Evidence for symmetry reduction in excited states of [Ru(bpy)3]+ and related compounds

Photoselection and other spectroscopic data for [Ru(bpy)₃]²⁺, [Ru(phen)₃]²⁺, [Ru(bpy)(py)₄]²⁺ and [Os(bpy)₃]²⁺ suggest that the emitting state for the tris compounds may be localized on a single ring.     

Zero-phonon and vibronic structure of [Os(bpy)32+ doped into single-crystal [Ru(bpy)3](ClO4)2

Highly resolved emission and absorption spectra of [Os(bpy)₃]²⁺, doped into single-crystal [Ru(bpy)₃](ClO₄)₂, are reported. Our investigations, at low temperatures (2⩽T⩽50 K) and high magnetic fields ( 0⩽H⩽6 T ), lead to the following results: The three lowest excited states of [Os(bpy)₃]²⁺ in this matrix are identified from zero-phonon transitions lying at 14169 ± cm⁻¹ (line I), 14230± cm⁻¹ (line II), and 14380 ± 2 cm⁻¹ (line III). These transitions are found at the same energies (within the experimental error of ± 2 cm⁻¹) in absorption and emission. The extinction coefficients of II and III are ≈ 10³ XXX mol⁻¹ cm⁻¹ while the transition |0>→ |I> (line I) is strongly forbidden. However, under high magnetic fields this absorption line grows in due to a mixing of |I> with |II>. A large number of vibronic peaks is identified in the emission spectra. The corresponding vibrational modes are compared to Raman and IR data of [Ru(bpy)₃]²⁺ and [Os(bpy)₃]²⁺. Several distinct modes couple more strongly to the transition from the lowest excited state |I>, others to the transition from |II>, as is shown by investigating the magnetic field dependence of the emission spectra.     

Assessing a Spectroelectrochemical Sensor’s Performance for Detecting [Ru(bpy)3]2+ in Natural and Treated Water

A spectroelectrochemical sensor that combines three modes of selectivity in a single device was evaluated in natural and treated water samples using tris‐(2,2′‐bipyridyl) ruthenium(II) dichloride hexahydrate, [Ru(bpy)₃]²⁺, as a model analyte. The sensor was an optically transparent indium tin oxide (ITO) electrode coated with a thin film of partially sulfonated polystyrene‐block‐poly(ethylene‐ran‐butylene)‐block‐polystyrene (SSEBS). As the potential of the ITO electrode was cycled from +0.7 to +1.3 V, the analyte changed from the colored [Ru(bpy)₃]²⁺ complex to colorless [Ru(bpy)₃]³⁺ complex and the change in absorbance at 450 nm was used as the optical signal for quantification. Calibration curves were obtained for [Ru(bpy)₃]²⁺ in natural well water, river water and treated tap water with detection limits of 108, 139 and 264 nM, respectively. A standard addition method was developed to determine an ‘unknown’ spike addition concentration of [Ru(bpy)₃]²⁺ in well water. The spectroelectrochemical sensor determined the concentration of [Ru(bpy)₃]²⁺ spiked into a sample of Hanford well water to be 0.39±0.03 µM versus the actual concentration of 0.40 µM.     

Formation of [Ru(bpy)3]2+‐Containing Microstructures Induced by Electrostatic Assembly and Their Application in Solid‐State Detection of Electrochemiluminescence

Tris(2,2′‐bipyridine)ruthenium(II) ([Ru(bpy)₃]²⁺) is one of the most extensively studied and used electrochemiluminescent (ECL) compounds owing to its superior properties, which include high sensitivity and stability under moderate conditions in aqueous solution. In this paper we present a simple method for the preparation of [Ru(bpy)₃]²⁺‐containing microstructures based on electrostatic assembly. The formation of such microstructures occurs in a single process by direct mixing of aqueous solutions of [Ru(bpy)₃]Cl₂ and K₃[Fe(CN)₆] at room temperature. The electrostatic interactions between [Ru(bpy)₃]²⁺ cations and [Fe(CN)₆]^3? anions cause them to assemble into the resulting microstructures. Both the molar ratio and concentration of reactants were found to have strong influences on the formation of these microstructures. Most importantly, the resulting [Ru(bpy)₃]²⁺‐containing microstructures exhibit excellent ECL behavior and, therefore, hold great promise for solid‐state ECL detection in capillary electrophoresis (CE) or CE microchips.     

The circular dichroism of the charge-transfer bands of M(bpy)2+3 (M = Re,Ru, Os)

The absolute configuration of (?)_D-Ru(bpy)₃(ClO₄)₂ has been determined to be the right-hand screw configuration Δ. CD spectra of M(bpy)²⁺₃ (M = Fe, Ru, Os) doped in a uniaxial host. Lattice lead to a new assignment of CD bands in the MLCT region. The CD arises from intrinsically allowed electronic and magnetic transition dipole moments, the latter coming from metal-centered transitions.     

1H NMR assignment corrections and 1H, 13C, 15N NMR coordination shifts structural correlations in Fe(II), Ru(II) and Os(II) cationic complexes with 2,2′‐bipyridine and 1,10‐phenanthroline

¹H, ¹³C and ¹⁵N NMR studies of iron(II), ruthenium(II) and osmium(II) tris‐chelated cationic complexes with 2,2′‐bipyridine and 1,10‐phenanthroline of the general formula [M(LL)₃]²⁺ (M = Fe, Ru, Os; LL = bpy, phen) were performed. Inconsistent literature ¹H signal assignments were corrected. Significant shielding of nitrogen‐adjacent protons [H(6) in bpy, H(2) in phen] and metal‐bonded nitrogens was observed, being enhanced in the series Ru(II) → Os(II) → Fe(II) for ¹H, Fe(II) → Ru(II) → Os(II) for ¹⁵N and bpy → phen for both nuclei. The carbons are deshielded, the effect increasing in the order Ru(II) → Os(II) → Fe(II). Copyright © 2010 John Wiley & Sons, Ltd.     

The electronic structure of the metal-to-ligand charge-transfer states of M(bpy)2+3 (M = Fe,Ru, Os)

New spectroscopic absorption and luminescence data for the ions M(bpy)²⁺₃ (M = Fe, Ru, Os) provide the basis for a theoretical model of the electronic structure of these ions. An important aspect of the model is the essential localization of the triplet states, in contrast to the singlet states which are delocalized. The model accounts very well for the new and existing spectroscopic data.     

Influence of dissociation of tris(2,2′-bipyridyl)iron(II) cations on the time dependence of currents in clay-modified electrodes

The time dependence of the voltammetric waves of [Fe(bpy)₃]²⁺ adsorbed in clay-modified electrodes (CMES) differed greatly from those of [Ru(bpy)₃]²⁺ and [Os(bpy)₃]²⁺. The currents obtained with the ruthenium and osmium cations were essentially constant in the first 2 h that the CME spent in the blank electrolyte. For [Fe(bpy)₃]²⁺, the maximum currents were twice as large. After a sharp rise in the first few scans, they decreased rapidly to less than half of their maximum values after 40 min. The decrease was more rapid when the potential was scanned continuously or when the pH of the electrolyte was increased. Coulometry shows that a larger fraction of the adsorbed [Fe(bpy)₃] ²⁺ cations were oxidized and that they were oxidized much more rapidly than the other two cations. The unique behaviour of [Fe(bpy)₃]²⁺ is attributed to its dissociation in the CME. UV—visible spectroscopy shows that significant dissociation of this cation occurred on the time-scale of the electrochemical measurements. Much larger currents were also found for CMEs containing cis- or trans-[Ru(bpy)₂(H₂O)₂] ²⁺, and these are attributed to the greater mobility of adsorbed bis-bipyridyl cations.     

Homo- und Hetero-Zweikernkomplexe des D2h-symmetrischen Bis(chelat)-Liganden 2,2′-Bipyrimidin mit den elektronenreichen Metallfragmenten Mo(CO)4, Re(CO)3Cl, [Cu(PPh3)2]+ und [Ru(bpy)2]2+

Homo- and Heterodinuclear Complexes of the D_2h-symmetric Bis(chelate) Ligand 2,2′-Bipyrimidine with Electron-Rich Metal Fragments Mo(CO)₄, Re(CO)₃Cl, [Cu(PPh₃)₂]⁺, and [Ru(bpy)₂]²⁺ All homo- and heterodinuclear complexes (L_nM)(μ-bpym)(ML_n)′, bpym = 2,2′-bipyrimidine, ML_n (ML_n)′ = Mo(CO)₄, Re(CO)₃Cl, [Cu(PPh₃)₂]⁺, [Ru(bpy)₂]²⁺, have been synthesized and studied by cyclic voltammetry, absorption spectroscopy, and by electron spin resonance of singly reduced forms. The individual capabilities of the low-valent metal fragments to undergo oxidation and to shift the reduction potential of the bpym π acceptor ligand on coordination combine to result in variable electrochemical potential differences. After consideration of different Franck-Condon factors, absorption intensities, additional low-lying unoccupied orbitals of the bridging acceptor ligand and solvatochromic effects, we have assigned the considerably varying metal-to-ligand charge transfer transitions in the visible.     

[Ru(bpy)3]2+-trivalent titanium. A photochemical system with hydrogen production from aqueous solutions by visible light

Molecular hydrogen, detected by gas-chromatographic and mass-spectrometric measurements, was obtained by irradiating with visible light aqueous hydrochloridic solutions of [Ru(bpy)₃]²⁺ and trivalent titanium. The active species is the ³CT of [Ru(bpy)₃]²⁺, which is quenched by Ti(III). The suggested mechanism is an electron transfer with Ti(II) formation. The back reaction between [Ru(bpy)₃]³⁺ and Ti(II) is hindered by the very fast competitive reaction of Ti(II) (not stable in acid aqueous solutions) with H⁺, carrying to hydrogen evolution.     

Base-Modified DNA Labeled by [Ru(bpy)3]2+ and [Os(bpy)3]2+ Complexes: Construction by Polymerase Incorporation of Modified Nucleoside Triphosphates,Electrochemical and Luminescent Properties,and Applications

Modified 2′-deoxynucleoside triphosphates (dNTPs) bearing [Ru(bpy)₃]²⁺ and [Os(bpy)₃]²⁺ complexes attached via an acetylene linker to the 5-position of pyrimidines (C and U) or to the 7-position of 7-deazapurines (7-deaza-A and 7-deaza-G) have been prepared in one step by aqueous cross-couplings of halogenated dNTPs with the corresponding terminal acetylenes. Polymerase incorporation by primer extension using Vent (exo-) or Pwo polymerases gave DNA labeled in specific positions with Ru²⁺ or Os²⁺ complexes. Square-wave voltammetry could be efficiently used to detect these labeled nucleic acids by reversible oxidations of Ru^2+/3+ or Os^2+/3+. The redox potentials of the Ru²⁺ complexes (1.1–1.25 V) are very close to that of G oxidation (1.1 V), while the potentials of Os²⁺ complexes (0.75 V) are sufficiently different to enable their independent detection. On the other hand, Ru²⁺-labeled DNA can be independently analyzed by luminescence. In combination with previously reported dNTPs bearing ferrocene, aminophenyl, and nitrophenyl tags, the Os-labeled dATP has been successfully used for “multicolor” redox labeling of DNA and for DNA minisequencing.     

[Ru(bpy)3] nanocomposites containing heteropolyacids: Simple preparation and stable solid-state electrochemiluminescence detection application

In order to solidify the electrochemiluminescence (ECL) luminophor tris(2,2′-bipyridyl) ruthenium(II) ([Ru(bpy)₃]²⁺) onto the electrode surfaces robustly, the negative charged heteropolyacids (HPAs) moieties were utilized to attract and bond cations [Ru(bpy)₃]²⁺ via an adsorption method. The compositions and microstructures of the hybrid complexes were characterized by elemental analysis (EDS), spectroscopic techniques (UV-vis, FTIR) and field-emission scanning electron microscopy (FE-SEM). The electrochemical and ECL behaviors of the [Ru(bpy)₃]²⁺/[PW₁₂O₄₀]³⁻ hybrid complex contained in the solid film of the nanocomposites formed on the electrode surfaces were also studied. It was found that the corresponding solid membranes exhibited a diffusion-controlled voltammetric feature and excellent electrochemiluminescence behaviors. Hence potential prospects as new electrochemiluminescent materials for application in electroanalytical detection are envisioned.     

Ru(bpy) 3 2+ sensitized photopolymerization ofN,N′-methylene-bisacrylamide

Photochemical polymerization ofN,N′-methylenebisacrylamide (MBA) initiated by the dye-reducing agent rhodamine-B-allylthiourea (ATU) system is enhanced by the addition of small amounts oftris(2,2′-bipyridine)-ruthenium(II), Ru(bpy) ₃ ²⁺ , a result attributed to the efficient formation of chain-initiating allylthiourea radicals in the presence of Ru(bpy) ₃ ²⁺ ions. The rate of polymerization was found to be proportional to [Ru(bpy) ₃ ²⁺ ]^0.5, [rhodamine-B]^0.5, [ATU]^0.5 and [MBA]^1.0. A probable mechanism consistent with the observed results is proposed and discussed. TMC 2391     

Cathodic electrochemiluminescence and reversible electrochemistry of [Ru(bpy)3]2+/1+ in aqueous solutions on tricresyl phosphate-based carbon paste electrode with extremely high hydrogen evolution potential

Many cathodic electrochemiluminescence (ECL) systems require very negative potentials; it is difficult to achieve stable cathodic ECL in aqueous solutions because of hydrogen evolution and instability of intermediates. In this study, tricresyl phosphate-based carbon paste electrode (CPE) was used to achieve cathodic ECL. It exhibits no obvious hydrogen evolution even at a potential up to ?1.6 V and dramatically stabilizes electrogenerated [Ru(bpy)₃]⁺. Therefore, a reversible wave of [Ru(bpy)₃]^2+/1+ in aqueous solutions at carbon electrode has been observed for the first time, and cathodic ECL of [Ru(bpy)₃]²⁺/S₂O ₈ ^2? has been achieved. Under the optimum conditions, the plots of the ECL versus the concentration of S₂O ₈ ^2? are linear in the range of 10^?6 to 10^?2 M with the detection limit of 3.98?×?10^?7 M. Common anions have no effect on the ECL intensity of the [Ru(bpy)₃]²⁺/S₂O ₈ ^2? system. Since CPEs have been widely used, CPEs with high hydrogen evolution potential are versatile platforms for electrochemical study and cathodic ECL study.     

Decay of Ru(BPY)3 3+ in thin nafion layers catalyzed by Co(II)

Catalytic oxidation of water by Ru(bpy)₃ ³⁺ in the presence of Co²⁺ ions, well known in homogeneous solution, has been investigated in thin Nafion layers. Nafion layers on ITO electrodes were equilibrated with Ru(bpy)₃ ²⁺. Ru(bpy)₃ ³⁺ was produced by electrochemical oxidation after which the electrode was transferred into the reaction cell containing buffered Co²⁺ solution. The build up of Ru(bpy)₃ ²⁺ absorbance at 454 nm was followed spectrophotometrically. The reaction rate is proportional to [Ru(III)], [Co²⁺] and [HPO₄ ^2-]. We found no evidence for a pH effect in the range 6–8, and no inhibition by Ru(II). A limiting rate of formation of Ru(II) is observed at high Co²⁺ or phosphate ion concentrations. At high local concentration of the Ru complex in the Nafion layer (~ 0.5 M), two Ru(II) formation processes are observed, their rates differ by one order, but other features (effects of [Ru(III)], [Ru(II)], [Co²⁺], phosphate and pH) remain unchanged. These results are in contrast with homogeneous solution where the rate of build up of Ru(II) has been previously reported to be proportional to [Ru(III)], [Co²⁺] and [OH^-]², and inversely proportional to [Ru(II)]. A mechanism is proposed which accounts for these observations.     

Photophysical Properties and Heterogeneous Photoredox Catalytic Activities of Ru(bpy)3@InBTB Metal–Organic Framework (MOF)

Metal–organic frameworks (MOFs) with negatively charged frameworks are suitable for selectively encapsulating cationic guest ions via a cation-exchange process. Encapsulating photoactive [RuL₃]²⁺ polypyridine complexes into the preorganized mesoscale channels of a MOF is a good method for stabilizing the excited states of the complexes. Three new RuL₃@InBTB MOFs were prepared by encapsulating cationic [Ru(bpy)₃]²⁺ (bpy=2,2′-bipyridine), [Ru(phen)₃]²⁺ (phen=1,10-phenanthroline), and [Ru(bpz)₃]²⁺ (bpz=2,2′-bipyrazine) into the mesopores of a three-dimensional (3D) InBTB MOF (H₃BTB=1,3,5-benzenetribenzoic acid). The photophysical properties of the resulting materials were investigated by photoluminescence (PL) analysis. The photoredox catalytic activities were also investigated for the aza-Henry reaction, hydrogenation of dimethyl maleate, and decomposition of methyl orange under visible light irradiation at room temperature. RuL₃@InBTB MOFs were found to be very stable and highly recyclable photoredox catalytic systems.     

手性络合物[M(bpy)_2(phen)]~(2+)和[M(phen)_2(bpy)]~(2+)(M=Ru,Os)圆二色谱的理论解析

应用密度泛函理论,在B3LYP/LanL2DZ水平上对C2对称性的混配络合物[M(bpy)2(phen)]2+和[M(phen)2(bpy)]2+(M=Ru、Os;bpy=2,2'-bipyridine;phen=1,10-phenanthroline)在水溶液中的几何构型进行了优化,并用TDDFT/B3LYP方法和相同的基组计算了其激发能、旋转强度和振子强度,绘制了相应的圆二色谱(CD).在分析有关跃迁性质的基础上,对实验圆二色谱的谱带进行了明确的解析和指认,同时讨论了短波区激子裂分的规律性.结果表明:四种络合物在长波区(λ>320nm)的CD吸收带主要是由d-π*跃迁产生的荷移谱带;短波区(λ<320nm)则是配体上平行于长轴的π-π*跃迁产生的激子耦合带,且对于Λ构型表现为正的手性激子裂分.其中,[M(bpy)2(phen)]2+只显示出正负两个激子带,分属于联吡啶和邻菲咯啉配体;而[M(phen)2(bpy)]2+则有三个激子带,其中左侧的两个(一负一正)属于邻菲咯啉配体,右侧的正带则属于联吡啶配体.此外,尽管激子耦合属于远程相互作用,但用TDDFT计算的激子裂分样式仍是正确的.这些结论对于深入理解有...     

Thiosemicarbazone complexes of the platinum metals. A story of variable coordination modes

Salicylaldehyde thiosemicarbazone (H₂saltsc) reacts with [M(PPh₃)₃X₂] (M = Ru, Os; X = Cl, Br) to afford complexes of type [M(PPh₃)₂(Hsaltsc)₂], in which the salicylaldehyde thiosemicarbazone ligand is coordinated to the metal as a bidentate N,S-donor forming a four-membered chelate ring. Reaction of benzaldehyde thiosemicarbazones (Hbztsc-R) with [M(PPh₃)₃X₂] also affords complexes of similar type, viz. [M(PPh₃)₂(bztsc-R)₂], in which the benzaldehyde thiosemicarbazones have also been found to coordinate the metal as a bidentate N,S-donor forming a four-membered chelate ring as before. Reaction of the Hbztsc-R ligands has also been carried out with [M(bpy)₂X₂] (M = Ru, Os; X = Cl, Br), which has afforded complexes of type [M(bpy)₂(bztsc-R)]⁺, which have been isolated as perchlorate salts. Coordination mode of bztsc-R has been found to be the same as before. Structure of the Hbztsc-OMe ligand has been determined and some molecular modelling studies have been carried out determine the reason for the observed mode of coordination. Reaction of acetone thiosemicarbazone (Hactsc) has then been carried out with [M(bpy)₂X₂] to afford the [M(bpy)₂(actsc)]ClO₄ complexes, in which the actsc ligand coordinates the metal as a bidentate N,S-donorformingafive-membered chelate ring. Reaction of H₂saltsc has been carried out with [Ru(bpy)₂Cl₂] to prepare the [Ru(bpy)₂(Hsaltsc)]ClO₄ complex, which has then been reacted with one equivalent of nickel perchlorate to afford an octanuclear complex of type [Ru(bpy)₂(saltsc-H)₄Ni₄](ClO₄)₄.     

金属离子对联吡啶钌电致化学发光影响的研究

在玻碳电极上, 联吡啶钌[Ru(bpy)₃^2＋]于＋1.50 V (vs. Ag/AgCl)左右被氧化为Ru(bpy)₃^3＋, 该氧化态离子与碱性水溶液中(pH 8.2)的OH•反应生成激发态的[Ru(bpy)₃^2＋*]而发光. 研究比较了15种金属离子对Ru(bpy)₃^2＋碱性水溶液电致化学发光的影响, 并对这些影响进行了初步的解释.     

Use of the Cationic Fragments [Ru(η5-C5H5) (MeCN)3]+ and [M(η6-C6H5R)(MeCN)3]+ (M=Os, Ru; R=H, Me) as Ionic Coupling Reagents in the Synthesis of the Clusters [Os4M2(CO)12(η6-C6H5R)], [Os4M(CO)12(η6-C6H6)(Au2dppm)] and [Os5Ru(CO)15(η5-C5H5)(AuPPh3)]*

The clusters [H₂Os₄M(CO)₁₂eta⁶-C₆H₆)] (M=Os, Ru) may be deprotonated to generate anions [Os₄M(CO)₁₂eta⁶-C₆H₆)]^2- which react with [M′eta⁶-C₆H₅R) (MeCN)₃]²⁺(M^′=Os, Ru; R=H, Me) to give the bicapped tetrahedral clusters [Os₄(CO)₁₂MM′eta⁶-C₆H₅R)₂]. Whereas [Os₄(CO)₁₂M₂eta⁶-C₆H₆)₂] (M=Os, Ru) have one Meta⁶-C₆H₆) unit in a site connected to three other metals, {3}, and one in a site connected to four other metals, {4}, [Os₄(CO)₁₂OsRueta⁶-C₆H₆)₂] has the Rueta⁶-C₆H₆) unit in the {3} site irrespective of whether the Os or Ru anion is capped. Coupling of these anions with Au₂dppm yields [Os₄M(CO)₁₂eta⁶-C₆H₆)(Au₂dppm)] (M=Os, Ru), which have the arene ligand in the axial site of a trigonal bipyramid and the digold unit capping two faces. Reduction of [H₂Os₅(CO)₁₅] with K/Ph₂CO and coupling with [Rueta⁵-C₅H₅)(MeCN)₃]²⁺yields the monoanion [Os₅(CO)₁₅Rueta⁵-C₅H₅)]^? which reacts with [AuPPh₃]⁺ generating [Os₅(CO)₁₅Rueta⁵-C₅H₅)(AuPPh₃)] with the “Ru(C₅H₅)” unit in the terminal {3} site.