PluS Nanoparticles as a tool to control the metal complex stoichiometry of a new thio-aza macrocyclic chemosensor for Ag(I) and Hg(II) in water

We report here the synthesis of a new thio-aza macrocyclic chemosensor based on the 2,5-diphenyl[1,3,4]oxadiazole in which two thioether groups were inserted in a macrocycle with the aim to make it suitable for the coordination of soft and heavy metal ions. In acetonitrile solution, the fluorescence of the chemosensor changes upon addition of different metal ions, such as Cu(II), Zn(II), Cd(II), Pb(II), Hg(II) and Ag(I), that form a not fluorescent ML species and a fluorescent M2L species characterized also via NMR experiments. The hosting of the chemosensor inside the PluS Nanoparticles leads to a high water solubility, allowing to perform the metal detection without the use of additional solvents and also induced an higher selectivity towards Ag(I) and Hg(II). Moreover, it was demonstrated for the first time the possibility to control the stoichiometry of the formed complex upon changing the number of ligands per nanoparticles. To our opinion, this possibility can give an additional tool for the tuning of the affinity and selectivity of the chemosensor that could be of great interest for the design of more and more efficient systems.