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Issue 33, 2012
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Self assembled composites of luminescent Ru(ii) metallopolymers and the Dawson polyoxometalate α-[Mo18O54(SO4)2]4−

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Abstract

The interaction of two luminescent metallopolymers; [Ru(bpy)2(PVP)10]2+ and [Ru(bpy)2(CAIP)co-poly7]+, where bpy is 2,2′-bipyridyl, PVP is polyvinylpyridine, and (CAIP)co-poly7 is poly(styrene6-co-p-(aminomethyl)styrene) amide linked to 2-(4-carboxyphenyl)imidazo[4,5-f] [1,10]phenanthroline, with the Dawson polyoxomolybdate α-[Mo18O54(SO4)2]4− is described. Both metallopolymers undergo electrostatic association with the polyoxometalate. From both electronic and luminescence spectroscopy the thermodynamic products were determined to be {[Ru(bpy)2(PVP)10]4.5[Mo18O54(SO4)2]}5+ and {[Ru(bpy)2(CAIP)co-poly7]5[Mo18O54(SO4)2]}+, i.e. in both instances, the number of ruthenium centres in the cluster exceeds the number required for charge neutralization of the molybdate centre. Association quenches the luminescence of the metallopolymer although, consistent with the excess of Ru(II) present in the associated composites, emission is not completely extinguished even when a large excess of [Mo18O54(SO4)2]4− is present. The observed emission lifetime was not affected by [Mo18O54(SO4)2]4− therefore quenching was deemed static. The luminescent intensity data was found to fit best to a (sphere of action) Perrin model from which the radii of the quenching were calculated as 4.6 Å and 5.8 Å for [Ru(bpy)2(PVP)10]2+ and [Ru(bpy)2(CAIP co-poly)7]+ respectively. Both UV/Vis and resonance Raman data indicate the presence of a new optical transition centered around 490 nm for the composite, {[Ru(bpy)2(PVP)10]4.5[Mo18O54(SO4)2]}5+ but not for {[Ru(bpy)2(CAIP)co-poly7]5[Mo18O54(SO4)2]}+. This indicates strong electronic interaction between the metal centres in the former composite, which despite good thermodynamic analogy, is not observed for {[Ru(bpy)2(CAIP)co-poly7]5[Mo18O54(SO4)2]}+. These results are consistent with photoelectrochemical studies of layer by layer assemblies of these films which indicate that the ruthenium centre sensitizes polyoxometalate photo-oxidation of benzyl alcohol in {[Ru(bpy)2(PVP)10]4.5[Mo18O54(SO4)2]}5+ but not in {[Ru(bpy)2(CAIP)co-poly7]5[Mo18O54(SO4)2]}+.

Graphical abstract: Self assembled composites of luminescent Ru(ii) metallopolymers and the Dawson polyoxometalate α-[Mo18O54(SO4)2]4−

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Supplementary files

Article information


Submitted
01 Mar 2012
Accepted
09 May 2012
First published
10 May 2012

Dalton Trans., 2012,41, 9928-9937
Article type
Paper

Self assembled composites of luminescent Ru(II) metallopolymers and the Dawson polyoxometalate α-[Mo18O54(SO4)2]4−

J. J. Walsh, J. Zhu, Q. Zeng, R. J. Forster and T. E. Keyes, Dalton Trans., 2012, 41, 9928
DOI: 10.1039/C2DT30503H

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