Search

Synthesis of an entirely new series of arene ruthenium complexes [Ru(η6-C6H6)(L1)Cl]PF6, (1), [Ru(η6-C10H14)(L1)Cl]PF6 (2), [Ru(η6-C6H6)(L2)Cl]PF6 (3) and [Ru(η6-C10H14)(L2)Cl]PF6 (4) involving 5-[2-(1H-pyrazol-1-yl)quinoline]-BODIPY (L1) and 5-[6-methoxy-2-(1H-pyrazol-1-yl)quinoline]-BODIPY (L2) was described. The ligands and complexes were thoroughly characterized by various physicochemical techniques and the structures of L1, 1 and 4 were determined by X-ray single crystal analyses. Photo-/ and electrochemical property, DNA binding, cytotoxicity, cellular uptake and apoptotic studies on 1-4 were performed by various methods, while singlet oxygen-mediated cytotoxicity via photo-irradiation by visible light was supported by 1,3-diphenylisobenzofuran titration studies. Binding of the complexes in the minor groove of CT-DNA via van der Waals forces and electrostatic interactions was affirmed by molecular docking studies. In vitro antiproliferative activity and photocytotoxicity of 1-4 were examined against the human cervical cancer cell line (HeLa) which clearly showed that these are extremely photocytotoxic under visible light (400-700 nm, 10 J cm-2; IC50 49.15, 1; 25.18, 2; 15.85, 3; 12.87, 4), less toxic in the dark (IC50 > 100 μM) and preferentially accumulate in the lysosome of the HeLa cells. Further, these complexes behave as a potential theranostic agent and their ability to kill cancer cells under visible light lies in the order 4 > 3 > 2 > 1.

A pyrazole-appended quinoline-based 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (L1, BODIPY) has been synthesized and used as a ligand for the preparation of iridium(III) complexes [Ir(phpy) 2 (L1)]PF 6 (1; phpy = 2-phenylpyridine) and [(η 5 -C 5 Me 5 )Ir(L1)Cl]PF 6 (2). The ligand L1 and complexes 1 and 2 have been meticulously characterized by elemental analyses and spectral studies (IR, electrospray ionization mass spectrometry, 1 H and 13 C NMR, UV/vis, fluorescence) and their structures explicitly authenticated by single-crystal X-ray analyses. UV/vis, fluorescence, and circular dichroism studies showed that complexes strongly bind with calf-thymus DNA and bovine serum albumin. Molecular docking studies clearly illustrated binding through DNA minor grooves via van der Waals forces and their electrostatic interaction and occurrence in the hydrophobic cavity of protein (subdomain IIA). Cytotoxicity, morphological changes, and apoptosis have been explored by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and Hoechst 33342 staining. IC 50 values for complexes (1, 30 μM; 2, 50 μM) at 24 h toward the human cervical cancer cell line (HeLa) are as good as that of cisplatin (21.6 μM) under analogous conditions, and their ability to kill cancer cells lies in the order 1 > 2. Because of the inherent emissive nature of the BODIPY moiety, these are apt for intracellular visualization at low concentration and may find potential applications in cellular imaging and behave as a theranostic agent.

With intent to fine tune the morphological and photophysical properties, three novel AIE luminogens (BQ1-BQ3) based on quinoline-BODIPY have been synthesized. A judicious choice of substituents (-H, -CH3, -OCH3) in these systems led to nanoballs in BQ1 and BQ2, while in BQ3 it led to reticulated nanofibers with diverse photophysical behaviours.