Synthesis, characterization, DNA-binding and photocleavage studies of [Ru(bpy)2(PPIP)]2+ and [Ru(phen)2(PPIP)]2+

A novel ligand 2-(4'-phenoxy-phenyl)imidazo[4,5-f][1,10]phenanthroline (PPIP) and its complexes [Ru(bpy)(2)(PPIP)](2+) (1) (bpy = 2,2'-bipyridine) and [Ru(phen)(2)(PPIP)](2+) (2) (phen = 1,10-phenanthroline) have been synthesized and characterized by mass spectroscopy, (1)H NMR and cyclic voltammetry. The interaction of two complexes with calf thymus DNA (CT-DNA) was investigated by spectroscopic and viscosity measurements. The results suggest that both complexes bind to DNA via an intercalative mode. Both complexes have also been found to promote the photocleavage of plasmid pBR 322 DNA under irradiated.     

Syntheses and DNA-binding studies of two ruthenium(II) complexes containing one ancillary ligand of bpy or phen: [Ru(bpy)(pp[2,3]p)2](ClO4)2 and [Ru(phen)(pp[2,3]p)2](ClO4)2

Two new ruthenium(II) complexes of [Ru(bpy)(pp[2,3]p)2](ClO4)2 and [Ru(phen)(pp[2,3]p)2](ClO4)(2) (bpy=2,2'-bipyridine, phen=1,10-phenanthroline, pp[2,3]p=pyrido[2',3':5,6]pyrazino[2,3-f][1,10]phenanthroline) have been synthesized and characterized by elemental analysis and 1H NMR spectra. The calf thymus DNA-binding properties of the two complexes were investigated by UV-visible and emission spectroscopy, competitive binding experiments with ethidium bromide and viscosity measurements. The results indicate that the two complexes intercalate between the base pairs of the DNA tightly with intrinsic DNA-binding constants of 3.08 x 10(6) and 6.53 x 10(6) M(-1) in buffered 50 mM NaCl, respectively, which are much larger than 6.9 x 10(5) M(-1) for [Ru(bpy)2(pp[2,3]p)](ClO4)2 containing two ancillary ligands of bpy.     

Syntheses,characterization and DNA-binding studies of ruthenium(II) terpyridine complexes: [Ru(tpy)(PHBI)]2+ and [Ru(tpy)(PHNI)]2+

Two novel tridentate ligands, 2-(2-benzimidazole)-1,10-phenanthroline (PHBI) and 2-(2-naphthoimidazole)-1,10-phenanthroline (PHNI), and their heteroleptic complexes [Ru(tpy)(PHBI)](ClO(4))(2).2H(2)O (1) and [Ru(tpy)(PHNI)](ClO(4))(2).H(2)O (2) (tpy=2,2':6',2"-terpyridyl) have been synthesized and characterized by elemental analysis, mass spectra, 1H NMR, and electronic spectroscopy. The electrochemical behaviors of the two novel complexes were studied by cyclic voltammetry. The DNA-binding properties of the two complexes were investigated by spectroscopic methods and viscosity measurements. The results indicated that the two complexes interact with DNA in different binding modes. Complex 1 may bind to DNA via electrostatic interaction, while complex 2 binds to DNA by partial intercalation via the extended naphthyl ring into the base pairs of DNA.     

Synthesis, characterization, DNA-binding and photocleavage of complexes [Ru(phen)2(6-OH-dppz)]2+ and [Ru(phen)2(6-NO2-dppz)]2+

Two new complexes, ([Ru(phen)(2)(6-OH-dppz)](2+)) (1) and ([Ru(phen)(2)(6-NO(2)-dppz)](2+)) (2) (phen=1,10-phenanthroline; 6-OH-dppz=6-hydroxyl-dipyrido[3,2-a:2',3'-c]phenazine; 6-NO(2)-dppz=6-nitro-dipyrido[3,2-a:2',3'-c]phenazine), have been synthesized and characterized by elemental analysis, ES-MS (electrospray mass spectra), (1)H NMR, UV-Vis (UV-visible) and CV (cyclic voltammetry). The DNA-binding behaviors of both complexes have been studied by spectroscopic methods and viscosity measurements. The results indicate that the two complexes all bind to calf thymus DNA (CT-DNA) in an intercalative mode, and the DNA-binding affinity of complex 2 is greater than that of complex 1. In addition, complex 1 can promote photocleavage of pBR322 DNA upon irradiation, whereas complex 2 can promote cleavage of pBR322 DNA both upon irradiation and in the dark, with more efficient cleavage occurring upon irradiation. Theoretical studies for these complexes have been also carried out with the density functional theory (DFT) method. The difference in the DNA-binding behaviors of the two complexes can be reasonably explained by the DFT calculations.     

Synthesis, characterization, and DNA-binding of chiral complexes delta- and lambda-[Ru(bpy)2(pyip)]2+

New chiral Ru(II) complexes delta and lambda-[Ru(bpy)(2)(pyip)](PF(6))(2) [(bpy = 2,2'-bipyridine; pyip = (2-(1-pyrenyl)-1H-imidazo[4,5-f] [1,10]phenanthroline] were synthesized and characterized by elemental analysis, (1)H NMR, ESI-MS, IR, and CD spectra. Their DNA-binding properties were studied by means of UV-vis, emission spectra, CD spectra and viscosity measurements. A subtle but detectable difference was observed in the interaction of both enantiomer with CT-DNA. Spectroscopy experiments indicated that each of these complexes could interact with the DNA. The DNA-binding of the Delta-enantiomer was stronger than that of Lambda-enantiomer. DNA-viscosity experiments provided evidence that both Delta- and Lambda-[Ru(bpy)(2)(pyip)](PF(6))(2) bound to DNA by intercalation. At the same time, the DNA-photocleavage properties of the complexes were investigated too. Under irradiation with UV light, Ru(II) complexes showed different efficiency of cleaving DNA.     

DNA Interaction and Photocleavage Properties of Ru (II) Complexes [Ru(bpy)2(pibi)]2+ and [Ru(phen)2(pibi)]2+

A new asymmetry ligand pibi (pibi = 2-(pyridine-2-yl)-1-H-imidazo[4,5-f]benzo[d]imidazolone) and its ruthenium complexes with [Ru(L)₂(pibi)]²⁺ (L = bpy (2, 2′-bipyridine), phen (1, 10-phenanthroline)), have been synthesized and characterized. The binding of two complexes with calf thymus DNA has been investigated by spectroscopic and viscosity measurement. The results indicate that both complexes can bind to CT-DNA through intercalative mode. Under irradiation at 365 nm, both complexes can partly promote the photocleavage of plasmid pBR322DNA. The low singlet oxygen generation abilities of the two complexes may be the factor for the low DNA photocleavage abilities.     

Syntheses, characterization and DNA-binding study of chiral complexes DeltaDelta- and LambdaLambda-[Ru(bpy)2(bdptb)Ru(bpy)2]4+

A novel bridging ligand bdptb(2,2'-bis(5,6-diphenyl-1,2,4-triazin-3-yl)-4,4'-bipyridine) and it's chiral diruthenium(II) complex DeltaDelta- and LambdaLambda-[Ru(bpy)2(bdptb)Ru(bpy)2]4+ (Ru2) have been synthesized and characterized by electrospray mass spectra, 1H NMR, UV/visible and circular dichroism spectra. Binding behavior of these dimeric complexes with calf thymus DNA have been investigated by absorption spectra, viscosity measurements, equilibrium dialysis experiments. The electronic absorption spectra hypochromism at the metal-ligand charge transfer of the DeltaDelta- and LambdaLambda-enantiomer are 26.4%, and 40%, and bathochromism of 13.5, and 14 nm in sequence. Equilibrium dialysis experiments results show also the binding-DNA of LambdaLambda-enantiomer is stronger than DeltaDelta-enantiomer. The increasing amounts of the novel dimeric ruthenium(II) complexes on the relative viscosities of calf thymus DNA is smaller than that of the classic intercalators such as [Ru(bpy)2(dppz)]2+ and larger than that of the non-classic intercalators such as Delta-[Ru(phen)3]2+. The experiments suggest the dimeric ruthenium(II) complex may be bound to DNA by groove binder.     

DNA-binding studies of mixed-ligand (ethylenediamine)ruthenium(II) complexes

A series of mixed-ligand ruthenium(II) complexes of the type [Ru(en)(2)bpy](2+) (bpy=2,2-bipyridine; 1), [Ru(en)(2)phen](2+) (phen=1,10-phenantroline; 2), [Ru(en)(2)IP](2+) (IP=imidazo[4,5-f][1,10]phenanthroline; 3), and [Ru(en)(2)PIP](2+) (PIP=2-phenylimidazo[4,5-f][1,10]phenanthroline; 4) have been isolated and characterized by UV/VIS, IR, and (1)H-NMR spectral methods. The binding of the complexes with calf thymus DNA has been investigated by absorption, emission spectroscopy, viscosity measurements, DNA melting, and DNA photo-cleavage. The spectroscopic studies together with viscosity measurements and DNA melting studies support that complexes 1 and 2 bind to CT DNA (=calf thymus DNA) by groove mode. Complex 2 binds more avidly to CT DNA than complex 1, complexes 3 and 4 bind to CT DNA by intercalation mode, 4 binds more avidly to CT DNA than 3. Noticeably, the four complexes have been found to be efficient photosensitisers for strand scissions in plasmid DNA.     

Synthesis,crystal structure,and nuclease activity of planar mono-heterocyclic base copper(II) complexes

A series of mononuclear copper(II) complexes having a 1:1 molar ratio of copper and the planar heterocyclic base like 1,10-phenanthroline (phen), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq) and dipyrido[3,2-a:2',3'-c]phenazine (dppz) are prepared from a reaction of copper(II) nitrate.trihydrate and the base (L) in ethanol or aqueous ethanol at different temperatures. The complexes [Cu(dpq)(NO(3))(2)] (2), [Cu(dpq)(NO(3))(H(2)O)(2)](NO(3)) (3), [Cu(dpq)(NO(3))(2)(H(2)O)(2)].2H(2)O (4.2H(2)O) and [Cu(dppz)(NO(3))(2)(H(2)O)].H(2)O (5.H(2)O) have been characterized by X-ray crystallography. The crystal structures show the presence of the heterocyclic base in the basal plane. The coordination geometries of the copper(II) centers are axially elongated square-pyramidal (4+1) in 2, 3 and 5, and octahedral (4+2) in 4. The nitrate anion in the coordination sphere displays unidentate and bidentate chelating bonding modes. The axial ligand is either H(2)O or NO(3) in these structures giving a Cu-L(ax) distance of approximately 2.4 A. The one-electron paramagnetic complexes (mu approximately 1.8 mu(B)) exhibit axial EPR spectra in DMF glass at 77 K giving g(parallel)>g( perpendicular ) with an A(parallel) value of approximately 170G indicating a [d(x)2(-y)2](1) ground state. The complexes are redox active and display a quasireversible cyclic voltammetric response for the Cu(II)/Cu(I) couple near 0.0 V vs. SCE giving an order of the E(1/2) values as 5(dppz)>2-4 (dpq)>[Cu(phen)(2)(H(2)O)](2+)>1 (phen). The complexes bind to calf thymus DNA giving an order 5 (dppz)>2 (dpq)>[Cu(phen)(2)(H(2)O)](2+)>1 (phen). An effect of the extended planar ring in dpq and dppz is observed in the DNA binding. The complexes show nuclease activity with pUC19 supercoiled DNA in DMF/Tris-HCl buffer containing NaCl in presence of mercaptopropanoic acid as a reducing agent. The extent of cleavage follows the order: [Cu(phen)(2)(H(2)O)](ClO(4))(2)>5>2 approximately 3 approximately 4>1. The bis-phen complex is a better cleaver of SC DNA than 1-5 having mono-heterocyclic base. Mechanistic investigations using distamycin reveal minor groove biding for the phen, dpq complexes, and a major groove binding for the dppz complex 5. The cleavage reactions are found to be inhibited in the presence of hydroxyl radical scavenger DMSO and the reactions are proposed to proceed via sugar hydrogen abstraction pathway. The ancillary ligand is found to have less effect in DNA binding but are of importance in DNA cleavage reactions.     

DNA-binding and photocleavage studies of cobalt(III) mixed-polypyridyl complexes containing 2-(2-chloro-5-nitrophenyl)imidazo [4,5-f][1,10]phenanthroline

The ligand 2-(2-chloro-5-nitrophenyl)imidazo[4,5-f][1,10]phenanthroline(CNOIP) and its complexes [Co(bpy)(2)(CNOIP)](3+) (1) and [Co(phen)(2)(CNOIP)](3+) (2) (bpy=2,2'-bipyridine; phen=1,10-phenanthroline) have been synthesized and characterized. Binding of the two complexes with calf thymus DNA has been investigated by spectroscopic methods, cyclic voltammetry, viscosity, and electrophoresis measurements. The experimental results indicate that both complexes bind to DNA through an intercalative mode. In comparison with their parent complexes containing PIP ligand (PIP=2-phenylimidazo[4,5-f][1,10]phenanthroline), the introduction of NO(2) and Cl groups to the PIP ligand decreased the binding affinity of complexes 1 and 2 to CT DNA. Both complexes have also been found to promote the photocleavage of plasmid pBR 322 DNA, the hydroxyl radical (OH*) is suggested to be the reactive species responsible for the cleavage.     

Synthesis, DNA-binding and photocleavage studies of ruthenium(II) complex with 2-(3'-phenoxyphenyl)imidazo[4,5-f][1,10]phenanthroline

A new polypyridyl ligand MPPIP {MPPIP=2-(3'-phenoxyphenyl)imidazo[4,5-f]-[1,10]phenanthroline} and its ruthenium(II) complexes, [Ru(bpy)(2)MPPIP](2+) (1) (bpy=2,2'-bipyridine) and [Ru(phen)(2)MPPIP](2+) (2) (phen=1,10-phenanthroline) have been synthesized and characterized. The binding of the two complexes to calf thymus DNA (CT-DNA) has been investigated with spectrophotometric methods, viscosity measurements, as well as equilibrium dialysis and circular dichroism spectroscopy. The results suggest that both complexes bind to CT-DNA through intercalation, and enantioselectively interact with CT-DNA in a way. However, complex 2 is a much better candidate as an enantioselective binder to CT-DNA than complex 1. When irradiated at 365nm, both complexes have also been found to promote the photocleavage of plasmid pBR322 DNA.     

Synthesis, characterization, DNA-binding and spectral properties of complexes [Ru(L)4(dppz)]2+ (L=Im and MeIm)

Two new Ru(II) complexes [Ru(L)(4)(dppz)](2+) (L=imidazole (Im), 1-methylimidazole (MeIm); dppz=dipyrido[3,2-a:2',3'-c]phenazine), have been synthesized and characterized in detail by elemental analysis, (1)H NMR, Electrospray ionization mass spectrometry (ESI-MS) and UV-visible (UV-Vis) spectroscopic techniques. The interaction of these complexes with calf thymus DNA (CT-DNA) has been explored by using electronic absorption titration, competitive binding experiment, circular dichroism (CD), thermal denaturation and viscosity measurements. The experimental results show that: both the two complexes can bind to DNA in an intercalation mode; the DNA-binding affinity of complex [Ru(Im)(4)(dppz)](2+)1 (K(b)=2.5 x 10(6)M(-1)) is greater than that of complex [Ru(MeIm)(4)(dppz)](2+)2 (K(b)=1.1 x 10(6)M(-1)). Moreover, it is very interesting to find that the circular dichroic spectrum of DNA-complex 1 adduct, in which both bands centered at 277 nm and 236 nm are all negative, is very different from those of DNA-complex 2 adduct and other Ru(II) complexes binding to DNA in general intercalation mode. It may be due to the hydrogen-bonding effect or the contribution of induced CD signals of complex 1. Another interesting finding is that the hypochromism of the complexes is not linear relation to their DNA-binding affinities. In order to deeply study these experimental phenomena and trends, the density functional theory (DFT) and time-dependent DFT (TDDFT) computations were carried out, and on the basis of the DFT/TDDFT results and the frontier molecular orbital theory, the trend in DNA-binding affinities, the spectral properties as well as the interesting phenomena of larger extent of hypochromism but relatively smaller K(b) values for the title complexes have been reasonably explained.     

Synthesis, DNA-binding and photocleavage studies of cobalt(III) mixed-polypyridyl complexes: [Co(phen)(2)(dpta)](3+) and [Co(phen)(2)(amtp)](3+)

Two novel cobalt(III) mixed-polypyridyl complexes [Co(phen)(2)(dpta)](3+) and [Co(phen)(2)(amtp)](3+) (phen=1,10-phenanthroline, dpta=dipyrido-[3,2-a;2',3'-c]- thien-[3,4-c]azine, amtp=3-amino-1,2,4-triazino[5,6-f]1,10-phenanthroline) have been synthesized and characterized. The interaction of these complexes with calf thymus DNA was investigated by spectroscopic, cyclic voltammetry, and viscosity measurements. Results suggest that the two complexes bind to DNA via an intercalative mode. Moreover, these Co(III) complexes have been found to promote the photocleavage of plasmid DNA pBR322 under irradiation at 365nm. The mechanism studies reveal that hydroxyl radical (OH()) is likely to be the reactive species responsible for the cleavage of plasmid DNA by [Co(phen)(2)(dpta)](3+) and superoxide anion radical (O(2)(-)) acts as the key role in the cleavage reaction of plasmid DNA by [Co(phen)(2)(amtp)](3+).     

DNA binding by Ru(II)–bis(bipyridine)–pteridinyl complexes

The interactions of five bis(bipyridyl) Ru(II) complexes of pteridinyl-phenanthroline ligands with calf thymus DNA have been studied. The pteridinyl extensions were selected to provide hydrogen-bonding patterns complementary to the purine and pyrimidine bases of DNA and RNA. The study includes three new complexes [Ru(bpy)(2)(L-pterin)](2+), [Ru(bpy)(2)(L-amino)](2+), and [Ru(bpy)(2)(L-diamino)](2+) (bpy is 2,2'-bipyridine and L-pterin, L-amino, and L-diamino are phenanthroline fused to pterin, 4-aminopteridine, and 2,4-diaminopteridine), two previously reported complexes [Ru(bpy)(2)(L-allox)](2+) and [Ru(bpy)(2)(L-Me(2)allox)](2+) (L-allox and L-Me(2)allox are phenanthroline fused to alloxazine and 1,3-dimethyalloxazine), the well-known DNA intercalator [Ru(bpy)(2)(dppz)](2+) (dppz is dipyridophenazine), and the negative control [Ru(bpy)(3)](2+). Reported are the syntheses of the three new Ru-pteridinyl complexes and the results of calf thymus DNA binding experiments as probed by absorption and fluorescence spectroscopy, viscometry, and thermal denaturation titrations. All Ru-pteridine complexes bind to DNA via an intercalative mode of comparable strength. Two of these four complexes-[Ru(bpy)(2)(L-pterin)](2+) and [Ru(bpy)(2)(L-allox)](2+)-exhibit biphasic DNA melting curves interpreted as reflecting exceptionally stable surface binding. Three new complexes-[Ru(bpy)(2)(L-diamino)](2+), [Ru(bpy)(2)(L-amino)](2) and [Ru(bpy)(2)(L-pterin)](2+)-behave as DNA molecular "light switches."     

Ruthenium(II) mixed-ligand complex containing 2-(4'-benzyloxy-phenyl)imidazo[4,5-f][1,10]phenanthroline: synthesis, DNA-binding and photocleavage studies

A novel polypyridyl ligand 2-(4'-benzyloxyphenyl)imidazo[4,5-f][1,10]phenanthroline (BPIP) and its complex [Ru(bpy)2(BPIP)]2+ (1) (bpy=2,2'-bipyridine) and (2) [Ru(phen)2(BPIP)]2+) (phen=1,10-phenanthroline) have been synthesized and characterized by elemental analysis, electrospray mass spectra and 1H NMR. The DNA-binding properties of the two complexes were investigated by spectroscopic and viscosity measurements. The results suggest that both complexes bind to DNA via an intercalative mode. Both complexes can enantioselectively interact with calf thymus DNA (CT-DNA) in a way. The Lambda enantiomer of complex 1 is slightly predominant for binding to CT-DNA to the Delta enantiomer. Under irradiation at 365 nm, both complexes have also been found to promote the photocleavage of plasmid pBR 322 DNA. Inhibitors studies suggest that singlet oxygen ((1)O2) and hydroxyl radical (*OH) play a significant role in the cleavage mechanism for both complexes. Moreover, the DNA-binding and photocleavage properties of both complexes were compared with that of [Ru(bpy)2(BPIP)]2+ and [Ru(phen)2(BPIP)]2+. The experimental results indicate that methene group existence or not have a significant effect on the DNA-binding and cleavage mechanism of these complexes.     

Synthesis, characterization and the effect of ligand planarity of [Ru(bpy)2L]2+ on DNA binding affinity.

Two structurally related ligands (L) 4,5,9,18-tetraazaphenanthreno[9,10-b] triphenylene (taptp) and 2,3-diphenyl-1,4,8,9-tetraazatriphenylene (dptatp), and their related complexes of [Ru(bpy)2L]2+ have been synthesized and characterized by elemental analyses, 1H NMR and mass spectra. Their electrochemical properties were also examined. Both complexes emit intense luminescence in organic solvent but are quenched in water to different extents. The interactions of the complexes with calf thymus DNA have been investigated by viscosity, absorption, emission and circular dichroism spectra. The intrinsic binding constants of [Ru(bpy)2(taptp)]2+ and [Ru(bpy)2(dptatp)]2+ are 1.7 x 10(5) and 3.8 x 10(4) M-1, respectively. All data indicate that both complexes bind enantioselectively to double-stranded calf thymus DNA via the intercalative mode, with stronger affinity for the fully planar ligand complex of [Ru(bpy)2(taptp)]2+.     

Different modes of DNA cleavage activity of dihydroxo-bridged dicopper(II) complexes having phenanthroline bases

Dihydroxo-bridged dicopper(II) complexes [(Cu(phen))(2)(mu-OH)(2)](ClO(4))(2) (1), [(Cu(dpq))(2)(mu-OH)(2)](ClO(4))(2) (2) and [(Cu(dppz)(DMF))(2)(mu-OH)(2)](PF(6))(2) (3), where phen, dpq and dppz are 1,10-phenanthroline, dipyridoquinoxaline and dipyridophenazine, respectively, are prepared and their DNA binding and cleavage properties studied. Complex 3 has been structurally characterized by X-ray crystallography. The complexes have a (Cu(2)(mu-OH)(2))(2+) core with an essentially planar arrangement of two CuN(2)O(2) basal planes. The complexes are avid binder to calf thymus DNA (K(app) value of 4.8 x 10(6) and 5.9 x 10(6) M(-1) for 2 and 3, respectively, from ethidium displacement assay) and exhibits significant cleavage of supercoiled (SC) pUC19 DNA in dark in presence of mercaptopropionic acid. Besides, the dpq and dppz complexes display photo-induced DNA cleavage on UV (312 nm) and red light (632.8 nm) irradiations in absence of any additives. Mechanistic investigations reveal minor groove binding for the phen and dpq complexes, and major groove preference for the dppz species. The oxidative DNA cleavage reactions in presence of mercaptopropionic acid as a reducing agent involve hydroxyl radicals. The photo-cleavage reactions at UV light involve singlet oxygen as the reactive species, while similar reactions on red light irradiation (632.8 nm) proceed through the formation of hydroxyl radical. The complexes show significant DNA hydrolase activity in absence of any additives under dark reaction conditions.     

Interaction of Lambda- and Delta-[Ru(bpy)2(pbmz)](PF6)2 with the oligonucleotide duplex d(CGCGAATTCGCG)2

The interaction of the enantiomeric complexes Lambda- and Delta-[Ru(bpy)(2)(pbmz)](PF(6))(2) (bpy=2,2'-bipyridine, pbmz=2-(2'-pyridyl)benzimidazole) with the DNA duplex d(CGCGAATTCGCG)(2) was investigated by means of 2D NMR techniques. The synthesis of the enantiomers was based on the optically pure complexes Lambda- and Delta-[Ru(bpy)(2)(py)(2)](2+) and were characterized by CD and NMR spectroscopy. NMR data indicate that both enantiomers bind weakly to the oligonucleotide, approaching from the minor groove at the centre of the helix. The perturbation of the B-DNA conformation is minor with an apparent absence of enantioselectivity. Molecular modelling calculations in conjunction with the NOE data support the suggestion that more than one binding modes are present. The imidazole amine group of the pbmz ligand is probably hydrogen bonded to the DNA phosphodiesteric backbone at the AATT step, and this may provide an explanation for the diminished enantioselectivity observed.     

Three new Cu(II) and Cd(II) complexes with 3-(2-pyridyl)pyrazole-based ligand: syntheses, crystal structures, and evaluations for bioactivities

Three new complexes [Cu(L)(2)(NO(3))](NO(3))(H(2)O)(1/2)(CH(3)OH)(1/2) (1), [Cd(L)(2)(NO(3))(2)](H(2)O)(3) (2) and [Cd(L)(2)(ClO(4))(CH(3)OH)](ClO(4))(H(2)O)(1/4)(CH(3)OH) (3) (L=1-[3-(2-pyridyl)pyrazol-1-ylmethyl]naphthalene) were synthesized and characterized by elemental analyses, IR and X-ray diffraction analysis. Among them, the Cu(II) and Cd(II) ions were both coordinated by four N donors from two distinct L ligands via N,N-bidentate chelating coordination mode. Additional weak interactions, such as the face-to-face pi-pi stacking and C-Hcdots, three dots, centeredO H-bonding interactions, linked the mononuclear unit into 1D chain and further into 2D network. Complexes 1-3 were subjected to biological assays in vitro against six different cancer cell lines. All of them exhibited cytotoxic specificity and notable cancer cell inhibitory rate. The interactions of 1-3 with calf thymus DNA were investigated by thermal denaturation, viscosity measurements, spectrophotometric and electrophoresis methods. The results indicate that these complexes bound to DNA by intercalation mode via the ligand L and had different nuclease activities, which were in good agreement with their DNA-binding strength. Moreover, the central metal ions of 1-3 played a vital role in DNA-binding behaviors, DNA-cleavage activities and cytotoxicities, whereas the contribution of the different counter anions to their bioactivities also should not be ignored.     

Synthesis, characterization and DNA binding studies of two mixed ligand complexes of ruthenium(II)

Two mixed ligand complexes [Ru(bpy)(2)(DMHBT)]Cl(2)(1) and [Ru(phen)(2)(DMHBT)]Cl(2) (2) (where DMHBT is 11,13-dimethyl-13H-4,5,9,11,14-hexaaza-benzo[b]triphenylene-10,12-dione) have been synthesized and characterized by electrospray ionization (ESI) mass, (1)H-(1)H correlation spectroscopy (COSY), electronic spectroscopy, fluorescence spectroscopy and cyclic voltammetry. Spectroscopic titration and viscosity changes of calf thymus (CT)-DNA in the presence of incremental amount of complexes 1 and 2 clearly demonstrate that both these complexes bind intercalatively to DNA, with binding constant 2.87+/-0.20 x 10(4)M(-1) and 1.01+/-0.20 x 10(5)M(-1) for complexes 1 and 2, respectively. All the experimental evidences suggest that the ancillary ligand 2,2'-bipyridine (bpy) and 1,10-phenanthroline (phen) influences the intercalative binding of these complexes to DNA.