Design of a Thiosemicarbazide-Functionalized Calix[4]arene Ligand and Related Transition Metal Complexes: Synthesis, Characterization, and Biological Studies.

In this study, we synthesized a new thiosemicarbazide-functionalized calix[4]arene and its Co, Ni, Cu, and Zn transition metal complexes. For characterization several techniques were employed: Fourier-transform infrared (FT-IR), H nuclear magnetic resonance (NMR), C-NMR, N-NMR, correlation spectroscopy (COZY), nuclear Overhauser enhancement spectroscopy (NOESY), electrospray ionization (ESI)-mass spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and elemental analysis. To explore the capability of the thiosemicarbazide function hosted on a calix[4]arene scaffold for growth inhibition of bacteria, fungi, and cancerous tumor cells, a series of biological evaluations were performed. For , the antimicrobial tests revealed a higher antibacterial activity against gram-positive and a lower activity against gram-negative bacteria ( and ), whereas the gram-positive shows resistance. All examined metal derivatives show an enhancement of the antibacterial activity against gram-negative bacteria, with a more significant improvement for the Ni and Zn complexes. MTT assays showed a considerable anticancer activity of Co, Ni, and Cu complexes against Saos-2 bone cancer cell lines. The activity is ascribable to the inorganic ions rather than calixarene ligand. Hemolysis assay results demonstrated that all compounds have high blood compatibility.