Enantioselective luminescence quenching of DNA light-switch [Ru(phen)2dppz]2+ by electron transfer to structural homologue [Ru(phendione)2dppz]2+

The quenching of the luminescence of [Ru(phen)(2)dppz](2+) by structural homologue [Ru(phendione)(2)dppz](2+), when both complexes are bound to DNA, has been studied for all four combinations of Delta and Lambda enantiomers. Flow linear dichroism spectroscopy (LD) indicates similar binding geometries for all the four compounds, with the dppz ligand fully intercalated between the DNA base pairs. A difference in the LD spectrum observed for the lowest-energy MLCT transition suggests that a transition, potentially related to the final localization of the excited electron to the dppz ligand in [Ru(phen)(2)dppz](2+), is overlaid by an orthogonally polarized transition in [Ru(phendione)(2)dppz](2+). This would be consistent with a low-lying LUMO of the phendione moiety of [Ru(phendione)(2)dppz](2+) that can accept the excited electron from [Ru(phen)(2)dppz](2+), thereby quenching the emission of the latter. The lifetime of excited Delta-[Ru(phen)(2)dppz](2+) is decreased moderately, from 664 to 427 ns, when bound simultaneously with the phendione complex to DNA. The 108 ns lifetime of opposite enantiomer, Lambda-[Ru(phen)(2)dppz](2+), is only shortened to 94 ns. These results are consistent with an average rate constant for electron transfer of approximately 1.10(6) s(-1) between the phenanthroline- and phendione-ruthenium complexes. At binding ratios close to saturation of DNA, the total emission of the two enantiomers is lowered equally much, but for the Lambda enantiomer, this is not paralleled by a decrease in luminescence lifetime. A binding isotherm simulation based on a generalized McGhee-von Hippel approach shows that the Delta enantiomer binds approximately 3 times stronger to DNA both for [Ru(phendione)(2)dppz](2+) and [Ru(phen)(2)dppz](2+). This explains the similar decrease in total emission, without the parallel decrease in lifetime for the Lambda enantiomer. The simulation also does not indicate any significant binding cooperativity, in contrast to the case when Delta-[Rh(phi)(2)bipy](3+) is used as quencher. The very slow electron transfer from [Ru(phen)(2)dppz](2+) to [Ru(phendione)(2)dppz](2+), compared to the case when [Rh(phi)(2)phen](3+) is the acceptor, can be explained by a much smaller driving free-energy difference.     

Synthesis,characterization and DNA binding and photocleavage studies of [Ru(bpy)2BDPPZ]2+, [Ru(dmb)2BDPPZ]2+ and [Ru(phen)2BDPPZ]2+ complexes and their antimicrobial activity

Polypyridyl ligand 9a,13a‐dihydro‐4,5,9,14‐tetraaza‐benzo[b]triphenylene‐11‐yl)‐phenyl‐methanone (BDPPZ) and its complexes [Ru(bpy)₂BDPPZ]²⁺, [Ru(dmb)₂BDPPZ]²⁺ and [Ru(phen)₂BDPPZ]²⁺ (where bpy = 2,2′‐bipyridine, dmb = 4,4′‐dimethyl‐2,2′‐bipyridine, phen = 1,10‐phenanthroline) have been synthesized and characterized by elemental analysis, IR, UV–vis, ¹H‐NMR, ¹³C‐NMR and mass spectra. The DNA‐binding properties of the complexes were investigated by absorption, emission, melting temperature and viscosity measurements. Experimental results indicate that the three complexes can intercalate into DNA base pairs. Photo activated cleavage of pBR‐322 DNA by the three complexes was also studied. Further, all three Ru(II) complexes synthesized were screened for their antimicrobial activity. Copyright © 2009 John Wiley & Sons, Ltd.     

Interaction of rac-[Ru(5,6-dmp)3]2+ with DNA: enantiospecific DNA binding and ligand-promoted exciton coupling

The X-ray crystal structure of the complex rac-[Ru(5,6-dmp)(3)]Cl(2) (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 (K(b), (8.0 +/- 0.2) x 10(4) M(-1)) much more strongly than its phen analogue. The emission intensity of the 5,6-dmp 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 Delta-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 Lambda-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 (1)H 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-dmp complex stabilizes CT DNA from electrocatalytic oxidation of its guanine base more than the phen analogue does.     

Ru(TAP)3]2+-photosensitized DNA cleavage studied by atomic force microscopy and gel electrophoresis: a comparative study

Topological modifications of plasmid DNA adsorbed on a variety of surfaces were investigated by using atomic force microscopy (AFM). On mica modified with 3-aminopropyltriethoxysilane (APS) or poly-L-lysine, the interaction between the plasmid DNA and the surface "freezes" the plasmid DNA conformation deposited from solution, and the AFM images resemble the projection of the three-dimensional conformation of the plasmid DNA in solution. Modified mica with low concentrations of Mg(2+) leads to a decrease in the interaction strength between plasmid DNA and the substrate, and the AFM images reflect the relaxed or equilibrium conformation of the adsorbed plasmid DNA. Under these optimized deposition conditions, topological modifications of plasmid DNA were produced under irradiation in the presence of [Ru(TAP)(3)](2+) (TAP = 1,4,5,8-tetraazaphenanthrene), which is a non-intercalating complex, and were followed as a function of illumination time. The observed structural changes correlate well with the conversion of the supercoiled covalently closed circular form (ccc form) into the open circular form (oc form), induced by a single-strand photocleavage. The AFM results obtained after fine-tuning of the plasmid DNA-substrate interaction compare well with those observed from gel electrophoresis, indicating that under the appropriate deposition conditions, AFM is a reliable technique to investigate irradiation-induced topological changes in plasmid DNA.     

Ru(phen)2(PHEHAT)]2+ and [Ru(phen)2(HATPHE)]2+: two ruthenium(II) complexes with the same ligands but different photophysics and spectroelectrochemistry

The properties of two mononuclear Ru(II) complexes formed with the extended planar ligand PHEHAT depend drastically on the chelation site by the metallic ion. When the chelation takes place on the HAT site of the ligand (case of the novel complex [Ru(phen)2(HATPHE)]2+), the emission behavior is quite similar to that of [Ru(phen)2(HAT)]2+. In contrast, when the chelation is on the phen motif of the ligand (case of [Ru(phen)2(PHEHAT)]2+), the spectroscopic (absorption and emission) and electrochemical data for the complex do not obey the linear spectroelectrochemical correlation and the emission behavior is comparable to that of the extensively studied dppz complex ([Ru(phen/bpy)2(dppz)]2+). Thus, for [Ru(phen)2(PHEHAT)]2+, the emission lifetimes and intensities as a function of temperature exhibit a maximum for nitrile solvents. However, in contrast to the dppz case, at least three different states (two emitting and one dark) participate in the deactivation with different contributions depending on the temperature. These different contributions explain the observed maximum. Moreover, the fact that the solvent is liquid or frozen also influences the nature of the luminescent species.     

Synthesis and spectroscopic DNA binding studies of [Ru(phen)2(tbtc)]2+ and [Ru(2,9-dmp)2(tbtc)]2+

A new polypyridyl ligand tbtc (tbtc=4,5,9,14-tetraaza-benzo[b]triphenylene-11-carboxylic acid methyl ester) and its complexes [Ru(phen)2(tbtc)]2+ (1) (phen=1,10-phenanthroline) and [Ru(2,9-dmp)2(tbtc)]2+ (2) (2,9-dmp=2,9-dimethyl-1,10-phenanthroline) were synthesized and characterized by element analysis, MS, and 1H NMR. The DNA binding properties of both complexes to calf thymus DNA (CT-DNA) were investigated by different spectrophotometric methods and viscosity measurements. The results suggest that both complexes bind to DNA via an intercalative mode, and the DNA binding affinity of complex 1 is much greater than that of complex 2. This difference in binding affinity probably was caused by the different ancillary ligands. Also, when irradiated at 365 nm, complex 1 was found to be a more-effective DNA-cleaving agent than complex 2.     

Photoinitiated DNA Binding by cis-[Ru(bpy)2(NH3)2]2+

The ligand-loss photochemistry of cis-[Ru(bpy)(2)(NH(3))(2)](2+) (bpy = 2,2'-bipyridine) was investigated in water and in the presence of added ligands such as bipyridine and chloride. Irradiation of the complex results in the covalent binding to 9-methyl- and 9-ethylguanine, as well as to single-stranded and double-stranded DNA. This photoinduced DNA binding is not observed for the control complex [Ru(bpy)(2)(en)](2+) (en = ethylenediamine) under similar irradiation conditions. The results presented here show that octahedral Ru(II) complexes with photolabile ligands may prove useful as photoactivated cisplatin analogs.     

Effect of the ancillary ligands on the binding of ruthenium(II) complexes [Ru(dmp)2(MCMIP)]2+ and [Ru(dmb)2(MCMIP)]2+ with DNA

Two polypyridine ruthenium(II) complexes, [Ru(dmp)₂(MCMIP)]²⁺ (1) (MCMIP = 2-(6-methyl-3-chromonyl)imidazo[4,5-f][1,10]-phenanthroline, dmp = 2,9-dimethyl-1,10-phenanthroline) and [Ru(dmb)₂(MCMIP)]²⁺ (2) (dmb = 4,4′-dimethyl-2,2′-bipyridine), have been synthesized and characterized by elemental analysis, ES-MS and ¹H NMR. The DNA-binding behaviors of these complexes were investigated by electronic absorption titration, fluorescence spectroscopy, viscosity measurements and thermal denaturation. The results show that 1 and 2 effectively bind to CT-DNA; the DNA-binding affinities are closely related to the ancillary ligand.     

Electronic structure and spectra of [Ru(NH3)5pyz]2+ and [(NH3)5Ru-pyz-Ru(NH3)5]4+

The electronic structure and spectra of [Ru(NH₃)₅pyz]²⁺ and [(NH₃)₅Ru-pyz-Ru(NH₃)₅]⁴⁺ are calculated by the INDO (CINDO-E/S) method. Changes in molecular orbitals, charge distributions, and bond order indices of the pyrazine molecule and [Ru(NH₃)₅pyz]²⁺ complex in the [(NH₃)₅Ru-pyz-Ru(NH₃)₅]⁴⁺ binuclear complex are analyzed. St. Petersburg State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 4, pp. 12–23, July–August, 1994. Translated by. O. Kharlamova     

Nanometer Channels and Cages within the Extended Basic Mercurous Cations [(Hg2)3(OH)2]4+ and [(Hg2)2O]2+

The two‐ and three‐dimensional mercurous cations [(Hg₂)₃(OH)₂]⁴⁺ and [(Hg₂)₂O]²⁺ crystallize with channels and cages of roughly 1 nm diameter from aqueous solutions dependent upon the acidity of the solution. Crystal structures were determined, for example, for [Zn(H₂O)₆][(Hg₂)₃(OH)₂](NO₃)₆ (trigonal, space group P321, a = 1183.5(2) pm, c = 534.8(1) pm, Z = 1, R1 = 0.0351 for I₀ > 2σ(I₀)) and for [(Hg₂)₂O][Pb(NO₃)₃]₂ (cubic, space group , a = 1543.1(2) pm, Z = 8, R1 = 0.0534 I₀ > 2σ(I₀)).     

Interaction studies of DNA binding of ruthenium(II) mixed-ligand complexes: [Ru(phen)2(dtmi)]2+ and [Ru(phen)2(dtni)]2+

Two new ligands, 3-(pyrazin-2-yl)-as-triazino[5,6-f]-5-methoxylisatin (dtmi), 3-(pyrazin-2-yl)-as-triazino[5,6-f]-5-nitroisatin (dtni) and their ruthenium(II) complexes [Ru(phen)2(dtmi)](ClO4)2 (1) and [Ru(phen)2(dtni)](ClO4)2 (2) have been prepared and characterized by elemental analysis, FAB-MS, ES-MS and 1H NMR. The DNA-binding behaviors of complexes have been studied by spectroscopic titration, viscosity measurements, thermal denaturation and circular dichromism (CD). The results indicate that the complexes 1 and 2 interact with calf thymus DNA (CT-DNA) by intercalative mode. The DNA-binding affinity of the complexes 2 is larger than that complex 1 does.     

Formal [(2+2)+2] and [(2+2)+(2+2)] nonconjugated dienediyne cascade cycloadditions

[reaction: see text] Fluoranthene 2 and heptacycle 3 are easily accessible from the reaction of diyne 1 and norbornadiene (NBD) in the presence of the rhodium catalyst. The unusual [(2+2)+(2+2)] adduct 3 was confirmed by the X-ray crystal structure analysis.     

Die darstellung von [(CH3)3PRu(CO)2Cl2]2 und [(Ch3)3P]2Ru(CO)2Cl2; Eine berichtigung zu: Die alkoholyse des triethylsilans katalysiert von [(Ch3)3P]2Ru(CO)2Cl2

The ruthenium(II) complex used as a catalyst in reactions of alcohols and Et₃SiH proved to be the dimer [(CH₃)₃PRu(CO)₂Cl₂]₂ and not the complex [(CH₃)₃P]₂ Ru(CO)₂Cl₂. Both complexes were prepared, characterized and their catalytic properties were compared.     

Turning the [Ru(bpy)2dppz]2+ light-switch on and off with temperature

We report temperature-dependent excited-state lifetime measurements on [Ru(bpy)(2)dppz](2+) in both protic and aprotic solvents. These experiments yield a unifying picture of the excited-state photophysics that accounts for observations in both types of solvent. Our measurements support the notion of bpy-like and phz-like states associated with the dppz ligand and show that the ligand orbital associated with the bright state is similar in size to the corresponding orbital in the (3)MLCT state of [Ru(bpy)(3)](2+). In contrast to the current thinking, the experiments presented here indicate that the light-switch effect is not driven by a state reversal. Rather, they suggest that the dark state is always lowest in energy, even in aprotic solvents, and that the light-switch behavior is the result of a competition between energetic factors that favor the dark state and entropic factors that favor the bright (bpy) state.     

Crystal Structure of[Ru(taab)(DMF)_2]·[(CIO_4)_2]

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Darstellung und Eigenschaften von [(Et2N)3TiC5H4]2Ru

Preparation and Properties of [ (Et₂N)₃TiC₅H₄]₂Ru Attempts have been made to prepare dialkylamido Ti derivatives of ruthenocene, but only the title compound II which forms yellow crystals has been isolated from the reaction of Ru(C₅H₄Li)₂ with (Et₂N)₃TiBr. A Ti^σ? C₅H₄^π-Ru structure is concluded from its n.m.r and i.r. spectra and the analogy to the corresponding Fe compound.     

Synthesis of C-arylglycosides via Ru(II)-catalyzed [2 + 2 + 2] cycloaddition

In the presence of catalytic amounts of Cp*RuCl(cod), the cycloaddition of 1,6-diynes with various C-alkynylglycosides proceeded at ambient temperature to afford C-arylglycosides in 46-93% yields.     

Trimethylaluminum mediated halomethylation of [(arene)2Fe]2+ cations

The arene salts [(arene)₂Fe](PF₆)₂ (arene = mesitylene 1a, and hexamethylbenzene, 1c) react readily with AlMe₃ in dichloromethane or dibromomethane to produce the novel exo-halomethyl-η⁵-cyclohexadienyl salts [(η⁵-exo-CH₂XC₆H₃Me₃)(η⁶-C₆H₃Me₃)Fe]PF₆ (X = Cl, 2d; X = Br, 2e) and [(η⁵-exo-CH₂XC₆Me₆)(η⁶-C₆Me₆)Fe]PF₆ (X = Cl, 2f; X = Br, 2g) which have been characterized spectroscopically and, in the case of 2f, crystallographically.     

Ru(TAP)2(dppz)]2+: a DNA intercalating complex, which luminesces strongly in water and undergoes photo-induced proton-coupled electron transfer with guanosine-5'-monophosphate

The lowest excited state of [Ru(TAP)2(dppz)]2+ (TAP = 1,4,5,8-tetraazaphenanthrene, dppz = dipyrido[3,2-a:2',3'-c]phenazine) 1 is strongly luminescent, even in water, and very oxidizing. Therefore it is able to oxidise not only guanosine-5'-monophosphate (GMP), as demonstrated by laser flash photolysis, but also guanine-containing polynucleotides such as calf thymus DNA and [poly(dG-dC)]2. The luminescence quenching was found to be faster in H2O than in D2O, as is the back reaction, indicating that both processes probably proceed by proton-coupled electron transfer. These properties, that are controlled by the triplet MLCT state in which the charge has been transferred from the Ru to a TAP ligand, contrast with those of the well known [Ru(phen)2(dppz)]2+ 2.