Incorporation of manganese complexes within hybrid resol-silica and carbon-silica nanoparticles

The incorporation of a luminescent probe into a nano-vector is one of the approaches used to design chemosensors and nanocargos for drug delivery and theranostics. The location of the nano-vector can be followed using fluorescence spectroscopy together with the change of environment that affects the fluorescence properties. The ligand 9-anthracene carboxylate is proposed in this study as a luminescent probe to locate two types of manganese complexes inside three series of porous nanoparticles of different composition: resol-silica, carbon-silica and pure silica. The manganese complexes are a tetranuclear Mn^III cluster [Mn^III 4(µ-O)₂ (µ-AntCO₂ )₆ (bpy)₂ (ClO₄ )₂ ] with a butterfly core, and a Mn^II dinuclear complex [{Mn^II (bpy)(AntCO₂ )}₂ (µ-AntCO₂ )₂ (µ-OH₂ )]. The magnetic measurements indicate that both complexes are present as dinuclear entities when incorporated inside the particles. Both the Mn complexes and the nanoparticles are luminescent. However, when the metal complexes are introduced into the nanoparticles, the luminescent properties of both are altered. The study of the fluorescence of the nanoparticles’ suspensions and of the supernatants shows that Mn^II compounds seem to be more retained inside the particles than Mn^III compounds. The resol-silica nanoparticles with Mn^II complexes inside is the material that presents the lowest complex leaching in ethanol.