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Coordination-mode pH-activated Molecular Switches based on Ruthenium(II) Oligopyridine Complex Architecture
Mälardalen University, School of Sustainable Development of Society and Technology.
Mälardalen University, School of Sustainable Development of Society and Technology.
University of Basel, Dept. of Chemistry.
University of Basel, Dept. of Chemistry.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

A number of [Ru(tpy)L] complexes (where L is a ligand based on the 6-thien-2-yl-2,2’-bipyridine motif) have been generated to study the ability of this terdentate motif to switch between a N,N,C and a N,N,S binding mode as a function of pH and irradiation. Whilst the parent system 6-thien-2-yl-2,2’-bipyridine (1) displayed facile switching between the orange and purple forms, heavier analogues displayed sluggish switching – most likely resulting from a large moment of inertia about the bond between the S/C-bonded thiophene ring and the chelating bipyridine unit. Prototypic unsymmetrical bimetallic complexes (C7S and C7C) have been generated in order to test if the binding mode of the switching unit can affect the oxidation potential of the remote [Ru(bpy)2(L)] unit. The results of cyclic voltammetry studies suggest that only weak electronic coupling between the metal cores exists, and that the coordination mode (N,N,C or N,N,S) of the thiophene moiety only has a small effect on the oxidation potential of the [Ru(bpy)2(L)] unit.

Keyword [en]
Ligand Effects, Ruthenium, Cyclic Voltammetry, Molecular Electronics, Coordination Modes
National Category
Organic Chemistry Inorganic Chemistry
Research subject
Biotechnology/Chemical Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-9619OAI: oai:DiVA.org:mdh-9619DiVA: diva2:320288
Available from: 2010-05-24 Created: 2010-05-24 Last updated: 2010-08-09Bibliographically approved
In thesis
1. Molecular Electronic Devices based on Ru(II) Thiophenyl Pyridine and Thienopyridine Architecture
Open this publication in new window or tab >>Molecular Electronic Devices based on Ru(II) Thiophenyl Pyridine and Thienopyridine Architecture
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
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 ultra-pure silicon, and therefore the computing power, will double every 18 to 24 months. However, around 2020 hardware manufacturers 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 wires, diodes, transistors and capacitors.

In this work we have synthesized a number of new bi- and terdentate thiophenyl pyridine and pyridyl thienopyridine ligands and compared the electrochemical, structural and photophysical properties of their corresponding Ru(II) complexes with 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 motifs. While the electrochemistry of the Ru(II) complexes were similar to that of unsubstituted [Ru(bpy)3]2+ and [Ru(tpy)2]2+, substantial differences in luminescence lifetimes were found. Our findings show that, due to steric interactions with the auxiliary bipyridyl ligands, luminescence is quenched in Ru(II) complexes that incorporate the 6-thiophen-2-yl-2,2'-bipyridine motif, while it was comparable with the luminescence of [Ru(bpy)3]2+ in the Ru(II) complexes of bidentate pyridyl thienopyridine ligands. The luminescence of the Ru(II) complexes based on the 4-thiophen-2-yl-2,2'-bipyridine motif was enhanced compared to [Ru(bpy)3]2+ which indicates that complexes of this category may be applicable for energy/electron-transfer systems.

At the core of molecular electronics is the search for molecular ON/OFF switches. Based on the ability of the ligand 6-thiophen-2-yl-2,2'-bipyridine to switch reversibly between cyclometallated and non-cyclometallated modes when complexed with Ru(tpy) we have synthesized a number of complexes, among them a bis-cyclometallated switch based on the ligand 3,8-bis-(6-thiophen-2-yl-pyridin-2-yl)-[4,7]phenanthroline, and examined their electrochemical properties. Only very weak electronic coupling could be detected, suggesting only little, if any, interaction between the ruthenium cores.

Place, publisher, year, edition, pages
Västerås: Mälardalen University, 2010. 92 p.
Series
Mälardalen University Press Dissertations, ISSN 1651-4238 ; 86
Keyword
Molecular Electronics, Organic Synthesis, Ruthenium, Pyridyl Complexes, Ligand Design, Fused Ligands
National Category
Chemical Engineering
Research subject
Biotechnology/Chemical Engineering
Identifiers
urn:nbn:se:mdh:diva-10084 (URN)978-91-86135-79-9 (ISBN)
Public defence
2010-09-03, Filen, Smedjegatan 37, Kv. Verktyget, Eskilstuna, 13:00 (English)
Opponent
Supervisors
Available from: 2010-08-09 Created: 2010-08-02 Last updated: 2010-08-19Bibliographically approved

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