Synthesis, characterization and investigation of fluorescent Sn2+ probe potential of pyrene-derived monomer and its oligo(azomethine) compound

A monomer (2-methoxy-6-((pyren-1-yl-imino)methyl)phenol, VP) was synthesized by the Schiff base reaction of o-vanillin (VA) and 1-aminopyrene (AP), and an oligomer (oligo-2-methoxy-6-((pyren-1-yl-imino)methyl)phenol, OVP) was synthesized from this monomer via oxidative polycondensation reaction. The structural characterization of the obtained monomer and oligomer by FT-IR, 1H NMR and 13C NMR; electrochemical properties with cyclic voltammetry (CV); optical properties with UV–Vis and photoluminescence (PL) spectroscopy; thermal stability with thermogravimetric analysis (TGA); and the molecular weight of the oligomer were determined by gel permeation chromatography (GPC). From the fluorescence titration, VP was found to be sensitive to Sn2+ out of a range of metal ions. When the VP solution, to which 1 equivalent amount of Sn2+ was added, was excited with 320 nm light, it was observed that it emits bright blue color at 445 nm. It was found that VP, whose limit of detection (LOD) was calculated as 4.24 nM for Sn2+, had a sensitive and selective fluorescence sensor potential. In addition, it was found that the obtained oligo[2-methoxy-6-((pyren-1-yl-imino)methyl)phenol] (OVP) had a molecular mass of 3450 Da and showed fluorescent properties. The maximum emission of the OVP excited with 380 nm light was observed at 443 nm, with green emission.