Variation of Arene Moiety in Ruthenium (II) Arene Halido Complexes of Quinoline and Benzazole-Derived Ligands: Development and Antiprostate Cancer Potential

Abstract

Castration-resistant prostate cancer (CRPC) is an advanced, treatment-refractory disease with high mortality and limited therapeutic options, necessitating novel metallodrugs with enhanced potency and reduced toxicity. Herein, we report the design and syntheses of two quinoline–benzazole hybrid bidentate ligands—2-(1H-benzo[d]imidazol-2-yl)quinoline (L1) and 2-(quinolin-2-yl)benzo[d]thiazol (L2)—along with four new half-sandwich ruthenium(II) arene chlorido complexes of the general formula [(η⁶-arene)(L)RuCl]PF₆, where arene = benzene (Bz) or hexamethylbenzene (Hmb), yielding complexes 1–4. The ligands and complexes were fully characterized by spectroscopic (¹H/¹³C NMR, IR, UV–vis) and analytical methods (elemental analysis, ESI-MS), with aqueous stability profiles confirming their suitability for biological evaluation. Cytotoxicity assays against the PC-3 CRPC cell line identified potent antiproliferative activity in selected complexes. Mechanistic studies revealed predominant G2/M phase cell cycle arrest, induction of apoptosis, and moderate-to-strong DNA binding affinities suggestive of intercalative/groove-binding modes. These results highlight the potential of quinoline–benzazole Ru(II) arene scaffolds as promising candidates for CRPC therapy, meriting further optimization.