Photophysical properties of supramolecular assemblies containing polypyridine complexes and pyrene chromophores

A supermolecule containing the complex [M(bpy)(2)(bpy-O-bpy)](2+) {M = Ru(II), Os(II); bpy-O-bpy = bis[4-(2,2'-bipyridinyl)ether]} and a pyrene derivative (1-pyreneacetic acid) is formed in the presence of Zn2+ ions in acetonitrile solution. In the case of the Os(II) complex all the energy absorbed by the supramolecular system is transferred to the Os-based unit, which retains the photophysical properties of the [Os(bpy)(2)(bpy-O-bpy)](2+) complex. In the Ru-based system, the excited state lifetime of the metal complex is extended to the microsecond range at room temperature, thanks to an equilibrium with the close-lying triplet excited state of the pyrene, as already found for analogous covalently linked systems. The main advantage of the supramolecular approach is essentially its high versatility, and it could find applications in many fields requiring luminescent probes possessing long lifetimes, such as clinical chemistry, chemical sensing, photocatalysis, and biophysics.