N‑Heterocyclic Carbene-Au(I)-Phosphine Complexes: Characterization, Theoretical Structure Analysis, and Anti-Cancer Properties

Derivatization of (NHC)­Au–Cl with monodentate and bidentate phosphine donors, such as PPh2Py, PPh3, PCy3, and dppf, produced heteroleptic mononuclear and binuclear Au­(I) complexes. The order of mixing reactants and the types of solvents used play crucial roles in obtaining a pure product. In the single-crystal X-ray diffraction analysis of complexes 1, 2, and 4, the Au­(I) centers exhibited linear geometry. Advanced computational analysis of these complexes using density functional methods provided insights into the nature of electronic transitions, noncovalent interactions, and fragmental bonding contributions. Complexes 1–4 were selected for biological activity studies, and their in vitro cellular tests were conducted on the human cancerous breast cell line MCF-7, with bimetallic complex 4 showing the lowest IC50 value of 63 nM and demonstrating the highest inhibitory effect on cell proliferation.