Intramolecular photoinduced electron transfer in a ruthenium polypyridyl functionalised β-cyclodextrin capped with a hydroxo bridged Cu(II) dimer

The synthesis of a novel donor–acceptor system comprising a ruthenium polypyridyl unit covalently linked to the secondary face of β-cyclodextrin which has a hydrxy bridged dinuclear copper(II) moiety on its primary face is described and the spectroscopic, electrochemical and photophysical properties of this complex are outlined. Photophysical studies demonstrate evidence for photoinduced electron transfer from the excited ruthenium to the copper centre. The rate of electron transfer, was estimated from luminescence lifetime studies to be 1.86 × 10−6 s−1. The parent ruthenium polypyridyl functionalized β-cyclodextrin complex binds to both Cu(II) and Zn(II) in alkaline aqueous solution and the affects of these cations on the luminescence intensity of this complex is explored and compared with the photophysics of the isolated supramolecular complex. Whereas Cu(II) statically quenches the ruthenium centre, Zn(II) has little effect. This work suggests luminescent CD complexes, with long-lived luminophores may have value in metal ion sensing.

Graphical abstractThe photophysics of a novel supramolecular donor–acceptor system comprising a ruthenium polypyridyl unit covalently linked to a hydroxo bridged dinuclear copper(II) β-cyclodextrin (CD) moiety indicates efficient photoinduced electron transfer is occurring. The parent ruthenium linked CD complex is readily quenched by copper ions at high pH whereas zinc ion has no impact on the photophysics of the complex. Although more commonly studied in the context of inclusion, such luminescently labelled CDs may have value in metal sensing.Figure optionsDownload full-size imageDownload as PowerPoint slide