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The octahedral ruthenium(II) complexes [Ru(Ln)(PPh3)2Cl2] [Ln = biphenyl furanyl pyridine derivatives] were synthesized and characterized using LC–MS, IR spectroscopy, elemental analysis and magnetic measurements. Complexes show enhancement in antibacterial activity compared to free ligands. From the binding mode investigation by absorption titration and viscosity measurement, it is observed that complexes bind to DNA via intercalation and also complexes promote the cleavage of supercoiled pUC19 plasmid DNA. Cytotoxicity analysis shows 100% mortality of Brine shrimp after 48 h. Keywords: Heterocyclic compound, Ruthenium(II) complexes, Nucleic acid intercalating agent, Cytotoxicity

A series of half sandwich η5-cyclopentadienyl Rh(III) and Ir(III) complexes bearing the general formula [Cp*LCl]Cl·2H2O (L = neutral bidentate pyridyl pyrimidine based ligands, Cp* = η5-C5Me5) have been synthesized. The neutral bidentate coordination of ligand with Rh(III) and Ir(III) via N atoms was confirmed by various analytical and spectroscopic techniques. The effect of position and electron releasing strength of substituents at ancillary ligands on DNA binding of metal complexes was checked by UV–Vis. absorption spectroscopy and hydrodynamic method. Molecular docking study was performed for the preferred orientation of stable DNA-metal complex associates to get an insight of binding site and binding affinity between these molecules, and binding energy data were evaluated to check the strength of association. The probable application of metal complexes as compelling chemical nuclease agent was assessed by gel electrophoresis. The cytotoxic nature of metal complexes was checked on a simple zoological organism-artemia cyst.

A series of substituted hydrazinyl pyridine based Schiff base ligands (L1–L6) and corresponding palladium(II) complexes were synthesized and characterized by conductivity measurement, 1H NMR, 13C NMR and liquid chromatography mass spectrometry (LC-MS). Synthesized compounds were screened against various biological activities. UV–Vis spectroscopy, fluorescence spectroscopy, viscosity measurement, and molecular docking studies were used to determine the binding mode between complexes and HS-DNA, which suggest intercalation mode of DNA binding. The protein binding study of complexes was evaluated by UV–visible spectroscopy. Antibacterial activity of the complexes was screened against two Gram (+ve) and three Gram (−ve) bacteria and the result shows that all complexes are more effective against microorganisms than their respective ligands. The cytotoxicity of the synthesized compounds was tested against brine shrimp and S. pombe cell. The LC50 values of the ligand and complexes are found in the range of 9.24–14.12 μg/mL and 5.68–7.94 μg/mL, respectively. The DNA cleavage activity of metal complexes was performed using agarose gel electrophoresis. All compounds were tested for anticancer activity against human colorectal (HCT-116) cancer cell lines. The result shows that all the compounds exhibited effective cytotoxicity against the tested cell line.

Half sandwich cationic mononuclear rhodium(III) and iridium(III) complexes [(η5-C5Me5)M(L)Cl]Cl·2H2O where L = dipyridylamine (dpa) (M = Rh, 1 and Ir, 2) and dipyridylketone (dpk) (M = Rh, 3 and Ir, 4) have been synthesized and characterized. The structure of a representative complex (1) was authenticated by single crystal X-ray diffraction analysis. Complexes 1–4 have been fully characterized by various physicochemical techniques, namely elemental analysis, spectral (IR, 1H, NMR, UV–Vis), electrochemical studies (cyclic voltammetry (CV) and differential pulse voltammetry (DPV)). Notably, the UV absorption spectral titrations of the synthesized complexes with DNA reveal that the complexes bind to calf thymus DNA (CT-DNA) through the intercalation mode. The DNA solution hydrodynamic volume (viscosity) measurements show that the interaction of the compounds with CT-DNA occurs by classical intercalation. A molecular docking study suggested intercalation between the synthesized compounds and nucleotide base pairs. Cyclic voltammetry studies of the complexes indicate irreversible oxidation and reduction potentials. A gel electrophoresis assay demonstrates the ability of the complexes to cleave pUC19 DNA. The antibacterial activities were assayed against selected Gram(−ve) and Gram(+ve) microorganisms. The cytotoxic properties of the metal complexes have been evaluated using a brine shrimp lethality bioassay. The results suggest that the binding affinity of 1–4 lies in the order 1 > 4 > 2 > 3.

Neutral N,S-donor bidentate ligands have been synthesized and characterized by NMR and IR spectroscopic techniques. The ligands have been used to synthesized ruthenium(II) complexes ([Ru(L1–L6)PPh3)2Cl2]) and ruthenium(III) complexes ([Ru(L1–L6)PPh3)Cl3]). Synthesized complexes have been characterized using elemental analysis, UV–Vis spectroscopy, magnetic measurements, LC–MS, and IR spectroscopy. Broth dilution technique was used to investigate antibacterial activity against two Gram-positive and three Gram-negative microorganisms and results show that all complexes are more potent than the respective ligands. UV–Vis absorption titration and viscosity measurements have been carried out to investigate the binding mode and binding strength of complexes with herring sperm DNA. The quantitative binding strength (K b) of the complexes was found in the range of 0.521 × 105–2.94 × 105 M−1 and indicate intercalative mode of binding. Gel electrophoresis study was carried out to study the cleavage of pUC19 supercoiled DNA. DNA nuclease activity data for the complexes are found higher than respective ligands and metal salt. Brine shrimp bioassay was carried out to perform cytotoxicity study. IC50 values of the complexes were found in the range of 5.69 ± 1.06–14.62 ± 0.87 μg cm−3.

Half sandwich complexes of the type [(η5-C5Me5)M(L1–3)Cl]Cl.2H2O were synthesized using [{(η5-C5Me5)M(μ-Cl)Cl}2], where M = Rh(III)/Ir(III) and L1–3 = pyrimidine-based ligands. The complexes were characterized by spectral analysis. DNA interaction studies by absorption titration and hydrodynamic measurement and suggest intercalative mode of binding of complexes with CT-DNA. The molecular docking study also supports intercalation of the complexes between the stacks of nucleotide base pairs. The gel electrophoresis assay demonstrated the ability of the complexes to interact and cleave plasmid DNA. Minimum inhibitory concentrations (MIC) of the complexes were investigated by the microdilution broth method. The cytotoxic properties of the metal complexes were evaluated using brine shrimp lethality bioassay.

The N,O-donor bidentate ligands (L 1 –L 7 ) derived from the reaction between chalcones and pyridinium salt of 2-acetyl furan were synthesized and characterized by IR and NMR spectroscopic techniques. Their complexes [1–7] of Cu(II) were synthesized and characterized by elemental analysis, magnetic measurements, TG analyses, IR and mass spectroscopy. Synthesized complexes were carried out for their biological elucidation using different biological experiments like minimum inhibitory concentration, DNA binding and cleavage study, cytotoxicity, and antiradical activity. Efficient cleavage of pUC19 DNA was observed for all the test complexes than the reference drug. Increase in DNA chain length and hence the relative viscosity as the complexes binds to DNA via intercalative mode and involves a strong stacking interaction between an aromatic chromophore and the DNA base pair.