Synthesis, Crystal Structure and Fluorimetric Study of 2-phenylphthalazin-1(2H)-one: a Highly Selective Florescent Chemosensor for Detection of Fe 3+ and Fe 2+ Metal Ions

A ligand, 2-phenylphthalazin-1(2H)-one ( K ), was synthesized by refluxing 2-formylbenzoic acid with phenyl hydrazine in presence of ethanol. FTIR, elemental analysis and single crystal XRD techniques were used to elucidate the structure. Fluorimetric turn-off response was recorded when solution of ligand ( K) in DMF was treated with aqueous solution of Fe 3+ and Fe 2+ metal ions. No specific changes were observed on addition of other metal ions (Pb 2+ , Cd 2+ , Mn 2+ , Zn 2+ , Ba 2+ , Ni 2+ , Al 3+ , Ag 1+ , Co 2+ , Ca 2+ , Cu 2+ , Mg 2+ , Cr 3+ ). Limit of Detection (LOD) was calculated for Fe 2 and Fe 3+ as 2.4 µM and 2.5µM respectively, which is quite below to the recommended value 5.4 µM of the Environment Protection Agency of USA. Association constants for Fe 3+ and Fe 2+ metal ions were determined as 6 × 10 –4 M −1 and 3.6 × 10 –4 M −1 respectively. Benesi-Hildebrand plot confirmed 1:1 binding ratio between metal ions and ligand. Graphical Abstract