Successive Reduction Processes Research Articles

A numerically stable flexural dynamics model of complex multi-span fluid-conveying pipes with flexible components and its application to clamp stiffness identification

Multi-span fluid-conveying pipelines (MFP) with multiple concentrated accessories, i.e., clamps, valves, flanges, vibration absorbers and flexible components, whose dynamic properties can be described by receptance, are widely used in many engineering fields. However, research on predicting the dynamics of such pipe structures has been rarely performed. In this study, we propose an improved transfer matrix method (TMM) to model the numerically stable dynamics of the MFP with multiple concentrated accessories and flexible components. An original receptance-based modeling method is developed to address boundary conditions induced by the presence of concentrated accessories and flexible components simultaneously. The method's advantage is that the flexible component is considered as an independent substructure before assembling, its receptance can be calculated or measured independently. Moreover, the numerical instability problem of the conventional transfer matrix method (CTMM) in the high-frequency range is resolved by utilizing a successive reduction process to reduce the length of the transfer path of the state vectors used to describe the overall dynamics of the pipe. One salient feature of the proposed method is that the size of the characteristic matrix will be specified as 4×4, which is inherited from CTMM. An optimization-based inverse method is proposed to identify the clamp stiffness with the developed numerically stable and efficient dynamics model. Also, a device is designed and developed to measure the approximate clamp stiffness values which are considered as the initial values during optimization. The experimental results indicate that the proposed method is effective and accurate; utilizing the approximate values of the clamp stiffness as the initial values can accelerate the stability of the iteration during the optimization.

Boron-embedded C3N nanosheets as efficient electrocatalysts for reduction of nitric oxide

The electrochemical reduction of nitric oxide (NO) is among the most efficient techniques for converting this poisonous gas into valuable compounds. This paper investigates the potential of boron (B)-doped C3N nanosheets for the catalytic reduction of NO molecules using density functional theory calculations. To achieve this goal, two unique B-doped C3N monolayers are investigated, namely, those in which the B atom is substituted with either a carbon (labeled as BC) or a nitrogen atom (labeled as BN). The findings reveal that the NO molecule might be sufficiently activated over both BC and BN electrocatalysts, with the successive reduction process producing NH3 at low coverages and N2 at high coverages. According to the Gibbs free energy diagrams, the BC nanosheet displays outstanding catalytic performance for NO reduction at normal temperature with no limiting potential. The strong coupling of the ∗HNO and NO species may result in the spontaneous formation of N2 at ambient temperature. The findings of this work might be used to develop metal-free electrocatalysts for removing hazardous NO molecules from the environment.

Tris(polypyridine)nickel(II) complexes: Synthesis, DFT and electrochemistry

A series of 13 tris(polypyridine)nickel(II) complexes were synthesized and subjected to electrochemical (using cyclic voltammetry) and theoretical (using density functional theory, DFT) studies. Experimentally, one oxidation and a couple successive reduction processes are observed for the tris(polypyridine)nickel(II) complexes. The experimental Ni(II/III) oxidation potential follows the same trend as the experimental metal(II/III) oxidation potential of related tris(polypyridine)metal(II) complexes, metal = Co, Os, Fe, Ru and Mn, with the tris(polypyridine)nickel(II) being oxidized at the most positive potential.DFT calculations show that the tris(polypyridine)nickel(II) complexes have an octahedral coordination sphere, while the oxidized tris(polypyridine)nickel(III) complexes exhibit a Jahn-Teller distorted geometry. The change in geometry from octahedral to Jahn-Teller distorted upon oxidation of tris(polypyridine)nickel(II), may contribute to the large peak current potential separations with small peak current ratios experimentally measured for the Ni(II/III) redox process. The DFT calculations further show that the reduced tris(polypyridine)nickel(II) complexes, [Ni(polypyridine)3]n+, contain a Ni(II) central ion ferromagnetically coupled to one (n = 1), two (n = 0) or three (n = -1) polypyridine radicals. The tris(polypyridine)nickel(II) complexes thus exhibit polypyridine ligand-based reduction.

A top-down chemical approach to tuning the morphology and plasmon resonance of spiky nanostars for enriched SERS-based chemical sensing

Gold-silver (AuAg) alloys, an important noble bimetallic system, have received significant attention due to their chemical stability and unique properties for use in catalysis, surface-enhanced Raman scattering (SERS) and biomedical applications. We report a chemical approach to reconstruct the morphology of AuAg spiky nanostars using additional metal ions, into nanostructures that exhibits enriched SERS-based chemical sensing. To achieve this, we developed a two-step reduction process involving the simultaneous reduction of gold and silver followed by a successive reduction process. First, AuAg nanostars were synthesized by reducing Au and Ag using a one-pot method. Secondly, Au and Ag ions were separately deposited on the as-prepared AuAg nanostars and reduced. Successive reduction of Ag onto the AuAg nanostar resulted in a layered core-shell nanostructure with minimal mixing of the two metals. The deposition of Au ions onto the AuAg nanostars yielded maximally mixed alloyed nanostructures. There was no significant change in the morphology of the spiky nanostars with the use of high or low Ag feed concentrations or low Au concentrations. However, a new star-like nanostructure was formed as a result of the successive reduction of Au ions at a high feed concentration. The properties evaluated by SERS studies reveals that the as-prepared maximally mixed random alloy outperforms the minimally mixed layered core-shell nanostructures.

Snapshots of Light Induced Accumulation of Two Charges on Methylviologen using a Sequential Nanosecond Pump-Pump Photoexcitation.

Methylviologen (MV2+) is perhaps the most used component as a reversible electron acceptor in photophysical studies. While MV2+ is most commonly implicated as a reversible one-electron mediator, its electrochemical properties clearly evidence two successive one-electron reduction processes. In this report, we have investigated on the light driven two-charge accumulation on MV2+ using a multicomponent system composed of the prototypical molecular photosensitizer [Ru(bpy)3]2+ and MV2+ in the presence of ascorbate as reversible electron donor. The sequential addition of two electrons on the methylviologen was tracked upon sequential excitation of the [Ru(bpy)3]2+ at optimized concentration of the electron acceptor. The charge accumulated state carries an energy of 0.9 eV above the ground state and has a lifetime of ca. 50 μs. We have reached a fairly good global yield of approximately 9% for the two-charge accumulation. This result clearly demonstrates the potential of this simple approach for applications in artificial photosynthesis.

Luminescent Dinuclear Bis-Cyclometalated Gold(III) Alkynyls and Their Solvent-Dependent Morphologies through Supramolecular Self-Assembly.

A series of luminescent bis-cyclometalated gold(III) complexes containing bridging alkynyl ligands of different natures has been synthesised and characterised. The photophysical properties of the complexes have been investigated through electronic absorption spectroscopy and emission studies. The vibronic emission bands are found to originate from the triplet intraligand (IL) π-π* excited states of the bis-cyclometalating ligands with some mixing of 3 IL π-π* character of the alkynyl ligands. The electrochemical study of a nonsymmetric dinuclear complex shows two successive reduction processes originating from the reductions of the two different cyclometalating ligands. The complexes are found to undergo supramolecular self-assembly processes driven by π-π stacking and hydrophobic/hydrophilic interactions to give honeycomb nanostructures, as revealed from the SEM images. Solvent-dependent morphological transformations have also been observed, which have been studied by SEM and 1 H NMR spectroscopy.

A new sandwich-type polyoxometalates containing mixed transition metals, [Cd2Zn2(H2O)2(P2W15O56)2]16−: Syntheses, spectrochemical characterization and its electrocatalytical activity comparison with [M4(H2O)2(P2W15O56)2]16− (M = Cd2+ and Zn2+) and [P2W15O56]12−

The mixed-metal sandwich-type polyoxometalate [Cd2Zn2(H2O)2(P2W15O56)2]16− (abbreviated Cd2Zn2P4W30) has been synthesized and characterized by FT-IR, 31P NMR, 113Cd NMR spectroscopies, cyclic voltammetry (CV) and elemental analysis. The electrochemical behavior of this sandwich-type complex in aqueous solution has been investigated, and also systematic comparisons of that have been made by [M4(H2O)2(P2W15O56)2]16− (M=Cd2+ and Zn2+) (abbreviated M4P4W30) and [P2W15O56]12− (abbreviated P2W15). All these compounds show successive reduction processes of the tungsten centers in a negative potential range, but in some cases, the electrochemistry involves redox reactions originating from cadmium ions. These sandwich-type complexes have efficient electrocatalytic activities towards the reduction of nitrite. However, there is a significant decrease in efficiency as the number of cadmium centers in the complex increases.

Tunable Electrochemical and Catalytic Features of BIAN- and BIAO-Derived Ruthenium Complexes.

This article deals with a class of ruthenium-BIAN-derived complexes, [Ru(II)(tpm)(R-BIAN)Cl]ClO4 (tpm = tris(1-pyrazolyl)methane, R-BIAN = bis(arylimino)acenaphthene, R = 4-OMe ([1a]ClO4), 4-F ([1b]ClO4), 4-Cl ([1c]ClO4), 4-NO2 ([1d]ClO4)) and [Ru(II)(tpm)(OMe-BIAN)H2O](2+) ([3a](ClO4)2). The R-BIAN framework with R = H, however, leads to the selective formation of partially hydrolyzed BIAO ([N-(phenyl)imino]acenapthenone)-derived complex [Ru(II)(tpm)(BIAO)Cl]ClO4 ([2]ClO4). The redox-sensitive bond parameters involving -N═C-C═N- or -N═C-C═O of BIAN or BIAO in the crystals of representative [1a]ClO4, [3a](PF6)2, or [2]ClO4 establish its unreduced form. The chloro derivatives 1a(+)-1d(+) and 2(+) exhibit one oxidation and successive reduction processes in CH3CN within the potential limit of ±2.0 V versus SCE, and the redox potentials follow the order 1a(+) < 1b(+) < 1c(+) < 1d(+) ≈ 2(+). The electronic structural aspects of 1a(n)-1d(n) and 2(n) (n = +2, +1, 0, -1, -2, -3) have been assessed by UV-vis and EPR spectroelectrochemistry, DFT-calculated MO compositions, and Mulliken spin density distributions in paramagnetic intermediate states which reveal metal-based (Ru(II) → Ru(III)) oxidation and primarily BIAN- or BIAO-based successive reduction processes. The aqua complex 3a(2+) undergoes two proton-coupled redox processes at 0.56 and 0.85 V versus SCE in phosphate buffer (pH 7) corresponding to {Ru(II)-H2O}/{Ru(III)-OH} and {Ru(III)-OH}/{Ru(IV)═O}, respectively. The chloro (1a(+)-1d(+)) and aqua (3a(2+)) derivatives are found to be equally active in functioning as efficient precatalysts toward the epoxidation of a wide variety of alkenes in the presence of PhI(OAc)2 as oxidant in CH2Cl2 at 298 K, though the analogous 2(+) remains virtually inactive. The detailed experimental analysis with the representative precatalyst 1a(+) suggests the involvement of the active {Ru(IV)═O} species in the catalytic cycle, and the reaction proceeds through the radical mechanism, as also supported by the DFT calculations.

Synthesis of Pt and bimetallic PtPd nanostructures on Au nanoparticles for use as methanol tolerant oxygen reduction reaction catalysts

Core–shell structured Au–PtPd/C and Au–Pt/C nanoparticles (NPs) were prepared using a successive reduction process on carbon supported Au with PtPd and Pt particles.

Characterization of copper–zinc nanoparticles synthesized via submerged arc discharge with successive reduction process

Two copper–zinc (Cu–Zn) alloy wires with different copper contents (90Cu/10Zn and 65Cu/35Zn) were used as sacrificed electrodes in submerged arc discharge process at ambient pressure. Three types of dielectric liquids including ethylene glycol, ethanol and deionized water were investigated. The microstructure, composition and size of the particles obtained were examined by high-resolution transmission electron microscopy with energy dispersive X-ray spectroscopy (TEM/EDS) and X-ray diffraction (XRD) analysis. The particles synthesized from both wires in all dielectric liquids were spherical with size in the range of 5–50 nm. Ethylene glycol yielded the smallest particles, in comparison deionized water yielded the largest particles. These particles contained Cu, Cu–Zn, and zinc oxide without copper oxide. l-Ascorbic acid was then used as a reducing agent to eliminate zinc oxide. Thus, the 5–50 nm spherical Cu/Cu–Zn nanoparticles with similar composition to the wires used, can be synthesized. However, ethanol cannot be used as dielectric liquid in case of 65Cu/35Zn wire, because high zinc content in ethanol with l-ascorbic acid formed zinc oxalate. Conductive ink was prepared from the particles synthesized by using 90Cu/10Zn in ethylene glycol, and screen printed on poly(ethylene terephthalate) (PET) substrate. The patterns printed could be sintered in air at 150 °C for 60 min. The patterns fabricated were characterized by scanning electron microscope with energy dispersive X-ray spectroscopy (SEM/EDS). The resistivity of the conductive pattern was measured by two-point probe at room temperature. The lowest volume resistivity of the pattern obtained was 125 µΩ·cm.

Synthesis and Characterization of Copper-Silver Core-Shell Nanoparticles by Polyol Successive Reduction Process

ABSTRACTIn this work, spherical copper (core) - silver (shell) nanoparticles with diameter of 40-50 nm were synthesized through polyol successive reduction process in glycerol with addition of sodium hydroxide (NaOH). The process involves microwave-assisted reduction of copper nitrate by glycerol under atmospheric conditions and successive reduction of silver nitrate at the surface of copper nanoparticles synthesized. We investigated the influence of synthesis parameters including molar ratio of NaOH:Cu (0:1, 1:1, 3:1 and 5:1), the molar ratio of Ag:Cu (0.01:1, 0.05:1, 0.10:1, 0.15:1 and 0.20:1) on the size, structure and composition of the resulting particles. High-resolution transmission electron microscopy with energy dispersive X-ray spectroscopy (TEM/EDS), scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis were used to characterize the particles obtained. The average size of the nanoparticles decreased with increasing of the ratio of sodium hydroxide. With the molar ratio of Ag:Cu greater than 0.05:1, the silver protective shell can prevent forming of copper oxide on the surface of nanoparticles.

Highly monodisperse Cu- and Ag-based bimetallic nanocrystals for the efficient utilization of noble metals in catalysis

Highly monodisperse Cu- and Ag-based bimetallic noble metal nanocrystals (BNMNs) with diameter 2-7 nm have been synthesized. The synthesis employs a successive reduction process by using inorganic metal salts as precursors at a low temperature (∼110 °C). HRTEM, XPS and XRD analytical techniques were applied for the structural analysis of BNMNs. Catalytic activity investigation (CO oxidation) over different supports (silicate nanotubes and CeO2 nanoparticles) shows that BNMNs have identical and even enhanced performance over pure noble metal nanocrystals with similar size and size distribution, which proves that these BNMNs can significantly reduce the amount and thus make full use of noble metals in catalysis.

Effect of pre-treatment approach of a carbon support on activity of PtSn/C electrocatalysts for direct ethanol fuel cells

Vulcan XC-72R carbon was pretreated using acid and thermal activation methods, and the carbons obtained were used as supports for a PtSn/C catalyst synthesized by a successive reduction process. Surface characteristics of the supports, including BET surface area, pHPZC and functional group, were analyzed using physical N2 adsorption, mass titration, acid–base titration, and Fourier transform infrared (FTIR) spectrometer technique, respectively. The prepared PtSn/C catalysts were characterized by X-ray diffractometer (XRD), energy dispersive X-ray spectrometer (EDX), inductively coupled plasma–atomic emission spectrometry (ICP–AES), and transmission electron microscope (TEM) techniques, and then were examined for their behavior under ethanol oxidation as well as for their performance in a direct ethanol fuel cell (DEFC). The results showed that pretreatment by HNO3 produced various oxygenated functional groups on the support surface and increased its acidic property. The strong acidity of the acid-treated support led to an unfavorable condition for the Pt reduction reaction and resulted in low Pt content but high Pt:Sn ratio in the PtSn/C catalyst. On the other hand, thermal activation increased the base functional groups on the carbon surface, which enhanced reduction of Pt precursor, and consequently, provided a small average metal particle size of 2.2 nm. The results from cyclic voltammetry, chronoamperometry and cell performance testing confirmed that the catalytic activity for ethanol oxidation and the performance in the direct ethanol fuel cell of the heat-treated carbon-supported PtSn catalyst was superior to the fresh PtSn/C catalyst and the acid-treated carbon-supported PtSn catalyst.

Ground and Excited Electronic States of Quininone-Containing Re(I)-Based Rectangles: a Comprehensive Study of Their Preparation, Electrochemistry, and Photophysics

The self-assembly of two rectangular compounds [{(CO)(3)Re(mu-QL)Re(CO)(3)}(2)(mu-bpy)(2)] (1, QL = 6,7-dimethyl 1,4-dioxido-9,10-anthraquinone (QL(1)); 2, QL = 1,4-dioxido-9,10-anthraquinone (QL(2)), bpy = 4,4'-bipyridine) via an orthogonal-bonding approach was achieved in high yields. Their structures were characterized by single-crystal X-ray diffraction analysis. The rectangles exhibited multielectron-redox properties. The introduction of a bridging quininone moiety made notable changes in two well-separated single-electron reductions of the bpy moiety, as compared with other 2,2'-bisbenzimidazolate (BiBzlm) or thiolate- or alkoxide-bridged rectangles, followed by quasi-reversible reduction of the quininone moiety to allow the existence of different redox states. Electrochemical assessment using cyclic voltammetry and UV-vis-NIR spectroelectrochemistry revealed reversibly accessible 0, 1-, and 2- redox states. The comproportionation constant of the successive reduction processes was K(c) = 4.18 x 10(8) for complex 1 and 4.08 x 10(8) for 2. In spite of the high K(c) values, no obvious intervalence charge transfer bands were detected in either the vis, NIR, or IR regions, suggesting very weak electronic coupling between the ligand centers in the mixed-valent intermediates. In the mixed-valent intermediate, the overlap between donor and acceptor orbitals of the two bpy ligands engendered weak electronic coupling associated with distance that exceeded van der Waals ligand/ligand distances and created a class I fully isolated, non-interacting, valence-localized situation. Furthermore, unusual ligand-to-metal-to-ligand charge-transfer (LMLCT) transitions of complexes 1 and 2 at 298 K were observed in the visible region. Molecule 2 exhibited multiple emissions from the triplet-centered pi-pi* intraligand ((3)IL), metal-to-ligand charge-transfer ((3)MLCT) and triplet ligand-ligand charge transfer ((3)LLCT) levels and showed biexponential decay. By contrast, in complex 1, (3)IL emission was absent and only single-exponential decay was observed. These results reveal the different nature of the electronically excited states between 1 and 2. The mechanisms of the photophysical deactivation processes in these systems can be explained in terms of the electronic characteristics of the quininone molecules and possible geometrical differences of the excited states involved. In addition, the energies, characteristics, and molecular structures of the ground and lowest triplet excited state were calculated using the density functional theory method.

Synthesis, characterization of magnesium-substituted tungstoarsenate, [formula omitted], and its electrochromism

The novel, magnesium-substituted tungstoarsenate, [As 2W 15Mg 3O 62] 18− (As 2W 15Mg 3) ( 1) has been synthesized from the lacunary precursor [As 2W 15O 56] 12− and characterized by elemental analysis, IR, UV and 183W NMR spectroscopy. The 183W NMR spectrum of 1 exhibits three lines of 1:2:2 intensity at −141.17, −147.86 and −183.02 ppm, as expected for the C 3 v structure of the tri-substituted α-Dawson anion. The electrochemical behavior of 1 in aqueous solution has been investigated. The compound exhibits successive reduction processes of the W atoms in a negative potential range. The compound As 2W 15Mg 3-containing monolayer and multilayer films have been fabricated on ITO substrate with poly(diallyldimethylammonium) chloride (PDDA) by layer-by-layer deposition. Thus-prepared multilayer films were characterized by cyclic voltammetry (CV), UV–vis spectroscopy and X-ray photoelectron spectroscopy (XPS). The electrochemical behavior of the multilayer films shows three reversible two-electron redox waves in acidic aqueous solution in the potential range of 0.4 to −0.7 V, which are same with that in the solutions. The electrochromic behavior of the multilayer films has been studied in situ CV–UV–visible spectroelectrochemical methods, indicating the multilayer films show suitable response times and good reproducibility of response. This study provides a new compound to explore the possibility of application as electrochromism material.

Reversible Redox-Switchable Second-Order Optical Nonlinearity in Polyoxometalate: A Quantum Chemical Study of [PW11O39(ReN)]n− (n = 3−7)

In this paper, the relationship between the reversible redox properties and the second-order nonlinear optical (NLO) responses for the title series of complexes has been systematically investigated by using the time-dependent density functional theory (TDDFT) method combined with the sum-over-states (SOS) formalism. The results reveal that the successive reduction processes of five PW11ReN redox states should be PW11ReVII (1) --> PW11ReVI (2) --> PW11ReV (3) --> PW11ReV1e ( 4) --> PW 11ReV2e (5). Furthermore, their electrochemical properties have been reproduced successfully. It is noteworthy that the second-order NLO behaviors can be switched by reversible redox for the present studied complexes. Full oxidation constitutes a convenient way to switch off the second-order polarizability (system 1). The incorporation of extra electrons causes significant enhancement in the second-order NLO activity, especially for the third reduced state (system 4), whose static second-order polarizability (betavec) is about 144 times larger than that of fully oxidized 1. The characteristic of the charge-transfer transition corresponding to the dominant contributions to the betavec values indicates that metal-centered redox processes influence the intramolecular donor or acceptor character. Therefore, these kinds of complexes with the facile and reversible redox states could become excellent switchable NLO materials.

Synthesis, Crystal Structure and Electrochemistry of Two Complexes (YLn)3+[PW12O40]3− (L=Me2SO, Me2NCHO)

The reaction of α-H3[PW12O40] with Y(NO3)3 in the presence of DMF or DMSO leads to two complexes with the formulae {Y(DMSO)7}·PW12O40(1) and {[Y(DMF)7]2PW12O40}·PW12O 40(2). The crystal structures indicate that complex 1 consists of discrete [YLn]3+ cations and α-Keggin heteropolyanions [PW12O40]3−, whereas, in complex 2, donor-acceptor interaction results in a cation-anion-cation triplet. In addition, the electrochemical behavior of the two complexes indicates the usual successive reduction processes of the W atoms in the anions.

Surface Structure of Pt-Modified Au Nanoparticles and Electrocatalytic Activity in Formic Acid Electro-Oxidation

Platinum-modified Au nanoparticles on a carbon support were prepared using carbon-supported Au nanoparticles as a substrate and a successive reduction process. These nanoparticles were applied as an electrocatalyst for formic acid electro-oxidation. The uniform Pt-modified Au nanoparticles (<5 nm in diameter) were highly dispersed on the carbon particles, and the Au surface was deposited with nanoscaled Pt. The Pt-modified Au nanoparticles showed higher electrocatalytic activities than the pure Pt electrocatalyst in the area- and mass-specific current densities. These results might be due to the enhancement effect of Au atoms and the high Pt utilization in the formic acid electro-oxidation reaction.

Oligothiophene-2-yl-vinyl bridged mono- and binuclear ruthenium(II) tris-bipyridine complexes: Synthesis, photophysics, electrochemistry and electrogenerated chemiluminescence

A series of mono- and binuclear ruthenium(II) tris-bipyridine complexes tethered to oligothienylenevinylenes have been synthesized and characterized by 1H NMR, 13C NMR and TOF-MS spectrometry. Photophysics, electrochemistry and electrogenerated chemiluminescence (ECL) properties of these complexes are investigated. The electronic absorption spectra of the mononuclear ruthenium complexes show a significant red shift both at MLCT (metal-to-ligand charge transfer) and π–π ∗ transitions of oligothienylenevinylenes with increase in the number of thiophenyl-2-yl-vinyl unit. For the binuclear complexes these two absorption bands are overlapped. All the metal complexes have very weak emission compared to that of the reference complex Ru(bpy) 2+ 3. The first reduction potentials of all mononuclear ruthenium complexes are less negative than that of Ru(bpy) 2+ 3, due to the moderate electron-withdrawing effect of oligothienylenevinylenes. For binuclear ruthenium complexes, only one Ru(II/III) oxidation peak ( E 1/2 = 0.96 V vs. Ag/Ag +) was observed, suggesting a weak interaction between two metal centers. Three successive reduction processes of bipyridine ligands are similar among all ruthenium complexes except for RuTRu, which has a very sharp peak owing to the accumulation of neutral product on the electrode surface. All these ruthenium complexes exhibited different ECL property in CH 3CN solution without any additional reductant or oxidant. For three mononuclear ruthenium complexes, the ECL intensity strengthens with increase in the number of thiophene-2-yl-vinyl unit. However, the ECL efficiency dramatically decreased in the binuclear ruthenium complexes. The ECL efficiencies of all the reported complexes do not exceed that of Ru(bpy) 2+ 3, where the ECL efficiency decreases in the order of RuTRu > Ru3T > Ru2T > RuT > Ru2TRu ( RuT,bis-2,2′-bipyridyl-(4-methyl-4′-(2-thienylethenyl)-2,2′-bipyridine) ruthenium dihexafluorophosphate; Ru2T, bis-2,2′-bipyridyl-(4-methyl-4′-{( E)-2-[5-(( E)-2-thienylethenyl)-thienylethenyl]}-2,2′-bipyridine) ruthenium dihexafluorophosphate; Ru3T, bis-2,2′-bipyridyl-(4-methyl-4′-{( E)-2-{( E)-2-[5-(( E)-2-thienylethenyl)-thienylethenyl]}}-2,2′-bipyridine) ruthenium dihexafluorophosphate; RuTRu, bis-2,2′-bipyridyl-ruthenium-bis-[2-(( E)-4′-methyl-2, 2′-bipyridinyl-4)-ethenyl]-thienyl-bis-2,2′-bipyridyl-ruthenium tetrahexafluorophosphate; Ru2TRu, bis-2,2′-bipyridyl-ruthenium-( E)-1,2-bis-{2-[2-(( E)-4′-methyl-2,2′-bipyridinyl-4)-ethenyl]-thienyl}-ethenyl-bis-2,2′-bipyridyl-ruthenium tetrahexafluorophosphate).

Synthesis, crystal structure and characterization of a series of complexes constructed from coordinated Lanthanides(III) and the heteropolyanion [SiMo12O40]4−

The reaction of α-[SiMo12O40]4− with trivalent cations Ln3+ and N-methyl-2-pyrrolidone leads to a series of complexes of formula [Ln(NMP)4(H2O) n ]H[SiMo12O40] · 2NMP · mH2O [where Ln = La (1), Pr (2), Nd (3), Sm (4), Gd (5), n = 4, Ln = Dy (6), Er (7), n = 3. NMP = N-methyl-2-pyrrolidone]. The syntheses, X-ray crystal structures, IR, and ESR spectra and thermal properties of the complexes 1, 2, 4, 6, 7 have been reported previously. Here, we report X-ray crystal structures, IR, UV, ESR spectra and thermal properties of the complexes [Nd(NMP)4(H2O)4]H[SiMo12O40] · 2NMP · 1.5H2O (3), and [Gd(NMP)4(H2O)4]H[SiMo12O40] · 2NMP · H2O (5). In addition, the electrochemical behaviour of this series of complexes in aqueous solution and aqueous-organic solution has been investigated and systematic comparisons have been made. All these complexes exhibit successive reduction process of the Mo atoms.