Exploring the Ability of Luminescent Metal Assemblies to Bind and Sense Anionic or Ionizable Analytes A Ru(phen)bipy-Based Dizinc Complex for Bisphenol A (BPA) Recognition.

The synthesis of a new Ru complex, in which the metal is coordinated by two 1,10-phenanthroline ligands and a 2,2'-bipyridyl unit linked, via methylene bridges in its 4 and 4' positions, to two 1,4,7,10-tetraazacyclododecane (cyclen) macrocycles ([Ru(phen) ]) is reported. Protonation and Zn binding by [Ru(phen) ] have been analyzed by potentiometric titration, evidencing the formation of mixed hetero-binuclear and hetero-trinuclear Zn/Ru complexes. These complexes were tested as bis-phenol A (BPA) binders. Only the dizinc complex with [Ru(phen) ] is able to bind BPA in aqueous solution, affording a remarkably stable {Zn[Ru(phen) ]BPA(H)} adduct at neutral pH, in which BPA is bound in its doubly deprotonated form to the two Zn ions. BPA binding was found to quench the luminescence emission of the Ru(phen)bipy core. Although the quenching effect is modest, this study demonstrates that appropriately designed dizinc complexes can be used for binding and optical sensing of BPA in water.