Direct ion exchange of tris(2,2'-bipyridine)ruthenium(II) into an alpha-zirconium phosphate framework

The first direct ion exchange of a luminescent metal complex into an alpha-zirconium phosphate framework has been accomplished. A hydrated form of alpha-ZrP, with an expanded 10.3 A interlayer distance, has been used for the intercalation of Ru(bpy)(3)(2+), resulting in further expansion to 15.2 A. The Ru(bpy)(3)(2+) luminescence band is slightly blue-shifted. High Ru(bpy)(3)(2+) loadings lead to luminescence self-quenching.     

Nanoscale-enhanced Ru(bpy)3(2+) electrochemiluminescence labels and related aptamer-based biosensing system

A unique multilabeling at a single-site protocol of the Ru(bpy)(3)(2+) electrochemiluminescence (ECL) system is proposed. Nanoparticles (NPs) were used as assembly substrates to enrich ECL co-reactants of Ru(bpy)(3)(2+) to construct nanoscale-enhanced ECL labels. Two different kinds of NP substrates [including semiconductor NPs (CdTe) and noble metal NPs (gold)] capped with 2-(dimethylamino)ethanethiol (DMAET) [a tertiary amine derivative which is believed to be one of the most efficient of co-reactants of the Ru(bpy)(3)(2+) system] were synthesized through a simple one-pot synthesis method in aqueous media. Although both CdTe and gold NPs realized the enrichment of ECL co-reactants, they presented entirely different ECL performances as nanoscale ECL co-reactants of Ru(bpy)(3)(2+). The different effects of these two NPs on the ECL of Ru(bpy)(3)(2+) were studied. DMAET-capped CdTe NPs showed enormous signal amplification of Ru(bpy)(3)(2+) ECL, whereas DMAET-capped gold NPs showed a slight quenching effect of the ECL signal. DMAET-capped CdTe NPs can be considered to be excellent nanoscale ECL labels of the Ru(bpy)(3)(2+) system, as even a NP solution sample of 10(-18) M was still detectable after an electrostatic self-assembly concentration process. DMAET-capped CdTe NPs were further applied in the construction of aptamer-based biosensing system for proteins and encouraging results were obtained.     

A Tetranuclear Ruthenium(II) Complex Containing both Electron-Rich and Electron-Poor Bridging Ligands. Absorption Spectrum, Luminescence, Redox Behavior, and Intercomponent Energy Transfer

The first luminescent and redox active multinuclear Ru(II) compound containing both electron-poor (2,3-bis(2-pyridyl)pyrazine, 2,3-dpp) and electron-rich (3,5-bis(pyridyn-2-yl)-1,2,4-triazole, Hbpt) polypyridine bridging ligands has been synthesized. The novel compound is [(bpy)(2)Ru(&mgr;-bpt)Ru{(&mgr;-2,3-dpp)Ru(bpy)(2)}(2)](7+) (1; bpy = 2,2'-bipyridine). Its absorption spectrum, luminescence properties, and redox behavior have been studied and are compared with the properties of the parent complexes [Ru{(&mgr;-2,3-dpp)Ru(bpy)(2)}(3)](8+) (2) and [(bpy)(2)Ru(&mgr;-bpt)Ru(bpy)(2)](3+) (3). The absorption spectrum of 1 is dominated by ligand-centered bands in the UV region and by metal-to-ligand charge transfer bands in the visible region. Excited states and oxidation and reduction processes are localized in specific sites of the multicomponent structure. However, perturbations of each component on the redox and excited states of the others, as well as electronic interactions between the chromophores, can be observed. Intercomponent energy transfer from the upper-lying (&mgr;-bpt)(bpy)Ru-->bpy CT excited state of the Ru(bpy)(2)(&mgr;-bpt)(+) component to the lower-lying (bpy)(2)Ru-->&mgr;-2,3-dpp CT excited state of the Ru(bpy)(2)(&mgr;-2,3-dpp)(2+) subunit(s) is efficient in 1 in fluid solution at room temperature, whereas this process is not observed in a rigid matrix at 77 K. A two-step energy transfer mechanism is proposed to explain the photophysical properties of the new compound.     

Self assembled composites of luminescent Ru(II) metallopolymers and the Dawson polyoxometalate α-[Mo18O54(SO4)2]4-

The interaction of two luminescent metallopolymers; [Ru(bpy)(2)(PVP)(10)](2+) and [Ru(bpy)(2)(CAIP)co-poly(7)](+), where bpy is 2,2'-bipyridyl, PVP is polyvinylpyridine, and (CAIP)co-poly(7) is poly(styrene(6)-co-p-(aminomethyl)styrene) amide linked to 2-(4-carboxyphenyl)imidazo[4,5-f] [1,10]phenanthroline, with the Dawson polyoxomolybdate α-[Mo(18)O(54)(SO(4))(2)](4-) is described. Both metallopolymers undergo electrostatic association with the polyoxometalate. From both electronic and luminescence spectroscopy the thermodynamic products were determined to be {[Ru(bpy)(2)(PVP)(10)](4.5)[Mo(18)O(54)(SO(4))(2)]}(5+) and {[Ru(bpy)(2)(CAIP)co-poly(7)](5)[Mo(18)O(54)(SO(4))(2)]}(+), i.e. in both instances, the number of ruthenium centres in the cluster exceeds the number required for charge neutralization of the molybdate centre. Association quenches the luminescence of the metallopolymer although, consistent with the excess of Ru(ii) present in the associated composites, emission is not completely extinguished even when a large excess of [Mo(18)O(54)(SO(4))(2)](4-) is present. The observed emission lifetime was not affected by [Mo(18)O(54)(SO(4))(2)](4-) therefore quenching was deemed static. The luminescent intensity data was found to fit best to a (sphere of action) Perrin model from which the radii of the quenching were calculated as 4.6 ? and 5.8 ? for [Ru(bpy)(2)(PVP)(10)](2+) and [Ru(bpy)(2)(CAIP co-poly)(7)](+) respectively. Both UV/Vis and resonance Raman data indicate the presence of a new optical transition centered around 490 nm for the composite, {[Ru(bpy)(2)(PVP)(10)](4.5)[Mo(18)O(54)(SO(4))(2)]}(5+) but not for {[Ru(bpy)(2)(CAIP)co-poly(7)](5)[Mo(18)O(54)(SO(4))(2)]}(+). This indicates strong electronic interaction between the metal centres in the former composite, which despite good thermodynamic analogy, is not observed for {[Ru(bpy)(2)(CAIP)co-poly(7)](5)[Mo(18)O(54)(SO(4))(2)]}(+). These results are consistent with photoelectrochemical studies of layer by layer assemblies of these films which indicate that the ruthenium centre sensitizes polyoxometalate photo-oxidation of benzyl alcohol in {[Ru(bpy)(2)(PVP)(10)](4.5)[Mo(18)O(54)(SO(4))(2)]}(5+) but not in {[Ru(bpy)(2)(CAIP)co-poly(7)](5)[Mo(18)O(54)(SO(4))(2)]}(+).     

Development of a heterobimetallic Ru(II)-Cu(II) complex for highly selective and sensitive luminescence sensing of sulfide anions

A heterobimetallic ruthenium(II)-copper(II) complex-based luminescent chemosensor, [Ru(bpy)(2)(bpy-DPA)Cu](4+) (bpy: 2,2'-bipyridine; bpy-DAP: 4-methyl-4'-[N,N-bis(2-picolyl)amino-methylene]-2,2'-bipydine), has been designed and synthesized for the highly selective and sensitive recognition and detection of sulfide anions in 100% aqueous solutions. Owing to the high affinity of sulfide to Cu(II), the non-luminescent chemosensor can specifically and rapidly react with sulfide to yield the corresponding ruthenium(II) complex, [Ru(bpy)(2)(bpy-DPA)](2+), accompanied by the remarkable luminescence enhancement. The dose-dependent luminescence enhancement of the sensor shows a good linearity with a detection limit of 20.7 nM for sulfide anions. The novel luminescence sensor has a widely available pH range from 4.5 to 10 and an excellent response selectivity to sulfide only even in the presence of various other anions. Based on this chemosensor, a rapid, selective and sensitive luminescence method for the detection of sulfide anions in wastewater samples was established. The coefficient variations (CVs) of the method are less than 3.1%, and the recoveries are in the range of 90.9-108.5%.     

Photophysical and novel charge-transfer properties of adducts between [RuII(bpy)3]2+ and [S2Mo18O62]4-

The photophysical properties of acetonitrile solutions of [Ru(bpy)(3)](2+) and [S(2)Mo(18)O(62)](4-) are described. We discuss evidence for ion cluster formation in solution and the observation that despite the strong donor ability of the excited state of [Ru(bpy)(3)](2+) and its inherent photolability, adducts with [S(2)Mo(18)O(62)](4-) were photostable. Photophysical studies suggest that the quenching of the [Ru(bpy)(3)](2+) excited state by [S(2)Mo(18)O(62)](4-) occurs via a static mechanism and that binding is largely electrostatic in nature. Evidence is provided from difference spectroscopy and luminescence excitation spectroscopy for good electronic communication between [Ru(bpy)(3)](2+) and [S(2)Mo(18)O(62)](4-) with the presence of a novel, luminescent, inter-ion charge-transfer transition. The identity of the transition is confirmed by resonance Raman spectroscopy.     

Ruthenium(II) dendrimers containing carbazole-based chromophores as branches

Three new luminescent and redox-active Ru(II) complexes containing novel dendritic polypyridine ligands have been synthesized, and their absorption spectra, luminescence properties (both at room temperature in fluid solution and at 77 K in rigid matrix), and redox behavior have been investigated. The dendritic ligands are made of 1,10-phenanthroline coordinating subunits and of carbazole groups as branching sites. The first and second generation species of this novel class of dendritic ligands (L1 and L2, respectively; see Figure 1 for their structural formulas) have been prepared and employed. The metal dendrimers investigated are [Ru(bpy)(2)(L1)](2+) (1; bpy = 2,2'-bipyridine), [Ru(bpy)(2)(L2)](2+) (2), and [Ru(L1)(3)](2+) (3; see Figure 2). For the sake of completeness and comparison purposes, also the absorption spectra, redox behavior, and luminescence properties of L1 and L2 have been studied, together with the properties of 3,6-di(tert-butyl)carbazole (L0) and [Ru(bpy)(2)(phen)](2+) (4, phen = 1,10-phenanthroline). The absorption spectra of the free dendritic ligands show features which can be assigned to the various subunits (i.e., carbazole and phenanthroline groups) and additional bands at lower energies (at lambda > 300 nm) which are assigned to carbazole-to-phenanthroline charge-transfer (CT) transitions. These latter bands are significantly red-shifted upon acid and/or zinc acetate addition. Both L1 and L2 exhibit relatively intense luminescence at room temperature in fluid solution (lifetimes in the nanosecond time scale, quantum yields of the order of 10(-2)-10(-1)) and at 77 K in rigid matrix (lifetimes in the millisecond time scale). Such a luminescence is assigned to CT states at room temperature and to phenanthroline-centered pi-pi triplet levels at 77 K. The room-temperature luminescence of L1 and L2 is totally quenched by acid or zinc acetate. The metal dendrimers exhibit the typical absorption and luminescence properties of Ru(II) polypyridine complexes. In particular, metal-to-ligand charge-transfer (MLCT) bands dominate the visible absorption spectra, and formally triplet MLCT levels govern the excited-state properties. Excitation spectroscopy evidences that all the light absorbed by the dendritic branches is transferred with unitary efficiency to the luminescent MLCT states in 1-3, showing that the new metal dendrimers can be regarded as efficient light-harvesting antenna systems. All the free ligands and metal dendrimers exhibit a rich redox behavior (except L2 and 3, whose redox behavior was not investigated because of solubility reasons), with clearly attributable reversible carbazole- and metal-centered oxidation and polypyridine-centered reduction processes. The electronic interaction between the carbazole redox-active sites of the dendritic ligands is affected by Ru(II) coordination.     

Preparation and multicolor electrochromic performance of a WO3/tris(2,2'-bipyridine)ruthenium(II)/polymer hybrid film

A tungsten trioxide (WO(3))/tris(2,2'-bipyridine)ruthenium(II) ([Ru(bpy)(3)](2+); bpy=2,2'-bipyridine)/poly(sodium 4-styrenesulfonate) (PSS) hybrid film was prepared by electrodeposition from a colloidal triad solution containing peroxotungstic acid (PTA), [Ru(bpy)(3)](2+), and PSS. A binary solution of [Ru(bpy)(3)](2+) and PTA (30 vol % ethanol in water) gradually gave an orange precipitate, possibly caused by the electrostatic interaction between the cationic [Ru(bpy)(3)](2+) and the anionic PTA. The addition of PSS to the binary PTA/[Ru(bpy)(3)](2+) solution remarkably suppressed this precipitation and caused a stable, colloidal triad solution to form. The spectrophotometric measurements and lifetime analyses of the photoluminescence from the excited [Ru(bpy)(3)](2+) ion in the colloidal triad solution suggested that the [Ru(bpy)(3)](2+) ion is partially shielded from electrostatic interaction with anionic PTA by the anionic PSS polymer chain. The formation of the colloidal triad made the ternary [Ru(bpy)(3)](2+)/PTA/PSS solution much more redox active. Consequently, the rate of electrodeposition of WO(3) from PTA increased appreciably by the formation of the colloidal triad, and fast electrodeposition is required for the unique preparation of this hybrid film. The absorption spectrum of the [Ru(bpy)(3)](2+) ion in the film was close to its spectrum in water, but the photoexcited state of the [Ru(bpy)(3)](2+) ion was found to be quenched completely by the presence of WO(3) in the hybrid film. The cyclic voltammogram (CV) of the hybrid film suggested that the [Ru(bpy)(3)](2+) ion performs as it is adsorbed onto WO(3) during the electrochemical oxidation. An ohmic contact between the [Ru(bpy)(3)](2+) ion and the WO(3) surface could allow the electrochemical reaction of adsorbed [Ru(bpy)(3)](2+). The composition of the hybrid film, analyzed by electron probe microanalysis (EPMA), suggested that the positive charge of the [Ru(bpy)(3)](2+) ion could be neutralized by partially reduced WO(3)(-) ions, in addition to Cl(-) and PSS units, based on the charge balance in the film. The electrostatic interaction between the WO(3)(-) ion and the [Ru(bpy)(3)](2+) ion might be responsible for forming the electron transfer channel that causes the complete quenching of the photoexcited [Ru(bpy)(3)](2+) ion, as well as the formation of the ohmic contact between the [Ru(bpy)(3)](2+) ion and WO(3). A multicolor electrochromic performance of the WO(3)/[Ru(bpy)(3)](2+)/PSS hybrid film was observed, in which transmittances at 459 and 800 nm could be changed, either individually or at once, by the selection of a potential switch. Fast responses, of within a few seconds, to these potential switches were exhibited by the electrochromic hybrid film.     

Luminescence of tris(2,2'-bipyridine)ruthenium(II) cations ([Ru(bpy)(3)]2+) adsorbed in mesoporous silicas modified with sulfonated phenethyl group

The adsorption of tris(2,2'-bipyridine)ruthenium(II) ([Ru(bpy)(3)]2+) complex cation into modified mesoporous silicas was investigated. In order to immobilize [Ru(bpy)(3)]2+, the mesopore surface was modified with sulfonic acid groups by the reactions between MCM-41 and phenethyl(dichloro)methylsilane and the subsequent sulfonation of the attached phenethyl groups with chlorosulfonic acid. The modified mesoporous silicas effectively adsorbed [Ru(bpy)(3)]2+ from ethanol solution. It was thought that the effective adsorption was the cause of the cooperative effects of the electrostatic interactions between [Ru(bpy)(3)]2+ cation and sulfonic acid group and the interactions between the phenyl rings on the mesopore surface and the bipyridine rings of the complex. The variation of the position and the intensity of the luminescence of [Ru(bpy)(3)]2+ suggested that the average distance between the adjacent [Ru(bpy)(3)]2+ changed with the loading amounts.     

Mononuclear and dinuclear complexes of dibenzoeilatin: synthesis, structure, and electrochemical and photophysical properties

This work describes a study of Ru(II) and Os(II) polypyridyl complexes of the symmetrical, fused-aromatic bridging ligand dibenzoeilatin (1). The synthesis, purification, and structural characterization by NMR of the mononuclear complexes [Ru(bpy)(2)(dbneil)](2+) (2), [Ru(tmbpy)(2)(dbneil)](2+) (3), and [Os(bpy)(2)(dbneil)](2+) (4), the homodinuclear complexes [[Ru(bpy)(2)](2)[micro-dbneil]](4+) (5), [[Ru(tmbpy)(2)](2)[micro-dbneil]](4+) (6), and [[Os(bpy)(2)](2)[micro-dbneil]](4+) (7), and the heterodinuclear complex [[Ru(bpy)(2)][micro-dbneil][Os(bpy)(2)]](4+) (8) are described, along with the crystal structures of 4, 6, and 7. Absorption spectra of the mononuclear complexes feature a low-lying MLCT band around 600 nm. The coordination of a second metal fragment results in a dramatic red shift of the MLCT band to beyond 700 nm. Cyclic and square wave voltammograms of the mononuclear complexes exhibit one reversible metal-based oxidation, as well as several ligand-based reduction waves. The first two reductions, attributed to reduction of the dibenzoeilatin ligand, are substantially anodically shifted compared to [M(bpy)(3)](2+) (M = Ru, Os), consistent with the low-lying pi orbital of dibenzoeilatin. The dinuclear complexes exhibit two reversible, well-resolved, metal-centered oxidation waves, despite the chemical equivalence of the two metal centers, indicating a significant metal-metal interaction mediated by the conjugated dibenzoeilatin ligand. Luminescence spectra, quantum yield, and lifetime measurements at room temperature in argon-purged acetonitrile have shown that the complexes exhibit (3)MLCT emission, which occurs in the IR-region between 950 and 1300 nm. The heterodinuclear complex 8 exhibits luminescence only from the Ru-based fragment, the intensity of which is less than 1% of that observed in the corresponding homodinuclear complex 5; no emission from the Os-based unit is observed, and an intramolecular quenching constant of k(q) > or = 3 x10(9) s(-)(1) is evaluated. The nature of the quenching process is briefly discussed.     

Comparison of Physical and Photophysical Properties of Monometallic and Bimetallic Ruthenium(II) Complexes Containing Structurally Altered Diimine Ligands

The physical and photophysical properties of a series of monometallic, [Ru(bpy)(2)(dmb)](2+), [Ru(bpy)(2)(BPY)](2+), [Ru(bpy)(Obpy)](2+) and [Ru(bpy)(2)(Obpy)](2+), and bimetallic, [{Ru(bpy)(2)}(2)(BPY)](4+) and [{Ru(bpy)(2)}(2)(Obpy)](4+), complexes are examined, where bpy is 2,2'-bipyridine, dmb is 4,4'-dimethyl-2,2'-bipyridine, BPY is 1,2-bis(4-methyl-2,2'-bipyridin-4'-yl)ethane, and Obpy is 1,2-bis(2,2'-bipyridin-6-yl)ethane. The complexes display metal-to-ligand charge transfer transitions in the 450 nm region, intraligand pi --> pi transitions at energies greater than 300 nm, a reversible oxidation of the ruthenium(II) center in the 1.25-1.40 V vs SSCE region, a series of three reductions associated with each coordinated ligand commencing at -1.3 V and ending at approximately -1.9 V, and emission from a (3)MLCT state having energy maxima between 598 and 610 nm. The Ru(III)/Ru(II) oxidation of the two bimetallic complexes is a single, two one-electron process. Relative to [Ru(bpy)(2)(BPY)](2+), the Ru(III)/Ru(II) potential for [Ru(bpy)(2)(Obpy)](2+) increases from 1.24 to 1.35 V, the room temperature emission lifetime decreases from 740 to 3 ns, and the emission quantum yield decreases from 0.078 to 0.000 23. Similarly, relative to [{Ru(bpy)(2)}(2)(BPY)](4+), the Ru(III)/Ru(II) potential for [{Ru(bpy)(2)}(2)(Obpy)](4+) increases from 1.28 to 1.32 V, the room temperature emission lifetime decreases from 770 to 3 ns, and the room temperature emission quantum yield decreases from 0.079 to 0.000 26. Emission lifetimes measured in 4:1 ethanol:methanol were temperature dependent over 90-360 K. In the fluid environment, emission lifetimes display a biexponential energy dependence ranging from 100 to 241 cm(-)(1) for the first energy of activation and 2300-4300 cm(-)(1) for the second one. The smaller energy is attributed to changes in the local matrix of the chromophores and the larger energy of activation to population of a higher energy dd state. Explanations for the variations in physical properties are based on molecular mechanics calculations which reveal that the Ru-N bond distance increases from 2.05 ? (from Ru(II) to bpy and BPY) to 2.08 ? (from Ru(II) to Obpy) and that the metal-to-metal distance increases from approximately 7.5 ? for [{Ru(bpy)(2)}(2)(Obpy)](4+) to approximately 14 ? for [{Ru(bpy)(2)}(2)(BPY)](4+).     

Solid-state light-emitting devices based on the tris-chelated ruthenium(II) complex. 4. High-efficiency light-emitting devices based on derivatives of the tris(2,2'-bipyridyl) ruthenium(II) complex

Light-emitting devices from the tris(2,2'-bipyridyl)ruthenium(II) complex [Ru(bpy)(3)(2+)] and new derivatives thereof were prepared. Due to the electrochemical nature of the device operation, single-layer devices in an ITO/ Ru(bpy)(3)(2+) complex + PMMA/Ag sandwich configuration achieved very high external quantum efficiencies. The derivatives of the Ru(bpy)(3)(2+) complex were designed and synthesized to inhibit self-quenching of the excited state by adding different alkyl substituents on the bipyridyl ligands. As a result, devices that contain these new Ru(bpy)(3)(2+) complexes show a higher photoluminescence and electroluminescence efficiency than devices made from the unmodified Ru(bpy)(3)(2+) complex. External quantum efficiencies up to 5.5% at brightnesses in the range of 10-50 cd/m(2) are reported. In addition, the response time of such devices (which is a result of the electrochemical operation) has been shortened dramatically. An "instantaneous" light emission is achieved for devices that employ smaller counterions such as BF(4)(-) to increase the ionic conductivity. Such a device shows a response time of less than 1 s to emit 10-20 cd/m(2) after the operating voltage of 2.4 V has been applied.     

DNA mismatch detection by resonance energy transfer between ruthenium(II) and osmium(II) tris(2,2'-bipyridyl) chromophores

Octahedral tris-chelate complexes [M(II)(bpy)(3)](2+) (M = Ru or Os, bpy = 2,2'-bipyridyl), covalently attached to the 3'- and 5'-phosphates of two oligonucleotides, are juxtaposed when hybridized contiguously to a fully complementary DNA target. Visible metal-to-ligand charge-transfer (MLCT) excitation of the [Ru(II)(bpy)(3)](2+) unit leads to resonance energy transfer to the MLCT state of the [Os(II)(bpy)(3)](2+) moiety, with the energy transfer efficiency depending on the degree of hybridization. The extent of attenuation of the intense red luminescence from the Ru(II) chromophore hence allows highly sensitive structural probing of the assembly and constitutes a novel approach to DNA sensing which is capable of detecting mutations.     

具不同官能团钌(Ⅱ)邻菲啰啉配合物氧淬灭性能的比较研究

设计并制备具不同官能团的钌(Ⅱ)邻菲啰啉配合物——[Ru(bpy)2(phen-NO2)](PF6)2(1),[Ru(bpy)2(phen-Br)](PF6)2(2),[Ru(bpy)2(phen-NH2)](PF6)2(3),[Ru(bpy)2(bphen)](PF6)2(4),其中,bpy为2,2’-联吡啶,phen-NO2为5-硝基-邻菲啰啉,phen-Br为5-溴-1,10-菲啰啉,phen-NH2为5-氨基-邻菲啰啉,bphen为4,7-二苯基-邻菲啰啉.借助核磁共振(NMR)、红外光谱(FTIR)、元素分析、紫外可见光谱(UV-vis)和荧光光谱法对其进行了分析与表征.结果表明:配合物2～4在蓝-紫色可见光区域有较强吸收、可发射出明亮的橙红色荧光、具荧光量子效率(Φ)高、激发态寿命(τ)长、Stocks位移值较大(147～180 nm)和优良的氧致荧光淬灭性能(Ksv≥3.5,(I0/I)max≥4.0)等光物理性质.其中,具接枝型官能团氨基的配合物3的量子效率(Φ)=10%,τ=381.8 ns,Ksv=3.49,(I0/I)max=4.33;而溴修饰的配合物2以高达18%的荧光量子效率、634.7 ns的激发态寿命、180 nm的Stocks位移和Ksv=4.59,氧淬灭参数(I0/I)max=5.29,使之最有希望成为接枝型、较高性能的光学氧传感器的候选氧敏指示剂.     

Dinuclear asymmetric ruthenium complexes with 5-cyano-1,10-phenanthroline as a bridging ligand

New dinuclear asymmetric ruthenium complexes of the type [(bpy)(2)Ru(5-CNphen)Ru(NH(3))(5)](4+/5+) (bpy = 2,2'-bipyridine; 5-CNphen = 5-cyano-1,10-phenanthroline) have been synthesized and characterized by spectroscopic, electrochemical, and photophysical techniques. The structure of the cation [(bpy)(2)Ru(5-CNphen)Ru(NH(3))(5)](4+) has been determined by X-ray diffraction. The mononuclear precursor [Ru(bpy)(2)(5-CNphen)](2+) has also been prepared and studied; while its properties as a photosensitizer are similar to those of [Ru(bpy)(3)](2+), its luminescence at room temperature is quenched by a factor of 5 in the mixed-valent species [(bpy)(2)Ru(II)(5-CNphen)Ru(III)(NH(3))(5)](5+), pointing to the occurrence of intramolecular electron-transfer processes that follow light excitation. From spectral data for the metal-to-metal charge-transfer transition Ru(II) --> Ru(III) in this latter complex, a slight electronic interaction (H(AB) = 190 cm(-1)) is disclosed between both metallic centers through the bridging 5-CNphen.     

Fused donor-acceptor ligands in RuII chemistry: synthesis, electrochemistry and spectroscopy of [Ru(bpy)3-n(TTF-dppz)n](PF6)2.

Three ruthenium(II) polypyridine complexes of general formula [Ru(bpy)(3-n)(TTF-dppz)n](PF6)2 (n=1-3, bpy=2,2'-bipyridine), with one, two or three redox-active TTF-dppz (4',5'-bis(propylthio)tetrathiafulvenyl[i]dipyrido[3,2-a:2',3'-c]phenazine) ligands, were synthesised and fully characterised. Their electrochemical and photophysical properties are reported together with those of the reference compounds [Ru(bpy)3](PF6)2, [Ru(dppz)3](PF6)2 and [Ru(bpy)2(dppz)](PF6)2 and the free TTF-dppz ligand. All three complexes show intraligand charge-transfer (ILCT) fluorescence of the TTF-dppz ligand. Remarkably, the complex with n=1 exhibits luminescence from the Ru(2+)-->dppz metal-to-ligand charge-transfer ((3)MLCT) state, whereas for the other two complexes, a radiationless pathway via electron transfer from a second TTF-dppz ligand quenches the (3)MLCT luminescence. The TTF fragments as electron donors thus induce a ligand-to-ligand charge-separated (LLCS) state of the form TTF-dppz- -Ru(2+)-dppz-TTF(+). The lifetime of this LLCS state is approximately 2.3 micros, which is four orders of magnitude longer than that of 0.4 ns for the ILCT state, because recombination of charges on two different ligands is substantially slower.     

Light-induced charge separation and photocatalytic hydrogen evolution from water using Ru(II)Pt(II)-based molecular devices: effects of introducing additional donor and/or acceptor sites

In our hopes to improve the photocatalytic efficiency of photo-hydrogen-evolving molecular devices, several new dyads and triads possessing a photosensitizing Ru(bpy)(phen)(2)(2+) (or Ru(phen)(3)(2+)) chromophore (abbreviated as Ru(II)) attached to both/either a phenothiazine moiety (abbreviated as Phz) and/or H(2)-evolving PtCl(2)(bpy) units (abbreviated as Pt), such as Phz-Ru(II)-Pt2 (triad), Ru(II)-Pt2 (dyad), and Ru(II)-Pt3 (dyad), were synthesized and their basic properties together with the photo-hydrogen-evolving characteristics were investigated in detail. The (3)MLCT phosphorescence from the Ru(II) moiety in these systems is substantially quenched due to the highly efficient photoinduced electron transfer (PET). Based on the electrochemical studies, the driving forces for the PET were estimated as -0.07 eV for Phz-Ru(II)-Pt2, -0.24 eV for Ru(II)-Pt2, and -0.22 eV for Ru(II)-Pt3, revealing the exergonic character of the PET in these systems. Luminescence lifetime studies revealed the existence of more than two decay components, indicative of a contribution of multiple PET processes arising from the presence of at least two different conformers in solution. The major luminescence decay components of the hybrid systems [τ(1) = 6.5 ns (Ru(II)-Pt2) and τ(1) = 1.04 ns (Phz-Ru(II)-Pt2) in acetonitrile] are much shorter than those of Phz-free/Pt-free Ru(bpy)(phen)(2)(2+) derivatives. An important finding is that the triad Phz-Ru(II)-Pt2 affords a quite long-lived charge separated (CS) state (τ(CS) = 43 ns), denoted as Phz(+)˙-Ru(Red)-Pt2, as a result of reductive quenching of the triplet excited state of Ru(bpy)(phen)(2)(2+) by the tethering Phz moiety, where Ru(Red) denotes Ru(bpy)(phen)(2)(+). Moreover, the lifetime of Phz(+)˙-Ru(Red)-Pt2 was observed to be much longer than that of Phz(+)˙-Ru(Red). The photocatalytic H(2) evolution from water driven by these systems was examined in an aqueous acetate buffer solution (pH 5.0) containing 4-19% dimethylsulfoxide (solubilising reagent) in the presence of EDTA as a sacrificial electron donor. Dyads Ru(II)-Pt2 and Ru(II)-Pt3 were found to exhibit improved photo-hydrogen-evolving activity compared to the heterodinuclear Ru-Pt dyads developed so far in our group. On the other hand, almost no catalytic activity was observed for Phz-Ru(II)-Pt2 in spite of the formation of a strongly reducing Ru(Red) site (Phz(+)˙-Ru(Red)-Pt2), indicating that the electron transfer from the photogenerated Ru(Red) unit to the PtCl(2)(bpy) unit is not favoured presumably due to the slow electron transfer rate in the Marcus inverted region.     

Ruthenium(II)(bpy)(2)L](2+), where L are imidazo[f]-1,10-phenanthrolines: synthesis, photophysics and binding with DNA

Three Ru(II) complexes of type as [Ru(II)(bpy)(2)L](2+) were synthesized, where L are l,10-phenanthroline derivatives of imidazole (1), having at position 2 alpha-naphthyl (2), 3-methoxy-4-hydroxy-phenyl (3). All complexes show intense MLCT transition both in acetonitrile and in water and also exhibit strong emission at room temperature, which is efficiently quenched by oxygen as well as, to some extent, by water. The binding of complexes 1-3 to calf thymus DNA was investigated by using electronic absorption, steady-state luminescence, luminescence quenching, excited-state lifetime and circular dichroism spectra. Hypochromic effect, luminescence enhancement, and quenching studies demonstrate the existence of intercalation mode. Circular dichroism spectra indicate the stereoselectivity of the binding. The binding of 1-3 with DNA is sensitive to the nature of ligands, such as planarity, pi-electron extension and hydrophobicity. Complex 3 exhibits the strongest binding with DNA, which can be attributed to hydrogen bonding.     

Theoretical study of O--O single bond formation in the oxidation of water by the ruthenium blue dimer

The first key step in the oxidation of water to O(2) by the oxidized species [(bpy)(2)(O)Ru(V)ORu(V)(O)(bpy)(2)](4+) of the Ru blue dimer is studied using density functional theory (DFT) and an explicit solvent treatment. In the model reaction system [L(2)(O)Ru(V)ORu(V)(O)L(2)](4+)·(H(2)O)(4)·W(76), the surrounding water solvent molecules W are described classically while the inner core reaction system is described quantum mechanically using smaller model ligands (L). The reaction path found for the O--O single bond formation involves a proton relay chain: direct participation of two water molecules in two proton transfers to yield the product [L(2)(HOO)Ru(IV)ORu(IV)(OH)L(2)](4+)·(H(2)O)(3)·W(76). The calculated ～3 kcal/mol reaction free energy and ～15 kcal/mol activation free energy barrier at 298 K are consistent with experiment. Structural changes and charge flow along the intrinsic reaction coordinate, the solvent's role in the reaction barrier, and their significance for water oxidation catalysis are examined in detail.     

Chemiluminescent investigation of tris(2,2'-bipyridyl)ruthenium(II) immobilized on a cationic ion-exchange resin and its application to analysis

Tris-(2, 2'-bipyridyl)ruthenium(II) complex, Ru(bpy)(3)(2+), was immobilized on the Dowex-50 W cationic ion-exchange resin. The chemiluminescent characteristics of Ru(bpy)(3)(2+) in solution and in resin form were compared by using batch and flow injection methods. A strong chemiluminescence was observed during the reaction of Ru(bpy)(3)(2+) both in solution and in resin with KMnO(4) or Ce(SO(4))(2) under acidic or basic conditions. The Ru(bpy)(3)(2+) immobilized resin is stable, which can be used at least for 6 months when it reacts with the dilute KMnO(4) solution. Based on this property, Ru(bpy)(3)(2+) immobilized in the resin phase was developed as a flow-through chemiluminescent sensor that could be used to determine oxalate, sulfite and ethanol chemically or electronically with Ru(bpy)(3)(3+) generation on the surface of resin. The limits of detection were 1 x 10(-6) M for oxalate, 0.5% (v/v) for ethanol and 1 x 10(-7) M for sulfite. The method has been successfully applied to determine sulfite in sugar.