Performance of Benzoylthiourea Derivatices as Selective and Specific Chemosensor for Copper (II) Ion Detection

Yap, Ynhuey (2025) Performance of Benzoylthiourea Derivatices as Selective and Specific Chemosensor for Copper (II) Ion Detection. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

Text Yap Ynhuey_Full Text.pdf Restricted to Registered users only Download (7MB)

Abstract

A low cost and highly selective chemosensor has attracted intention for detection of metal ions. In this project, two novel para-substituted benzoylthiourea-based ligands, p-CH3 BT and p-Br BT (where BT = benzoylthiourea), were successfully synthesized through a two-step reaction and purified via supersaturated recrystallization. The ligands were characterized using FT-IR spectroscopy, UV-Vis spectroscopy, CHNS elemental analysis, and 1H and 13C NMR spectroscopy. The melting point ranges of both ligands were measured using a melting point apparatus, yielding 153-155 °C for p-CH3 BT and 157-159 °C for p-Br BT. To obtain accurate melting point values and further assess purity, Differential Scanning Calorimetry (DSC) was performed, revealing exact melting points of 153.73 °C for p-CH3 BT and 158.85 °C for p-Br BT. CHNS elemental analysis confirmed the elemental composition of both ligands. FT-IR spectra of both ligands showed characteristic peaks corresponding to functional groups: N–H (3207–3592 cm-1), C=O (1670–1672 cm-1), C–N (1150–1153 cm-1), and C=S (1006–1017 cm-1), confirming the presence of these key moieties. In the UV-Vis spectra, both ligands dissolved in DMSO exhibited two n → π* transitions, while π → π* transitions were absent due to DMSO's cut-off wavelength at 260 nm. These spectral results were in good agreement with DFT and TD-DFT calculations. 1H NMR spectra revealed chemical shifts for CONH (~11 ppm), CSNH (~10 ppm), aliphatic protons (2.36-3.85 ppm) and aromatic protons (7.20–7.90 ppm), while 13C NMR showed signals for C=S (180.40–180.70 ppm), C=O (167–168 ppm), aliphatic carbons (21.55-46.71 ppm) and aromatic carbons (126–144 ppm), supporting the proposed structures. The total number of protons obtained from the integration in the 1H NMR spectra and the total number of carbons from the 13C NMR spectra matched the expected structures of the two ligands, confirming their successful synthesis. Following characterization, the ligands were evaluated for their application as selective colorimetric chemosensors. Both p-CH3 BT and p-Br BT showed a selective color change when exposure to Cu2+ ions, but not to other metal ions such as Co2+, Fe2+, Fe3+, Pb2+, Hg2+, Ni2+, or Zn2+. Upon binding with Cu2+ ions, the initially colorless ligand solutions turned pale yellow-green, with a new absorption band observed at 412.5 nm (p-CH3 BT) and 422.5 nm (p-Br BT). Using Job's plot method, the ligand-to-Cu2+ binding ratio was determined to be 2:1, suggesting that Cu2+ coordinates with each of the two nitrogen atoms in the N–H groups. Both ligands serve as effective fluorescent chemosensors for Cu2+, showing quenching effect upon Cu2+ addition, resulting in dimmer appearance under UV light. The limits of detection (LOD) for p-CH3 BT and p-Br BT were found to be 3.3085 × 10-5 M and 1.7355 × 10-5 M, respectively. These findings highlight the promising potential of p-CH₃ BT and p-Br BT as effective and selective colorimetric and fluorescent chemosensors for Cu2+ ions.