Synthesis and characterization of p-dimethylaminobenzaldehyde benzoylthiourea and study towards selective and sensitive fluorescent sensor for detection of iron (III) cation in aqueous solution

Benzoyl thiourea derivatives ligand backbones contain Oxygen (O), Nitrogen (N), and Suphur (S) donor atoms can react with transition metal ions and form stable metal complexes. A new ligand was synthesized by the reaction of benzoyl isothiocyanate with diethylenetriamine and characterized by using Elemental Analysis (EA), Infrared (IR) spectroscopy and proton Nuclear Magnetic Resonance (¹H NMR) spectroscopy. The monofunctionalize ligand were synthesized using 1:1 condensation of p-dimethylaminobenzaldehyde with diethylenetriamine and confirmed by disappearance of carbonyl group, C=O at 1656 cm^-1 with the appearance of peak C=N in the range 1633 - 1638 cm^-1 in the IR spectrum. This monofunctionalize ligand was synthesis by using Schiff base technique. Benzoyl thiourea derivatives, HN are synthesis from the 1:1 condensation of benzoyl isothiocyanates with monofunctionalized ligand. HN ligand was verified by the presence of peaks v(N-H), v(C=O), v(C=N) v(C-N) and v(C=S) at 3317 - 3336 cm-1, 1612 -1660 cm-1, 1550 -1589 cm-1, 1234-1366 cm-1 and 709-767 cm-1 respectively while ¹H NMR show peaks of alkane (CH₂), benzene (Ar-H), CONH, CSNH at 3.75, 6.73 – 7.33, 8.19, and 8.25 respectively. The total percent composition of C, H, N, O, and S using Elemental Analysis for HN, C₂₁H₂₇N₅OS found was 85.23%. For application, further study on selectivity and sensitivity of HN ligand was conducted on several metal ions. The fluorescent emission spectroscopy shown that HN is a selective fluorescent sensor for Fe³⁺ and Cu²⁺ ions but not for other metal ions such as Co²⁺, Ni²⁺, Mn²⁺, Cr³⁺ and Zn²⁺. However, HN ligand shows more sensitive towards Fe³⁺ ions than Cu²⁺ ions which provide rapid detection of Fe³⁺ ions at concentrations as low as 4.5 x 10^-7 M than 2.9 x 10^-6 M of Cu²⁺ ions. As conclusion, HN ligand was expected to be useful as efficient chemical sensor for detection of Fe³⁺ ion.