Characterization, quantum, antibacterial, antifungal and antioxidant studies on Hg(II) and Cd(II) complexes of allyl and ethyl thiosemicarbazides derived from 2-aminothiazole-4-yl acetohydrazide

•Preparation of Cd(II) and Hg(II) complexes of the new thiosemicarbazide.•Elemental analysis, spectral characterization of the ligands and their Cd(II) and Hg(II) complexes.•Thermal behaviour of the solid metal complexes was studied using TGA technique.•The compounds were screened for antibacterial, antifungal, antioxidant and antitumor activity.

Two thiosemicarbazide ligands were derived from the addition of 2-(2-aminothiazol-4-yl) acetohydrazide to both ethyl isothiocyanate (H2TAET) and allyl isothiocyanate (H2TAAT) where their Cd (II) and Hg (II) complexes were synthesized and characterized by traditional techniques. The complexes were assigned the formulas [Cd(HTAET)(H2O)Cl](H2O)2, [Hg(TAET)(H2O)2]2, [Cd(HTAAT)(H2O)Cl]H2O and [Hg(H2TAAT)(H2O)Cl2], respectively. In Cd (II) complexes, the IR spectra show that the ligands behave as monobasic bidentate through (CN) thiazole ring and deprotonated enolized (CO). In Hg (II) complexes, H2TAET acts as dibasic tridentate (NSO) via thiol (CS), enolized (CO) and new azomethine (NC)* groups, while H2TAAT acts as neutral tridentate (NNO) through (CN) of thiazole ring, (CO) and new (CN) due to SH formation. A tetrahedral geometry for Cd (II) complexes, square pyramidal geometry for [Hg(TAET)(H2O)2]2 and octahedral geometry for [Hg(H2TAAT)(H2O)Cl2] were proposed. The data of theoretical and experimental vibrational frequencies of ligands are comparable. The calculated HOMO-LUMO energies gap data decided the possibility of charge transfer within the molecule. The binding energies calculations showed that the stability of complexes is higher than that of ligands. The kinetic and thermodynamic parameters of the Cd (II) complexes have been calculated by Coats–Redfern and Horowitz–Metzger methods. Moreover, the antimicrobial activities of the compounds have been discussed using a wide spectrum of bacterial and fungal strains. Representatives of the synthesized compounds were tested and evaluated for anti-oxidant and antitumour activities.