Kishalay Bhar

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 [(η ⁶ ‐arene)(L)RuCl]PF ₆ , where arene = benzene (Bz) or hexamethylbenzene (Hmb), yielding complexes 1–4. The ligands and complexes were fully characterized by spectroscopic ( ¹ H/ ^{1 3} C 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.

In the current study, four novel mononuclear Cu(II) complexes with terpyridine (L) and different co-ligands (phen, bipy, and imd) were synthesized and characterized in detail, where L is 4′-(3,4,5-trimethoxyphenyl)-2,2′:6′,2′′-terpyridine. The identity and purity of all complexes were determined by elemental analysis, spectroscopic techniques (UV-vis, FTIR, ESI-MS, and EPR) and CV, including single crystal X-ray determination of three complexes ([Cu(L)(phen)](ClO₄)₂ (C-I), [Cu(L)₂](ClO₄)₂ (C-II) and [Cu(L)(imd)(ClO₄)](ClO₄) (C-IV). DNA binding studies were performed using fluorescence assay and the binding constants were calculated using the Stern–Volmer equation and the modified Stern–Volmer equation. The magnitude of K_app of all complexes was 10⁵ M⁻¹, indicating moderate intercalative binding between CT-DNA and the complexes. Agarose gel electrophoresis clearly reflected their ability to cleave a double stranded pET-28b plasmid in the presence of an external reducing agent (3-mercapto propionic acid). Steady-state fluorescence quenching was performed to understand their interactions with BSA. The studies suggested a mixed quenching mechanism with an initial static process. Furthermore, the antiproliferative activity of the complexes was evaluated against lung cancer A549 cells and primary mice splenocytes. Interestingly, the complexes show 25–200 fold greater toxicity towards the A549 cells than primary splenocytes, indicating their selectivity towards the former. The good binding behavior of all four complexes towards DNA and BSA and their cytotoxicity render these compounds promising potent anticancer drugs.

The synthesis, detailed characterization, and investigation of the DNA- and BSA-binding affinity and cytotoxicity of three half-sandwich Ru(II) arene chlorido complexes (1–3) are reported. Specifically, organometallic complexes [(η⁶-p-cymene)(L₁)RuCl]Cl (1), [(η⁶-p-cymene)(L₂)RuCl]Cl (2) and [(η⁶-p-cymene)(L₃)RuCl]Cl (3) [L₁ = 2-(1H-benzo[d]imidazol-2-yl)quinolone, L₂ = 2-(quinolin-2-yl)benzo[d]oxazole, and L₃ = 2-(quinolin-2-yl)benzo[d]thiazole] were synthesized using [((η⁶-p-cymene)Ru(μ-Cl)Cl)₂] and L₁–L₃. All the complexes were characterized by various spectroscopic and analytical methods. Complex 1 was also characterized by single crystal X-ray diffraction analysis, the results of which are in-line with the piano-stool structure elucidated from the spectroscopic methods. Cyclic voltammetry of 1–3 showed good stability of the Ru(II) state. The interactions of 1–3 with CT-DNA were investigated by UV-Vis studies and competitive binding with ethidium bromide (EthBr) using emission spectroscopy. Steady-state fluorescence quenching and synchronous fluorescence studies were performed to understand the interactions between 1–3 and bovine serum albumin (BSA). The geometry optimization of 1–3 was performed using the density functional theory (DFT). Complexes 1 and 2 were investigated for DNA binding using theoretical calculations. Molecule complexes 1-DNA and 2-DNA were huge (482–483 atoms, 2442 electrons) for any level of quantum chemical analysis. The semi-empirical PM6 method, which is more accurate than the force-field methods, was used, and the result suggested that several strong and weak electrostatic and intermolecular hydrogen bonding interactions exist between the outer edge of DNA and complexes 1 and 2. In addition, the in vitro cytotoxicity of L₁–L₃ and complexes 1–3 against a breast cancer cell line (MCF-7) was investigated by MTT cytotoxicity analyses. The studies performed here show that these complexes exhibit a good binding behavior with DNA and BSA and show good anticancer potency towards MCF-7 cells.

One Co(ii) SCO coordination polymer [Co(enbzpy)(μ_1,5-dca)]_n(PF₆)_n (1·PF₆) has been isolated and characterised structurally and magnetostructurally. Contrasting magnetic behavior of 1·PF₆ in comparison to 1·ClO₄ has been analysed in terms of structural factors.