Zn(II) and Cd(II) complexes of dithiocarbamate ligands: synthesis, characterization, anticancer, and theoretical studies

A potassium 4-(ethoxycarbonyl)phenyldithiocarbamate, (4-etphdtc), and 6-ethoxybenzothiazol)-dithiocarbamate, (6-etbedtc), ligands have been isolated and four metal dithiocarbamate complexes of the type [M(4-etphdtc)₂] and [M(6-etbedtc)₂] (M = Zn, Cd;) were synthesized and characterized by elemental analysis and spectroscopic techniques (FT-IR,¹H and¹³C{¹H}-NMR, HRMS, UV–vis). Thermogravimetric studies of all four complexes were performed and the final product of the thermal decomposition was metal sulfides. The theoretical study with density functional theory (DFT) has been utilized to optimize the structures of the complexes for HOMO–LUMO energy calculation. Non-bonding orbitals (NBO) analysis was performed to determine the numerous hyper-conjugative interactions responsible for the stability of the compound. In addition, Molecular Electrostatic Potential (MEP) analysis was conducted to identify the compounds’ electron-rich, electron-poor, reactive sites, and bonding characteristics. The Electron Localization Function (ELF), and AIM Charges are also calculated. In vitro cytotoxicity, the complexes were examined against cervical cancer cells (HeLa) to assess their reactivity. Molecular docking studies were conducted to confirm the biological activity by simulating the binding orientation and affinity of the ligands and their complexes against VEGFR-2 kinase, The investigated ligands interact with the binding site as; hydrophilic (Lys868, Glu885, His1026, Cys1045, and Asp1046) and hydrophobic (Val889 and Leu889) for 4-etphdtc; hydrophilic (Lys868, Glu885, Cys1045, and Asp1046) and hydrophobic (Val889, Leu889, Leu1035, and Phe1047) for 6-etphdtc_. The calculated binding free energy values for Zn(4-etphdtc)₂ and Zn(6-etphdtc)₂complexes are – 9.700 kcal/mol, – 10.003 kcal/mol, respectively.