Phenanthroline complexes bearing fused dipyrrolylquinoxaline anion recognition sites: efficient fluoride anion receptors

Novel anion recognition host molecules, tris-1,10-phenanthroline cobalt(III) and bis-2,2'-bipyridine mono-1,10-phenanthroline ruthenium(II) complexes bearing fused dipyrrolylquinoxaline moieties have been synthesized. As determined by UV-vis spectroscopic and electrochemical studies, these metal complexes bind fluoride with high affinity in polar media both in absolute terms and relative to the metal-free phenanthroline dipyrrolylquinozaline precursor from which they are derived (fluoride is bound to the tris-1,10-phenanthroline cobalt(III) dipyrrolylquinoxaline system with a 1:1 binding constant of 54 000 M-1 in DMSO). The large observed binding constants are ascribed to two factors, (i) the presence of a phenanthroline-coordinated cationic charge that decreases the electron density on the pyrrole NH protons and (ii) pure electrostatic effects.     

Theoretical studies on the elimination of hydrogen fluoride from alkyl fluoride and its substituent effect

The reaction mechanism of the α, α and α, β elimination of hydrogen fluorides from alkyl fluorides has been studied theoretically. For fluoroethane as a reactant, the transition state (TS) optimized at the level of the 6-31G** basis set shows that the α, β elimination proceeds via a four membered-ring TS with a barrier height 64.6 kcal/mol, while the α, α elimination, via a three-membered ring TS with a 83.7 kcal/mol barrier. Four substituents, CH₃, CN, F, and NH₂, were used to investigate the substituent effect of elimination by using the 3-21G basis set. The calculated barriers show that NH₂-substituted alkyl fluorides favor both the α, α and α, β elimination and these two reactions would be expected to proceed simultaneously. © 1996 John Wiley & Sons, Inc.     

Influence of nature of the fluoride ion on the electrochemical behaviors of Nb(V) in molten NaCl-KCl

Journal of Solid State Electrochemistry - In this research, the reduction mechanism of Nb(V) under various [F−]/[Nbn+] ratios (α) was investigated by a series of electrochemical...     

A new optical and electrochemical sensor for fluoride ion based on the functionalized boron-dipyrromethene dye with tetrathiafulvalene moiety

A new tetrathiafulvalene (TTF) derivative with the boron-dipyrromethene (BODIPY) moiety shows selectively optical and electrochemical sensing for fluoride ion. The mechanism of anion recognition has been investigated by ¹H NMR titration and DFT calculations. The results show that the receptor with redox active TTF moiety and fluorescent BODIPY subunits may be useful as sensors for detecting and sensing fluoride ion.     

Interface synthesis of mesoporous MnO2 and its electrochemical capacitive behaviors

Mesoporous MnO(2) has been synthesized by means of a novel, facile, and template-free method by virtue of a soft interface between CCl(4) and H(2)O without any surfactants or organometallic precursors or ligands. X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy analysis, scanning electron microscopy, and an ASAP2010 autoadsorption analyzer were applied to investigate the composition and microstructure of the as-synthesized MnO(2). The structure characterizations indicated a good mesoporous structure for as-prepared MnO(2) with an adsorption average pore diameter of 9.7 nm, mesoporous volume of 0.58 cm(3) g(-1), and Brunauer-Emmett-Teller specific surface area of 239 m(2) g(-1). Electrochemical properties of the mesoporous MnO(2) were elucidated by cyclic voltammograms, galvanostatic charge-discharge, and electrochemical impedance spectroscopy in 1 M Na(2)SO(4) electrolyte. Electrochemical data analysis demonstrated that as-synthesized MnO(2) had good capacitive behavior due to its unique mesoporous structure. A specific capacitance of ca. 220 F g(-1) could still be delivered for the mesoporous MnO(2) even at a scan rate of 100 mV s(-1).     

A study of ion charge transfer on electrochemical behaviors of poly(vinylidene fluoride)-derived carbon electrodes

In this work, porous carbon with a high specific surface area as electrode materials for supercapacitors are obtained by a carbonization process at various temperatures from 700 °C to 1000 °C without activation process using poly(vinylidene fluoride) (PVDF) as a carbon precursor. The electrochemical performance is characterized by cyclic voltammetry and galvanostatic charge–discharge cycling performance using two-electrode system in 6.0 M KOH as an aqueous electrolyte. The results indicate that carbonization temperature significantly affected the specific surface area and pore volume of the PVDF-derived carbons and their capacitive behavior. In particular, the electrochemical performance of the prepared PVDF-derived carbon is determined by both the electric double-layer capacitance and the pseudo-capacitance resulting from the residual surface functional groups on PVDF-derived carbons.     

Studies on electrochemical behaviors of acyclovir and its voltammetric determination with nano-structured film electrode

A multi-wall carbon nanotubes (MWNTs)-dihexadecyl hydrogen phosphate (DHP) film-coated glassy carbon electrode (GCE) was fabricated, and the electrochemical behaviors of acyclovir on the MWNTs-DHP film-coated GCE were investigated by using cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and chronocoulometry (CC). The oxidation peak current of acyclovir increased significantly and the peak potential shifted negatively at the MWNTs-DHP film-modified GCE, compared with that at a bare GCE. The results showed that this nano-structured film electrode exhibited excellent enhancement effects on the electrochemical oxidation of acyclovir. Consequently, a simple and sensitive electroanalytical method was developed for the determination of acyclovir. The oxidation peak current was proportional to the concentration of acyclovir from 8.0 × 10⁻⁸ to 1.0 × 10⁻⁵ mol/L. The detection limit was about 3.0 × 10⁻⁸ mol/L for 60 s accumulation at 0.00 V. The proposed method was demonstrated by using acyclovir tablets and the result was satisfying.     

Reactions of trivacant lone-pair-containing tungstobismutate and electrochemical behaviors of its sandwich-type products

We report the crystal structure of dimeric precursor Na₁₂[(Na(H₂O)₂)₆(α-BiW₉O₃₃)₂] (1), and the interaction of this precursor with transition metal ions. Interaction of 1 with Cu²⁺ in neutral medium leads to the formation of a Hervé-type sandwich polyoxoanion [(Cu(H₂O))₃(α-BiW₉O₃₃)₂]^12? (2) in high yield. Interaction of 1 with M²⁺ (M?=?Zn, Ni, Co, Mn) in acidic aqueous medium leads to formation of Krebs-type sandwich polyoxoanions [(M(H₂O)₃)₂(WO)₂(β-BiW₉O₃₃)₂]^10? (3–6). Coordination geometry of the M²⁺ ions, counterions and precursors can affect the structure of products. In our experiments, only the interaction of 1 with Cu²⁺ forms a trisubstituted sandwich-type product. The method using [α-Bi^IIIW₉O₃₃]^9? as starting material is a convenient and effective route for the synthesis of sandwich-type tungstobismutates in high purity and yield. The electrochemical properties of these sandwich-type tungstobismutates in aqueous solution are described.     

单层碳纳米管修饰电极上盐酸曲普利啶的电化学行为及其应用研究

应用循环伏安法研究了盐酸曲普利啶在碳纳米管修饰电极上的电化学行为.结果表明:在0.1 mol/L磷酸盐缓冲溶液(pH 6.9)中,盐酸曲普利啶产生一灵敏的氧化峰,其峰电位为0.81 V(vs.Ag/AgCl),峰电流与盐酸曲普利啶在1.0×10-6～1.3×10-4 mol/L浓度范围内呈线性关系,检出限为5.0×10-7mol/L,已用于片剂中盐酸曲普利啶的测定.     

甘草苷在悬汞电极上的电化学行为及方法研究

运用循环伏安法(CV)考察了甘草苷在悬汞电极(HMDE)上的电化学还原行为,在-0.7~-1.7 V(vs.SCE)电位窗口及0.10 mol/L(NH4)2SO4溶液中甘草苷在HMDE上的循环伏安行为是一在低扫描速度(<100 mV/s)下受吸附控制,在高扫描速度下受扩散控制的不可逆还原过程,还原峰电位(Epc)为-1.491 V。运用计时库仑法(CC)、计时电流法(CA)测定并计算了甘草苷的电荷传递系数α、扩散系数D以及表观速率常数Kf等电极过程动力学参数。初步探讨了甘草苷在HMDE上的反应机理,同时运用方波伏安法(SWV)研究了甘草苷在HMDE上的方波伏安行为,还原峰电流与其浓度在1.2×10-6~1.2×10-5mol/L及1.2×10-5~1.2×10-3mol/L范围内呈良好的线性关系,相关系数R=0.9936及0.9966,检出限8.0×10-7mol/L,据此可建立直接电化学测定甘草苷含量的方法。     

青蒿素及其衍生物电化学性质的研究I. 青蒿素在汞电极上的电化学还原

青蒿素及其衍生物代表着一类新型抗疟药。青蒿素分子中过氧基与抗疟活性密切相关。本文采用多种电化学方法研究了青蒿素分子中过氧基在Hg电极上的还原, 还原电位在0.0V(vs.Ag/AgCl)附近, 电极过程为不可逆还原, 反应电子数n=2, 半波电位E1/2=0.012V, 电子转移系数α=0.66, 表观标准电极反应速率常数ks'=6.34×10^-^6cm/s, 扩散系数D=4.3×10^-^6cm^2/s。反应产物在电极表面具有吸附性, 文中提出了可能的电化学反应机理。     

The electrochemical fluorination of acetyl fluoride

The electrochemical fluorination of acetyl fluoride in anhydrous hydrogen fluoride to produce trifluoroacetyl fluoride was investigated in a microprocessor-aided modified Simons' reactor. The product was recovered in acetic acid as trifluoroacetic acid. The experiments were carried out at a controlled anodic potential using a Cu/CuF₂ reference electrode. Product yields of 36 - 45%, current efficiencies of 30 to 50% and energy efficiencies of 11 – 23% were obtained.Experimental results of this investigation are presented and discussed.     

Study on optical recognition and electrochemical sensing of a 1,1′‐ferrocenedicarbonylhydrazine derivative for fluoride

A new compound, 1,1′‐di‐(p‐nitrophenylhydrazino‐β‐carbonyl)‐ferrocene ( 1 ) was designed as an anion receptor based on its hydrogen bonding interaction with anions. Investigation of UV–vis spectra showed that it was an excellent optical sensors for F^?. Furthermore, the nature of interaction between it and F^? was investigated by ¹H NMR titration experiments. In addition, the efficiency of the receptor applied as an electrochemical sensor for F^? was discussed by cyclic voltammetry (CV). Copyright © 2008 John Wiley & Sons, Ltd.     

Surface stoichiometry of zinc sulfide and its effect on the adsorption behaviors of xanthate

ABSTRACT: In this paper, the surface stoichiometry, acid-base properties as well as the adsorption of xanthate at ZnS surfaces were studied by means of potentiometric titration, adsorption and solution speciation modeling. The surface proton binding site was determined by using Gran plot to evaluate the potentiometric titration data. Testing results implied that for stoichiometric surfaces of zinc sulfide, the proton and hydroxide determine the surface charge. For the nonstoichiometric surfaces, the surface charge is controlled by proton, hydroxide, zinc and sulfide ions depending on specific conditions. The xanthate adsorption decreases with increasing solution pH, which indicates an ion exchange reaction at the surfaces. Based on experimental results, the surface protonation, deprotonation, stoichiometry and xanthate adsorption mechanism were discussed.     

Synthesis, structures, and magnetic properties of three fluoride-bridged lanthanide compounds: effect of bridging fluoride ions on magnetic behaviors

A family of fluoride-bridged lanthanide compounds, [Dy(III)F(oda)(H(2)O)(3)] (1, oda = oxidiacetate) and [Ln(III)(2)F(2)(oda)(2)(H(2)O)(2)] (Ln = Tb(2) and Dy(3)), was synthesized and characterized. To investigate the effects of bridging ligands on magnetic behaviors, two hydroxyl-bridged complexes of formulas [Ln(III)(2)(OH)(2)(oda)(2)(H(2)O)(4)] (Ln = Tb(4) and Dy(5)) were also synthesized. Magnetic measurements show that the magnetic behaviors of the compounds are obviously distinct. Compounds 1, 2, and 3 show ferromagnetic interactions, while only antiferromagnetic interactions are observed in compounds 4 and 5. Among these compounds, 1 and 3 show frequency-dependent ac-susceptibility indicative of slow magnetic relaxation. Because the structures of Dy(2) cores are very similar in compounds 3 and 5, it may be inferred that the differences of bridging ligands are mainly responsible for the distinct magnetic exchange interactions and relaxation dynamics.     

The effect of cationic disorder on the optical and electrochemical behavior of nanocrystalline ZnO preparedfrom peroxide precursors

The relation between particle size and the optical and electrochemical behavior of nanocrystalline ZnO was studied on materials prepared by the thermal decomposition of zinc peroxide. The formation of zinc oxide starts at 180°C and yields particles of characteristic size bigger than 10 nm. Smaller particles (r∼2–5 nm) may be prepared at reduced pressure and at a temperature of 150°C. The particle radius of synthesized nanocrystals increases proportionally to synthesis temperature. Regardless of actual particle size, synthesized ZnO samples show cationic disorder, with Zn distributed between 2b and 2a sites. The fraction of “octahedrally” coordinated Zn in 2a position decreases with increasing synthesis temperature. Zn disorder causes a narrowing of band gap, which results in the “red shift” of the absorption edge in the UV–Vis spectra of prepared samples with respect to bulk ZnO. The effect of the disorder on the band gap width is partially compensated by quantum size effects when the characteristic particle size drops below 5 nm. A decrease in particle size results in an asymmetric shift of valence and conduction band edges, which can be assigned to uneven effective masses of electrons and holes in nanocrystalline ZnO. Prepared nanocrystalline samples were (photo)electrochemically active; their activity, however, decreases with particle size.

2,7-Diaminofluorene-based organic dyes for dye-sensitized solar cells: effect of auxiliary donor on optical and electrochemical properties

New organic dyes containing a diarylaminofluorene unit as an electron donor and cyanoacrylic acid as acceptor and anchoring group in a donor-π-donor-π-acceptor architecture have been synthesized and characterized as sensitizers for nanocrystalline TiO(2)-based dye-sensitized solar cells. They have shown three major electronic absorptions originating from the π-π* and charge-transfer transitions covering the broad visible range (250-550 nm) in solution. The charge-transfer transition of the dyes exhibited negative solvatochromism, suggesting a polarized ground state. They have also displayed acidochromism in solution owing to the presence of a protonation-deprotonation equilibrium. On comparison with the triphenylamine and carbazole-based parent dyes (E)-2-cyano-3-(4-(diphenylamino)phenyl)acrylic acid and (E)-2-cyano-3-(9-ethyl-9H-carbazol-3-yl)acrylic acid they exhibited longer wavelength absorptions and facile oxidation, indicating the stronger electron-donating ability of the auxiliary chromophores. In addition, they exhibited nearly two times larger light-to-electron conversion efficiency under simulated AM 1.5 G irradiation (100 mW cm(-2)) with an aperture mask when compared to the parent dyes. Among the new dyes, the one containing the naphthylphenylamine segment showed better device characteristics attributable to the higher HOMO energy level which probably facilitates the regeneration of the dye and effective suppression of the back reaction of the injected electrons with the I(3)(-) in the electrolyte. The optical properties of the dyes were modeled using TDDFT simulations employing different theoretical models (B3LYP, CAM-B3LYP, and MPW1K), and the best correlations with the observed parameters have been found for CAM-B3LYP and MPW1K calculations. The electron lifetimes extracted from the electrochemical impedance measurements of the dye-sensitized solar cells were used to interpret the solar cell efficiency alternations.     

BODIPY-bridged push-pull chromophores: optical and electrochemical properties

A series of BODIPY bridged push-pull chromophores were prepared by a sequence of reactions involving: i) cross-coupling reactions promoted by palladium complexes; ii) Knoevenagel condensation leading to dicyano derivatives; iii) [2+2] cycloaddition. The last reaction is regioselective, providing mono-derivatives with anisole substituents. With dimethylaminophenyl donor groups, double addition is feasible, providing highly colored dyes displaying remarkable electrochemical properties.     

Core-extended terrylene diimide on the bay region: synthesis and optical and electrochemical properties

Two novel core-extended terrylene diimides on the bay region (CETDIs) were synthesized via annulation of the four additional ethylene units or benzene units on the bay region of the terrylene diimide core. The optical and electrochemical properties of the two compounds were investigated. These CETDIs exhibited broad absorption spectra with high extinction coefficients, which span a wide range in the ultraviolet and visible spectrum from 300 to 700 nm. Furthermore, the redox process of the CETDIs increased from two waves to four waves, and the lowest unoccupied molecular orbital (LUMO) levels were enhanced from -4.00 to -3.59 eV.     

二茂铁甲基季铵盐的电化学行为

二茂铁是具有夹心型结构和芳香性的高度富电子体系,热稳定性好,有良好的电化学反应活性,具有易受环境影响的可逆氧化还原电对的特点。通过分子设计将二茂铁衍生物引入自组装单分子膜体系,考察其电子转移过程以及与膜结构的对应关系,可以为更深层次的分子设计和功能组装反馈信息;以二茂铁衍生物结构单元设计合成的氧化还原型大环化合物对离子的选择性迁移、氧化还原催化及发展为新一代的传感器有着诱人的应用前景。