Abstract

Metal ion sensing properties of thiophene based hydrazone (TH) have been studied using UV-Vis and DFT studies. In comparison to heavy transition metal ions, TH especially binds to Cu2+ and Fe3+ ions. The lower limit of detection (LOD) of the compound is 6 μM and 9 μM for Cu2+ and Fe3+ ions respectively. The binding constant for the compound: Cu2+ and compound: Fe3+ complexes are obtained as 3 x 104 M-1 and 4.5 x 103 M-1 respectively using the Benesi-Hildebrand plot. The stoichiometry ratio for compound: Cu2+ complex 2:1 is obtained using Job's plot. The complex is more stable than the free compound and is validated through computation of HOMO-LUMO orbital energy and band gap of compound and complex using density functional theory. TH exhibits antioxidant properties against the DPPH radical with IC50: 23 μM. The possible mechanism of quenching of radical is suggested through single electron transfer followed by a proton transfer mechanism. From the above studies, it can be concluded that the hydrazone TH detects both Cu2+ and Fe3+ ions up to micromolar concentration and quenches the DPPH radical with IC50 comparable to vitamin E.

Keywords: Antioxidant, Density Functional Theory, Sensor, Thiophene, UV-Vis.