Synthesis and characterization of η6-p-cymene ruthenium(II) complexes containing alkyl- and methoxy-substituted triarylphosphines

Abstract Neutral Ru(II)-arene complexes [Ru(η6‐p-cymene)(PAr3)Cl2], PAr3 where Ar = 3,5-((CH3)3C)2C6H3–, 3,5-(CH3)2C6H3–, 4-CH3O-3,5-(CH3)2C6H2– and 4-CH3O-C6H4– were synthetized and fully characterized including single-crystal X-ray diffraction. The ligands have empirical logPow = 10.29, 7.38, 7.08, 5.43 (vs. PPh3 = 5.14). They have sufficiently low solubility to form Langmuir monolayers on water in accordance with overall molecular sizes. Density functional theory (DFT) calculations were performed to determine the molecular and electronic structures and to interpret the results of voltammetry and UV-Vis spectroscopy. Cytotoxicity assays were evaluated against MRC-5 (non-tumoral lung), A549 (lung cancer) and MDA-MB-231 (breast cancer) cell lines. The complexes with Ar = 3,5-((CH3)3C)2C6H3–, 4-CH3O-3,5-(CH3)2C6H2– and 4-CH3O-C6H4– show high cytotoxicity, whilst the first complex is inactive towards the (healthy) MRC-5 cell line, indicating a degree of selectivity.