Novel bis naphthalene-2-ol based colorimetric chemosensor for the detection of Fe2+ in physiological pH and its DFT calculation studies

A novel bis naphthalene-2-ol-based multi-functional chromogenic chemosensor was synthesized in a single step and thoroughly characterized by Fourier-Transform Infrared Spectroscopy, Mass spectrometry, Nuclear Magnetic Resonance and Single Crystal-X-ray for the detection of Fe²⁺ and CN⁻ ions in physiological pH. The detection limit of Fe²⁺ was initiated as 4.35 μM is much superior to the United States Environmental Protection Agency parameter value for drinking water (5.37 μM). The 3-Fe²⁺ complex we can reversibly reuse after the treatment with CN⁻ ion. A noteworthy red-shifted with hypochromic shift spectrum and “naked eye” colour change has been observed from yellow colour to light pink colour within 5 s for Fe²⁺ ion but not for other competing metal ions. Without any complex pretreatment, our chemosensor easily discriminates Fe²⁺ and Fe³⁺ ions. From Job's plot analysis, ¹H NMR titration and MS analysis confirm the binding stoichiometry among probe 3 and Fe²⁺ metal ion as 1:1. The experimental active molecular binding site results are correlated well with the Density Functional Theory calculation to understand the sensing mechanism.