Optical properties of porphyrin–Eu-beta-diketonate supramolecular nanostructures

Hybrid nanostructures obtained by the assembly of organic/inorganic chemical systems can show novel molecular properties. The combination of different optical properties belonging to different molecular components represents an advanced method to manufacture hybrid assemblies useful for improved optical applications. In our study, silanized quartz substrates were functionalized with a covalent tetrakis hydroxyphenyl porphine monolayer. The remaining hydroxyphenyl substituents, not involved in the covalent bond with the silane coupling layer, allowed additional functionalization with the tris(dibenzoylmethane) mono(5-amino-1,10-phenanthroline)europium(III) complex by means of ionic interactions. X-ray photoelectron spectroscopy and UV-visible spectrophotometry gave indication of the porphyrin–Eu-complex grafting mode. In these supramolecular architectures both through bond (covalent) and through space (mainly ionic) electronic interactions between the two molecular units resulted in unprecedented macroscopic properties. In fact, emission measurements confirmed that the porphyrin and Eu-complexes influence each other and the photoluminescence relative intensities are strongly affected.