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(I I), Os(II); bpy-O-bpy = bis[4-(2,2'-bipyridinyl)ether]} and a pyrene deriva tive (1-pyreneacetic acid) is formed in the presence of Zn2+ ions in aceton itrile 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 ret ains the photophysical properties of the [Os(bpy)(2)(bpy-O-bpy)](2+) comple x. 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 equi librium with the close-lying triplet excited state of the pyrene, as alread y found for analogous covalently linked systems. The main advantage of the supramolecular approach is essentially its high versatility, and it could f ind applications in many fields requiring luminescent probes possessing lon g lifetimes, such as clinical chemistry, chemical sensing, photocatalysis, and biophysics.