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The photophysics of a luminescent ruthenium polypyridyl complex with pendant β-cylodextrin; pH modulation of lifetime and photoinduced electron transfer

  • Muath Atmeh
  • Noel R. Russell
  • Robert J. Forster
  • Tia E. Keyes
Original Article

Abstract

At room temperature, [Ru(bpy)2(phen-CD)][PF6]2, (phen-CD is 6 A -(5-amino-1, 10-phenanthroline)-6 A -deoxy- β-Cyclodextrin and bpy is 2,2'-bipyridine) exhibits an intense metal ligand charge transfer (MLCT) transition at 452 nm and a long lived luminescence, centred at 618 nm. We demonstrate, for the first time, that the luminescence quantum yield and lifetime of the Ru (II) polypyridyl centre depends markedly on the solution pH. The pH sensitive range extends from pH 3.9 to pH 13.2 and the luminescence quantum yield changes by more than 60% over this range. This pH sensitivity is attributed to protonation/deprotonation of the secondary amine group bridge between the phenanthroline unit and CD. The complex exhibits strong host-guest binding to anthraquinone and anthraquinone-2-carboxylic acid, with concomitant quenching of the [Ru(bpy)2(phen-CD)]2+ excited state. This quenching arises from efficient intramolecular electron transfer. The sensitivity of this photoinduced process to the protonation state of the bridge is discussed.

Keywords

Cyclodextrin Ruthenium polypyridyl Luminescence pH Anthraquinone Quenching Electron transfer 

Notes

Acknowledgements

The authors would like to express their gratitude to Mr Damien McGuirk, School of Chemical Sciences, DCU, for electrospray mass spectrometry and the Dublin Institute of Technology Postgraduate Scholarship Fund for funding.

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Copyright information

© Springer Science+Business Media, Inc. 2007

Authors and Affiliations

  • Muath Atmeh
    • 1
    • 2
  • Noel R. Russell
    • 2
  • Robert J. Forster
    • 1
  • Tia E. Keyes
    • 1
  1. 1.School of Chemical Sciences, National Centre for Sensor ResearchDublin City UniversityGlasnevin, Dublin 9Ireland
  2. 2.School of ChemistryDublin Institute of TechnologyDublin 8Ireland

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