LAUSR

Abstract A new Schiff base, 1,5-dimethyl-4-(2-hydroxy-1,2-diphenylethylideneamino)-2-phenylpyrazol-3-one (L) was synthesized by the condensation of 4-amino-2,3-dimethyl-1-phenyl-3-pyrazolin-5-one (4-aminoantipyrine) with 2-hydroxy-1,2-di(phenyl)ethanone (benzoin). It was characterized by elemental analysis and spectroscopic techniques. The optical response of the compound, L towards various metal ions like Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Al3+, Mg2+, Ca2+, Ba2+, Pb2+, Cd2+ and Hg2+ was monitored in methanol solution. L showed a remarkable colourimetric response towards Fe3+ and fluorescence “turn-on” behavior towards Al3+. Binding with Fe3+ induced a “naked-eye” purple coloration under day light. The recognition of L with Al3+ was responsible for blue fluorescent emission at 463 nm. The UV–Visible and fluorescent spectral studies of L with different metal ions were consistent with the visual observation. Due to the transient nature of the complex formed between L and Fe3+ in methanol, the stability of the complex formed in an aprotic solvent, acetonitrile was also ascertained. The stoichiometry and association constant of the complex formed were calculated.