Phenothiazine attached Ru(bpy)32+ derivative as highly selective “turn-ON” luminescence chemodosimeter for Cu2+

Abstract

The design of a highly selective “turn-ON” luminescence chemodosimeter for Cu²⁺ is reported. The design strategy made use of the ability of Cu²⁺ ions to oxidize aromatic amines in acetonitrile solution. The aromatic amine employed here is a phenothiazine moiety which is covalently linked to one of the bipyridine units of Ru(bpy)₃²⁺. Excitation of the Ru(bpy)₃²⁺ leads to electron transfer from the phenothiazine moiety to the MLCT excited state of Ru(bpy)₃²⁺ which resulted in efficient quenching of the luminescence. In the presence of excess Cu²⁺, phenothiazine moiety is oxidized to a stable entity which is incapable of electron donation to the MLCT excited state of Ru(bpy)₃²⁺. The emission of the Ru(bpy)₃²⁺ moiety is thus restored and we show that this strategy can be used as the basis for sensing micromolar amounts of Cu²⁺. Only Cu²⁺ is capable of this reaction, making this an interesting, hitherto unexplored strategy for the selective detection of micromolar amounts of Cu²⁺.