Synthesis,DNA-binding,and photocleavage properties of Ru(II) complexes containing dppz-based ligand

A ligand ipdp (ipdp?=?indeno[1′,2′?:?5,6]pyrazino[2,3-i]dipyrido[3,2-a?:?2′,3′-c]phenazine-8-one) and its ruthenium complexes, [Ru(L)₂(ipdp)]²⁺ (L?=?bpy (2,2′-bipyridine), phen (1,10-phenanthroline)), have been synthesized and characterized by elemental analysis, electrospray mass spectra, and ¹H NMR. The interaction between the complexes and calf thymus DNA (CT-DNA) has been investigated by spectroscopic methods and viscosity measurements. The results indicate that the complexes can bind to CT-DNA in an intercalative mode. In addition, both complexes promote the photocleavage of plasmid pBR322 DNA under irradiation. The mechanistic studies reveal that singlet oxygen ¹O₂ plays a significant role in DNA photocleavage.     

Effects of the ancillary ligands of polypyridyl ruthenium(II) complexes on the DNA-binding and photocleavage behaviors

The new polypyridyl ligand MIP {MIP = 2-(2,3-methylenedioxyphenyl)imidazo[4,5-f]1,10-phenanthroline} and its ruthenium(II) complexes [Ru(phen)₂(MIP)]²⁺ (1) (phen = 1,10-phenanthroline) and [Ru(dmp)₂(MIP)]²⁺ (2) (dmp = 2,9-dimethyl-1,10-phenanthroline) were synthesized and characterized by elemental analysis, MS and ¹H NMR spectroscopy. The DNA-binding properties of the two complexes to calf-thymus DNA (CT-DNA) were investigated by different spectrophotometric methods and viscosity measurements, as well as equilibrium dialysis and circular dichroism spectroscopy. The results suggest that complex 1 binds to CT-DNA through intercalation, and complex 2 binds to CT-DNA via a partial intercalative mode. This difference in binding mode probably is caused by the different ancillary ligands. Also, when irradiated at 400 nm, complex 1 was found to be a more-effective DNA-cleaving agent than complex 2.     

Synthesis, DNA-binding and photocleavage studies of [Ru(phen)2(pbtp)] and [Ru(bpy)2(pbtp)] (phen = 1,10-phenanthroline; bpy = 2,2′-bipyridine; pbtp = 4,5,9,11,14-pentaaza-benzo[b]triphenylene)

Based on the ligand dppz (dppz = dipyrido-[3,2-a:2′,3′-c]phenazine), a new ligand pbtp (pbtp = 4,5,9,11,14-pentaaza-benzo[b]triphenylene) and its polypyridyl ruthenium(II) complexes [Ru(phen)₂(pbtp)]²⁺ (1) (phen = 1,10-phenanthroline and [Ru(bpy)₂(pbtp)]²⁺ (2) (bpy = 2,2′-bipyridine) have been synthesized and characterized by elemental analysis, ES-MS and ¹H NMR spectroscopy. The DNA-binding of these complexes were investigated by spectroscopic methods and viscosity measurements. The experimental results indicate that both complexes 1 and 2 bind to CT-DNA in classical intercalation mode, and can enantioselectively interact with CT-DNA. It is interesting to note that the pbtp ruthenium(II) complexes, in contrast to the analogous dppz complexes, do not show fluorescent behavior when intercalated into DNA. When irradiated at 365 nm, both complexes promote the photocleavage of pBR 322 DNA.     

Synthesis, characterization and DNA-binding and DNA-photocleavage studies of two Ru(II) complexes containing two main ligands and one ancillary ligand

DNA-binding and DNA-photocleavage properties of two Ru(II) complexes, [Ru(L¹)(dppz)₂](PF₆)₄ (1) and [Ru(L²)(dppz)₂](PF₆)₄ (2) (L¹ = 5,5′-di(1-(triethylammonio)methyl)-2,2′-dipyridyl cation; L² = 5,5′-di(1-(tributylammonio)methyl)-2,2′-dipyridyl cation; dppz = dipyrido[3,2-a:2′,3′-c]phenazine, have been investigated. Experimental results show that the DNA-binding affinity of complex 1 is greater than that of 2, both complexes emit luminescence in aqueous solution, either alone or in the presence of DNA, complex 1 can bind to DNA in an intercalative mode while 2 most likely interacts with DNA in a partial intercalation fashion, and complex 2 serves as a better candidate for enantioselective binding to CT-DNA compared with 1. Moreover, complex 1 reveals higher efficient DNA cleavage activity than 2, during which supercoiled DNA is converted to nicked DNA with both complexes. Theoretical calculations for the two complexes have been carried out applying the density functional theory (DFT) method at the level of the B3LYP/LanL2DZ basis set. The calculated results can reasonably explain the obtained experimental trends in the DNA-binding affinities and binding constants (K_b) of these complexes.     

Study of the interaction between ruthenium(II) complexes and CT-DNA: synthesis,characterisation, photocleavage and antimicrobial activity studies

Two polypyridyl ligands 6-fluro-3-(1H-imidazo [4,5-f] [1,10]-phenanthroline-2-yl)-4H-chromen-4-one (FIPC), 6-chloro-3-(1H-imidazo [4,5-f] [1,10]-phenanthroline-2-yl)-4H-chromen-4-one (ClIPC) polypyridyl ligands and their Ru(II) complexes [Ru(bipy)₂FIPC]²⁺(1), [Ru(dmb)₂FIPC]²⁺(2), [Ru(phen)₂FIPC]²⁺(3), [Ru(bipy)₂ClIPC]²⁺(4), [Ru(dmb)₂ClIPC]²⁺(5) and [Ru(phen)₂ClIPC]²⁺(6) ((bipy = 2,2′-bipyridine, dmb = 4,4′-dimethyl-2,2′-bipyridine and phen = 1,10-phenanthroline) have been synthesised and characterised by elemental analysis, Mass spectra, IR, ¹H and ¹³C-NMR. The DNA-binding of the six complexes to calf-thymus DNA (CT-DNA) has been investigated by different spectrophotometric, fluorescence and viscosity measurements. The results suggest that 1–6 complexes bind to CT-DNA through intercalation. The variation in binding affinities of these complexes is rationalised by a consideration of electrostatic, steric factors and nature of ancillary ligands. Under irradiation at 365 nm, the three complexes have also been found to promote the photocleavage of plasmid pBR 322 DNA. Inhibitor studies suggest that singlet oxygen (¹O₂) plays a significant role in the cleavage mechanism of Ru(II) complexes. Thereby, under comparable experimental conditions [Ru(phen)₂FIPC]²⁺(3), [Ru(phen)₂ClIPC]²⁺(6) cleaves DNA more effectively than 1, 2, 4 and 5 complexes do. The Ru(II) polypyridyl complexes (1–6) have been screened for antimicrobial activities.     

Synthesis,crystal structure and DNA-binding properties of ruthenium(II) polypyridyl complexes with dicationic 2,2′-dipyridyl derivatives as ligands

New Ru(II) complexes with dicationic ligand, [Ru(phen)₂L¹]⁴⁺(1) and [Ru(phen)₂L²]⁴⁺(2) (phen = 1,10-phenanthroline; L: L¹ = 5,5′-di(1-(triethylammonio)methyl)-2,2′-dipyridyl cation; L² = 5,5′-di(1-(tributylammonio)methyl)-2,2′-dipyridyl cation) have been synthesized and structurally characterized. The interaction of these complexes with calf thymus DNA (CT-DNA) has been investigated. The intrinsic binding constants (K_b: 1, 7.73 × 10⁴ M⁻¹; 2, 2.50 × 10⁴ M⁻¹) determined by absorption spectral titrations of these complexes with CT-DNA indicate the DNA-binding affinity of 1 is stronger than that of 2. Both complexes can display luminescence either alone in aqueous solution or in the presence of DNA. Equilibrium dialysis experiments monitored by CD spectroscopy reveal the preferential binding of the Δ-enantiomer to the right-handed CT-DNA. DNA-viscosity studies suggest that the binding modes are different, 1 may partially intercalate between DNA base-pairs while 2 most likely interact with DNA in an electrostatic binding mode.     

Synthesis, characterization and DNA-binding studies of ruthenium(II) mixed-ligand complexes containing dipyrido[1,2,5]oxadiazolo[3,4-b]quinoxaline

A novel ligand dipyrido[1,2,5]oxadiazolo[3,4-b]quinoxaline (dpoq) and its complexes [Ru(bpy)₂(dpoq)]²⁺ and [Ru(phen)₂(dpoq)]²⁺ (bpy = 2,2′-bipyridine; phen = 1,10-phenanthroline) have been synthesized and characterized by elemental analysis, electrospray mass spectra and ¹H NMR. The interaction of Ru(II) complexes with calf thymus DNA (CT-DNA) was investigated by absorption spectroscopy, fluorescence spectroscopy, thermal denaturation and viscosity measurements. Results suggest that two Ru(II) complexes bind to DNA via an intercalative mode.     

Synthesis,characterization, DNA-binding and DNA-photocleavage studies of [Ru(bpy)2(BPIP)] and [Ru(phen)2(BPIP)] (BPIP = 2-(4′-biphenyl)imidazo[4,5-f][1,10]phenanthroline)

New ligand 2-(4′-biphenyl)imidazo[4,5-f][1,10]phenanthroline (BPIP) and its complexes [Ru(bpy)₂(BPIP)]²⁺ (1) (bpy = 2,2′-bipyridine) and [Ru(phen)₂(BPIP)]²⁺ (2) (phen = 1,10-phenanthroline) have been synthesized and characterized by mass spectroscopy, ¹H NMR and cyclic voltammetry. The interaction of two Ru(II) complexes with calf thymus DNA (CT-DNA) was investigated by spectroscopic and viscosity measurements. Results indicate that both complexes bind to DNA via an intercalative mode and the DNA-binding affinity of complex 2 is much greater than that of complex 1. Furthermore, when irradiated at 365 nm, both complexes have also been found to promote the photocleavage of plasmid pBR 322 DNA.     

Synthesis of a ruthenium(II) polypyridine complex with 1,10-phenanthrolineselenazole as ligand and investigation of its G-quadruplex DNA-binding properties

A new Ru(II) complex, [Ru(bpy)₂L](ClO₄)₂ (bpy?=?2,2′-bipyridine, L?=?1,10-phenanthrolineselenazole), has been synthesized and structurally characterized by elemental analysis, ESI-MS, and ¹H NMR. The interaction of human telomeric oligomer 5′-AG₃(T₂AG₃)₃-3′ with the Ru(II) complex was explored by competition FRET experiment, ?uorescence titration, circular dichroism spectroscopy, thermal denaturation, polymerase chain reaction stop assay, and TRAP assay. The Ru(II) complex can selectively bind to G-quadruplex DNA. The results indicated that the complex not only induces a remarkable conformational change of human telomeric DNA, but also has the ability to stabilize the G-quadruplex.     

Synthesis,structural characterization,antimicrobial, DNA-binding,and photo-induced DNA cleavage activity of some bio-sensitive Schiff base copper(II) complexes

Schiff base mixed-ligand copper complexes [CuL¹(phen)Cl₂], [CuL¹(bipy)Cl₂], [Cu(L¹)₂Cl₂], [Cu(L²)₂Cl₂], [CuL²(bipy)Cl₂], and [CuL²(phen)Cl₂] (where L^1?=?4-[3,4-dimethoxy-benzylidene]-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazole-3-one; L^2?=?4-[3-hydroxy-4-nitro-benzylidene]-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazole-3-one; phen?=?1,10-phenanthroline; and bipy?=?2,2′-bipyridine) have been synthesized and characterized. Their DNA-binding properties have been studied by electronic absorption spectra, viscosity, and electrochemical measurements. The absorption spectral and viscosity results suggest that the copper(II) complexes bind to DNA via partial intercalation. The addition of DNA resulting in the decrease of the peak current of the copper(II) complexes indicates their interaction. Interaction between the complexes and DNA has also been investigated by submarine gel electrophoresis. The copper complexes cleave supercoiled pUC19 DNA to nicked and linear forms through hydroxyl radical and singlet oxygen in the presence of 3-mercaptopropionic acid as the reducing agent. These copper complexes promote the photocleavage of pUC19 DNA under irradiation at 360?nm. Mechanistic study reveals that singlet oxygen is likely to be the reactive species responsible for the cleavage of plasmid DNA by the synthesized complexes. The in vitro antimicrobial study indicates that the metal chelates have higher activity against the bacterial and fungal strains than the free ligands.     

Synthesis,characterization and DNA-binding properties of Ru(II) complexes coordinated by ofloxacin as potential antitumor agents

Three Ru complexes coordinated by oxfloxacin, [Ru(L)₂(OFX)]Cl·2H₂O (L = bpy, 1; dmbpy, 2; phen, 3; and OFX = ofloxacin), were synthesized and characterized. These complexes can inhibit the growth of cervical cancer HeLa cells efficiently. Furthermore, these three complexes exhibited excellent binding affinities with DNA, as confirmed by spectroscopy methods and viscosity experiments. Therefore, the synthesized Ru(II) complexes have excellent DNA-binding abilities with potential applications in cancer chemotherapy.     

Synthesis,structures, and characterization of copper(II), nickel(II), and cobalt(III) metal complexes derived from an asymmetric bidentate Schiff-base ligand

An asymmetric bidentate Schiff-base ligand (2-hydroxybenzyl-2-furylmethyl)imine (L–OH) was prepared. Three complexes derived from L–OH were synthesized by treating an ethanolic solution of the appropriate ligand with an equimolar amount of metallic salt. Three complexes, Cu₂(L–O^?)₂Cl₂ (1), Ni(L–O^?)₂ (2) and Co(L–O^?)₃ (3), have been structurally characterized through elemental analysis, IR, UV spectra and thermogravimetric analysis. Single crystal X-ray diffraction shows metal ions and ligands reacted with different proportions 1?:?1, 1?:?2 and 1?:?3, respectively, so copper(II), nickel(II), and cobalt(III) have different geometries.     

Synthesis,characterization, and DNA binding of ruthenium(II) complexes with 2-benzo[b] furan-2-yl-1H-imidazo[4,5f][1,10]phenanthroline as an intercalative ligand

DNA-binding properties of a number of ruthenium complexes with different polypyridine ligands are reported. The new polypyridine ligand BFIP (=2-benzo[b] furan-2-yl-1H-imidazo[4,5-f][1,10]phenanthroline) and its ruthenium complexes [Ru(bpy)₂BFIP]²⁺ (bpy = 2,2′-bipyridine), [Ru(dmb)₂BFIP]²⁺ (dmb = 4,4′-dimethyl-2,2′-bipyridine), and [Ru(phen)₂BFIP]²⁺ (phen = 1,10-phenanthroline) have been synthesized and characterized by elemental analysis, mass spectra, IR, UV-Vis, ¹H- and ¹³C-NMR, and cyclic voltammetry. The DNA binding of these complexes to calf-thymus DNA (CT-DNA) was investigated by spectrophotometric, fluorescence, and viscosity measurements. The results suggest that ruthenium(II) complexes bind to CT-DNA through intercalation. Photocleavage of pBR 322 DNA by these complexes was also studied, and [Ru(phen)₂BFIP]²⁺ was found to be a much better photocleavage agent than the other two complexes.     

DNA-binding and cleavage activity of polypyridyl ruthenium(II) complexes

Polypyridyl ruthenium(II) complexes [Ru^II(3-bptpy)(dmphen)Cl]ClO₄ (1), [Ru^II(3-cptpy)(dmphen)Cl]ClO₄ (2), [Ru^II(2-tptpy)(dmphen)Cl]ClO₄ (3), and [Ru^II(9-atpy)(dmphen)Cl]ClO₄ (4) {where 3-bptpy?=?4′-(3-bromophenyl)-2,2′:6′,2″-terpyridine, 3-cptpy?=?4′-(3-chlorophenyl)-2,2′:6′,2″-terpyridine, 2-tptpy?=?4′-(2-thiophenyl)-2,2′:6′,2″-terpyridine, 9-atpy?=?4′-(9-anthryl)-2,2′:6′,2″-terpyridine, dmphen?=?2,9-dimethyl-1,10-phenanthroline} have been synthesized and characterized. The DNA-binding properties of the complexes with Herring Sperm DNA have been investigated by absorption titration and viscosity measurements. The ability of complexes to break the pUC19 DNA has been checked by gel electrophoresis. The experimental results suggest that all the complexes bind DNA via partial intercalation. The results also show that the order of DNA-binding affinities of the complexes is 4?<?3?<?2?<?1, confirming that planarity of the ligand in a complex is very important for DNA-binding.     

DNA-binding and photocleavage of fluorescein-porphyrinatozinc complexes

Three fluorescein-porphyrinatozinc(II) complexes, Zn(Fl-HPTTP) (1) (Fl-HPTTP?=?5-(4-fluoresceinhexyloxy)phenyl-10,15,20-tritolylporphyrin), Zn(Fl-HPTPP) (2) (Fl-HPTPP?=?5-(4-fluoresceinhexyloxy)phenyl-10,15,20-triphenylporphyrin), and Zn(Fl-HPTCPP) (3) (Fl-HPTCPP?=?5-(4-fluoresceinhexyloxy)phenyl-10,15,20-tri(4-chloro)phenylporphyrin), have been synthesized and characterized by elemental analysis, IR, UV-Vis, ES-MS, and ¹H NMR. The DNA-binding behaviors of these complexes with calf-thymus DNA (ct-DNA) were investigated by UV-Vis absorption titration, fluorescence spectra, viscosity measurements, thermal denaturation, and circular dichroism. The results suggest that 1, 2, and 3 interact with ct-DNA by intercalation and the DNA-binding affinities of these fluorescein-porphyrinatozinc(II) complexes may be closely associated with electronic effects of the substituent group introduced on the porphyrin ring of the ligands. The DNA-binding affinity (K _b values) follows the order 1?>?2?>?3. In addition, their photocleavage reactions with pBR322 supercoiled plasmid DNA were investigated by gel electrophoresis experiments. All complexes exhibit significant DNA cleavage activity. The cleavage ability of the fluorescein-porphyrinatozinc(II) complexes follows the order 1?>?2?>?3, in parallel to the magnitude of their intrinsic binding constants.     

Syntheses and crystal structures of nickel(II), copper(II), and zinc(II) complexes with a biphenyl-bridged bis(pyrrole-2-yl-methyleneamine) ligand

The reactions of nickel(II), copper(II), and zinc(II) acetate salts with a potentially tetradentate biphenyl-bridged bis(pyrrole-2-yl-methyleneamine) ligand yielded three complexes with different coordination geometries. X-ray crystal structural analysis reveals that in the nickel(II) complex each nickel is five-coordinate, distorted trigonal bipyramid. In the copper(II) complex, each copper is four-coordinate, between square planar and tetrahedral. In the zinc(II) complex, each zinc is four-coordinate with a distorted tetrahedral geometry and the molar ratio of the zinc and ligand is 1 : 2.     

The DNA-binding behavior and DFT calculation of ruthenium(II) complexes [Ru(phen)2L](ClO4)2 (L = HMOPIP and MOHPIP)

Two ruthenium(II) complexes, [Ru(phen)₂HMPIP]²⁺ (1) and [Ru(phen)₂MHPIP]²⁺ (2), have been synthesized and characterized by elemental analysis, ESI-MS, and ¹H NMR spectroscopy. The DNA-binding properties of 1 and 2 have been investigated by electronic and emission spectra and viscosity experiments. The results show that both 1 and 2 can bind to DNA in intercalating mode, with 1 exhibiting stronger binding affinity. These were confirmed by the strong hypochromism at IL and MLCT absorption bands in both complexes when DNA was added into solution, and the increase in relative viscosity of CT-DNA in the presence of both complexes. Moreover, the calculated intrinsic binding constant for 1 and 2 from the decay of electronic spectra is 3.82 × 10⁵ and 2.06 × 10⁵ M^?1, respectively. Finally, the effects of the substituent groups on the DNA-binding behavior of ruthenium(II) complexes have also been rationally discussed by computer calculation of density functional theory (DFT) methods.     

Syntheses,crystal structures,and DNA-binding of some nickel(II) complexes of 1,3-bis(2-pyridylmethylthio)propane and pseudohalides

A series of neutral octahedral nickel(II) complexes of 1,3-bis(2-pyridylmethylthio)propane (L) and pseudohalide (X), formulated as [Ni^II(L)X₂] (where X?=?azide (1), cyanate (2), and isothiocyanate (3)), was synthesized. The complexes were characterized by physico-chemical and spectroscopic methods, and 1 and 3 also by single-crystal X-ray diffraction analyses. The structural study shows nickel in a distorted octahedral geometry comprised of the tetradentate NSSN ligand with trans pyridines and monocoordinated pseudohalides in cis positions. In dimethylformamide solution, the complexes had quasi-reversible Ni^II/Ni^III redox couples in cyclic voltammograms with E _1/2 values of +0.732, +0.747, and +0.815?V for 1, 2, and 3, respectively. To examine the biological activities of these complexes, interaction of 3 with calf thymus DNA was studied spectroscopically, showing groove-binding interaction.