M. C. Prabhakara

Synthesis, DNA binding and cleavage studies of Ni(II) complexes with fused aromatic N-containing ligands

The three Ni(II) complexes of fused aromatic N-containing ligands such as [Ni(bnp)(3)](PF(6))(2) (1), [Ni(phen)(2)(bnp)](PF(6))(2) (2) and [Ni(bpy)(2)(bnp)](PF(6))(2) (3) (where bnp=dibenzo(b)1,8-naphthpyridine, phen=1,10-phenanthroline and bpy=bipyridine) were synthesized and structurally characterized. Elemental analysis, magnetic and spectroscopic data suggested octahedral geometry for all the complexes. Binding of these complexes with (ds)DNA were analyzed by absorption spectra, viscosity and thermal denaturation studies. Detailed analysis revealed that the metal complexes intercalates into the DNA base stack as intercalator. The oxidative cleavage activities of the complexes were studied with supercoiled (SC)pUC19 DNA by using gel electrophoresis, and the results show that complexes have potent nuclease activity.

Co(III) and Ni(II) Complexes Containing Bioactive Ligands: Synthesis, DNA Binding, and Photocleavage Studies

DNA binding and photocleavage characteristics of a series of mixed ligand complexes of the type [M(bpy)2qbdp](PF6)n·xH2O (where M = Co(III) or Ni(II), bpy = 2.2′-bipryidine, qbdp = Quinolino[3,2-b]benzodiazepine, n = 3 or 2 and x = 5 or 2) have been investigated. The DNA binding property of the complexes with calf thymus DNA has been investigated by using absorption spectra, viscosity measurements, as well as thermal denaturation studies. Intrinsic binding constant (K b) has been estimated under similar set of experimental conditions. Absorption spectral studies indicate that the Co(III) and Ni(II) complexes intercalate between the base pairs of the CT-DNA tightly with intrinsic DNA binding constant of 1.3 × 106 and 3.1 × 105 M−1 in Tris-HCl buffer containing 50 mM NaCl, respectively. The proposed DNA binding mode supports the large enhancement in the relative viscosity of DNA on binding to quinolo[3,2-b]benzodiazepine. The oxidative as well as photo-induced cleavage reactions were monitered by gel electrophoresis for both complexes. The photocleavage experiments showed that the cobalt(III) complex can cleave pUC19 DNA effectively in the absence of external additives as an effective inorganic nuclease.

Binding and oxidative cleavage studies of DNA by mixed ligand Co(III) and Ni(II) complexes of quinolo [3,2-b]benzodiazapine and 1,10-phenanthroline.

Two mixed ligand complexes of the type [M(phen)2(qbdp)](PF6)n.xH2O where M = Co(III) and Ni(II), qbdp = quinolo[3,2-b] benzodiazepine and phen = 1,10-phenanthroline, n = 3 or 2, x = 2 or 3 have been synthesized and characterized by employing analytical and spectral methods. The DNA binding property of the complexes with calf thymus-DNA has been investigated by using absorption spectra, viscosity measurements as well as thermal denaturation studies. The absorption spectral results indicate that the Co(III) and Ni(II) complexes intercalate between the base pairs of the DNA tightly with intrinsic DNA binding constant of 6.4 × 104 and 4.8 × 104 M−1 in Tris HCl buffer containing 50 mM NaCl, respectively. The large enhancement in the relative viscosity of DNA on binding to the quinolo [3,2-b] benzodiazepine supports the proposed DNA binding modes. The complexes on reaction with super coiled (SC) DNA shows nuclease activity.

Studies on Characterization, Optical Absorption, and Photoluminescence of Yttrium Doped ZnS Nanoparticles

Pure ZnS and ZnS:Y nanoparticles were synthesized by a chemical coprecipitation route using EDTA-ethylenediamine as a stabilizing agent. X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectrometry (FTIR), thermogravimetric-differential scanning calorimetry (TG-DSC), and UV-visible and photoluminescence (PL) spectroscopy were employed to characterize the as-synthesized ZnS and ZnS:Y nanoparticles, respectively. XRD and TEM studies show the formation of cubic ZnS:Y particles with an average size of ~4.5 nm. The doping did not alter the phase of the zinc sulphide, as a result the sample showed cubic zincblende structure. The UV-visible spectra of ZnS and ZnS:Y nanoparticles showed a band gap energy value, 3.85 eV and 3.73 eV, which corresponds to a semiconductor material. A luminescence characteristics such as strong and stable visible-light emissions in the orange region alone with the blue emission peaks were observed for doped ZnS nanoparticles at room temperature. The PL intensity of orange emission peak was found to be increased with an increase in yttrium ions concentration by suppressing blue emission peaks. These results strongly propose that yttrium doped zinc sulphide nanoparticles form a new class of luminescent material.

Transition metal complexes of quinolino[3,2-b]benzodiazepine and quinolino[3,2-b]benzoxazepine: synthesis, characterization, and antimicrobial studies.

The synthesis and characterization of title complexes of the ligand Quinolino[3,2-b]benzodiazepine (QBD) and Quinolino[3,2-b]benzoxazepine (QBO) are reported. The complexes have been characterized by elemental analysis, molar conductance, magnetic studies, IR, H1 NMR, and UV-visible studies. They have the stoichiometry [ML2C12], where M=Co(II)/Ni(II), L=QBD/QBO, and [MLC12], where M=Zn(II)/Cd(II), L=QBD/QBO. The antibacterial and antifungal activity of the metal complexes has been investigated. The complexes were found to have higher antimicrobial activity than the parent ligand.

Fe(II) Complexes Containing Bioactive Ligands: Synthesis, DNA Binding, and Cleavage Studies

The two Fe(II) complexes of fused aromatic N and S containing ligands of the type [Fe(HMq)3] (PF6)2 [complex (1)] and [Fe(HSeq)3] (PF6)2 [complex (2)] (where HMq = 2-mercapto-4-methylquinoline and HSeq = 2-seleno-4-methylquinoline) were synthesized and structurally characterized. The DNA binding property of the complexes with calf thymus DNA has been investigated using absorption spectra, viscosity measurements, as well as thermal denaturation experiments. Intrinsic binding constant Kb has been estimated at room temperature. The absorption spectral studies indicate that the complexes intercalate between the base pairs of the CT-DNA tightly with intrinsic DNA binding constant of 1.9 × 106 M−1 for complex (1) and 2.5 × 106 M−1 for complex (2) in 5 mM Tris-HCl/50 mM NaCl buffer at pH 7.2, respectively. Detailed analysis revealed that the metal complexes intercalates into the DNA base stack as intercalator. The oxidative cleavage activity of the complexes (1) and (2) were studied by using gel electrophoresis and the results show that complexes have potent nuclease activity.

Synthesis, Characterization and Antimicrobial Activity of Methylquinolino(3,2-b)(1,5)benzodiazepine and Methylquinolino(3,2-b)(1,5)benzoxazepine and its Various Metal Complexes

2-Chloro-6-methylquinoline-3-carbaldehyde was condensed with o-Phenylenediammine and 2-aminophenol in presence of potassium iodide. The resulting Methylquinolino[3,2-b][1,5]benzodiazepine (MQBD) and Methylquinolino[3,2-b][1,5]benzoxazepine(MQBO) were characterized by elemental analysis and spectral studies. The metal chelates viz Pd(II), Rh(III) and Ru(III) of ligands were prepared and characterized by metal-ligand (M:L) ratio, UV-Visible, IR, 1H NMR spectroscopes and magnetic properties. The antibacterial and antifungal activity of MQBD, MQBO and its metal complexes were screened against various bacteria and fungi. The results show that all these samples are good antimicrobial agents.

One‐Pot Solvent Free Synthesis and DNA Binding Studies of Thieno[2,3‐b]‐1,8‐Naphthyridines

Abstract With the aim of evaluating interaction between double‐stranded calf thymus (ds)DNA and sulphur containing fused planar rings, the derivatives of 1,8‐naphthyridine containing thiono groups were synthesized by the condensation of 2‐mercapto‐3‐formyl[1,8]naphthyridines using 1‐chloroacetone, 2‐chloroacetamide, chloroaceticacid, and 2‐chloro‐1‐phenylethanone in the presence of anhydrous potassium carbonate as s catalyst under solvent free microwave irradiation. The structures of the compounds were elucidated on the basis of elemental analysis, IR, 1H NMR, and mass spectra. The interaction of thieno[2,3‐b]‐1,8‐naphthyridine‐2‐carboxylic acid (TNC) (3a) with ct‐DNA was studied by UV‐Vis spectrophotometry, viscosity, thermal denaturation, as well as cyclic voltammetry experiments. On binding to DNA, the absorption spectrum underwent bathochromic and hypochromic shifts. Binding parameters, determined from spectrophotometric measurements indicated a binding constant of K b =2.1×106 M−1. The thieno[2,3‐b]‐1,8‐naphthyridine‐2‐carboxylic acid (3a) increases the viscosity of sonicated rod‐like DNA fragments. The binding of TNC to DNA increased the melting temperature by about 4°C. The decrease in peak current heights and shifts of peak potential values are observed by the addition of calf thymus DNA in cyclic voltammetry studies.

Transition Metal Complexes of Methyl-quinolino[3,2-b][1,5]benzodiazepine and Methylquinolino [3,2-b][1,5]benzoxazepine: Synthesis, Characterisation and Antimicrobial Studies

The synthesis and characterisation of title complexes of the ligand Methylquinolino[3,2-b][1,5]benzodiazepine (MQBD) and Methyl-quinolino[3,2-b][1,5]benzoxazepine (MQBO) are reported. The complexes have been characterized by elemental analysis, molar conductance, magnetic studies, IR, 1H NMR and UV-visible studies. They have the stoichiometry [ML2Cl2] where M=Co(II)/Ni(II), L=MQBD/MQBO and [MLCl2] where M=Zn(II)/Cd(II), L=MQBD/MQBO. The antibacterial and antifungal activity of the metal complexes has been investigated.