Synthesis of symmetrical and unsymmetrical benzoylthiourea ligand as potential chemosensor for selective determination of Cu(II) ion / Nurul Asma Hamedan

Design of a new specific colorimetric and fluorescence chemosensor for detection of Cu2+ is a challenge in the context of interference from coexisting metal ions in an aqueous solution. Therefore, new chemosensor were synthesized: symmetrical (LI, L2, L3) and unsymmetrical (L4, L5, L6, L7) benzoylthiourea ligand. The symmetrical ligands were synthesized by the reaction of benzoyl isothiocyanate with diethylenetriamine (2:1). The unsymmetical ligands were synthesized involving two steps. The first step was undergoing 1:1 condensation of 4- dimethylaminobenzaldehyde with diethylenetriamine. The reaction was completed by adding benzoyl isothiocyanate to form unsymmetrical ligands. All ligands were characterized by using Elemental Analysis (EA), Fourier Transform Infrared (FTIR) spectroscopy and proton Nuclear Magnetic Resonance (*H NMR) spectroscopy. For application, further study on selectivity, sensitivity, stoichiometry, binding constant, and the competition of ligands were conducted. Ultraviolet visible spectroscopy (UV Vis) was used to study the symmetrical ligands and fluorescent emission spectroscopy (FES) was applied for all unsymmetrical ligands. All ligands showed more selective towards Cu than other metal ions (Fe , Co , Ni , Mn , Cr and Zn ). However, only L4 shows selective towards both Fe3+ and Cu2+ ions which is not a selective sensor. In conclusion, LI is more sensitive (6.2 x 10"6 M) than L2 (1.5 x 10"6 M) and L3 (1.15 x 10"5 M) by forming a stable 1:2 (metal:ligand) complexes while for unsymmetrical ligand, L7 (9.7 x 10"6 M) is more sensitive than L5 (1.46 x 10"5 M) and L6 (9.7 x 10"5 M) by forming 2:1 (metal:ligand) complexes.