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Bis-cyclometallated Molecular Switches Based on 4,7-phenantroline and 1,5-naphthyridine Architecture
Mälardalen University, School of Sustainable Development of Society and Technology.
University of Queensland, Dept. of Chemistry, School of Molecular & Microbial Sciences .
Mälardalen University, School of Sustainable Development of Society and Technology.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Two new bis-terdentate ligands,  3,8-bis-(6-thiophen-2-yl-pyridin-2-yl)-[4,7]phenanthroline (L1) and 2,6-bis(6-(thiophen-2-yl)pyridin-2-yl)-1,5-naphthyridine (L2), capable of reversible double cyclometallation have been synthesized. Both syntheses proceeded via a Skraup synthesis followed by Stille cross-coupling with 2-thiophen-2-yl-6-tributylstannylpyridine to yield the final product. The Ru2(tpy)2-complex of L1 was shown to be capable of reversible cyclometallation, where the bis-cyclometallated (C,C) isomer of the complex had an oxidation potential of +249 mV while the oxidation potential of the doubly S-coordinated (S,S) complex was +987 mV. No ground state interaction between the Ru cores was however found. In theory the complex should display a third, mixed, state. An S,C-coordinated isomer would open the way for molecular electronic applications based on ternary logic. However, despite attempts the S,C-coordinated complex could not be generated.

Keyword [en]
Molecular Electronics, Ruthenium, Coordination Modes, N ligands, heterocycles
National Category
Organic Chemistry Inorganic Chemistry
Research subject
Biotechnology/Chemical Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-9620OAI: oai:DiVA.org:mdh-9620DiVA: diva2:320293
Projects
Molekylär elektronik
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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