Synthesis and structure of cycloruthenated carbonyl complexes and their emission, redox and biological properties

An interesting series of mononuclear organoruthenium complexes of formulation [Ru(CO)(PPh3)2(ap-R)] (where ap-R = -H, -Cl, -Me, -OMe, -OEt) have been synthesized from the reaction of five 2-(arylazo)phenol ligands with ruthenium(II) precursor [RuH(Cl)(CO)(PPh3)3] in benzene under reflux. The 2-(arylazo)phenolate ligands behave as dianionic tridentate ligand and are coordinated to ruthenium through C, N and O by dissociation of the phenolic and phenyl proton at the ortho position of the phenyl ring forming two five-membered chelate rings. These complexes have been characterized by elemental analysis, FT-IR, 1H NMR and UV-visible spectroscopy. In dichloromethane solution all the metal complexes exhibit characteristic metal-to-ligand charge transfer (MLCT) absorption and emission bands in the visible region. The structures of [Ru(CO)(PPh3)2(ap-H)] and [Ru(CO)(PPh3)2(ap-Cl)] have been determined by X-ray crystallography. Cyclic voltammetric data of all the complexes show a Ru(III)/Ru(II) oxidation and reduction Ru(II)/Ru(I) within the range 0.74-0.84 V and -0.38 to -0.50 V vs saturated calomel electrode (SCE) respectively. The potentials are observed with respect to the electronic nature of substituents (R) in the 2-(arylazo)phenolate ligands. Further, the free ligands and their ruthenium complexes have also been screened for their antibacterial and antifungal activities, which have shown great promise in inhibiting the growth of both gram +ve and gram -ve bacteria Staphylococcus aureus and Escherichia coli and fungus Candida albicans and Aspergillus niger. These results made it desirable to delineate a comparison between free ligands and their complexes.     

DNA-binding and photoactivated enantiospecific cleavage of chiral polypyridyl ruthenium(II) complexes

A series of enantiomeric polypyridyl ruthenium(II) complexes Delta- and Lambda-[Ru(bpy)2CNOIP](PF6)2 (Delta-1 and Lambda-1; BPY=2,2'-bipyridine, CNOIP=2-(2-chloro-5-nitrophenyl)imidazo[4,5-f][1,10]phenanthroline), Delta- and Lambda-[Ru(bpy)2HPIP](PF6)2 (Delta-2 and Lambda-2; HPIP=2-(2-hydroxyphenyl)imidazo[4,5-f][1,10]phenanthroline), Delta- and Lambda-[Ru(bpy)2DPPZ](PF6)2 (Delta-3 and Lambda-3; DPPZ=dipyrido[3,2:a-2',3':c]-phenazine), Delta- and Lambda-[Ru(bpy)2TAPTP](PF6)2 (Delta-4 and Lambda-4; TAPTP=4,5,9,18-tetraazaphenanthreno[9,10-b] triphenylene) have been synthesized. Binding of these chiral complexes to calf thymus DNA has been studied by spectroscopic methods, viscosity, and equilibrium dialysis. The experimental results indicated that all the enantiomers of these complexes bound to DNA through an intercalative mode, but the binding affinity of each chiral complex to DNA was different due to the different shape and planarity of the intercalative ligand. After binding to DNA, the luminescence property of complex 1 was distinctly different from complexes 2 to 4. Upon irradiation at 302 nm, complexes 2-4 were found to promote the cleavage of plasmid pBR 322 DNA from supercoiled form I to nicked form II, and obvious enantioselectively was observed on DNA cleavage for the enantiomers of complexes 2 and 4. The mechanisms for DNA cleavage by these enantiomeric complexes were also proposed.     

He(I) and He(II) photoelectron spectra of Hyprrole-2-CHN′t-Bu and the biscarbonyl Rh(I) and Ir(I) complexes of its anion

The He(I) and He(II) photoelectron spectra of a series of [(LL)M(CO)₂] (LL = pyrrole-2-CHN′ R; R = t-Bu; M = Rh, Ir) complexes are reported. Assignments are proposed based on He(I)/He(II) intensity differences, on molecular orbital calculations of related complexes and of free ligands, and by comparison with the spectra of the free ligands Hpyrrole-2-CHN′t-Bu, Hpyrrole-2-carbaldehyde and Hpyrrole.The electronic structure of the complexes is discussed and conclusions are drawn about the metal-ligand interaction.     

Chiral ruthenium(II) anthraquinone complexes as dual inhibitors of topoisomerases I and II

Abstract  

DNA topoisomerases (I and II) have been one of the excellent targets in anticancer drug development. Here two chiral ruthenium(II) anthraquinone complexes, Δ- and Λ-[Ru(bpy)₂(ipad)]²⁺, where bpy is 2,2′-bipyridine and ipad is 2-(anthracene-9,10-dione-2-yl)imidazo[4,5-f][1,10]phenanthroline, were synthesized and characterized. As expected, both of the Ru(II) complexes intercalate into DNA base pairs and possess an obviously greater affinity with DNA. Topoisomerase inhibition and DNA strand passage assay confirmed that the two complexes are efficient dual inhibitors of topoisomerases I and II by interference with the DNA religation. In MTT cytotoxicity studies, two Ru(II) complexes exhibited antitumor activity against HeLa, MCF-7, HepG2 and BEL-7402 tumor cell lines. Flow cytometry analysis shows an increase in the percentage of cells with apoptotic morphological features in the sub-G1 phase for Ru(II) complexes. Nuclear chromatin cleavage has also been observed from AO/EB staining assay and alkaline single-cell gel electrophoresis (comet assay). The results demonstrated that Δ- and Λ-[Ru(bpy)₂(ipad)]²⁺ act as dual inhibitors of topoisomerases I and II, and cause DNA damage that can lead to cell cycle arrest and/or cell death by apoptosis.     

Tris (phenanthroline) metal complexes: probes for DNA helicity

The intercalative binding of chiral tris(phenanthroline) metal complexes to DNA is stereo-selective. The enantiomeric selectivity is based upon the differential steric interactions between the two non-intercalating phenanthroline ligands of each isomer with the DNA phosphate backbone. Gel electrophoretic assays of helical unwinding, optical enrichment studies by equilibrium dialysis and luminescence titrations with separated enantiomers of (phen)3Ru2+ all indicate that the delta isomer binds preferentially to the right-handed duplex. The chiral discrimination is governed by the DNA helical asymmetry. Complete stereospecifity is seen with isomers of the bulkier RuDIP (tris-4,7-diphenylphenanthrolineruthenium(II]. While both isomers bind to Z-DNA, a poor template for discrimination, binding of lambda-RuDIP to B-DNA is precluded. These chiral complexes therefore serve as a chemical probe to distinguish left and right-handed DNA helices in solution.     

Conformational studies on chiral rhodium complexes by ECD and VCD spectroscopy

This article reports vibrational circular dichroism (VCD) and electronic circular dichroism (ECD) spectroscopic studies in acetonitrile on the chiral Rh(2)(O-Phe-Cbz)(1)(OAc)(3) and Rh(2)(O-Phe-Ac)(1)(OAc)(3) complexes (abbreviated Rh(2)Z(1) and Rh(2)Ac(1) , respectively; Phe, L-phenylalanine; Cbz, benzyloxycarbonyl; Ac, acetyl) supported by theoretical calculations. The ECD spectra of the complexes depend on temperature that indicates the conformational mobility of the chiral ligands. Calculations of the VCD spectra were performed at ab initio (DFT) level of theory using Gaussian 03 [B3LYP functional combined with the LANL2DZ basis set for the dirhodium core and the 6-31G(d) basis set for other atoms]. The population-weighted sums of the computed VCD spectra of the conformers are in excellent agreement with the experimental VCD spectra. The combination of the VCD and ECD spectroscopic methods led us to the structural characterization of the complexes.     

Synthesis,characterization, redox behavior,DNA and protein binding and antibacterial activity studies of ruthenium(II) complexes of bidentate schiff bases

Two new ruthenium(II) complexes of Schiff base ligands (L) derived from cinnamaldehyde and ethylenediamine formulated as [Ru(L)(bpy)₂](ClO₄)₂, where L¹ = N,N’-bis(4-nitrocinnamald-ehyde)ethylenediamine and L² = N,N’-bis(2-nitrocinnamaldehyde)-ethylenediamine for complex 1 and 2, respectively, were isolated in pure form. The complexes were characterized by physicochemical and spectroscopic methods. The electrochemical behavior of the complexes showed the Ru(III)/Ru(II) couple at different potentials with quasi-reversible voltammograms. The interaction of the complexes with calf thymus DNA (CT-DNA) using absorption, emission spectral studies and electrochemical techniques have been used to determine the binding constant, K_b and the linear Stern–Volmer quenching constant, K_SV. The results indicate that the ruthenium(II) complexes interact with CT-DNA strongly in a groove binding mode. The interactions of bovine serum albumin (BSA) with the complexes were also investigated with the help of absorption and fluorescence spectroscopy tools. Absorption spectroscopy proved the formation of a ground state BSA-[Ru(L)(bpy)₂](ClO₄)₂ complex. The antibacterial study showed that the Ru(II) complexes (1 and 2) have better activity than the standard antibiotics but weak activity than the ligands.     

Effects of the substitution positions of Br group in intercalative ligand on the DNA-binding behaviors of Ru(II) polypyridyl complexes

Two new polypyridyl ligands containing substituent Br at different positions in the phenyl ring, PBIP [PBIP=2-(4-bromophenyl)imidazo[4,5-f]1,10-phenanthroline], OBIP [OBIP=2-(2-bromophenyl)imidazo[4,5-f]1,10-phenanthroline] and their Ru(II) complexes, [Ru(phen)2PBIP]2+ 1, [Ru(phen)2OBIP]2+ 2 (phen=1,10-phenanthroline), have been synthesized and characterized. The binding strength of the two complexes to calf thymus DNA (CT DNA) was investigated with spectrophotometric methods, viscosity measurements, as well as equilibrium dialysis and circular dichroism spectroscopy. The theoretical calculations for these two complexes were also carried out applying the density functional theory (DFT) method. The experimental results show that the Br group substituting H at different positions of the phenyl ring in the intercalated ligand has significant effects on the spectral properties and the DNA-binding behaviors of Ru(II) complexes. Both the complexes can bind to CT DNA in intercalative mode and interact with CT DNA enantioselectively. Moreover, complex 1 can bind to CT DNA more strongly than complex 2, and complex 2 can become a much better candidate as an enantioselective binder to CT DNA than complex 1. The theoretical calculations show that both intercalative ligands, PBIP and OBIP, in these two complexes are essentially planar, and the obtained electronic structures of the complexes can be used to explain reasonably some of their experimental regularities or trends. Such experimental and theoretical information will be useful in design of novel probes of nucleic acid structures.     

Organometallic Ruthenium and Osmium Compounds of Pyridin-2- and -4-ones as Potential Anticancer Agents

Organometallic Ru(II) compounds are among the most widely studied anticancer agents. Functionalizing metal centers with biomolecule-derived ligands has been shown to be a promising strategy to improve the antiproliferative activity of metal-based chemotherapeutics. Herein, the synthesis of a series of novel 3-hydroxypyridin-2-one-derived ligands and their M(II) (η(6) -p-cymene) half-sandwich complexes (M=Ru, Os) is described. The compounds were characterized by 1D- and 2D-NMR spectroscopy, and elemental analysis.     

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.     

Mixed ligand ruthenium(II) complexes of 5,6-dimethyl-1,10-phenanthroline: The role of ligand hydrophobicity on DNA binding of the complexes

A series of mixed ligand Ru(II) complexes of 5,6-dimethyl-1,10-phenanthroline (5,6-dmp) as primary ligand and 1,10-phenanthroline (phen), 2,2′-bipyridine (bpy), pyridine (py) and NH₃ as co-ligands have been prepared and characterized by X-ray crystallography, elemental analysis and ¹H NMR and electronic absorption spectroscopy. The X-ray crystal structure of the complex [Ru(phen)₂(bpy)]Cl₂ reveals a distorted octahedral coordination geometry for the RuN₆ coordination sphere. The DNA binding constants obtained from the absorption spectral titrations decrease in the order, tris(5,6-dmp)Ru(II) > bis(5,6-dmp)Ru(II) > mono(5,6-dmp)Ru(II), which is consistent with the trend in apparent emission enhancement of the complexes on binding to DNA. These observations reveal that the DNA binding affinity of the complexes depend upon the number of 5,6-dmp ligands and hence the hydrophobic interaction of 5,6-dimethyl groups on the DNA surface, which is critical in determining the DNA binding affinity and the solvent accessibility of the exciplex. Among the bis(5,6-dmp)Ru(II) complexes, those with monodentate py (4) or NH₃ (5) co-ligands show DNA binding affinities slightly higher than the bpy and phen analogues. This reveals that they interact with DNA through the co-ligands while both the 5,6-dmp ligands interact with the exterior of the DNA surface. All these observations are supported by thermal denaturation and viscosity measurements. Two DNA binding modes - surface/electrostatic and strong hydrophobic/partial intercalative DNA interaction - are suggested for the mixed ligand complexes on the basis of time-resolved emission measurements. Interestingly, the 5,6-dmp ligands promote aggregation of the complexes on the DNA helix as a helical nanotemplate, as evidenced by induced CD signals in the UV region. The ionic strength variation experiments and competitive DNA binding studies on bis(5,6-dmp)Ru(II) complexes reveal that EthBr and the partially intercalated and kinetically inert [Ru(phen)₂(dppz)]²⁺ (dppz = dipyrido[3,2-a:2′,3′-c]phenazine) complexes revert the CD signals induced by exciton coupling of the DNA-bound complexes with the free complexes in solution.     

Platinum group metal complexes of bis(2-(diphenylphosphino)ethyl benzylamine and bis(2-(diphenylarsino)ethyl)benzylamine

Rh(I), Ir(I), Pd(II) and Pt(II) metal complexes of bis(2-diphenylphosphino)ethyl)benzylamine(DPBA) and bis(2-diphenylarsino)ethyl)benzylamine (DABA) have been synthesized using various starting materials. Reaction of RhCl(CO)(AsPh₃)₂ with DPBA or DABA in methanol resulted in the formation of cationic complexes of the composition, [Rh(CO)(L)]Cl (L = DPBA or DABA). Interaction of [IrCl(COD)]₂ with DPBA in benzene resulted in the formation of a neutral complex [IrCl(DPBA)]. Reaction of [PdCl₂(COD)] with the ligand DPBA in benzene resulted in a cationic complex of the composition [PdCl(DPBA)]Cl. Interaction of [PdCl(DPBA)]BPh₄ with SnCl₂ gave the complex [Pd(SnCl₃)(DPBA)]BPh₄. The ligands DPBA and DABA react with PtCl₂(COD) in acetone to give neutral, Pt(II) complexes of the type, [PtCl₂L] (L = DPBA or DABA). All the complexes were fully characterized by elemental analysis, conductivity measurements, IR and far-IR and ³¹P{¹H} NMR spectral data.     

DNA binding and cleavage properties of certain tetrammine ruthenium(II) complexes of modified 1,10-phenanthrolines--effect of hydrogen-bonding on DNA-binding affinity

A series of ruthenium(II) mixed ligand complexes of the type [Ru(NH(3))(4)(L)](2+), where L=imidazo[4,5-f][1,10]phenanthroline (ip), 2-phenylimidazo[4,5-f][1,10]phenanthroline (pip), 2-(2-hydroxyphenyl)imidazo[4,5-f][1,10]phenanthroline (hpip), 4,7-diphenyl-1,10-phenanthroline (dip), naphtha[2,3-a]dipyrido[3,2-h:2',3'-f]phenazine-5,18-dione (qdppz), 5,18-dihydroxynaphtho[2,3-a]dipyrido[3,2-H:2',3'-f]phenazine (hqdppz), have been isolated and characterized. The interaction of these complexes with calf thymus DNA (CT DNA) has been explored by using absorption, emission, and circular dichroic spectral methods, thermal denaturation studies and viscometry. All these studies suggest the involvement of the modified phenanthroline 'face' rather than the ammonia 'face' of the complexes in DNA binding. An intercalative mode of DNA binding, which involves the insertion of the modified phenanthroline ligands in between the base pairs, is suggested. The results from absorption spectral titration and circular dichroism (CD), thermal denaturation and viscosity experiments indicate that the qdppz and hqdppz complexes (K(b) approximately 10(6) and Delta T(m)=11-13 degrees C) bind more avidly than the ip, pip and hpip complexes (K(b) approximately 10(5), Delta T(m)=6-8 degrees C). Intramolecular hydrogen bonding in the hpip and hqdppz complexes increases the surface area of the intercalating diimines and enhances the DNA binding affinity substantially. The ammonia co-ligands of the complexes are possibly involved in hydrogen bonding with the intrastrand nucleobases to favour intercalation of the extended aromatic ligands. Circular dichroism spectral studies reveal that all the complexes effect certain structural changes on DNA duplex; [Ru(NH(3))(4)(ip)](2+) induces a B to A transition while [Ru(NH(3))(4)(qdppz)](2+) a B to Psi conformational change on CT DNA. Cleavage efficiency of the complexes were determined using pBR322 supercoiled plasmid DNA. All the complexes, except hqdppz complex, promote the cleavage of supercoiled plasmid (form I) to relaxed circular form (form II).     

Synthesis, characterisation and antiamoebic activity of new thiophene-2-carboxaldehyde thiosemicarbazone derivatives and their cyclooctadiene Ru(II) complexes

Reaction of new thiosemicarbazones (1-4) derived from thiophene-2-carboxaldehyde and cycloalkylaminothiocarbonylhydrazine with [Ru(eta(4)-C8H12)(CH3CN)2Cl2] leads to form complexes (1a-4a) of the type [Ru(eta(4)-C8H12)(TSC)Cl2] (where TSC=thiosemicarbazone). All the compounds have been characterised by elemental analysis, IR, 1H NMR, electronic spectra and thermogravimetric analysis. It is concluded that the thionic sulphur and the azomethine nitrogen atom of the ligands are bonded to the metal ion. In vitro antiamoebic screening against (HK-9) strain of Entamoeba histolytica indicated that the Ru(II) complexes of thiophene-2-carboxaldehyde thiosemicarbazones were found more active than the thiosemicarbazones.     

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.     

Effect of substitution pattern of ancillary ligands on the DNA-binding behavior of two new Ru(II)-polypyridyl complexes

The new ligand 2-(4-phenoxyphenyl)-1H-imidazo[4,5-f][1,10]phenanthroline (ppip) and its Ru(II) complexes [Ru(2,9-dmp)2(ppip)]2+ (1) and [Ru(4,7-dmp)2(ppip)]2+ (2; 2,9- and 4,7-dmp = 2,9- and 4,7-dimethyl-1,10-phenanthroline, resp.) were synthesized and characterized. The binding properties of the two complexes towards calf-thymus DNA (CT-DNA) in buffered H2O (pH 7.2) were investigated by different spectrophotometric methods and viscosity measurements. Both 1 and 2 strongly bind to CT-DNA by means of intercalation, but with different binding strengths. In contrast to the more tightly bound complex 2, the sterically more-demanding complex 1 showed no fluorescence emission, neither alone nor in the presence of CT-DNA. Our results demonstrate that the position of Me groups on phenanthroline (phen) ancillary ligands significantly affects the overall DNA-recognition propensities of Ru(II)-polypyridyl complexes. Further, the partly resolved complex 2 was shown by circular dichroism (CD) to stereoselectively recognize CT-DNA, in contrast to 1.     

Enantioselective host-guest complexation of Ru(II) trisdiimine complexes using neutral and anionic derivatized cyclodextrins

Enantioselective host-guest complexation between five racemic Ru(II) trisdiimine complexes and eight derivatized cyclodextrins (CDs) has been examined by NMR techniques. The appearance of non-equivalent complexation-induced shifts of between the Δ and Λ-enantionomers of the Ru(II) trisdiimine complexes and derivatized CDs is readily observed by NMR. In particular, sulfobutyl ether-β-cyclodextrin sodium salt (SBE-β-CD), R-naphtylethyl carbamate β-cyclodextrin (RN-β-CD), and S-naphtylethyl carbamate β-cyclodextrin (SN-β-CD) showed good enantiodiscrimination for all five Ru complexes examined, which indicates that aromatic and anionic derivatizing groups are beneficial for chiral recognition. The complexation stoichiometry between SBE-β-CD and [Ru(phen)₃]²⁺ was found to be 1:1 and binding constants reveal that Λ-[Ru(phen)₃]²⁺ binds more strongly to SBE-β-CD than the Δ-enantiomer. Correlations between this NMR method and separative techniques based on CDs as chiral discriminating agents (i.e., selectors) are discussed in detail.     

Mixed-ligand complexes of ruthenium(II) containing new photoactive or electroactive ligands: synthesis, spectral characterization and DNA interactions

Mixed-ligand ruthenium(II) complexes of three photoactive ligands, viz., (E)-1-[2-(4-methyl-2-pyridyl)-4-pyridyl]-2-(1-naphthyl)-1-ethene (mppne), (E)-1-(9-anthryl)-2-[2-(4-methyl-2-pyridyl)-4-pyridyl]-1-ethene (mppae) and (E)-1-[2-(4-methyl-2-pyridyl)-4-pyridyl]-2-(1-pyrenyl)-1-ethene (mpppe), in which a 2,2′-bipyridyl unit is linked via an ethylinic linkage to either a naphthalene, an anthracene or a pyrene chromophore and three electroactive ligands, viz., 4-(4-pyridyl)-1,2-benzenediol (catpy), 5,6-dihydroxy-1,10-phenanthroline (catphen) and 1,2-benzenediol (cat), were synthesized in good to moderate yields. Complexes [Ru(bpy)₂(mppne)]²⁺ (bpy is 2, 2′–bipyridyl), [Ru(bpy)₂(mppae)]²⁺, [Ru(bpy)₂(mpppe)]²⁺, [Ru(bpy)₂(sq-py)]⁺, [Ru(bpy)₂(sq-phen)]⁺ and [Ru(phen)₂(bsq)]⁺ (phen is 1,10-phenanthroline) were fully characterized by elemental analysis, IR, ¹H NMR, fast-atom bombardment or electron-impact mass, UV–vis and cyclic voltammetric methods. In the latter three complexes, the ligands catpy, catphen and cat are actually bound to the metal center as the corresponding semiquinone species, viz., 4-(4-pyridyl)-1,2-benzenedioleto(+I) (sq-py), 1,10-phenanthroline-5,6-dioleto(+I) (sq-phen) and 1,2-benzenedioleto(+I) (bsq), thus making the overall charge of the complexes formally equal to + 1 in each case. These three complexes are electron paramagnetic resonance active and exhibit an intense absorption band between 941 and 958 nm owing to metal-to-ligand charge transfer (MLCT, d _Ru→π*_sq) transitions. The other three ruthenium(II) complexes containing three photoactive ligands, mppne, mppae and mpppe, exhibit MLCT (d _Ru→π*_bpy ) bands in the 454–461-nm region and are diamagnetic. These can be characterized by the ¹H NMR method. [Ru(bpy)₂(mppne)]²⁺, [Ru(bpy)₂(mppae)]²⁺ and [Ru(bpy)₂(mpppe)]²⁺ exhibit redox waves corresponding to the Ru^III/Ru^II couple along with the expected ligand (bpy and substituted bpy) based ones in their cyclic and differential pulse voltammograms (CH₃CN, 0.1 M tetrabutylammonium hexafluorophosphate)—corresponding voltammograms of [Ru(bpy)₂(sq-py)]⁺, [Ru(bpy)₂(sq-phen)]⁺ and [Ru(phen)₂(bsq)]⁺ are mainly characterized by waves corresponding to the quinone/semiquinone (q/sq) and semiquinone/1,2-diol (sq/cat) redox processes. The results of absorption and fluorescence titration as well as thermal denaturation studies reveal that [Ru(bpy)₂(mppne)]²⁺ and [Ru(bpy)₂(mppae)]²⁺ are moderate-to-strong binders of calf thymus DNA with binding constants ranging from 10⁵ to 10⁶ M⁻¹. Under the identical conditions of drug and light dose, the DNA (supercoiled pBR 322) photocleavage activities of these two complexes follow the order:[Ru(bpy)₂(mppne)]²⁺>[Ru(bpy)₂(mppae)]²⁺, although the emission quantum yields follow the reverse order. The other ruthenium(II) complexes containing the semiquinone-based ligands are found to be nonluminescent and inefficient photocleavage agents of DNA. However, experiments shows that [Ru(bpy)₂(sq)]⁺-based complexes oxidize the sugar unit and could be used as mild oxidants for the sugar moiety of DNA. Possible explanations for these observations are presented.Electronic Supplementary Material Supplementary material is available for this article at .     

Photo-cross-linking between polymers derivatized with photoreactive ruthenium-1,4,5,8-tetraazaphenanthrene complexes and guanine-containing oligonucleotides

We have shown previously that complexes containing 1,4,5,8-tetraazaphenanthrene (TAP) ligands are able to form photoadducts with the guanine bases of DNA and oligonucleotides. In this work, we have exploited this specific photoreaction for carrying out photo-cross-linkings between guanine-containing oligonucleotides (G-ODNs) and biodegradable polymers derivatized with the photoreactive Ru(II) compounds. The aim in the future is to use these polymer conjugates as vectorizing agents of the metallic compounds inside the cells. Thus, photooxidizing Ru(II) complexes such as [Ru(TAP)3]2+ and [Ru(TAP)2phen]2+ (phen = 1,10-phenanthroline) have been derivatized by an oxyamine function to attach them, via an oxime ether linkage, to a soluble 6 or 80 kDa poly-[N-(2-hydroxyethyl)-l-glutamine] polymer that contains pendent aldehyde groups. It is demonstrated that the resulting Ru-labeled polymers exhibit photophysical properties and a photochemistry that are comparable with those of the free, nonattached complexes. The photo-cross-linkings with the G-ODNs are clearly detected by gel electrophoresis with the 6 kDa Ru conjugates upon illumination.     

Synthesis,electrochemistry and spectroscopy of novel ruthenium and rhodium complexes bound to 2,2′-Bi-1,3-dithiol (TTF)

The (TTF)₂MCl₃ (M = Ru(II) and Rh(I), TTF (tetrathiafulvalene) = 2,2′-bi-1,3-dithiol) complexes have been prepared by direct reaction of TTF and the MCI₃ salt. Ultraviolet-visible spectra of the complexes are reported and indicate formation of a TTF⁺ cation with a reduced metal center. The presence of the oxidized TTF⁺ is further confirmed by resonance raman peaks near 1416 cm⁻¹. Electrochemistry indicates oxidation/reduction of the complexes is localized on the TTF ligand rather than from the metal.