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Towards Practical Molecular Devices: the Incorporation of a Solid Substrate as an Active Component in Molecular Assemblies
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Towards Practical Molecular Devices: the Incorporation of a Solid Substrate as an Active Component in Molecular Assemblies

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COST D19 International Workshop on Nanochemistry, Sept 26-28 2002, Vienna, Austria

COST D19 International Workshop on Nanochemistry, Sept 26-28 2002, Vienna, Austria


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  • 1. Towards Practical Molecular Devices: the Incorporation of a Solid Substrate as an Active Component in Molecular Assemblies Noel M. O’Boyle,a Wesley R. Browne,a Steve Welter,b Ron T.F. Jukes,b Luisa De Cola,b Colin G. Coates,c John J. McGarvey,c Johannes G. Vosa a National Centre for Sensor Research, School of Chemical Sciences, Dublin City University, Dublin 9, Ireland b Molecular Photonics Group, IMC, University of Amsterdam, Nieuwe Achtergracht 166, NL-1018 WV Amsterdam, the Netherlands c Queens University Belfast, School of Chemistry, Belfast BT9 5AG, Northern Ireland N Ru(bpy)2(H2dcb) N N Introduction Ru Figure 2 N NRuthenium polypyridyl complexes have been widely used as covalentlybound dyes in solar energy devices based on nanocrystalline TiO2. In HOOC N COOHaddition it has been shown that nanocrystalline TiO2 surfaces modifiedwith dinuclear RuOs polypyridyl complexes respond in a uniformmanner to irradiation as shown below in Figure 1. Results The emission spectrum and absorption spectra (both steady-state and transient) of [Ru(bpy)2(dcb)2-] are shown in Figure 3 while the emission Ru Os Ru Os lifetimes obtained for the partially deuteriated complexes are shown in the Table A. Deuteriation reduces the rate of non-radiative deactivation of theFigure 1 e- excited state. This leads to increased emission lifetimes provided the excited state is based on the deuteriated ligand. e- 2+ Ru(bpy)3 180000 Ru(bpy)2(dcb) e- 160000 0.4 140000In most cases the molecular components have been covalently attached 120000via 4,4’-dicarboxy-2,2’-bipyridine (H2dcb) type ligands. It is generally Counts per second Absorbance 100000assumed that in these assemblies injection into the TiO2 surface isenhanced by the fact that the excited state is based on the dcb2- ligand. 0.2 80000 Figure 3 60000This assumption is tested here for the model compound[Ru(bpy)2(dcb)2-] (see Figure 2) by the use of deuteriation in 40000combination with emission lifetime measurements and resonance 20000Raman spectroscopy. 0.0 0 400 500 600 700 800 Deuteriation Wavelength (nm) D 3C D D CD 3 HOOC D D COOH D 2O [O] D D D D Excited-state resonance Raman measurements (Figure 4) clearly show N N NaOD N N N N D D D D that the excited state is localised on the dcb2-. Resonances due to the d6-H2dcb dcb3–• anion radical are observed at 1312 and 1212 cm-1. Scheme 1 1491 cm 1450 cm bpy bpy 3- 3- 1604 cm dcb* dcb* 3- [Ru([H8]-bpy)2([H6]-dcb )] 2- dcb* 1312 cm 2- 1212 cm [Ru([H8]-bpy)2([D6]-dcb )]  (ns) -1 2- -1 [Ru([D8]-bpy)2([H6]-dcb )] -1 2- [Ru([D8]-bpy)2([D6]-dcb )] -1 -1 Ru(bpy)2 (dcb2-) 562Table A Figure 4 Ru(bpy)2(d6 -dcb2-) 633 Ru(d8-bpy)2(dcb2-) 573 Ru(d8-bpy)2(d6-dcb2-) 679 1600 1500 1400 1300 1200 -1 Wavenumber in cm Conclusions Both the variation in emission lifetime as well as the rR spectra observed confirm that the excited state in bpy/dcb2- complexes is dcb2- based. The results clearly indicate that deuteriation is a powerful method for the study of the nature of the excited state in complexes of ruthenium. Acknowledgements This work was supported by Enterprise Ireland and COST D19. The National Centre for Sensor Research