A Novel Ligand System Comprising N-Heterocyclic Carbene and Schiff Base Ligands: Spectroscopic and Electrochemical Analysis, Investigation of Silver and Gold Complexation, and Their Biological Effects

Schiff base condensation of 2,6-dimethylaniline with 3-(3-formyl-4-hydroxybenzyl)-3-methylimidazolium chloride, 1, which contains an aldehyde and methylimidazole chloride, allowed the preparation of compound 2. Using the templating effect of zinc ions, an ionic metal complex 3 was obtained, which served as a precursor to a new class of organometallic supramolecular architectures. This was achieved through the self-assembly of the two molecular units of 4 in the presence of silver oxide. This coordination-driven self-assembly process facilitated the cofacial arrangement of two Schiff base linkers. Both compound 5 and gold(I) complex 6 were characterized using multinuclear NMR spectroscopy and ESI-MS spectrometry techniques. The anticancer potentials of compounds 5 and 6 were evaluated. The low IC50 value indicates that compound 5 can efficiently induce cell death in breast cancer cells. The IC50 values of complexes 5 and 6 are 1.63 μM and 16.76 μM, respectively. Further studies have also demonstrated that complex 5 can eliminate cancer cells by halting the cell cycle in the G2 phase, leading to apoptotic cell death. Additionally, cytotoxicity evaluation using an MCF-7-derived organoid platform confirmed the ability of compound 5 to eliminate cancer cells, especially within the central region of the model.