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Influence of polystyrenesulfonate on electron transfer quenching of ruthenium trisbipyridine luminescence by viologens: non-covalent assembly and covalent tethering of the ruthenium complex
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Dr Eimer Tuite
Tuite EM, Rose DB, Ennis PM, Kelly JM
Physical Chemistry Chemical Physics
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A new copolymer (RuB PSS) of ruthenium(II)(bis-bipyridine)(vinyl bipyridine) and styrene sulfonate was prepared which tethers the ruthenium chromophore directly to the polymer backbone. The photophysical properties of the copolymer, and its luminescence quenching by viologens, were compared with those of ruthenium(II)tris-bipyridine, [Ru(bpy)3]2+, bound non-covalently to polystyrenesulfonate (PSS) via hydrophobic and electrostatic interactions. Enhancement of ruthenium polypyridyl complex luminescence in both systems is due to decreased rates of non-radiative decay as well as reduced oxygen quenching. Molecular dynamics simulations corroborate an open PSS chain conformation with induction of local curvature around the ruthenium centres cause local curvature of PSS. Quenching by O2 is hindered for both systems due to combined coulombic and viscosimetric effects that influence local concentrations and diffusion of reactants. Electron transfer quenching of the Ru centre by zwitterionic propyl viologen sulfonate (PVS0) and cationic methyl viologen (MV2+) is enhanced for Ru(bpy)3]2+/PSS, but retarded for RuB PSS, despite the attraction of the quenchers for PSS. PSS binding hinders separation of the electron transfer products relative to aqueous solution, excepting an increase for RuB PSS/PVS0. We conclude that anionic hydrophobic polymers such as PSS can differentially influence forward- and reverse-electron transfer reactions depending on the charge and hydrophobicity of the reactants. In this context, we find that PSS provides a tenable model for DNA, excluding intercalation.
Royal Society of Chemistry
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