ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

A novel receptor for detection of Zn²⁺ metal ion and F⁻, H₂PO₄ ⁻ and AcO⁻ anions in aqueous media: a DFT study

Masoumeh Orojloo, Raziyeh Arabahmadi, Fatemeh Naderi, Fatemeh Parchegani, Mohammad Solimannejad, Peyman Zolgharnein, and Saeid Amani

Arak University, Arak, Iran

E-mail: s-amani@araku.ac.ir

Abstract: A new colorimetric chemosensor L, containing electron-donating moieties attached to the thiazole-based Schiff base was synthesized. The optical and colorimetric sensing properties of L for anions and cations were investigated using naked eye, UV–Vis and computational studies. The receptor L displays visual changes towards anions like F⁻, H₂PO₄ ⁻ and AcO⁻ and also towards cation such as Zn²⁺ in DMSO. Other anions such as Cl ⁻, Br⁻, I⁻, NO₃ ⁻ and HSO₄ ⁻ did not cause any color change. On the addition of other metal ions such as Cr³⁺, Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Cd²⁺, Hg²⁺ and Pb²⁺, the receptor did not show any significant change. The binding constant (K _a ) and stoichiometry of the host–guest complex formed were calculated by the Benesi–Hildebrand (B–H) plot and Job’s plot method, respectively. Computational studies and UV–Vis titration were further used to emphasize the sensing behavior of the receptor. Quantum chemical calculations and molecular studies using Density Functional Theory and Molecular Electrostatic Potential surface studies were carried out to supplement the experimental results and gain deeper insights about the structural as well as the spectral aspects of the complex. Receptor L proved to be a fluorescence and colorimetric Zn (II), fluoride (F⁻¹), di-hydrogen phosphate (H₂PO ₄ ⁻¹ ) and acetate (AcO⁻¹) sensor. This new chromogenic receptor shows a highly selective coloration for the above ions. The chemosensor showed a color change upon addition of Zn (II), or fluoride or di-hydrogen phosphate or acetate ions.