Bao-Hui Ye

POLYPYRIDYL RUTHENIUM(II) COMPLEXES CONTAINING INTRAMOLECULAR HYDROGEN-BOND LIGAND : SYNTHESES, CHARACTERIZATION, AND DNA-BINDING PROPERTIES

Two new ligands containing an intramolecular hydrogen bond, 2-(2-hydroxyphenyl)imidazo[4,5-f][1,10]phenanthroline (HPIP) and 2-(2-hydroxy-1-naphthyl)imidazo[4,5-f][1,10]phenanthroline (HNAIP), and their complexes [Ru(bpy)2(HPIP)](PF6)2·H2O (1) and [Ru(bpy)2(HNAIP)](PF6)2·2H2O (2) (bpy=2,2′-bipyridine) have been synthesized and characterized by UV–Vis, IR, 1H NMR, and mass spectra. The electrochemical behaviors of the two complexes were studied by cyclic voltammetry. The binding of the two complexes with calf thymus DNA has been investigated by absorption, luminescence titrations, steady-state emission quenching, and viscosity measurements. The results suggest that complex 1 intercalates into DNA base pairs via the ligand HPIP, while complex 2 binds with DNA by partially intercalating the ligand HNAIP. Complex 1 shows higher affinity to DNA than complex 2. The intrinsic binding constants K for complexes 1 (6.5±0.3×105 M−1) and 2 (8.3±0.4×104 M−1) together with [Ru(bpy)2PIP]2+ (4.7±0.2×105 M−1, PIP=2-phenylimidazo[4,5-f][1,10]phenanthroline) were determined by absorption titration.

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+.

Synthesis, characterization and DNA-binding properties of novel dipyridophenazine complex of ruthenium (II) : [Ru(IP)2(DPPZ)]2+

Abstract A novel ruthenium(II) complex of dipyridophenazine (DPPZ) with the ancillary ligand imidazole[4,5- f ] [1,10]phenanthroline (IP), [Ru(IP) 2 (DPPZ)] (PF 6 ) 2 , has been synthesized and characterized by elemental analysis, 1D and 2D 1 H NMR, fast-atom bombardment mass spectra (FABMS), electronic spectroscopy and cyclic voltammetry. The DNA-binding properties of the complex were studied by spectroscopic methods. The intrinsic binding constant, K =2.1 × 10 7 M −1 , of the complex to calf thymus DNA has been determined by absorption titration in 5 mmol dm −3 Tris-HCl, 50 mmol dm −3 NaCl buffer (pH 7.0). The excited state lifetimes and luminescence quenching with [Fe(CN) 6 ] 4− as the quencher in the presence of DNA were also tested and mono-exponentiality was observed for the emission decay curves. Viscosity measurements together with the optical titrations unambiguously proved that the complex bound with DNA intercalatively and that the binding affinity to DNA was several times larger than that of the parent complex [Ru(bpy) 2 (DPPZ)] 2+ .

Enantiomeric ruthenium(II) complexes binding to DNA: binding modes and enantioselectivity

Δ- and Λ-[Ru(bpy)2(HPIP)](PF6)2 (Δ-1 and Λ-1; bpy =2,2′-bipyridine, HPIP=2-(2-hydroxyphenyl)imidazo[4,5-f][1,10]phenan-throline), Δ- and Λ-[Ru(bpy)2(HNAIP)](PF6)2 (Δ-2 and Λ-2; HNAIP=2-(2-hydroxy-1-naphthyl)imidazo[4,5-f][1,10]phenanthroline), Δ- and Λ-[Ru(bpy)2 (HNOIP)](PF6)2 (Δ-3 and Λ-3; HNOIP=2-(2-hydroxy-5-nitrophenyl)imidazo[4,5-f][1,10]phenanthroline), and Δ- and Λ-[Ru(bpy)2(DPPZ)](PF6)2 (Δ-4 and Λ-4; DPPZ=dipyridophenazine), have been synthesized. Binding behavior of these chiral complexes to calf thymus DNA (CT-DNA) has been investigated by electronic absorption, steady-state emission, and circular dichroism spectroscopies, as well as by viscosity measurements and equilibrium dialysis binding studies. Several points came from the results. (1) The DNA-binding properties were distinctly different for the [Ru(bpy)2L]2+ (L=HPIP, HNAIP, HNOIP) series of ruthenium(II) complexes, which indicates that the photophysical behavior of the complexes on binding to DNA can be modulated through ligand design. (2) Different binding rates of individual enantiomers of complexes 1 and 4 to DNA were observed through dialysis experiments. The Λ enantiomer bound more rapidly than the Δ enantiomer and their different intercalative binding geometries were suggested to be responsible. (3) Both Δ-2 and Λ-2 bound weakly to CT-DNA; Δ-2 may bind through a partial intercalation mode, whereas Λ-2 may bind in the DNA groove. (4) There was no noticeable enantioselectivity for complexes 1, 3, and 4 on binding to CT-DNA. Both of their enantiomers can intercalate into DNA base pairs. It is noted that Δ-3 and Λ-3 exhibited almost identical spectral changes on addition of CT-DNA, and a similar binding manner of the isomers to the double helix was proposed.

Reaction of divalent metal acetate and 2,2′-bipyridine. Syntheses and structural characterization of mono-, bi- and tri-nuclear complexes

Abstract The reactions of divalent metal acetate (M=Cd II , Co II , Cu II , Mn II and Ni II ) with 2,2′-bipyridine (bpy) were systematically observed at a ratio of 1:1 in methanol solution. Three kinds of complexes were isolated: mononuclear [Ni(bpy)(OAc) 2 (H 2 O) 2 ] ( 6 ), binuclear [Cd 2 (bpy) 2 (OAc) 4 (H 2 O) 2 ] ( 7 ) and [Cu 2 (bpy) 2 (OAc) 4 ]·2H 2 O ( 8 ), linear trinuclear [M 3 (bpy) 2 (OAc) 6 ] (M=Co II ( 11 ) and Mn II ( 12 )). When 1.5 equivalent NaClO 4 was added to the reaction solution, respectively two kinds of complexes were obtained: mononuclear [M(bpy) 2 (OAc)](ClO 4 )· n H 2 O (M=Cd II ( 1 ), Co II ( 2 ), Mn II ( 3 ) and Ni II ( 4 )) and binuclear [M 2 (bpy) 2 (μ-OAc) 3 ](ClO 4 ) (M=Cu II ( 9 ) and Zn II ( 10 )). The structures of complexes 1 , 7 and 11 were determined by X-ray diffraction analysis. Complex 7 is the first example of a dicadmium complex linked by two monoatomic bridging acetate ligands with the longest distance of 3.380(4) A between the dangling acetate oxygen and metal atoms. Several novel structural features in complex 7 have been found in comparison with the monodentate bridging carboxylate with no or only weak interaction between the dangling acetate oxygen atom and metal atom. The structure of complex 11 consists of linear trinuclear molecules; each pair of cobalt atoms are bridged by three acetate groups, two of them acting as bidentate bridging mode and the third as a monoatomic bridge plus bidentate chelating mode, at a distance of 3.459 A. The central cobalt(II) coordinates by six oxygen atoms from six different acetate groups, and the terminal ones have a distorted environment of four oxygen atoms and two nitrogen atoms from a bpy ligand.

Ruthenium(II) 2,2′-Bibenzimidazole Complex as a Second-Sphere Receptor for Anions Interaction and Colorimeter

A ruthenium(II) complex [Ru(bpy) 2(H 2bbim)](PF 6) 2 ( 1) as anions receptor has been exploited, where Ru(II)-bpy moiety acts as a chromophore and the H 2bbim ligand as an anion binding site. A systematic study suggests that 1 interacts with the Cl (-), Br (-), I (-), NO 3 (-), HSO 4 (-), and H 2PO 4 (-) anions via the formation of hydrogen bonds. Whereas 1 undergoes a stepwise process with the addition of F (-) and OAc (-) anions: formation of the monodeprotonated complex [Ru(bpy) 2(Hbbim)] with a low anion concentration, followed by the double-deprotonated complex [Ru(bpy) 2(bbim)], in the presence of a high anion concentration. These stepwise processes concomitant with the changes of vivid colors from yellow to orange brown and then to violet can be used for probing the F (-) and OAc (-) anions by naked eye. The deprotonation processes are not only determined by the basicity of the anion but also related to the strength of hydrogen bonding, as well as the stability of the formed compounds. Moreover, a double-deprotonated complex [Ru(bpy) 2(bbim)].CH 3OH.H 2O ( 3) has been synthesized, and the structural changes induced by the deprotonation has also been investigated. In addition, complexes [Ru(bpy) 2(Hbbim)] 2(HOAc) 3Cl 2.12H 2O ( 2), [Ru(bpy) 2(Hbbim)](HCCl 3CO 2)(CCl 3CO 2).2H 2O ( 4), and [Ru(bpy) 2(H 2bbim)](CF 3CO 2) 2.4H 2O ( 5) have been synthesized to observe the second sphere coordination between the Ru(II)-H 2bbim moiety and carboxylate groups via hydrogen bonds in the solid state.

Syntheses and characterization of two monomeric zinc complexes containing aqua ligands

Abstract Two monomeric zinc complexes, [Zn(H2biim)2(H2O)2](OAc)2·OHCH2CH2OH (H2biim=2,2′-biimidazole) (1) and [Zn(bipy)2(H2O)(CF3CO2)](ClO4) (bipy=2,2′-bipyridine) (2), have been synthesized and characterized by NMR and single-crystal structural analysis. The zinc ions in both complexes are coordinated in a distorted N4O2 octahedral geometry: the zinc ion in complex 1 is surrounded by two aqua [Zn–O 2.150 (3) A] and two H2biim ligands (Zn–N 2.150 A), the acetate groups act as counter-anions and form hydrogen bonds with H2biim; the zinc ion in 2 is ligated by two bipy ligands (Zn–N 2.144 A), one aqua molecule [Zn–O 2.148(2) A] and one monodentate carboxylate [Zn–O 2.154(2) A]. In both complexes, the aqua ligand forms strong donor hydrogen bonds with the hydroxyl or carboxylate groups, being analogous to those found for the active sites of several zinc enzymes.

Syntheses, structures, and photoluminescence studies of [2∶2] metallomacrocyclic silver(I) complexes with 1,3-bis(4,5-dihydro-1H-imidazol-2-yl)benzene

Five new silver(I) complexes with dimeric units, namely [Ag2(bib)2](BrO3)21, [Ag2(bib)2](ClO3)22, [Ag2(bib)2](ClO4)23, [Ag2(bib)2](NO3)2·2H2O 4 and [Ag2(bib)2(SCN)2] 5 (bib = 1,3-bis(4,5-dihydro-1H-imidazol-2-yl)benzene), have been synthesized and characterized by X-ray diffraction to observe the influence of the counter anions on crystal structures. Each bib acts as a bidentate ligand and every two bib ligands ligate a pair of Ag(I) ions resulting in a [2∶2] metallomacrocyclic motif that is further stabilized by intracyclic π–π interactions. 3 exhibits a dimeric structure, while 1, 2 and 4 are 1-D coordination polymers extended via interconnection of the dimeric units by the oxygen atoms from XO3− (X = Br and Cl) anions or Ag(I)⋯Ag(I) interactions. In 5, each Ag(I) ion is four-coordinate, and each dimeric unit is linked to the four adjacent dimeric units by four μ-sulfur atoms from SCN− groups into 2-D layer and further packed in 3-D network via hydrogen bonds. The photoluminescent properties of 1–4 have been observed in the solid state and dichloromethane solution at room temperature. The possible emission mechanisms have been proposed based on molecular orbital (MO) calculations.

Synthesis, electrochemical and spectroscopic properties of ruthenium(II) complexes containing 1,3-bis([1,10]phenanthroline-[5,6-d]imidazol-2-yl)benzene

1,3-Bis([1,10]phenanthroline-[5,6-d]imidazol-2-yl)benzene (mbpibH2) and its (bpy)2Ru2+ complexes (bpy=2,2′-bipyridine) have been synthesized and characterized. The electrochemical and spectroscopic studies of the mono- and dinuclear complexes have shown that there is very little or no interaction between the linked metal centers. The absorption spectra of the mono- and dinuclear complex are both strongly dependent on the solution pH. The deprotonation of the bridging ligand mbpibH2 also induces a pertubation on the spectral and redox properties of the dinuclear complex.

Synthesis, characterization and DNA-binding properties of [Ru(phen)2taptp]2+ and [Ru(phen)2dptatp]2+

Abstract Two structurally related complexes [Ru(phen)2taptp]2+ (1) and [Ru(phen)2dptatp]2+ (2), where taptp is 4,5,9,18-tetraazaphenanthreno[9,10-b]triphenylene and dptatp is 2,3-diphenyl-1,4,8,9-tetraazatriphenylene, were synthesized and characterized by elemental analyses and 1H NMR. The spectroscopic and electrochemical properties of complexes 1 and 2 were also examined. Both complexes can luminesce in organic solvent but are quenched in water to different extents. The interaction of the complexes with calf thymus DNA was studied by absorption and emission spectra, as well as viscosity and lifetime measurements. All the data indicate that both complexes bind with double-stranded calf thymus DNA via intercalative mode. Unlike its analog [Ru(bpy)2taptp]2+, [Ru(phen)2taptp]2+ shows negligible luminescence in water buffer but bright luminescence on binding to DNA, enabling it to be a sensitive probe for DNA conformation.