Hg²+ recognition by 2-naphthol: Experimental and quantum computational insights

Abstract

Mercury is regarded as a particularly dangerous metal ion because of its fatal effects on humans and the ecosystem. Herein, we have reported the synthesis of a novel chemosensor, L, including a 2-naphthol-derived azo framework, which has been designed and evaluated for the selective and sensitive detection of mercury (II) ions (Hg²⁺). The complexation behavior of L with Hg²⁺ is validated using UV–Vis, ATR-FTIR, NMR and FESEM studies. Job’s plot indicates a 1:1 binding stoichiometry. The association constant (Kₐ) of 1.07 × 10⁴ M⁻¹ and a detection limit of 6.21 × 10⁻⁷ M, demonstrating robust affinity and elevated sensitivity. DFT calculations clarify the binding affinity and electronic rearrangement, while frontier molecular orbital (FMO) and density of states (DOS) analysis reveal substantial orbital overlap indicative of a metal-to-ligand charge transfer (MLCT) mechanism. Topological analyses (QTAIM, NCI, RDG, ELF, LOL) provide additional characterization of noncovalent interactions and electron density redistribution. Molecular docking with estrogen receptor-α (PDB ID: 3ERT) demonstrates a favorable binding energy of −7.8 kcal/mol, underscoring the sensor's potential biological significance.