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1,3,5-Triazine derivative of dipyridyl amine (dpyatriz) and the Cu(II), Zn(II) complexes have been prepared, characterized by CHN, IR, NMR and mass measurements and interacted with HTelo8 and HTelo20, the two types of human telomere repeat DNA (TTAGGG)n; n = 8, 20. The telomere DNAs have been treated with all three compounds (dpyatriz, Cu-dpyatriz and Zn-dpyatriz) under parallel/antiparallel and random coiled conditions. The interactions are followed by circular dichrosim measurements, fluorescent intercalator displacement (FID) assays and molecular docking studies through MOE program. The free ligand and its Cu(II) and Zn(II) complexes stabilize predominantly antiparallel G-quadruplex form under antiparallel and no salt conditions. The binding constant (Kb) values calculated for the ligand and complexes are in the range of 1.9 x 105 M-1 to 4.2 x 107 M-1 under various conditions show the higher affinity of G-quadruplex conformations. The FID assay using thiazole orange with HTelo20 clearly depicts the G-quadruplex stabilization through strong binding mode. Also, all the three compounds dpyatriz, Cu-dpyatriz and Zn-dpyatriz show an intercalative mode of interaction with antiparallel G quadruplex DNA in molecular docking studies. The compounds show cytotoxicity with the IC50 values in the range of 50 - 90 nM, and antitelomerase activity in the range of 5 to 10 µM. [ABSTRACT FROM AUTHOR]

The synthetic, spectroscopic, structural, and biological studies of a bis(arylimino)pyridine Ru(III) chloride compound containing the ligand, 2,6-bis(2,4,6-trimethylphenyliminomethyl)pyridine are reported. The findings from the studies could be applied to design a new generation of potential antineoplastic Ru(III) and Ru(II) complexes with a bis(arylimino)pyridine ligands.

The synthesis and characterization of two new copper complexes, [Cu(pbt)[Br.sub.2], [[Cu(pbt)[Br.sub.2](dmf)].sub.2] and a zinc complex, [Zn(pbt)[Cl.sub.2]], where pbt = 2-(2-pyridyl)benzthiazole) and dmf = dimethylformamide are reported. Both the pure ligand and [Cu(pbt)[Br.sub.2] were found to exhibit remarkable cytotoxic effects against selected cancer cell lines and [Cu(pbt)[Br.sub.2] in DMF cleaved with DNA oxidatively while the pure ligand pbt did not.

The reaction of Zn(NO3)2.6H2O or Cu(NO3)2.3H2O with the star-shaped ligand 2,4,6-tris(di-2-picolylamino)[1,3,5]-triazine in acetonitrile results in the formation of the mono- pr trinuclear coordination compounds, depending on the metal-to-ligand ratios used during the crystallization process. New theoretical investigations are conducted on nitrate-pi interactions, taking into account the particular position of the anion toward the aromatic ring observed in the crystal structures.

The reactions of the ligand 2-(2-pyridyl)benzthiazole (pbt) with CuBr2 and ZnCl2 in acetonitrile produce the complexes [Cu(pbt)Br2} (1) and [Zn(pbt)Cl2] (3), respectively. When complex 1 is dissolved in DMF, complex 2 is obtained as light-green crystals. The reaction of pbt with CuBr2 in DMF also yields the complex [Cu(pbt)Br2(dmf)] (2) (dmf = dimethylformamide). Complexes 1-3 were characterized by X-ray crystallography. Complexes 1 and 3 have distorted tetrahedral coordination environments, and complex 2 is constituted of two slightly different copper centers, both exhibiting distorted trigonal bipyramidal geometries. Complexes 1 and 2 cleave ϕX174 phage DNA, both in the presence and the absence of reductant. The free ligand pbt does not show any DNA-cleaving abilities. The poor solubility of complex 3 makes it not applicable for biological tests. The occurrence of DNA breaks in the presence of various radical scavengers suggests that no diffusible radicals are involved in the DNA cleavage by complex 1, as none of the scavengers inhibit the cleavage reaction. The DNA-cleavage products are not religated with the enzyme T4 DNA ligase, which is an additional proof that the cleavage is nonhydrolytic. Most probably the cleaving reaction involves reactive oxygen species, which could not be trapped, leading to an oxidative mechanism. An easy oxidation of CuII(pbt)Br2 to CuIII in DMF and the reduction of the same to CuI, under similar electrochemical conditions may lead to the in situ activation of molecular oxygen, resulting in the formation of metal solvated nondiffusible radicals able to prompt the oxidative cleavage of DNA. Complex 1 and the pure ligand exhibit remarkable cytotoxic effects against the cancer cell lines L1210 and A2780 and also against the corresponding cisplatin-resistant mutants of these cell lines. [ABSTRACT FROM AUTHOR]

The reaction of Zn(NO3)2·6H2O or Cu(NO3)2·3H2O with the star-shaped ligand 2,4,6-tris(di-2-picolylamino)[1,3,5]-triazine (dipicatriz) in acetonitrile results in the formation of the mono- or trinuclear coordination compounds [Zn- (dipicatriz)(NO3)2] (1), [Zn3(dipicatriz)(NO3)6](CH3CN)3 (2), and [Cu3(dipicatriz)(NO3)2(H2O)6](NO3)4 (3), depending on the metal-to-ligand ratios used during the crystallization process. Their crystal structures exhibit unique supramolecular interactions. Compounds 1 and 2 show anion-π interactions between coordinated nitrate ions and the π-triazine ring. Compound 3 exhibits remarkable interactions between two noncoordinated nitrate anions and the two faces of the electron-deficient heteroaromatic ring, corroborating earlier theoretical investigations in this area. New theoretical investigations have been carried out on nitrate-π interactions, taking into account the particular position of the anion toward the aromatic ring observed in the crystal structures. [ABSTRACT FROM AUTHOR]

The X-ray crystal structure of the complex rac-[Ru(5,6-dmp)3]Cl2 (5,6-dmp = 5,6-dimethyl-1,10-phenanthroline) reveals a distorted octahedral coordination geometry with the Ru-N bond distances shorter than in its phen analogue. Absorption spectral titrations with CT DNA reveal that rac-[Ru(5,6-dmp)3]2+ interacts (Kb, (8.0 ± 0.2) ⊗ 104 M-1) much more strongly than its phen analogue. The emission intensity of the 5,6-drop complex is dramatically enhanced on binding to DNA, which is higher than that of the phen analogue. Also, interestingly, time-resolved emission measurements on the DNA-bound complex shows biexponential decay of the excited states with the lifetimes of short- and long-lived components being higher than those for the phen analogue. The CD spectral studies of rac-[Ru(5,6-dmp)3]2+ bound to CT DNA provide a definite and elegant evidence for the enantiospecific interaction of the complex with B-form DNA. Competitive DNA binding studies using rac-[Ru(phen)3]2+ provide support for the strong binding of the complex with DNA. The Δ-enantiomer of rac-[Ru(5,6-dmp)3]2+ binds specifically to the right-handed B-form of poly d(GC)12 at lower ionic strength (0.05 M NaCl), and the Δ-enantiomer binds specifically to the left-handed Z-form of poly d(GC)12 generated by treating the B-form with 5 M NaCl. The strong electronic coupling of the DNA-bound complex with the unbound complex facilitates the change in its enantiospecificity upon changing the conformation of DNA. The ¹H NMR spectra of rac-[Ru(5,6-dmp)3]2+ bound to poly d(GC)12 reveal that the complex closely interacts most possibly in the major grooves of DNA. Electrochemical studies using ITO electrode show that the 5,6-drop complex stabilizes CT DNA from electrocatalytic oxidation of its guanine base more than the phen analogue does. [ABSTRACT FROM AUTHOR]

The article focuses on the square-planar cytotoxic complex acts as an efficient DNA cleaver without reductant. The DNA-cleaving abilities and the cytotoxic effects of the title complex have been studied. The copper complex is obtained easily from Hpyramol, a readily available ligand. Experiments strongly indicate a self-activating mechanism which is most likely initiated by the intercalation of the highly planar conjugated copper complex between the base pairs.

The zinc(II) complexes reported here have been synthesised from the ligand 4-methyl-2-N-(2-pyridylmethyl)aminophenol (Hpyramol) with chloride or acetate counterions. All the five complexes have been structurally characterised, and the crystal structures reveal that the ligand Hpyramol gradually undergoes an oxidative dehydrogenation to form the ligand 4-methyl-2-N-(2-pyridylmethylene)aminophenol (Hpyrimol), upon coordination to Zn(II). All the five complexes cleave the phiX174 phage DNA oxidatively and the complexes with fully dehydrogenated pyrimol ligands were found to be more efficient than the complexes with non-dehydrogenated Hpyramol ligands. The DNA cleavage is suggested to be ligand-based, whereas the pure ligands alone do not cleave DNA. The DNA cleavage is strongly suggested to be oxidative, possibly due to the involvement of a non-diffusible phenoxyl radical mechanism. The enzymatic religation experiments and DNA cleavage in the presence of different radical scavengers further support the oxidative DNA cleavage by the zinc(II) complexes.