The Signal Amplification in Electrochemical Detection of Chloramphenicol Using Sulfonated Polyaniline‐chitosan Composite as Redox Capacitor

In this work, a novel redox capacitor was designed for signal amplification in electrochemical detection. It was fabricated by co‐electrodeposition of a conducting polymer, sulfonated polyaniline (SPAN) and chitosan on a glass carbon electrode, and its function was evaluated for being a localized source to transfer electron between FcCOOH (Fc) and Ru(NH₃)₆Cl₃ in solution via redox cycling. Furthermore, the electrochemical detection of chloramphenicol, a broad‐spectrum antibiotic was performed using the redox capacitor in the presence of Fc. A significant amplification in cathodic current response of chloramphenicol was obtained through a continuous redox‐cycling reaction. The performance of the amplifying signal responded linearly to chloramphenicol in a concentration range of 0.05 to 50.0 μmol L⁻¹ with a low detection limit of 0.01 μmol L⁻¹. The proposed approach exhibited good reproducibility and stability, and could be used for detection of chloramphenicol in eye drops by standard addition method with the recoveries from 96.5 % to 103.0 %.     

Switching the Electron-Donating Ability of Phosphines through Proton-Responsive Imidazolin-2-ylidenamino Substituents

Stimuli-responsive ancillary ligands are valuable tools to control the activity and selectivity of transition-metal catalysts. The synthesis and characterization of a series of metal complexes containing phosphines with proton-responsive imidazolin-2-ylidenamino substituents are reported. Determination of the ligand-donor properties revealed that protonation of each substituent increases the Tolman electronic parameter (TEP) of the phosphine by 22 cm⁻¹, hence allowing for switching of the electron-donor power of phosphine 2 within an unprecedented range (ΔTEP=43.4 cm⁻¹).     

Ferrocene Tethered Polyvinyl Alcohol/Silica Film Electrode for Electrocatalytic Sulfite Sensing

Ferrocene was linked to polyvinyl alcohol polymer via ethylene dioxi‐bis‐ethylamine (PV‐Fc) spacer and the synthesized redox polymer was characterised by FT‐IR and H¹NMR spectroscopy. Aqueous solution of PVA‐Fc was used to prepare its silica composite with tetraethylorthosilicate (TEOS). The immobilized PVA‐Fc/silica film showed E⁰ about 0.245 V and apparent diffusion coefficient was measured to be 2.76×10⁻⁸ cm² s⁻¹. The ferrocene with flexible spacer in PVA‐Fc/silica film showed an excellent electrocatalytic activity towards the sulfite oxidation at 0.35 V, that was minimum 0.3 V negative shift of the overpotential than the bare electrode. The effect of the interfearing species like acetate, ammonium, carbonate, phosphate and sulfate has been checked for the sulfite detection. Under the optimized conditions the prepared composite showed sulfite oxidation in the linear range of 5×10⁻⁷ M to 1×10⁻⁴ M and lower detection limits of 1.5×10⁻⁷ M.     

Fe（C5H4-CH2-Trp-OMe）2的合成、晶体结构及金属离子识别性能

摘要： 以优化的两步一锅反应法合成了生物金属有机化合物Fe（C₅H₄-CH₂-Trp-OMe）₂（FcL）,通过NMR、HRMS及IR等对其结构进行了表征,利用X射线单晶衍射测定了分子结构。循环伏安法研究表明FcL在0.00~0.90 V电位范围内,给出一稳定的、形态良好的氧化还原峰,这归于化合物中Fc/Fc⁺电对的氧化还原过程。电化学金属离子识别研究显示FcL在过渡金属离子Zn²⁺和Cu²⁺的存在下,导致了配体Fc/Fc⁺式量电位的显著阳极移动,其△E^0''对Zn²⁺和Cu²⁺分别为342和335 mV,表明了FcL对Zn²⁺和Cu²⁺具有良好的识别能力。     

Preparation of hole transporting polymers by condensation polymerization of triphenylamine derivatives

Hole transporting polymers were prepared by condensation polymerization of triphenylamine and N,N,N',N'‐tetraphenylbenzidine (TPD) having alkyl group with aldehydes in the presence of p‐toluenesulfonic acid. The obtained polymers had molecular weight higher than 10,000 and good film formation ability. It was found that the aromatic amine monomers were connected with aldehyde monomer at the p‐position of the phenyl group. TPD‐aldehyde polymers had almost the same UV absorption and redox potentials as those of TPD monomer indicating that the electronic structure of amine unit did not change by the polymerization. The hole transporting mobility was in the range of 10⁻³‐10⁻⁶cm²/Vs. The electroluminescent device consisting of ITO/TPD polymer/Alq/Mg‐Ag had a maximum luminance of 9000 cd/m².     

Fe(C_5H_4-CH_2-Trp-OMe)_2的合成、晶体结构及金属离子识别性能

以优化的两步一锅反应法合成了生物金属有机化合物Fe(C_5H_4-CH_2-Trp-OMe)2(Fc L),通过NMR、HRMS及IR等对其结构进行了表征,利用X射线单晶衍射测定了分子结构。循环伏安法研究表明Fc L在0.00~0.90 V电位范围内,给出一稳定的、形态良好的氧化还原峰,这归于化合物中Fc/Fc+电对的氧化还原过程。电化学金属离子识别研究显示FcL在过渡金属离子Zn~(2+)和Cu~(2+)的存在下,导致了配体Fc/Fc+式量电位的显著阳极移动,其ΔE0′对Zn~(2+)和Cu~(2+)分别为342和335 m V,表明了Fc L对Zn~(2+)和Cu~(2+)具有良好的识别能力。     

C−H Bond Activation by Iridium(III) and Iridium(IV) Oxo Complexes

Oxidation of an iridium(III) oxo precursor enabled the structural, spectroscopic, and quantum-chemical characterization of the first well-defined iridium(IV) oxo complex. Side-by-side examination of the proton-coupled electron transfer thermochemistry revealed similar driving forces for the isostructural oxo complexes in two redox states due to compensating contributions from H⁺ and e⁻ transfer. However, C−H activation of dihydroanthracene revealed significant hydrogen tunneling for the distinctly more basic iridium(III) oxo complex. Our findings complement the growing body of data that relate tunneling to ground state properties as predictors for the selectivity of C−H bond activation.     

Proton-Reservoir Hydrogel Electrolyte for Long-Term Cycling Zn/PANI Batteries in Wide Temperature Range

Advanced aqueous batteries are promising for next generation flexible devices owing to the high safety, yet still requiring better cycling stability and high capacities in wide temperature range. Herein, a polymeric acid hydrogel electrolyte (PAGE) with 3 M Zn(ClO₄)₂ was fabricated for high performance Zn/polyaniline (PANI) batteries. With PAGE, even at −35 °C the Zn/Zn symmetrical battery can keep stable for more than 1 500 h under 2 mA cm⁻², and the Zn/PANI battery can provide ultra-high stable specific capacity of 79.6 mAh g⁻¹ for more than 70 000 cycles at 15 A g⁻¹. This can be mainly ascribed to the −SO₃⁻H⁺ function group in PAGE. It can generate constant protons and guide the (002) plane formation to accelerate the PANI redox reaction kinetics, increase the specific capacity, and suppress the side reaction and dendrites. This proton-supplying strategy by polymeric acid hydrogel may further propel the development of high performance aqueous batteries.     

Pulse radiolysis and cyclic voltammetry studies of redox properties of phenothiazine radicals

One-electron transfer equilibria between seven phenothiazines were characterized by pulse radiolysis, producing radical-cations via oxidation by Br₂^·− or (SCN)₂^·− radicals. The reduction potentials of the phenothiazine radicals were determined by cyclic voltammetry. As an independent check, the redox equilibrium between one phenothiazine and the redox indicator ABTS was investigated. The data establish phenothiazines as useful indicators for radical redox properties. However, there are potential problems of aggregation, additional reactions with Br⁻/Br₂^·− and reactivity of the radicals towards buffers or other nucleophiles.     

A symmetric aqueous redox flow battery based on viologen derivative

Due to the diversity and feasibility of structural modification for organic molecules,organic-based redox flow batteries(ORFBs) have been widely investigated,especially in aqueous solution under neutral circumstance.In this work,a symmetric aqueous redox flow battery(SARFB) was rationally designed by employing a bipolar redox active molecule(N,N'-dimethyl-4,4-bipyridinium diiodide,MVI_2) as both cathode and anode materials and combining with an anion exchange membrane.For one MVI_2 flow battery,MV~(2+)/MV~(·+) and I~-/I_3~-serve as the redox couples of anode and cathode,respectively.The MVI_2 battery with a working voltage of 1.02 V exhibited a high voltage efficiency of 90.30% and energy efficiency of 89.44% after 450 cycles,and crossover problem was prohibited.The comparable conductivity of MVI_2 water solution enabled to construct a battery even without using supporting electrolyte.Besides,the bipolar character of MVI_2 battery with/without supporting electrolyte was investigated in the voltage range between-1.2 V and 1.2 V,showing excellent stable cycling stability during the polarity-reversal test.     

Diphosphoryl-functionalized Polyoxometalates: Structurally and Electronically Tunable Hybrid Molecular Materials

Herein, we report the synthesis and characterization of a new class of hybrid Wells–Dawson polyoxometalate (POM) containing a diphosphoryl group (P₂O₆X) of the general formula [P₂W₁₇O₅₇(P₂O₆X)]⁶⁻ (X=O, NH, or CR¹R²). Modifying the bridging unit X was found to impact the redox potentials of the POM. The ease with which a range of α-functionalized diphosphonic acids (X=CR¹R²) can be prepared provides possibilities to access diverse functionalized hybrid POMs. Compared to existing phosphonate hybrid Wells–Dawson POMs, diphosphoryl-substituted POMs offer a wider tunable redox window and enhanced hydrolytic stability. This study provides a basis for the rational design and synthesis of next-generation hybrid Wells–Dawson POMs.     

Electroreductive Radical Borylation of Unactivated (Hetero)Aryl Chlorides Without Light by Using Cumulene-Based Redox Mediators**

Single-electron transfer (SET) plays a critical role in many chemical processes, from organic synthesis to environmental remediation. However, the selective reduction of inert substrates (E_p/2<−2 V vs Fc/Fc⁺), such as ubiquitous electron-neutral and electron-rich (hetero)aryl chlorides, remains a major challenge. Current approaches largely rely on catalyst photoexcitation to reach the necessary deeply reducing potentials or suffer from limited substrate scopes. Herein, we demonstrate that cumulenes–organic molecules with multiple consecutive double bonds–can function as catalytic redox mediators for the electroreductive radical borylation of (hetero)aryl chlorides at relatively mild cathodic potentials (approximately −1.9 V vs. Ag/AgCl) without the need for photoirradiation. Electrochemical, spectroscopic, and computational studies support that step-wise electron transfer from reduced cumulenes to electron-neutral chloroarenes is followed by thermodynamically favorable mesolytic cleavage of the aryl radical anion to generate the desired aryl radical intermediate. Our findings will guide the development of other sustainable, purely electroreductive radical transformations of inert molecules using organic redox mediators.     

Controlling Selectivity in Shuttle Hetero-difunctionalization Reactions: Electrochemical Transfer Halo-thiolation of Alkynes

Shuttle hetero-difunctionalization reaction, in which two chemically distinct functional groups are transferred between two molecules, has long been an unmet goal due to the daunting challenges in controlling the chemo-, regio-, and stereoselectivity. Herein, we disclose an electrochemistry enabled shuttle reaction (e-shuttle) to selectively transfer one RS⁻ and one X⁻ group between β-halosulfides and unsaturated hydrocarbons via a consecutive paired electrolysis mechanism. The preferential anodic oxidation of one anion over the other, which is controlled by their distinct redox potentials, plays a pivotal role in controlling the high chemoselectivity of the process. This easily scalable methodology enables the construction of a myriad of densely functionalized β-halo alkenyl sulfides in unprecedented chemo-, regio-, and stereoselectivity using benign surrogates, e.g., 2-bromoethyl sulfide, avoiding the handling of corrosive and oxidative RS–Br reagents. In a broader context, these results open up new strategies for selective shuttle difunctionalization reactions.     

Conjugated and Non-conjugated Polymers Containing Two-Electron Redox Dihydrophenazines for Lithium-Organic Batteries

Organic p-type cathode materials have recently attracted increasing attention due to their higher redox potentials and rate capabilities in comparison to n-type cathodes. However, most of the p-type cathodes based on one-electron redox still suffer from limited stability and low specific capacity (<150 mAh g⁻¹). Herein, two polymers, conjugated poly(diethyldihydrophenazine vinylene) ( CPP ) and non-conjugated poly(diethyldihydrophenazine ethylidene) ( NCPP ) containing two-electron redox dihydrophenazine, have been developed as p-type cathode materials. It is experimentally and theoretically found that the conjugated linkage among the redox centers in polymer CPP is more favorable for the effective charge delocalization on the conjugated polymer backbone and the sufficient oxidation in the higher potential region (3.3–4.2 V vs. Li/Li⁺). Consequently, the CPP cathode displays a higher reversible specific capacity of 184 mAh g⁻¹ with excellent cycling stability.     

Constructing 2D Sandwich-like MOF/MXene Heterostructures for Durable and Fast Aqueous Zinc-Ion Batteries

Two-dimensional metal–organic frameworks (2D MOFs) can be used as the cathodes for high-performance zinc-ion battery due to their large one-dimensional channels. However, the conventionally poor electrical conductivity and low structural stability hinder their advances. Herein, we report an alternately stacked MOF/MX heterostructure, exhibiting the 2D sandwich-like structure with abundant active sites, improved electrical conductivity and exceptional structural stability. Ex situ characterizations and theoretical calculations reveal a reversible intercalation mechanism of zinc ions and high electrical conductivity in the 2D heterostructure. Electrochemical tests confirm excellent Zn²⁺ migration kinetics and ideal pseudocapacitive behaviors. As a consequence, Cu-HHTP/MX shows a superior rate performance (260.1 mAh g⁻¹ at 0.1 A g⁻¹ and 173.1 mAh g⁻¹ at 4 A g⁻¹) and long-term cycling stability of 92.5 % capacity retention over 1000 cycles at 4 A g⁻¹.     

Electrode processes of Cr(II) in non-complexing and complexing media

The formal potentials and the kinetics parameters for the electrode process: Cr²⁺+2 e⁻ = Cr^o occurring at a mercury electrode in solutions of NaClO₄, NaCI, NaBr, and NaSCN, were determined from the analysis of irreversible anodic and cathodic chronocoulometric waves. The interaction of Cr(II) with Cl⁻ was found to be negligible (equilibrium constant K <1) whereas the interaction with Br⁻ and SCN⁻ was weak (K₁(Br⁻)=1 M⁻¹ and β₂(SCN⁻) = 25 M⁻²). The results of the analysis of the formal rate constant of this and other amalgam forming reactions suggested that the formation of amalgam was the most important step in the whole process.     

Remark on the ground state potentials and dissociation energies of the alkali hydrides

The ground state Rydberg—Klein—Rees (RKR) potentials and the corresponding molecular constants of the alkali hydrides, recommended in a recent article by Stwalley et al. (J. Phys. Chem. Ref. Data, to be published [1]) are critically evaluated in the framework of the reduced potential curve (RPC) scheme. A comparison with the older RPC analysis of the ground states of the alkali hydrides is briefly discussed. The efficiency of the RPC method for the detection of errors in the RKR potential (spectroscopic constants) and for the estimation of the dissociation energy is emphasized. Although the RKR potentials of NaH and RbH are known only up to 54 and 57% of D_e, respectively, the RPC method permitted here at least a substantial reduction of the uncertainty in the lower limit of D_e(NaH) (by 70 cm⁻¹) and in the lower and upper limits of D_e(RbH) (by 250 and 500 cm⁻¹, respectively) which are now estimated as 15 870, 14 230 and 14 680 cm⁻¹, respectively. The RPC picture even suggests that the values 14 380 and 14 580 cm⁻¹ may possibly be taken as reasonable limits for D_e(RbH). Accurate extensions of the inner wings of the potentials of NaH, RbH and CsH were calculated using the generalized reduced potential curve (GRPC) method. The limit of error of these extensions should be smaller than 0.002 Å if the potentials are correct.     

Competition between dopants on redox reaction of polypyrrole

The surface of PPy prepared in a multiple electrolyte solution such as NaDS-NaClO₄ in H₂O shows a coarser structure than that of the polymer prepared in a single electrolyte system. DS⁻ with a large aliphatic chain is used as a dopant in preparation of PPy. The dopant is trapped in PPy when the polymer is reduced in an aqueous system. A cation Na⁺ or K⁺ is inserted into the polymer to balance the free DS⁻ liberated form and remained in it on reduction. PPy doped with DS⁻ shows a high degree of redox reactivity in the system of TBADS-AN but a poor stability in repeated redox process. The degree and rate of redox reactivity enhance when an aqueous solution of NaClO₄ is used as an electrolyte system. Both Na⁺ and ClO₄⁻take part in the redox reaction and the reduction process is intense at only one current potential.     

A hexaazatriphenylene-based porous organic polymer for high performance supercapacitor

Porous organic polymers (POPs) with high physiochemical stability and pseudocapacitive activity are crucial for supercapacitors with high specific capacitance and long cycle life. We report herein a hexaazatrinaphthylene-based POP (HPOP-1) for high-performance supercapacitor by introducing redox-active hexaazatrinaphthylene (HATN) moiety through Sonogashira–Hagihara coupling reaction. HATN moiety can undergo a proton-induced electron transfer redox reaction, which endows HPOP-1 with high pseudocapacitive activity. As electrode materials for supercapacitor application, HPOP-1 exhibits high specific capacitance (667 F g⁻¹ at 0.5 A g⁻¹) and long-term cyclic stability (90% capacitance retention after 10,000 cycles at 5 A g⁻¹) in a three-electrode system with 1 M H₂SO₄ as the electrolyte. In addition, HPOP-1 also exhibits a specific capacitance of 376 F g⁻¹ at 0.5 A g⁻¹ in 1 M KOH electrolyte. An asymmetric supercapacitor was further fabricated with HPOP-1 as negative electrode and rGO as positive electrode, respectively. The device delivers a specific capacitance of 63 F g⁻¹ at 0.5 A g⁻¹ and a rate performance of 37 F g⁻¹ at 5 A g⁻¹. Our work provides a facile approach for the design and preparation of pseudocapacitive POPs with high specific capacitance and long cycle life.