Synthesis, Crystal Structure and Fluorimetric Study of 2-phenylphthalazin-1(2H)-one: a Highly Selective Florescent Chemosensor for Detection of Fe3+ and Fe2+ 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 Fe³⁺ and Fe²⁺ metal ions. No specific changes were observed on addition of other metal ions (Pb²⁺, Cd²⁺, Mn²⁺, Zn²⁺, Ba²⁺, Ni²⁺, Al³⁺, Ag¹⁺, Co²⁺, Ca²⁺, Cu²⁺, Mg²⁺, Cr³⁺). Limit of Detection (LOD) was calculated for Fe² and Fe³⁺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 Fe³⁺ and Fe²⁺ 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.