Synthesis, Structural Characterization, and Analysis of DFT and TD-DFT for IR and UV-Vis of Benzoyl Thiourea Ligand As Colorimetric Chemosensor

Goh, Hua Yong (2024) Synthesis, Structural Characterization, and Analysis of DFT and TD-DFT for IR and UV-Vis of Benzoyl Thiourea Ligand As Colorimetric Chemosensor. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

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Abstract

In this project, three novel para substituted benzoyl thiourea based ligand, BT, p CH 3 BT and p Br BT (where BT= benzoyl thiourea) with different substituent bind with benzoyl thiourea have been synthesized and characterized by FT IR spectroscopy, UV Vis spectroscopy, CHNS element al analyzer, 1 H and 13 C NMR spectroscopy, and XRD. The melting point for BT, p CH 3 BT and p Br BT ligand w ere investigate using melting point apparatus and DSC to determine their purity. The melting point s of the synthesized ligand s were 212.20 ⁰ C , 223.34 ⁰ C and 221.65 ⁰ C respectively. The percentage s of carbon, hydrogen, nitrogen, and sulfur obtained from CHNS element al ana lyzer for the three synthesized ligand closely matched the matched the calculated analytical result s . All three ligands displayed important functional groups including N H, C=O, and C=S at the expected wavenumber range s in the FT IR spectrum 3299 3328 cm 1 , 1664 1678 cm 1 and 1060 1075 cm 1 respectively. All ligands dissolved in acetonitrile displayed one π → π * and two n → π * transitions in UV Vis spectra. The results from FT IR result and UV Vis spectroscopy were in good agreement with the DFT and TD DFT calculations . The 1 H NMR results indicated peaks for CONH, CSNH and aromatic ring (Ar H) protons at approximately 14 ppm, 12 ppm and 7.0 8.0 ppm respectively. Meanwhile, the 13 C NMR result s showed peaks for C=S, C=O and aromatic r ing carbons at approximately 177 ppm, 169 ppm and 121.1 159.2 ppm respectively. After characterization, the three novel ligands were tested for selectivity, sensitivity as colorimetric chemosensor s . The three novel ligands show ed a positive result when te sted with Cu 2+2+, while metal ions Cd 2+2+, Co 2+2+, Fe 2+2+, Fe 3+3+, Pb 2+2+, Hg 2+2+, Ni 2+2+, and Zn 2 + show ed negative result s . The initially colorless solution s turned light yellow and displayed an absorption in visible region at 408 nm for BT and p Br BT ligand s and at 402 nm for p CH 3 BT ligand. Th e ligand to Cu 2+ binding ratio was found to be 1: 1 using Jobs’ plot method and the Cu 2+ was proposed to coordinate with the N atom in N H group. The limit s of detection of BT, p CH 3 BT and p Br BT ligand was found to be 2.95 × 10 6 M, 3.71 × 10 6 M and 4.07 × 10 6 M respectively. These findings highlight the potential of BT, p CH 3 BT and p Br BT ligands as effective and selective colorimetric chemosensors for Cu 2+ ions.