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The Synthesis of Molecular Switches Based Upon Ru(II) Polypyridyl Architecture for Electronic Applications
Mälardalen University, Department of Biology and Chemical Engineering.
2007 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

According to the famous axiom known as Moore’s Law the number of transistors that can be etched on a given piece of silicon, and therefore the computing power, will double every 18 to 24 months. For the last 40 years Moore’s prediction has held true as computers have grown more and more powerful. However, around 2020 hardware manufac-turers will have reached the physical limits of silicon. A proposed solution to this dilemma is molecular electronics. Within this field researchers are attempting to develop individual organic molecules and metal complexes that can act as molecular equivalents of electronic components such as diodes, transistors and capacitors. By utilizing molecular electronics to construct the next generation of computers processors with 100,000 times as many components on the same surface area could potentially be created.

We have synthesized a range of new pyridyl thienopyridine ligands and compared the electrochemical and photophysical properties of their corresponding Ru(II) complexes with that with the Ru(II) complexes of a variety of ligands based on 6-thiophen-2-yl-2,2´-bipyridine and 4-thiophen-2-yl-2,2´-bipyridine. While the electrochemistry of the Ru(II) complexes were similar to that of unsubstituted [Ru(bpy)3]2+, substantial differences in luminescence lifetimes were found. Our findings show that, due to steric interactions with the auxiliary bipy-ridyl ligands, luminescence is quenched in Ru(II) complexes that in-corporate the 6-thiophen-2-yl-2,2´-bipyridine motif, while it is on par with the luminescence of [Ru(bpy)3]2+ in the Ru(II) complexes of the pyridyl thienopyridine ligands. The luminescence of the Ru(II) com-plexes based on the 4-thiophen-2-yl-2,2´-bipyridine motif was en-hanced compared to [Ru(bpy)3]2+ which indicates that complexes of this category are the most favourable for energy/electron-transfer sys-tems.

At the core of molecular electronics are the search for molecular ON/OFF switches. We have synthesized a reversible double cyclome-tallated switch based on the Ru(tpy) complex of 3,8-bis-(6-thiophen-2-yl-pyridin-2-yl)-[4,7]phenanthroline. Upon treatment with acid/base the complex can be switched between the cyclometallated and the S-bonded form. This prototype has potentially three different states which opens the path to systems based on ternary computer logic.

Place, publisher, year, edition, pages
Institutionen för biologi och kemiteknik , 2007. , p. 133
Series
Mälardalen University Press Licentiate Theses, ISSN 1651-9256 ; 77
Keywords [en]
Molecular Electronics, ruthenium, pyridyl complexes, ligand design, ligand synthesis
National Category
Organic Chemistry
Research subject
Biotechnology/Chemical Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-356ISBN: 978-91-85485-55-0 (print)OAI: oai:DiVA.org:mdh-356DiVA, id: diva2:120845
Presentation
2007-08-30, Filen, Verktyget, Smedjegatan 37, Eskilstuna, 13:15
Opponent
Supervisors
Available from: 2007-08-21 Created: 2007-08-21 Last updated: 2016-01-19
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, p. 1295-1300Article 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
Keywords
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: 2017-12-14Bibliographically 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
Show others...
2008 (English)In: European Journal of Inorganic Chemistry, ISSN 1434-1948, no 11, p. 1784-1794Article 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

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