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Design, Synthesis and Properties of Bipyridine-capped Oligothiophenes for Directed Energy and Electron Transfer in Molecular Electronic Applications
Mälardalen University, Department of Biology and Chemical Engineering.
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The earliest landmark in computer technology was construction of the Electronic Numerial Integrator and Computer, ENIAC. Computational switching was performed with vacuum tubes and relays, rather large in size, making this computer rather unwieldy. The next milestone came with the integration of transistors into computers as the switching component. Since then, transistors have been miniaturised dramatically, resulting in the amount of components integrated on a computer chip increasing logarithmically with time. The components are nowadays so small and so densely packed that problems with leak currents and cross-talk can arise and the lower limit for transistor size will soon be reached. In order to meet increasing demands on the size and performance of electronics, a new paradigm is due – the molecular electronics approach.

Oligothiophenes have been shown to possess the physical and chemical characteristics required for electron/energy transport in molecular systems. However oligothiophenes must be electronically coupled to other components within a molecular circuit for them to be functional. In this work, different modes of incorporation of [2,2’]-bipyridinyl functionalities onto the ends of prototypic oligothiophene wires have been examined. The bipyridine connectors allow complexation to metal centres which can then function as a source or sink of electrons in the circuit. Ruthenium tris-bipyridine complexes, in particular, possess interesting electrochemical and photophysical characteristics, making them suitable for use in molecular electronics.

This thesis reports synthetic strategies to a range of novel ligands based on the [2,2’]-bipyridinyl system, together with a study of the redox and fluorescence properties of their ruthenium tris-bipyridine complexes. The mode of connection between the chelating bipyridine and the first member of the oligothiophene chain was found to have a profound effect upon the fluorescence lifetimes and intensities of the resulting complexes. The discovery of complexes exhibiting long and intense fluorescence (a requirement for directed electron/energy transfer within molecular networks) thus forms an important design element in future prototypes.

Place, publisher, year, edition, pages
Institutionen för biologi och kemiteknik , 2007. , 110 p.
Series
Mälardalen University Press Dissertations, ISSN 1651-4238 ; 54
Keyword [en]
Molecular Electronics, Organic Synthesis, Ruthenium, Pyridyl Complexes, Ligand Design
National Category
Chemical Engineering
Research subject
Biotechnology/Chemical Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-455ISBN: 978-91-85485-62-8 (print)OAI: oai:DiVA.org:mdh-455DiVA: diva2:120974
Public defence
2007-12-10, Filen, Verktyget, Smedjegatan 37, Eskilstuna, 10:15
Opponent
Supervisors
Available from: 2007-11-09 Created: 2007-11-09 Last updated: 2016-01-19Bibliographically approved
List of papers
1. Synthesis of the Fused Heterobicycles 5-pyridin-2-yl-thieno[3,2-b]pyridine, 6-pyridin-2-yl-thieno[2,3-b]pyridine and 6-pyridin-2-yl-thieno[3,2-c]pyridine
Open this publication in new window or tab >>Synthesis of the Fused Heterobicycles 5-pyridin-2-yl-thieno[3,2-b]pyridine, 6-pyridin-2-yl-thieno[2,3-b]pyridine and 6-pyridin-2-yl-thieno[3,2-c]pyridine
2006 (English)In: Synthesis (Stuttgart), ISSN 0039-7881, E-ISSN 1437-210X, Vol. 8, 1295-1300 p.Article in journal (Refereed) Published
Abstract [en]

Three new pyridyl thienopyridines 5-pyridin-2-yl-thieno[3,2-b]pyridine (1), 6-pyridin-2-yl-thieno[2,3-b]pyridine (2) and 6-pyridin-2-yl-thieno[3,2-c]pyridine (3) have been synthesized. 1 was synthesized via a chalcone-like precursor derived from (2-formyl-thiophen-3-yl)-carbamic acid ethyl ester (9). Removal of the carbamate group with HBr led to an immediate ring-closure of the intermediate amine to give 1 in an overall yield of 32% after 5 steps. 2 was synthesized by a Beckmann rearrangement of E-1-(5-bromo-thiophen-2-yl)-ethanone oxime (16) to yield N-(5-bromo-thiophen-2-yl)-acetamide (18). Reaction of 18 under modified Vilsmeier conditions led to the ring-closed product, 2-bromo-6-chloro-thieno[2,3-b]pyridine (19). Debromination followed by a Negishi cross-coupling with 2-pyridyl zinc bromide gave 2 in an overall yield of 8%. 3 was synthesized via formylation of 2-thiophen-3-yl-[1,3]dioxolane (22). A Wittig reaction between 22 and triphenyl-pyridin-2-yl-phosphonium bromide (25) gave the alkene, 2-[2-(3-[1,3]dioxolan-2-yl-thiophen-2-yl)-vinyl]­pyridine (26) in moderate yield.   Deprotection and ring closure of the oxime derivative of the resulting aldehyde gave 3 in an overall yield of 7.5% for this six step reaction.

Place, publisher, year, edition, pages
Stuttgart: Georg Thieme verlag, 2006
Keyword
ring closure, fused-ring systems, heterocycles, pyridines, conjugation
Identifiers
urn:nbn:se:mdh:diva-1484 (URN)10.1055/s-2006-926416 (DOI)000237076800011 ()2-s2.0-33646272206 (Scopus ID)
Projects
Molekylär elektronik
Available from: 2008-10-23 Created: 2008-10-23 Last updated: 2016-01-19Bibliographically approved
2. The role of isomeric effects on the luminescence lifetimes and electrochemistry of oligothienyl-bridged dinuclear tris(2,2′-bipyridine) ruthenium(II) complexes
Open this publication in new window or tab >>The role of isomeric effects on the luminescence lifetimes and electrochemistry of oligothienyl-bridged dinuclear tris(2,2′-bipyridine) ruthenium(II) complexes
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2008 (English)In: European Journal of Inorganic Chemistry, ISSN 1434-1948, no 11, 1784-1794 p.Article in journal (Refereed) Published
Abstract [en]

The luminescence lifetimes (in CH 3CN at room temperature) and electrochemical potentials (in CH 3CN) of a range of mono- and bis(bidentate) 2,2′-bipyridine-capped oligothiophene-bridged Ru II complexes based on the 6-(2-thienyl)-2,2′-bipyridine and 4-(2-thienyl)-2,2′-bipyridine motifs have been measured. The redox potentials occurred in a very narrow range and showed only small shifts from that of [Ru(bpy) 3] 2+, which indicates that the inductive effects of the substituents on the 2,2′-bipyridine ligands are very similar across this series. In the complexes that incorporated a bithiophene moiety the oxidation of the bithienyl group occurred at higher potentials than the metal-centered Ru III/II oxidation. No or very weak interaction between the metal cores in the dinuclear complexes was observed. It was found that the luminescence lifetimes of the complexes where the attachment point of the oligothiophene bridge is in the 4-position of a 2,2′-bipyridine ligand were extended compared to [Ru(bpy) 3] 2+, whereas the luminescence was very short-lived (<30 ns) or completely quenched in the complexes where the oligothiophene bridge was attached in the 6-position. The difference in lifetimes is probably due to steric interactions between the thienyl bridge and the auxiliary bipyridyl ligands, resulting in disturbances in coordination symmetry of the metal core.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:mdh:diva-4135 (URN)10.1002/ejic.200701118 (DOI)000255358200007 ()2-s2.0-53349168133 (Scopus ID)
Available from: 2007-11-09 Created: 2007-11-09 Last updated: 2014-06-23Bibliographically approved
3. The effects of pendant vs. fused thiophene attachment upon the luminescence lifetimes and electrochemistry of tris(2,2 '-bipyridine)ruthenium(II) complexes
Open this publication in new window or tab >>The effects of pendant vs. fused thiophene attachment upon the luminescence lifetimes and electrochemistry of tris(2,2 '-bipyridine)ruthenium(II) complexes
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2008 (English)In: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-0682, no 26, 4101-4110 p.Article in journal (Refereed) Published
Abstract [en]

The electrochemical and photophysical properties for a range of ruthenium(II) tris-2,2’-bipyridine complexes in which a thiophene substituent is attached to one of the bipyridine ligands via either a pendant or a fused mode have been determined. The fused mode of attachment eliminates torsional movement between the thiophene unit and the chelating bipyridine, thereby offering optimal overlap between the p systems of the chelating unit and the attached thiophene unit. The electrochemical properties of these complexes were found to be similar, however the luminescence lifetimes and intensities (in CH3CN at room temperature) were found to be correlated to the mode of attachment. The longest luminescence lifetime was

observed for the complex [Ru(bpy)2(4-thiophen-2-yl-[2,2']-bipyridine)]2+ (3000 ns), as compared to the prototypic [Ru(bpy)3]2+ (1745 ns). This complex also had the highest quantum yield (0.045). In the four isomeric complexes where the thiophene ring was fused to the b or c face of the pyridine the lifetimes fell in the interval 275-1510 ns and the quantum yield ranged between 0.0047-0.014.

 

(© WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Place, publisher, year, edition, pages
Weinheim: Wiley-VCH Verlag GmbH, 2008
Keyword
Luminescence, N ligands, Ruthenium, Ligand design, cyclic voltammetry
National Category
Chemical Sciences
Identifiers
urn:nbn:se:mdh:diva-1482 (URN)10.1002/ejic.200800456 (DOI)000259654700007 ()2-s2.0-53549135493 (Scopus ID)
Projects
Molekylär elektronik
Available from: 2008-10-23 Created: 2008-10-23 Last updated: 2013-06-26Bibliographically approved
4. Coordination-mode pH and Light-activated Molecular Switches based on Ruthenium(II) Oligopyridine Complex Architecture
Open this publication in new window or tab >>Coordination-mode pH and Light-activated Molecular Switches based on Ruthenium(II) Oligopyridine Complex Architecture
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(English)Manuscript (Other academic)
National Category
Chemical Sciences
Identifiers
urn:nbn:se:mdh:diva-4137 (URN)
Available from: 2007-11-09 Created: 2007-11-09 Last updated: 2017-02-22Bibliographically approved
5. Use of Heck Methodology for the formation of Mono- and Di-pyridyl Thienopyridines
Open this publication in new window or tab >>Use of Heck Methodology for the formation of Mono- and Di-pyridyl Thienopyridines
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(English)Manuscript (Other academic)
National Category
Chemical Sciences
Identifiers
urn:nbn:se:mdh:diva-4138 (URN)
Available from: 2007-11-09 Created: 2007-11-09 Last updated: 2017-03-08Bibliographically approved
6. The Kröhnke Reagent is Dead. Long Live Kröhnke Chemistry: The Syntesis of Bi- and Terpyridines Revisited
Open this publication in new window or tab >>The Kröhnke Reagent is Dead. Long Live Kröhnke Chemistry: The Syntesis of Bi- and Terpyridines Revisited
(English)Manuscript (Other academic)
Identifiers
urn:nbn:se:mdh:diva-4139 (URN)
Available from: 2007-11-09 Created: 2007-11-09 Last updated: 2016-01-08Bibliographically approved

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