Long-lifetime metal-ligand complexes as luminescent probes for DNA

We examined the intensity and anisotropy decays of DNA labeled with two ruthenium metalligand complexes, [Ru(bpy)₂(dppz)]²⁺ and [Ru(phe)₂(dppz)]²⁺. Both complexes display high emission anisotropies in the absence of rotational diffusion, making them suitable probes for rotational motions. When bound to DNA, these complexes display decay times as long as 294 ns, providing long-lived probes of DNA dynamics. The decay times of both complexes were rather insensitive to dissolved oxygen. We examined anisotropy decays of these complexes bound to B-form DNA. The anisotropy decays revealed correlation times near 10, 50, and several hundred nanoseconds, suggesting that these probes are sensitive to a wide range of DNA motions. The use of metalligand complexes should allow resolution of both the torsional and bending motions of DNA, the latter of which has been mostly inaccessible using shorter-lived fluorescent probes bound to DNA. Dedicated to Professor Robert F. Steiner upon his retirement     

Synthesis,Characterization, DNA Binding,Light Switch “On and Off”, Docking Studies and Cytotoxicity,of Ruthenium(II) and Cobalt(III) Polypyridyl Complexes

The novel ligand (dmbip) 2-(4-N, N-dimethylbenzenamine)1H-imidazo[4, 5-f][1, 10]phenanthroline and its complexes [Ru(phen)₂dmbip]²⁺ (1), [Ru(bpy)₂dmbip]²⁺ (2), [Co(phen)₂dmbip]³⁺ (3) and [Co(bpy)₂dmbip]³⁺ (4) [where phen?=?1, 10-phenanthroline, bpy?=?2, 2^′-bipyridine], 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, quenching studies, light switch “on and off”, salt dependent, sensor (cation and anion) studies, viscosity measurements, cyclic voltammetry, molecular modeling and docking studies. The four complexes were screened for Photo cleavage of pBR322 DNA, antimicrobial activity and cytotoxicity. The experimental results indicate that the four complexes can intercalate into DNA base pairs. The DNA-binding affinities of these complexes follow the order [Ru(phen)₂dmbip]²⁺ > [Co(phen)₂dmbip]³⁺ > [Ru(bpy)₂dmbip]²⁺ > [Co(bpy)₂dmbip]³⁺.     

Study of DNA Light Switch Ru(II) Complexes : Synthesis,Characterization, Photocleavage and Antimicrobial Activity

The three Ru(II) complexes of [Ru(phen)₂dppca]²⁺ (1) [Ru(bpy)₂dppca]²⁺ (2) and [Ru(dmb)₂dppca]²⁺ (3) (where phen = 1,10 phenanthroline, bpy = 2,2-bipyridine, dmb = 2 ,2-dimethyl 2′,2′-bipyridine and polypyridyl ligand containing a single carboxylate functionality dppca ligand (dipyridophenazine-11-carboxylic acid) have been synthesized and characterized. These complexes have been shown to act as promising calf thymus DNA intercalators and a new class of DNA light switches, as evidenced by UV-visible and luminescence titrations with Co²⁺ and EDTA, steady-state emission quenching by [Fe(CN)₆]⁴⁻ and KI, DNA competitive binding with ethidium bromide, viscosity measurements, and DNA melting experiments. The results suggest that 1, 2, and 3 complexes bind to CT-DNA through intercalation and follows the order 1 > 2 > 3. Under irradiation at 365 nm, the three complexes have also been found to promote the photocleavage of plasmid pBR322 DNA.     

Synthesis, DNA-binding, Cytotoxicity, Photo Cleavage, Antimicrobial and Docking Studies of Ru(II) Polypyridyl Complexes

Three Ruthenium(II) polypyridine complexes, [Ru(phen)₂(mipc)]²⁺(1), [Ru(bpy)₂(mipc)]²⁺ (2) and [Ru(dmb)₂(mipc)]²⁺(3) [mipc?=?2-(6-methyl-3-(1H-imidazo[4, 5-f][1,10]-phenanthroline-2-yl)-4H-chromene-4-one, phen?=?1,10-phenanthroline,bpy?=?2, 2′bipyridine,dmb?=?4, 4′-dimethyl-2, 2′-bipyridine] have been synthesized and characterized by elemental analysis, IR, UV–Vis, ¹H& ¹³C NMR and mass spectra. The DNA-binding properties of the Ruthenium(II) complexes were investigated by spectrophotometric methods, viscosity measurements and light switch studies. These three complexes have been focused on photo activated cleavage studies with pBR-322 and antimicrobial studies. Experimental results indicate that the three complexes intercalate into DNA base pairs and follows the order of 1?>?2?>?3 respectively. Molecular docking studies also support the DNA interactions with complexes through hydrogen bonding and vander Waal’s interactions. Cytotoxicity studies with Hela cell lines has been revealing about anti tumor activity of these complexes.     

Study of transient luminescence of three kinds of Ru complexes bound to DNA

The transient luminescence of three kinds of ruthenium complexes [Ru(bpy)₂(7-CH₃-dppz)]²⁺, [Ru(bpy)₂(7-F-dppz)]²⁺ and [Ru(phen)₂(7-F-dppz)]²⁺ bound to calf thymus DNA (ctDNA) has been studied by using the time-resolved spectroscopy. The results show that the luminescence is due to the radiative decay from the charge-transfer states to the ground state. By the interaction with DNA, the radiativeless rate of the photoexcited Ru complex molecules decreases, which results in the increase of luminescence lifetime and efficiency. The structure of the Ru complex has an important impact on the interaction with DNA. The [Ru(bpy)₂(7-CH₃-dppz)]²⁺ shows the longest luminescence lifetime (about 382 ns), while the [Ru(bpy)₂(7-F-dppz)]²⁺ shows the shortest lifetime (about 65 ns). The possible origin of the luminescence dynamics is discussed. Supported by the National Natural Science Foundation of China (Grant Nos. 60478013 and 20571089), the Key Program of Natural Science Foundation of Guangdong Province of China (Grant No. 05101819), the Doctoral Program Foundation of Institutions of Higher Education of China (Grant No. 20040558031) and the Scientific Research Foundation of Maoming College (Grant No. 203346)     

Synthesis,Characterization, DNA Binding Properties,Fluorescence Studies and Toxic Activity of Cobalt(III) and Ruthenium(II) Polypyridyl Complexes

The new ligand 4-(isopropylbenzaldehyde)imidazo[4,5-f ][1,10]phenanthroline (ippip) and its complexes [Ru(phen)₂(ippip)]²⁺(1),[Co(phen)₂(ippip)]³⁺(2),[Ru(bpy)₂(ippip)]²⁺(3),[Co(bpy)₂(ippip)]³⁺(4)(bpy=2,2-bipyridine) and (phen=1,10-phenanthroline) were synthesized and characterized by ES⁺-MS, ¹H and ¹³C NMR. The DNA binding properties of the four complexes were investigated by different spectrophotometric methods and viscosity measurements. The results suggest that complexes bind to calf thymus DNA (CT-DNA) through intercalation. When irradiated at 365 nm, the complexes promote the photocleavage of pBR322 DNA, and complex 1 cleaves DNA more effectively than 2, 3, 4 complexes under comparable experimental conditions. Furthermore, photocleavage studies reveal that singlet oxygen (¹O₂) plays a significant role in the photocleavage.     

The key Cl− ligand for metal‐to‐ligand charge transfer in mononuclear terpyridine ruthenium(II) and binuclear ruthenium(II) tetrapyridylpyrazine complexes

Electronic structures of binuclear ruthenium complexes [Ru₂(terpy)₂(tppz)]⁴⁺ ( 1A ) and [Ru₂Cl₂(L)₂(tppz)]²⁺ {L = bpy ( 2A ), phen ( 3A ), and dpphen ( 4A )} were studied by density functional theory calculations. Abbreviations of the ligands (Ls) are bpy = 2,2′‐bipyridine, phen = 1,10‐phenanthroline, dpphen = 4,7‐diphenyl‐1,10‐phenanthroline, terpy = 2,2′:6′,2″‐terpyridine, and tppz = tetrakis(2‐pyridyl)pyrazine. Their mononuclear reference complexes [Ru(terpy)₂]²⁺ ( 1B ) and [RuClL(terpy)]⁺ {L = bpy ( 2B ), phen ( 3B ), and dpphen ( 4B )} were also examined. Geometries of these mononuclear and binuclear Ru(II) complexes were fully optimized. Their geometric parameters are in good agreement with the experimental data. The binuclear complexes were characterized by electrospray ionization mass spectrometry, UV–Vis spectroscopy, and cyclic voltammograms. Hexafluorophosphate salts of binuclear ruthenium complexes of 3A and 4A were newly prepared. The crystal structure of binuclear complex 1A (PF₆)₄ was also determined. Orbital interactions were analyzed to characterize the metal‐to‐ligand charge‐transfer (MLCT) states in these complexes. The Cl^? ligand works to raise the orbital energy of the metal lone pair, which leads to the low MLCT state. Copyright © 2011 John Wiley & Sons, Ltd.     

Hypersensitivity in the Luminescence and 4f?C4f Absorption Properties of Mono- and Dinuclear EuIII and ErIII Complexes Based on Fluorinated ??-Diketone and Diimine/ Bis-Diimine Ligands

The results of our investigation on the sensitized luminescence properties of three Eu(III) ??-diketonate complexes of the form [Eu₂(fod)₆(??-bpm)], [Eu(fod)₃(phen)] and [Eu(fod)₃(bpy)] and 4f?C4f absorption properties of their Er(III) analogues ( fod = anion of 6,6,7,7,8,8,8- heptafluoro-2,2-dimethyl-3,5-octanedione, bpm = 2,2??-bipyrimidine, phen = 1,10-phenanthroline and bpy = 2,2??-bipyridyl) in a series of non-aqueous solvents are presented. The Eu(III) complexes are highly luminescent and their luminescence properties (intensity and band shape) are sensitive to the changes in the inner coordination sphere of the Eu(III) ion. The luminescence intensity of the mononuclear complexes in pyridine is drastically decreased. The coordination structure of the complexes in pyridine is transformed into a more symmetrical one which results into a slow radiative rate of the emission from the complexes. The ancillary ligands, phen and bpy are found better co-sensitizers as compared to the bpm to sensitize Eu(III)-luminescence. The 4f?C4f absorption properties (oscillator strength and band shape) of the Er(III) complexes demonstrate that ⁴G_11/2 ?? ⁴I_11/2 and ²H_11/2 ?? ⁴I_15/2 hypersensitive transitions of Er(III) are very sensitive in some coordinating solvents which reflects complex?Csolvent interaction in solution. The hypersensitive transitions of [Er(fod)₃(phen)] remain unaffected in any of the solvents and this complex retains its bulk composition in solution. The erbium complexes as well as the Er(fod)₃ chelate are invaded by DMSO. This solvent enters the inner coordination sphere by replacing heterocyclic ligand and the complexes acquire similar structure [Er(fod)₃(DMSO)₂] in this solvent. The results reveal that the luminescence and absorption properties of lanthanide complexes in solution can be controlled by tuning the coordination structure through ancillary ligands and donor solvents. This work shall prove useful in designing new biological applications with such probes.     

A Study on the Spectra Characterization of Ruthenium(Ii) Complexes

Abstract

A series of Ru(II) complexes have been synthesized, and their electronic spectra and NMR spectroscopy properties were characterized. the chemical shifts of aromatic protons of [Ru(bpy)₃] (PF₆)₂, [Ru(phen)₃](ClO₄)₂ and [Ru(bqdi)₃](PF₆) move downfield, but the resonance peaks of cis-Ru(bpy)₂Cl₂ shift upfield. Within the visible spectra of the ruthenium(II) complexes appear a relatively high oscillator strength which is referred to as the π(Ru)→? (ligands) transition.     

Fabrication of Ru(bpy)3-titanate nanotube nanocomposite and its application as sensitive solid-state electrochemiluminescence sensor material

A novel and facile method for effective immobilization of Ru(bpy)₃²⁺ within titanate nanotubes (TiNTs) and its application as a sensitive solid-state electrochemiluminescence (ECL) sensor material was studied. The process involved the formation of Ru(bpy)₃²⁺-titanate nanotube nanocomposite (Ru-TiNTs) via electrostatic interactions by mixing TiNTs and Ru(bpy)₃(ClO₄)₂ in aqueous medium. Then Ru-TiNTs were attached to the surface of a Pt electrode to form an ECL sensor. Characterization of Ru(bpy)₃²⁺-titanate nanotube nanocomposite was accomplished by transmission electron microscopy, X-ray photoelectron spectrum, and field emission scanning electron microscope. The electrochemistry and ECL behavior of Ru(bpy)₃²⁺ immobilized on TiNTs were studied with tripropylamine as a coreactant. As-prepared Ru-TiNTs exhibited very good stability and Ru(bpy)₃²⁺ species contained showed excellent ECL behavior. Therefore, the as-prepared Ru(bpy)₃²⁺-titanate nanotube nanocomposite exhibited great promise as new luminescent materials for solid-state ECL detection.     

Optical oxygen sensing materials based on trinuclear starburst ruthenium(II) complexes assembled in mesoporous silica

The preparation and oxygen sensing properties of optical materials based on two trinuclear starburst ruthenium(II) complexes: [Ru₃(bpy)₆(TMMB)]⁶⁺ (1) and [Ru₃(phen)₆(TMMB)]⁶⁺ (2) (bpy=2,2′-bpyridine, phen=1,10-phenathroline, TMMB=1,3,5-tris[2-(2′-pyridyl)benzimidazoyl]methylbenzene) assembled in two mesoporous silicate (MS) are described in this paper. The luminescence of Ru complexes/silicate assemble materials can be quenched by molecular oxygen with good sensitivity (I₀/I₁>5 for 2/MS and I₀/I₁>3 for 1/MS), indicating that trinuclear starburst Ru(II) complexes/MS systems are sensitive to oxygen molecules.     

Sonochemiluminescence in an aqueous solution of Ru(bpy)3Cl2

The sonochemiluminescence spectra of electron-excited ions ^*[Ru(bpy)₃]²⁺ was registered for the first time during sonolysis of argon saturated aqueous solutions of Ru(bpy)₃Cl₂ with low concentration. At single-bubble sonolysis, the luminescence band of ruthenium is recorded at a concentration of Ru(bpy)₃Cl₂ from 10⁻⁶ M, and at multibubble from 10⁻⁵ M. Possible mechanisms for the appearance of the band of a tris-bipyridyl ruthenium(II) complex on the background of an structureless continuum of water in the spectra of sonoluminescence are analyzed. Based on the results of the comparison of the sonoluminescence spectra of Ru(bpy)₃Cl₂ aqueous solutions with the sonoluminescence spectra of aqueous solutions of rhodamine B (which has a high quantum yield of photoluminescence) it was established that a possible mechanism of sonophotoluminescence does not play a decisive role in ruthenium sonoluminescence. The effect of radical acceptors (O₂, C₂H₅OH, Cd²⁺, I⁻) on ruthenium sonoluminescence is analyzed. The most significant mechanism for the formation of electron-excited ions ^*[Ru(bpy)₃]²⁺ during sonolysis is the sonochemiluminescence in oxidation-reduction reactions involving [Ru(bpy)₃]²⁺ ions and radical products of sonolysis of water (OH, H, e⁻_aq) in the solution volume.     

钌(Ⅱ)配合物与DNA相互作用的瞬态发光特性

以三种新合成的钌配合物[Ru(bpy)₂(7-CH₃-dppz)]²⁺、[Ru(bpy)₂(7-F-dppz)]²⁺、[Ru(phen)₂(7-F-dppz)]²⁺为研究对象,采用时间分辨的荧光光谱技术分别测量了这三种钌配合物与小牛胸腺DNA相互作用时的瞬态荧光动力学过程。结果表明:[Ru(bpy)₂(7-CH₃-dppz)]²⁺的发光寿命最长(约382 ns),而[Ru(bpy)₂(7-F-dppz)]²⁺的发光寿命最短(约65 ns)。分析表明:钌配合物的发光来源于配合物分子中的电荷转移态到基态的辐射跃迁。通过钌配合物与DNA的相互作用,使得配合物激发态分子的无辐射弛豫几率减小,从而导致发光寿命的增加。配合物的分子与DNA相互作用越强,激发态分子的无辐射弛豫几率越小,发光寿命也越长,最终导致高的发光效率。配合物的分子结构对配合物的分子与DNA的相互作用具有重要的影响。     

Mössbauer studies of photochemical reaction products of Ru(bpy)3 2+ iron cyanide double complexes

The reductive and the oxidative electron-transfer photochemical reaction system of light-irradiated the mix solutions of Ru(bpy)₃ ²⁺ with [Fe(CN)₆]^4–, [Fe(CN)₆]^3–, [Fe(CN)₅NO]^2– and PB (Prussian Blue) have been studied. The double complexes which isolated from the precipitates of the photochemical reaction have been identified by means of Mössbauer spectroscopy. In order to clarify the chemical states of these isolated double complexes, we have (prepared and) studied Mössbauer spectra of the double complexes such as [Ru(bpy)₃]₃[Fe(CN)₆]₂.14H₂O, [Ru(bpy)₃]₂[Fe(CN)₆].10H₂O, [Ru(bpy)₃][Fe(CN)₅NO].4H₂O, and [Ru(bpy)₃][PB]₂.xH₂O.     

Synthesis,Characterization and Luminescence Sensitivity with Variance in pH,DNA and BSA Binding Studies of Ru(II) Polypyridyl Complexes

Three ruthenium(II) polypyridyl complexes, [Ru(phen)₂(mip)](ClO₄)₂ (1) (phen =1,10-Phenanthroline), [Ru(bpy)₂(mip)](ClO₄)₂ (2) (bpy = 2,2’bipyridyl) and [Ru(dmb)₂(mip)](ClO₄)₂ (3) (dmb = 4, 4′-dimethyl 2, 2′-bipyridine), were synthesized with an intercalative ligand mip (2-morpholino-1H-imidazo[4,5-f][1, 10]phenanthroline) and characterized by ¹H, ¹³C–NMR, IR, UV-vis, mass spectra and elemental analysis. pH effect, ion selectivity (cations, anions) and solvent sensitivity of complexes were studied. The interaction of these complexes with DNA was performed using absorption, emission spectroscopy and viscosity measurements. The experimental results indicated that the two complexes interacted with calf thymus DNA (CT-DNA) by intercalative mode. BSA (Bovine Serum Albumin) protein binding of these complexes was studied by UV-visible and fluorescence techniques. The binding capacity of these complexes was explained theoretically by molecular docking method.     

Photoactive Ru Complex Embedded in Mesostructured MCM-41 Nanoparticles

The synthesis and characterization of photoactive hybrid materials based on [Ru(bpy)₃]²⁺ physically adsorbed within the channels of mesoporous MCM-41 silica nanoparticles is presented. A set of photoactive mesostructured hybrids with different guest loading has been prepared and characterized by X-ray diffraction, High Resolution Transmission Electron Microscopy, volumetric analyses, Diffuse Reflectance UV-Vis and Photoluminescence spectroscopies and lifetime measurements. The hybrids synthesis and the washing procedures, performed to investigate the host-guest interaction and the stability of the complex within the mesopores, didn??t affect the integrity of the structure and morphology of MCM-41 nanoparticles. The dispersion of [Ru(bpy)₃]²⁺ within the channels varied depending on the loading value and this is reflected in the different and peculiar photoluminescence features of the resulting hybrid materials. Photoluminescence spectroscopy evidenced that the use of MCM-41 nanoparticles ensures a better dispersion of the complex within the mesopores, if compared with traditional MCM-41. Further studies are in progress to investigate the interesting and promising features exhibited by such photoactive systems for advanced applications of electrochemiluminescence in optoelectronics and diagnostics.     

Ru L2,3 XANES theoretical simulation with DFT: A test of the core-hole treatment

Density functional theory (DFT)-based relativistic calculations were performed to model the Ru L-edge X-ray absorption near edge structure (XANES) spectra of the hexaammineruthenium complex [Ru(NH₃)₆]³⁺ and “blue dimer” water oxidation catalyst, cis,cis- [(bpy)₂(H₂O)Ru^IIIORu^III(OH₂)(bpy)₂]⁴⁺ (bpy is 2,2-bipyridine). Two computational approaches were compared: simulations without the core-hole and by modeling of the core-hole within the Z+1 approximation. Good agreement between calculated and experimental XANES spectra is achieved without including the core-hole. Simulations with algorithms beyond the Z+1 approximation were only possible in a framework of the scalar relativistic treatment. Time-dependent DFT (TD-DFT) was used to compute the Ru L-edge spectrum for [Ru(NH₃)₆]³⁺ model compound. Three different core-hole treatments were compared in a real-space full multiple scattering XANES modeling within the Green function formalism (implemented in the FEFF9.5 package) for the [Ru(Mebimpy)(bpm)(H₂O)]²⁺ complex. The latter approaches worked well in cases where spin–orbit treatment of relativistic effects is not required.     

Spectroscopy and photophysics of chloro-bis-bipyridyl complexes of ruthenium(II) with pyridine ligands

The absorption, luminescence, and luminescence excitation spectra of ruthenium(II) complexes cis-[Ru(bpy)₂(L)Cl]⁺[bpy=2,2′-bipyridyl; L=NH₃, pyrazine, pyridine, 4-aminopyridine, 4-picoline, isonicotinamide, 4-cyanopyridine, 4,4′-bipyridyl, or trans-1,2-bis(4-pyridyl)ethylene] in alcoholic (4: 1 EtOH-MeOH) solutions are studied. At 77 K, the quantum yields and decay times of the luminescence of the complexes are measured and the deactivation rate constants of the lowest electronically excited metal-to-ligand charge transfer state (³MLCT) are determined. The linear correlation between the energy of the lowest state ³MLCT d _π(Ru)>π*(bpy) of the cis-[Ru(bpy)₂(L)Cl]⁺ complexes and the parameter pK_a of the free 4-substituted pyridines and pyrazine used as ligands is established.     

Electrogenerated chemiluminescence quenching of Ru(bpy)3 2+ (bpy=2,2′-bipyridine) in the presence of acetaminophen,salicylic acid and their metabolites

Quenching of Ru(bpy) ₃²⁺ (bpy=2,2′-bipyridine) coreactant electrogenerated chemiluminescence (ECL) has been observed in the presence of acetaminophen, salicylic acid and related complexes. However, no quenching is observed with the acetylsalicylic acid. In most instances, quenching is observed with 100-fold excess of quencher (compared to ECL luminophore) with complete quenching observed between 10,000 and 100,000 fold excess. Fluorescence and UV–vis experiments coupled with bulk electrolysis support the formation of benzoquinone products upon electrochemical oxidation. The mechanism of quenching may involve the interaction of the electrochemically generated benzoquinone species with (i) the ^?Ru(bpy)₃²⁺ excited state or (ii) highly energetic coreactant radicals.     

甲基对钌配合物与DNA相互作用的瞬态发光特性的影响

采用时间分辩的发光光谱技术,测量了新合成的钌配合物［Ru(phen)2(7 CH3 dppz)］2+与小牛胸腺DNA相互作用的瞬态发光动力学过程,并与以往研究的配合物［Ru(phen)2(dppz)］2+和［Ru(phen)2(dppx)］2+的瞬态发光特性进行对比,更全面地研究了甲基对钌配合物与DNA相互作用的瞬态发光特性的影响.［Ru(phen)2(7 CH3 dppz)］2+的结构介于［Ru(phen)2(dppz)］2+和［Ru(phen)2(dppx)］2+之间,但发光寿命却比这两种配合物短,表明了甲基的疏水性、空间位阻及推电子能力对配合物的发光寿命均有影响.该结论为进一步研究配合物分子与DNA的相互作用的机理提供了一定的依据.