Microwave-Assisted Synthesis, Characterisation, and DNA-Binding Properties of RuII Complexes Coordinated by Norfloxacin as Potential Tumour Inhibitors

Three novel norfloxacin-based ruthenium(ii) complexes, [Ru(bpy)2(NFLX)]Cl·2H2O (1), [Ru(phen)2(NFLX)]Cl·2H2O (2), and [Ru(dmbpy)2(NFLX)]Cl·2H2O (3) (bpy=2,2′-bipyridine, phen=1,10-phenanthroline, dmbpy=4,4′-dimethyl-2,2′-bipyridine, and NFLX=norfloxacin), were synthesised and characterised with electrospray ionisation mass spectrometry and 1H and 13C NMR spectroscopy. The antitumour properties were evaluated by MTT assay, and the data revealed that 2 can inhibit the growth of human lung adenocarcinoma A549 efficiently. Furthermore, the DNA-binding behaviours of these complexes were investigated by a multiple spectroscopy assay and viscosity study. The results indicated that these complexes interact with calf thymus DNA through electrostatic interactions with a strong binding affinity in the order 2>3>1. Therefore, these results suggested that 2 might be a suitable anticancer agent due to its excellent DNA-binding abilities.

Synthesis of Camphor-Derived Bis(pyrazolylpyridine) Rhodium(III) Complexes: Structure-Reactivity Relationships and Biological Activity

Two novel rhodium(III) complexes, namely, [Rh^III(X)Cl₃] (X = 2 2,6-bis((4 S,7 R)-7,8,8-trimethyl-4,5,6,7-tetrahydro-1 H-4,7-methanoindazol-3-yl)pyridine or 2,6-bis((4 S,7 R)-1,7,8,8-tetramethyl-4,5,6,7-tetrahydro-1 H-4,7-methanoindazol-3-yl)pyridine), were synthesized from camphor derivatives of a bis(pyrazolylpyridine), tridentate nitrogen-donor chelate system, giving [Rh^III(H₂L*)Cl₃] (1a) and [Rh^III(Me₂L*)Cl₃] (1b). A rhodium(III) terpyridine (terpy) ligand complex, [Rh^III(terpy)Cl₃] (1c), was also synthesized. By single-crystal X-ray analysis, 1b crystallizes in an orthorhombic P2₁2₁2₁ system, with two molecules in the asymmetric unit. Tridentate coordination by the N,N,N-donor localizes the central nitrogen atom close to the rhodium(III) center. Compounds 1a and 1b were reactive toward l-methionine (l-Met), guanosine-5'-monophosphate (5'-GMP), and glutathione (GSH), with an order of reactivity of 5'-GMP > GSH > l-Met. The order of reactivity of the Rh^III complexes was: 1b> 1a > 1c. The Rh^III complexes showed affinity for calf thymus DNA and bovine serum albumin by UV-vis and emission spectral studies. Furthermore, 1b showed significant in vitro cytotoxicity against human epithelial colorectal carcinoma cells. Since the Rh^III complexes have similar coordination modes, stability differences were evaluated by density functional theory (DFT) calculations (B3LYP(CPCM)/LANL2DZp). With (H₂L*) and (terpy) as model ligands, DFT calculations suggest that both tridentate ligand systems have similar stability. In addition, molecular docking suggests that all test compounds have affinity for the minor groove of DNA, while 1b and 1c have potential for DNA intercalation.