chemical sciences

han vos - research interests

The design of multinuclear ruthenium and osmium polypyridyl compounds as components in molecular devices
Investigation of energy and electron transfer pathways at supramolecular assemblies involving of molecular components and a solid surface
Chemical modification of carbon nanotubes
Development of novel synthetic methods in inorganic chemistry
The partial deuteriation of polypyridyl type ligands
The investigation of the effect of partial deuteriation on the photophysical properties of ruthenium and osmium polypyridyl complexes
Electrochemistry of polymer-modified electrode surfaces
The design of luminescent and electrochemical sensors

There is at present a great interest in the development of molecular devices containing organised or supramolecular arrangements of molecular components. For many years the Dublin City University Group has been involved in the design and study of multinuclear (Figure 1) and polymeric complexes (Figure 2) based on ruthenium and osmium polypyridyl moities. This family of compounds has excellent photophysical and electrochemical properties and with appropriate design multinuclear systems with strong interaction between the metal centres can be synthesised. They are therefore ideal components for the construction of molecular devices and offer great potential for real life applications in areas such as solar energy devices, sensing systems and in molecular electronics.

Figure 1

Figure 2

The investigations carried out in the group are interdisciplinary in nature and cover a wide range of subjects ranging from organic and inorganic synthesis, to spectroscopy, electrochemistry and photophysics (in collaboration with Prof. L. Hammerström, University of Uppsala, and Prof. S. Campagna, University of Messina) [3]. Areas of interest include the separation (in collaboration with Prof. Villani, University of Rome) and photophysical properties of stereoisomers [6], the deuteriation of polypyridyl ligands [9], energy and electron transfer processes in supramolecular assemblies [7][8] and the development of novel synthetic techniques in inorganic chemistry. Of particular interest is also the application of partial deuteriation techniques in photophysical studies (in collaboration with Prof. J.J. McGarvey, Queens University Belfast) [4].

Large emphasis is also placed on the investigation of ruthenium and osmium complexes immobilised on solid substrates. One area of interest is the interaction of mononuclear as well as dinuclear compounds (Figures 3 and 4) with solid surfaces such as TiO₂, concentrating on the study and control of the direction of energy and electron transfer processes [5].

Figure 3

Figure 4

Another area of research is the investigation of electrodes modified with polymers such as that shown in Figure 2 [2]. These studies are aimed at the understanding of charge transfer processes in these ultra-thin films and gaining an understanding of the important relationship between structure and properties (in collaboration with Prof. R. Hillman, University of Leicester) [1].

Recently, work has also started on the synthesis and characterisation of ruthenium and osmium complexes with potential to act as linkers and molecular switches between solid substrates such as electrode surfaces and nanoparticles (Figure 5). These studies are part of research carried in the Research Training Network SUSANA, funded by the European Commission's 5^th Framework Improving Human Potential programme (www.cordis.lu/improving) , which aims to investigate electron transfer across solid and liquid/liquid interfaces.

Figure 5

Figure 6

Ruthenium polypyridyl complexes have also been used to link carbon nanotubes. Intermolecular carbon nanotube junctions were formed through amide linkage of amino-functionalised multiwall carbon nanotubes and [Ru(dcbpy)(bpy)₂](PF₆)₂ (in collaboration with Dr. M. in het Panhuis, Trinity College Dublin) [10]. Figure 6 shows visualisation of nanotube interconnects using Atomic Force Microscopy.

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