Electochemiluminescence of CdTe/CdS Quantum Dots with Triproprylamine as Coreactant in Aqueous Solution at a Lower Potential and Its Application for Highly Sensitive and Selective Detection of Cu2+

Anodic electrochemiluminescence (ECL) of 3‐mercaptopropionic acid (MPA)‐ capped CdTe/CdS core‐shell quantum dots (QDs) with tripropylamine (TPrA) as the co‐reactant were studied in aqueous (Tris buffer) solution for the first time. The results suggest that the oxidation of TPrA at a glassy carbon electrode (GCE) surface participated in the ECL of QDs, and the onset potential and the intensity of ECL of CdTe/CdS QDs were affected seriously by TPrA, as the co‐reactant, in Tris buffer solution. The onset potential of ECL in this new system was about +0.5 V (vs. Ag/AgCl) and the ECL intensity greatly enhanced when TPrA was present. Various influencing factors, such as the electrolyte, pH, QDs concentration, potential range and scan rates on the ECL were studied. Based on the selective quenching by Cu²⁺ to the light emission from CdTe/CdS QDs/TPrA system, a highly sensitive and selective method for the determination of Cu²⁺ was developed. At the optimal conditions, the relative ECL intensity, I₀/I, was proportional to the concentration of Cu²⁺ from 14 nM to 0.21 μM with the detection limit of 6.1 nM based on the signal‐to‐noise ratio of 3. The possible ECL mechanism of QDs and the quenching mechanism of ECL were proposed.     

Gold nanoparticle-modified ITO electrode for electrogenerated chemiluminescence: well-preserved transparency and highly enhanced activity

Although it is desirable to use transparent indium tin oxide (ITO)-coated glass substrates as working electrodes for electrogenerated chemiluminescence (ECL), their applications in ECL studies of the Ru(bpy)32+ (bpy, 2,2'-bipyridine)/tri-n-propylamine (TPrA) system have been limited because of the large overpotential of TPrA oxidation and the instability of the ITO surface at high anodic potentials. Here, we describe a simple method to achieve high ECL activity using ITO electrodes modified with gold nanoparticles (GNPs). The GNPs have been capped with fluorosurfactant ligands (i.e., Zonyl FSO). Much more facile TPrA oxidation was achieved by using the modified electrode, and an intense low-oxidation-potential (LOP) ECL signal was observed at approximately 0.88 V versus SCE. The electrode transmittance drop upon modification was generally less than 5% over the visible spectrum when small-sized GNPs (approximately 4 nm) were employed. The well-preserved transparency and highly enhanced activity make the modified electrode promising for ECL studies.     

Enhancement of Electrochemiluminescence of Porous Silicon with Tri‐n‐propylamine as Co‐reactant

Visible light emission can be stimulated by applying a cyclic bias to a porous silicon/tri‐n‐propylamine (PS/TPrA) solid/liquid system. With the presence of 2.5 mM TPrA, the electrochemiluminescence intensity of the in situ formed PS electrode is 450 times higher than the blank solution. An applied voltage as low as 1.2 V is capable of generating light emission, indicating that current‐induced chemical reactions are an aid to the generation of charge carriers. A mechanism involving oxidation of TPrA followed by hole injection is proposed. The system also shows good ECL stability. In addition, the ECL emission can be inhibited by diphenols rather than phenol.     

Effects of electron withdrawing and donating groups on the efficiency of tris(2,2'-bipyridyl)ruthenium(II)/tri-n-propylamine electrochemiluminescence

The effects of electron withdrawing and electron donating groups on the electrochemiluminescent (ECL) properties of tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)3(2+) where bpy = 2,2'-pyridine) are reported. The electrochemistry, photophysics and ECL of (bpy)2Ru(DC-bpy)2+, and (bpy)2Ru(DM-bpy)2+ (DC = 4,4'-dicarboxy-2,2'-bipyridine; DM = 4,4'-dimethyl-2,2'-bipyridine) have been studied relative to Ru(bpy)3(2+) in 50:50 (v/v) acetonitrile(CH3CN):H2O (0.1 M KH2PO4), and aqueous solutions. Furthermore, the effects of Triton X-100 (polyethylene glycol tert-octylphenyl ether) on the electrochemical, spectroscopic and ECL properties of these compounds are reported. The anodic oxidation of Ru(bpy)3(2+), (bpy)2Ru(DC-bpy)2+, and (bpy)2Ru(DM-bpy)2+ produces ECL in the presence of tri-n-propylamine (TPrA) in all solvent systems. ECL efficiencies (phi(ecl), photons produced per redox event) of 0.73 and 0.84 for (bpy)2Ru(DC-bpy)2+, and (bpy)2Ru(DM-bpy)2+ were obtained in aqueous buffered solution, using Ru(bpy)3(2+) as a relative standard (phi(ecl) = 1.0). Addition of 0.4 mM Triton X-100 results in a greater than 2-fold increase in ECL efficiences (i.e., 3.8, 2.4 and 2.3 for Ru(bpy)3(2+), (bpy)2Ru(DC-bpy)2+, and (bpy)2Ru(DM-bpy)2+, respectively) using aqueous Ru(bpy)3(2+) containing no surfactant as standard (phi(ecl) = 1.0). ECL efficiencies of 27.4, 16.5 and 26.1 were found in 50:50 (v/v) CH3CN:H2O (0.1 M KH2PO4) for Ru(bpy)3(2+), (bpy)2Ru(DC-bpy)2+, and (bpy)2Ru(DM-bpy)2+, respectively, using aqueous Ru(bpy)3(2+) containing no surfactant as standard (phi(ecl) = 1.0). Detailed studies support adsorption of surfactant on the electrode surface, thus facilitating TPrA and ruthenium oxidation.     

Characterization of the low-oxidation-potential electrogenerated chemiluminescence of tris(2,2′-bipyridine)ruthenium(II) with tri-n-propylamine as coreactant

The electrogenerated chemiluminescence (ECL) of the Ru(bpy)₃²⁺ (bpy, 2,2′-bipyridine)/tri-n-propylamine (TPrA) system can be produced at an oxidation-potential well before the oxidation of Ru(bpy)₃²⁺. Here, we describe the unique features of the low-oxidation-potential (LOP) ECL. The LOP ECL exhibited strong dependence on solution pH with the maximum emission at pH  7.7. Compared with the conventional ECL, the LOP ECL was much more significantly diminished at high pH (>10), probably due to the short lifetime of TPrA cation radical which is a crucial intermediate for the LOP emission. It was also found that the preceding deprotonation step played an important role in TPrA oxidation at neutral pH and would remarkably influence the emission intensity. As excess intermediate radicals were produced upon rapid TPrA oxidation, only 5 mM TPrA was needed to achieve the maximum LOP ECL intensity in detecting trace Ru(bpy)₃²⁺ (<1 μM) and the LOP ECL response to Ru(bpy)₃²⁺ concentration was linear. Compared with the conventional Ru(bpy)₃²⁺/TPrA ECL, the LOP ECL technique not only produces higher emission intensity at lower oxidation-potential, but also significantly reduces the amount of the coreactant.     

Anodization in oligo(ethylene glycol) as an initial derivatization tool for preparing glassy carbon electrodes covalently modified with amino compounds: effective access to a 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-modified glassy carbon electrode

Anodization in HO(CH2CH2O)nH (1a, n=2; 1b, n=3; 1c, n=4) as an initial derivatization tool for preparing glassy carbon (GC) electrodes covalently modified with amino compounds was explored. As an amino compound to be immobilized, 4-amino-2,2,6,6-tetramethylpiperidinyl-1-oxyl (4-amino-TEMPO) was selected. When GC electrodes anodized at 2.0 V vs. Ag wire coated with AgCl in 1 containing RCH2CH2SO3Na (2a, R=H; 2b, R=OH) were treated with a N,N-dimethylformamide (DMF) or CH2Cl2 solution of 4-amino-TEMPO and 1,3-dicyclohexylcarbodiimide (DCC), TEMPO-modified GC electrodes were afforded. Coverage (gammaTEMPO) of the electrode surfaces by TEMPO was estimated by cyclic voltammetry in CH3CN containing NaClO4. A TEMPO-modified GC electrode with the best gammaTEMPO (1.36 x 10(-10) mol/cm2) was obtained by anodization in 1b containing 2a at the expense of 3.0 C followed by amidization in DMF for 7 d. On cyclic voltammetry, the TEMPO-modified GC electrode showed good and stable electrocatalytic ability for oxidation of allyl alcohol in the presence of 2,6-lutidine.     

乙腈溶剂中三氯化苄在银阴极上的脱氯反应

用常规循环伏安(CV)法和恒电位电解法研究了含0.1 mol·L^-四丁基高氯酸铵(TBAP)乙腈溶剂中三氯化苄在银电极上的还原脱氯机理; 用以银和氯离子的氧化还原反应为基础的阳极区拓宽CV法探测了还原脱氯反应生成氯离子在银电极上的吸附情况. 循环伏安实验表明: (1) 银电极对三氯化苄的电还原脱氯反应具有比汞电极更优良的电催化活性; (2) 三氯化苄在低扫描速率(v)下得到的第一个还原峰对应反应受吸附控制, 电子转移系数约为0.25, 遵守协同电子转移机理; (3) 三氯化苄还原脱氯反应生成氯离子在银电极上的吸附电位为-0.75 - -1.75 V (vs Ag/Ag⁺). 电解实验表明, 通过改变银电极电位可以有效控制三氯化苄还原反应的电解产物.     

electrochemical generation of a nonheme oxoiron(IV) complex

The complex [Fe(IV)O(N4Py)]2+ (N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine) has been prepared by bulk electrolysis in aqueous CH3CN and CH2Cl2, and its redox properties characterized. Bulk chronocoulometry and spectropotentiometry experiments in CH3CN show that [Fe(II)(N4Py)(NCCH3)]2+ can be oxidized quantitatively to its iron(III) derivative at an applied potential of +0.71 V vs ferrocene and then to the oxoiron(IV) complex (in the presence of added water) at potentials above +1.3 V. The E1/2 value for the Fe(IV/III) couple has been estimated to be +0.90 V from spectropotentiometric titrations in CH3CN and cyclic voltammetric measurements in CH2Cl2.     

Determination of Amino Acids by Ru(bpy)_3~(2+) Cathodic Electrochemiluminescence with High Sensitivity

The unique cathodic electrochemiluminescence(ECL) emission of Ru(bpy)32+(bpy=2,2′-bipyridine) was observed via Nafion film at Au electrode[Au/Nafion/Ru(bpy)32+] at about 0.20 V(vs. Ag/AgCl) and applied to the determination of several amino acids without prior derivatization with high sensitivity. The cathodic electrochemilumi-nescence(ECL) exhibits the detection limits and linear ranges of several amino acids comparable to or better than those of capillary electrophoresis with conventional ECL detection method(at 1.10—1.20 V vs. Ag/AgCl) based on precolumn derivatization. The results suggest that the cathodic ECL is promising for the detection of amino acids in bioanalysis.     

Reactivity of the indole ring in palladium(II) complexes of 2N1O-donor ligands: cyclopalladation and pi-cation radical formation

The Pd(II) complexes of new 2N1O-donor ligands containing a pendent indole, 3-[N-2-pyridylmethyl-N-2-hydroxy-3,5-di(tert-butyl)benzylamino]ethylindole (Htbu-iepp), 1-methyl-3-[N-2-pyridylmethyl-N-2-hydroxy-3,5-di(tert-butyl)benzylamino]ethylindole (Htbu-miepp), 3-[N-2-pyridylmethyl-N-2-hydroxy-3,5-di(tert-butyl)benzylamino]methylindole (Htbu-impp), and 3-(N-2-pyridylmethyl-N-4-hydroxybenzylamino)ethylindole (Hp-iepp) (H denotes a dissociable proton), were synthesized, and the structures of [Pd(tbu-iepp)Cl] (1a), [Pd(tbu-iepp-c)Cl] (1b), [Pd(tbu-miepp)Cl] (3), and [Pd(p-iepp-c)Cl] (4) (tbu-iepp-c and p-iepp-c denote tbu-iepp and p-iepp bound to Pd(II) through a carbon atom, respectively) were determined by X-ray analysis. Complexes 1a prepared in CH(2)Cl(2)/CH(3)CN and 3 prepared in CH(3)CN have a pyridine nitrogen, an amine nitrogen, a phenolate oxygen, and a chloride ion in the coordination plane. Complex 1b prepared in CH(3)CN has the same composition as 1a and was revealed to have the C2 atom of the indole ring bound to Pd(II) with the Pd(II)-C2 distance of 1.973(2) A. The same Pd(II)-indole C2 bonding was revealed for 4. Interconversion between 1a and 1b was observed for their solutions, the equilibrium being dependent on the solvent used. Reaction of 1b and 4 with 1 equiv of Ce(IV) in DMF gave the corresponding one-electron-oxidized species, which exhibited an ESR signal at g = 2.004 and an absorption peak at approximately 550 nm, indicating the formation of the Pd(II)-indole pi-cation radical species. The half-life, t(1/2), of the indole radical species at room temperature was calculated to be 20 s (k(obs) = 3.5 x 10(-)(2) s(-)(1)) for 1b. The cyclic voltammogram for 1b in DMF gave two irreversible oxidation peaks at E(pa) = 0.68 and 0.80 V (vs Ag/AgCl), which were ascribed to the oxidation processes of the coordinated indole and phenolate moieties, respectively.     

Electrochemiluminescence of Ru(II) complexes immobilized on a magnetic microbead surface: distribution of magnetic microbeads on the electrode surface and effect of azide ion

The electrochemiluminescence (ECL) of magnetic microbeads modified with tris(2,2'-bipyridine)ruthenium(II) ([Ru(bpy)3]2+) was studied in the presence of tri-n-propylamine (TPA) to develop highly sensitive ECL detection system, where the employed microbead has a diameter of 4.5 microm. The ECL signal of the [Ru(bpy)3]2+ derivative-modified magnetic microbeads was found to be affected by the geometrical distribution of the magnetic microbeads on the electrode surface. The ECL peak intensity increased with increasing the number of the beads on the electrode surfaces up to 1.6 x 10(6) beads cm(-2), although above 1.6 x 10(6) beads cm(-2), it decreased. The ECL decrease arises from the physical prevention of the ECL from reaching the photomultiplier tube by the excessive beads. The observed peak ECL signal of the [Ru(bpy)3]2+ derivative-modified magnetic microbeads in the presence of NaN3, which serves as a preservative substance, mainly appeared at a potential of +0.90 V vs Ag/AgCl where [Ru(bpy)3]2+ is hardly oxidized, whereas the ECL signal in the absence of NaN3 appeared at a potential of +1.15 V. The presence of NaN3 on the electrode surface retards formation of an oxide layer on the electrode surfaces and promotes TPA oxidation. The ECL response at +0.90 V was mainly attributed to ECL reaction of excited-state [Ru(bpy)3]2+* formed by oxidation of [Ru(bpy)3]+ with TPA radical cation, where the [Ru(bpy)3]+ was generated by reduction of [Ru(bpy)3]2+ with TPA radical.     

Highly efficient quenching of coreactant electrogenerated chemiluminescence by phenolic compounds

We describe the quenching effects of phenolic compounds on the electrogenerated chemiluminescence (ECL) of the Ru(bpy)3(2+) (bpy = 2,2'-bipyridine)/tri-n-propylamine (TPrA) system in aqueous solution. First, the emissions via different ECL routes were examined in the presence of 1,4-benzoquinone. It was found that the interception of the ECL intermediate radicals by the quencher molecules significantly influenced the light emission, especially when the direct coreactant oxidation played a predominant role in producing ECL. The most efficient quenching was observed for the low-oxidation-potential (LOP) ECL at a low concentration of TPrA (<5 mM). The Stern-Volmer constant (K(SV)) of the LOP ECL quenching could be as high as 1.3 x 10(6) M(-1), approximately 700 times larger than that of the photoluminescence quenching. Other phenolic compounds, such as phenol, hydroquinone, catechol, and dopamine, would be oxidized at the potential where the ECL was generated, and the benzoquinone-containing products exhibited ECL quenching effects similar to that of 1,4-benzoquinone. The highly efficient quenching of the LOP ECL by the phenolic compounds may provide a new approach for the determination of these pharmaceutically and environmentally important molecules.     

Enhanced electrochemiluminescence from Os(phen)2(dppene) (phen=1,10-phenanthroline and dppene=bis(diphenylphosphino)ethene) in the presence of Triton X-100 (polyethylene glycol tert-octylphenyl ether)

The effects of the non-ionic surfactant Triton X-100 (polyethylene glycol tert-octylphenyl ether) on the properties of Os(phen)₂(dppene)²⁺ (phen=1,10-phenanthroline and dppene=bis(diphenylphosphino)ethene) electrochemiluminescence (ECL) have been investigated. The anodic oxidation of Os(phen)₂(dppene)²⁺ produces ECL in the presence of tri-n-propylamine (TPrA) in aqueous surfactant solution. Increases in ECL efficiency (≥3-fold) and TPrA oxidation current (≥2.0-fold) have been observed in surfactant media with experiments supporting adsorption of surfactant on the electrode surface.     

Electrochemical fabrication of novel fluorescent polymeric film: Poly(pyrrole–pyrene)

We describe herein the electrochemical characterization and polymerization of 4-pyren-1-yl-butyric acid 11-pyrrol-1-yl-decyl ester (pyrrole–pyrene) in CH₃CN. The electrochemical oxidation of the pyrrole group at 0.77 V vs Ag/Ag + 10 mM in CH₃CN led to the first example of a fluorescent polypyrrole film. The mechanism of deposition on platinum electrode was studied by voltammetry and chronoamperometry. The optical properties of the polymeric films electrogenerated on ITO electrodes were examined by UV–visible spectroscopy and fluorescence microscopy indicating an increase in fluorescence properties by increased polymer thickness. The electrochemical oxidation of pyrenyl group linked to the polypyrrole backbone was carried out at 1.2 V. This additional polymerization was demonstrated by UV–visible spectroscopy and induced the loss of the fluorescence properties of the resulting polymeric film.     

Multiple mixed-valence behavior in trans,trans-[(tpy)(Cl)2Os(III)(mu-1,3-N3)Os(III)(Cl)2(tpy)]+. An azido bridge from the reaction between trans-[Os(VI)(tpy)(Cl)2(N)]+ and NH3

Reaction between the Os(VI)-nitrido complex, trans-[OsVI(tpy)(Cl)2(N)]PF6 (tpy = 2,2':6',2' '-terpyridine), and ammonia (NH3) under N2 in dry CH3CN gives the mu-1,3-azido bridged [OsII-N3-OsII]- dimer, trans,trans-NH4[(tpy)(Cl)2OsII(N3)OsII(Cl)2(tpy)]. It undergoes air oxidation to give the [OsIII-N3-OsIII]+ analogue, trans,trans-[(tpy)(Cl)2OsIII(N3)OsIII(Cl)2(tpy)]PF6 ([OsIII-N3-OsIII]PF6), which has been isolated and characterized. The structural formulation as a mu-1,3-N3 bridged complex has been established by infrared and 15N NMR measurements on the 15N-labeled forms, [OsIII-14N=15N=14N-OsIII]+, [OsIII-15N=14N=15N-OsIII]+, and [OsIII-15N=15N=15N-OsIII]+. Cyclic voltammetric measurements in 0.2 M Bu4NPF6/CH3CN reveal the existence of five chemically reversible waves from 1.40 to -0.12 V for couples ranging from OsV-OsIV/OsIV-OsIV to OsIII-OsII/OsII-OsII. DeltaE1/2 values for couples adjacent to the three mixed-valence forms are 0.19 V for OsIII-OsII, 0.52 V for OsIV-OsIII, and >0.71 V for OsV-OsIV. In CH3CN at 60 degrees C, [OsIII-N3-OsIII]+ undergoes a [2 + 3] cycloaddition with CH3CN at the mu-N3- bridge followed by a solvolysis to give trans-[OsIII(tpy)(Cl)2(5-MeCN4)] and trans-[OsIII(tpy)(Cl)2(NCCH3)]PF6.     

Enhanced Electrogenerated Chemiluminescence of Tris(2,2′‐bipyridyl) Ruthenium(II)/tripropylamine in the Presence of Pyridine and Its Analogues

In the present work, we conducted an investigation on the electrochemical and ECL behavior of Ru(bpy) /TPrA system in the presence of pyridine and its analogues on platinum and gold electrode. Results showed that pyridine and its analogues enhanced Ru(bpy) /TPrA ECL signal and exhibited different enhancement effects on different electrodes. On platinum electrode, the maximum enhancement factor of about 5 was obtained. On gold electrode, a low‐oxidation‐potential (LOP) ECL signal occurred and increased.     

Mono- and dinuclear Ru(II) complexes of 1,4-bis(3-(2-pyridyl)pyrazol-1-ylmethyl)benzene): synthesis, structure, photophysical properties and electrochemiluminescent determination of diuretic furosemide

Mononuclear ruthenium complex 1 and dinuclear complex 2 were synthesized by reaction of the appropriate bidentate pyrazolyl-pyridyl-based ligand L (L = 1,4-bis(3-(2-pyridyl)pyrazol-1-ylmethyl)benzene) with cis-Ru(bipy)(2)Cl(2)·2H(2)O. They were characterized by elemental analyses, ESI-MS, (1)H spectroscopy, and X-ray crystallography for 2. Compounds 1 and 2 both emit strongly in solid states and in solutions at 298 K with the lifetimes in the microsecond range. Electrogenerated chemiluminescence (ECL) of complexes 1 and 2 in the absence or presence of coreactant tri-n-propylamine (TPrA) or 2-(dibutylamino)ethanol (DBAE) at different working electrodes in acetonitrile and phosphate buffer solutions (PBS, pH 7.5) was studied. The ECL spectra are identical to the photoluminescence spectra, indicating that the ECL emissions are due to the metal to ligand charge transfer (MLCT). In all cases, ECL quantum efficiencies of dinuclear complex 2 are higher than those of mononuclear complex 1, and ECL quantum efficiencies of complexes 1 and 2/TPrA system are higher than those of DBAE system. It is noted that diuretic furosemide tends to decrease the ECL intensity of complex 2/TPrA system in PBS (pH 7.5) at GC working electrode. A novel ECL method for the determination of diuretic furosemide was developed with a linear range between 2.0 × 10(-7) mol L(-1) and 1.0 × 10(-6) mol L(-1), and a detection limit of 1.2 × 10(-8) mol L(-1) based on 3 times the ratio of signal-to-noise.     

鲁米诺在铂电极上阳极电致化学发光的机理研究

研究了碱性鲁米诺溶液在多晶铂电极上的阳极电致化学发光(ECL)行为,观察到电极的预极化处理和溶解氧跟发光峰强度和峰形有直接关系。结合XPS谱图和Pt,Pt|S~a~d~s修饰电极的循环伏安特性,给出了鲁米诺阳极ECL两个发光通道的可能反应机理:(1)鲁米诺阴离子在表面有新鲜Pt原子的电极上氧化生成鲁米诺自由基,然后迅速与溶液中的氧反应形成0.22V(vs.Ag)处的发光肩峰;(2)电极表面的铂氧化物能加速原子态氧的发生过程,并增大0.60V(vs.Ag)附近ECL主峰的发光强度。     

Synthesis, structures, and properties of ruthenium(II) complexes of N-(1,10-phenanthrolin-2-yl)imidazolylidenes

Mononuclear ruthenium complexes [RuCl(L1)(CH(3)CN)(2)](PF(6)) (2a), [RuCl(L2)(CH(3)CN)(2)](PF(6)) (2b), [Ru(L1)(CH(3)CN)(3)](PF(6))(2) (4a), [Ru(L2)(CH(3)CN)(3)](PF(6))(2) (4b), [Ru(L2)(2)](PF(6))(2) (5), [RuCl(L1)(CH(3)CN)(PPh(3))](PF(6)) (6), [RuCl(L1)(CO)(2)](PF(6)) (7), and [RuCl(L1)(CO)(PPh(3))](PF(6)) (8), and a tetranuclear complex [Ru(2)Ag(2)Cl(2)(L1)(2)(CH(3)CN)(6)](PF(6))(4) (3) containing 3-(1,10-phenanthrolin-2-yl)-1-(pyridin-2-ylmethyl)imidazolylidene (L1) and 3-butyl-1-(1,10-phenanthrolin-2-yl)imidazolylidene (L2) have been prepared and fully characterized by NMR, ESI-MS, UV-vis spectroscopy, and X-ray crystallography. Both L1 and L2 act as pincer NNC donors coordinated to ruthenium (II) ion. In 3, the Ru(II) and Ag(I) ions are linked by two bridging Cl(-) through a rhomboid Ag(2)Cl(2) ring with two Ru(II) extending to above and down the plane. Complexes 2-8 show absorption maximum over the 354-428 nm blueshifted compared to Ru(bpy)(3)(2+) due to strong σ-donating and weak π-acceptor properties of NHC ligands. Electrochemical studies show Ru(II)/Ru(III) couples over 0.578-1.274 V.     

Synthesis of Pt(dpk)Cl(4) and the reversible hydration to Pt(dpk-O-OH)Cl(3).H-phenCl: X-ray, spectroscopic, and electrochemical characterization

We report on the synthesis of a platinum(IV) compound containing a di-2-pyridyl ketone (dpk) ligand that is stable both in its anhydrous form [Pt(dpk)Cl(4)] (1) and in its hydrated form [Pt(dpk-O-OH)Cl(3)].H-phenCl (2). The crystal structure of the hydrated form shows that one of the hydroxide groups from the resulting gem-diol has undergone a cyclometalation/condensation reaction resulting in an oxygen atom directly coordinated to the Pt(IV) center and the formation of H-phenCl. We correlate our physical data with predictions made by molecular modeling, and we propose an explanation for the unusual activity found for this dpk ketone. Spectroscopic and solubility studies are presented here, as well. Electrochemical studies of 1 indicate that it undergoes a highly irreversible reduction at a potential of about -0.45 V vs Ag(+)/Ag in CH(3)CN and that the irreversibility is likely due to an EC mechanism, the nature of which is currently under further investigation. Another distinct redox pair, apparently reversible, appears at a potential of about -1.1 V vs Ag(+)/Ag.