Fluorescent macrocyclic chemosensor for Zn(II) detection at alkaline pH values AmbrosiGianluca MicheloniMauro PaderniDaniele FormicaMauro GiorgiLuca FusiVieri 2020 <p>The new macrocyclic ligand <b>L</b> (28,29-dimethoxy-27-oxa-8,11,14,17,25,26-hexaazatetracyclo[22.2.1.1(2,6).1(19,23)]nonacosa-2,4,6(28),19,21,23(29),24,26(1)-octaene) has been synthesised. It contains a tetramine chain and the 2,5-bis(2-methoxy-3-metyl-phenyl)-1,3,4-oxadiazole (PPD-OMe) chromophore, acting as coordinating and sensing units, respectively.</p> <p>The fluorescent emission of <b>L</b> depends on the pH being highly fluorescent at pH = 2 and not emitting from pH >10. The studies highlighted that <b>L</b> is a PET mediated emitting chemosensor, being the PET effect regulated by the degree of the tetraamine protonation.</p> <p><b>L</b> coordinates metal ions (Cu(II), Zn(II) and Cd(II)) in water giving rise to an OFF-ON fluorescent response for the presence of Zn(II) ion thus signalling its presence in the medium. This response is particularly notable at pH = 9 allowing to extend the Zn(II) sensing also in the alkaline pH field.</p>