mV). The viologen-nucleobase derivatives, particularly viologens capped by thymine, were used as building blocks to create self-assembled functional nanostructures in the presence of complementary templates such as oligonucleotides or ssPNA analogues via thymine-adenine interactions. The viologen-thymine derivatives were found to partially precipitate oligonucleotides or plasmid DNA by mean of coulombic interactions and form stable polyplexes that could be used as potential gene delivery vectors. It was found that the number of positive charges, as well as the number of thymine units per viologen-thymine derivative determines whether the interaction with DNA is dominated by electrostatic or by hydrogen bonding interactions. New electroactive ionic liquid crystals were prepared by ion pairing of viologen-nucleobase dicationic species with amphiphilic 3,4,5-tris(dodecyloxy)benzene sulfonate anion. The nucleobases with ability to self-associate by hydrogen bonding were found to influence not just the thermotropic behavior, by decreasing transition temperature from crystalline to mesophase state, but also the supramolecular arrangement in solution. A versatile approach to functionalize mesoporous TiO2 film with viologen-nucleobase derivatives was developed consisting of hydrogen bonding layer-by-layer deposition of viologen-nucleobase derivatives on TiO2 surface using the thymine-adenine molecular recognition as driving force for immobilization. This method is promising and represents an easy way to construct optoelectronic device components as was demonstrated with the construction of a switchable electrochromic device.
URL:	https://osnadocs.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-2015050413190
Subject Keywords:	viologen; nucleobase; hydrogen bonding; charge transfer; ionic liquid crystals; optoelectronic devices
Issue Date:	4-May-2015
Type of publication:	Dissertation oder Habilitation [doctoralThesis]
Appears in Collections:	FB05 - E-Dissertationen

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