Electron Redox Processes Research Articles

DFT Study on the Second-Order NLO Responses of 2-Phenyl Benzoquinoline Ir(III) Complexes by Substituents and Redox Effects.

Metal complexes have received extensive attention in nonlinear optical (NLO) materials because of their advantages, such as shorter response times and more flexible structural properties. Density functional theory is used in investigating the geometric structures, electronic structures, charge centroid, and first hyperpolarizability (βtot) of a series of selected 15 coordinated Ir(III) complexes. The substitute effect and one-electron redox process effects on the structures and properties of 15 coordinated Ir(III) complexes are considered. When the electron-withdrawing group is introduced into the ligand, the HOMO-LUMO energy gap decreases and the βtot value increases, positively correlating with the electron-withdrawing ability. The single electron redox process can also improve the NLO responses of complexes, especially the reduction process. The βtot value of complex 4- is the largest, 2078 times higher than that of complex 4. The analysis shows that the variation of NLO responses of complexes is ascribed to the change of electronic structures and the charge transfer modes induced by the ligand modification and redox process, which are considered to be two effective methods in enhancing the NLO responses of 2-phenyl benzoquinoline Ir(III) complexes. This study aims to offer design insights into high-performance nonlinear optical materials.

Full‐Hexacyanometallate Aqueous Redox Flow Batteries Exceeding 1.5 V in an Aqueous Solution

AbstractAqueous redox flow batteries (RFBs) have attracted significant attention as energy storage systems by virtue of their inexpensive nature and long‐lasting features. Although all‐vanadium RFBs exhibit long lifetimes, the cost of vanadium resources fluctuates considerably, and is generally expensive. Iron–chromium RFBs take advantage of utilizing a low‐cost and large abundance of iron and chromite ore; however, the redox chemistry of CrII/III generally involves strong Jahn–Teller effects. Herein, this work introduces a new Cr‐based negolyte coordinated with strong‐field ligands capable of mitigating strong Jahn–Teller effects, thereby facilitating low redox potential, high stability, and rapid kinetics. The balanced full‐cell configuration features a stable lifetime of 500 cycles with energy density of 14 Wh L−1. With an excessive posolyte, the full‐cell can attain a high energy density of 38.6 Wh L−1 as a single electron redox process. Consequently, the proposed system opens new avenues for the development of high‐performance RFBs.

Functionalized Hf3C2 and Zr3C2 MXenes for suppression of shuttle effect to enhance the performance of sodium–sulfur batteries

Sodium-sulfur batteries show great potential for storing large amounts of energy due to their ability to undergo a double electron-redox process, as well as the plentiful abundance of sodium and sulfur resources. However, the shuttle effect caused by intermediate sodium polysulfides (Na2Sn) limits their performance and lifespan. To address this issue, here we propose using Hf3C2T2 and Zr3C2T2 (T = F, O), two functionalized MXenes, as cathode additives to suppress the shuttle effect. By using density-functional theory calculations, we investigate nature of the interactions between Na2Sn and MXene, such as the strength of adsorption energy, the electronic density of states, the charge exchange, and the dissociation energy of the Na2S molecule. Our findings show that both Hf3C2T2 and Zr3C2T2 systems inhibit the shuttle effect by binding to Na2Sn with a binding energy stronger than the commonly used electrolyte solvents. These MXenes retain their metallicity during this process and the decomposition barrier for Na2Sn on the oxygen-functionalized MXenes gets reduced which enhances the electrochemical process. Among the MXene systems studied, Zr3C2O2 shows the best performance in suppressing the shuttle effect and catalyzing the electrochemistry process and, thus, increasing the battery's reversible capacity and lifespan.

Cyclic voltammetric studies of electron transfer reactions associated with bioactive iron–KA complexation at different biological pH

This study explores electrochemical interactions of a pharmaceutical drug, kojic acid (5-hydroxy-2-hydroxymethyl-4 H-pyran-4-one, KA), with bioactive iron Fe(III) at different pH systems by using cyclic voltammetric technique. For this study, buffers relevant to physiological pH of blood and digestive system have been selected. Bioactive iron was found to form an electroactive complex [Fe(III)L3] in the presence of KA at all studied pH, whereas electrochemical behavior of KA was also changed by complex formation. This electrochemical investigation reveals that under the experimental conditions, [Fe(III)L3] complex undergoes a diffusion controlled, one electron redox process that is quasi-reversible in nature. It was also found that [Fe(III)L3] complex undergoes coupled chemical reaction according to EC (an electron transfer reaction followed by a chemical reaction) mechanism, and this interaction is pH dependent. Modified Nicholson and Shain, Gileadi, and Kochi methods were used to determine standard heterogeneous electron transfer rate constant ( k0) of [Fe(III)L3] complex. It was found to be in the range of 10−3 to 10−5 cm/s.

Enabling two-electron redox chemistry of P-type organic cathode for high-capacity aluminium-ion batteries

P-type organic cathodes (p-OCs) hold great promise in aluminium-ion batteries (AIBs), however current p-OCs exhibit apparent one or less than one electron redox processes and low capacities. Herein, we report a compromised electron-donating substitution strategy to excite 1-aminopyrene (ANP), a pyrene (Pyr) derivative, to undergo two-electron transfer, achieving a high specific capacity of 212 mA g−1 and excellent rate/long cycling performances (e.g., 106 mAh g−1 at 10 A g−1 for 12,000 cycles), superior over reported organic AIB cathodes. The electronic and steric effects of substitutes in a variety of Pyr derivatives on their functionality have been revealed. The electron-donating effect of the amino group plays two different roles, one in favoring the electron removal of neutral Pyr derivatives, another in reducing the positive charge density of oxidized radical cations. Collectively, ANP with the compromised electron-donating effect exhibits the highest binding energy with AlCl4- and reasonable voltage within the electrolyte working threshold, enabling the unprecedented two-electron transfer.

Unlocking New Redox Activity in Alluaudite Cathodes through Compositional Design

Sodium (Na)-ion conducting polyanionic structures are among the most promising cathode materials to enable more sustainable Na-based battery chemistries to replace current Li-based energy storage systems. Materials adopting the alluaudite structure have been found to reversibly intercalate Na, with phosphate and sulfate derivatives exhibiting moderate to high capacities when used as Na-ion cathodes. However, the development of alluaudite cathodes has been hampered by the fact that largely only Fe2+/3+ redox has been observed in this structure. Herein, we show that the Mn2+/3+ redox couple can be activated through compositional tuning of alluaudite compounds. Specifically, vanadate compounds were explored to increase the electrical conductivity as compared to the phosphates and sulfates. Al substitution was also employed to buffer the Jahn–Teller distortions of Mn(III)O6 octahedra, further facilitating electron transfer and redox processes. We report the synthesis of a series of new Na2Mn3–xAlx(VO4)3 alluaudite cathodes and employ synchrotron X-ray diffraction, solid-state nuclear magnetic resonance, scanning electron microscopy, density functional theory, X-ray absorption spectroscopy, and magnetometry to characterize the structure, morphology, electronic, and magnetic properties of the as-synthesized materials. Electrochemical Na de(intercalation) in Na2Mn3–xAlx(VO4)3 (x = 0, 0.05, 0.2) was probed through galvanostatic cycling, galvanostatic intermittent titration technique, and ex situ synchrotron X-ray diffraction. While these materials are all redox active, Al substitution results in a more than 2-fold increase in discharge capacity. The successful activation of a higher voltage Mn2+/3+ redox couple opens up a new compositional space for alluaudite-type Na-ion cathodes.

The aprotic electrochemistry of quinones

Quinones play important roles in biological electron transfer reactions in almost all organisms, with specific roles in many physiological processes and chemotherapy. Quinones participate in two-electron, two-proton reactions in aqueous solution at equilibrium near neutral pH, but protons often lag behind the electron transfers. The relevant reactions in proteins are often sequential one electron redox processes without involving protons. Here we report the aprotic electrochemistry of the two half-couples, Q/Q.- and Q.−/Q=, of 11 parent quinones and 118 substituted 1,4-benzoquinones, 91 1,4-naphthoquinones, and 107 9,10-anthraquinones. The measured redox potentials are fit quite well with the Hammett para sigma (σpara) parameter. Occasional exceptions can involve important groups, such as methoxy substituents in ubiquinone and hydroxy substituents in therapeutics. These can generally be explained by reasonable conjectures involving steric clashes and internal hydrogen bonds. We also provide data for 25 other quinones, 2 double quinones and 15 non-quinones, all measured under similar conditions.

Iron(II) Complexes Featuring a Redox-Active Dihydrazonopyrrole Ligand.

Nature uses control of the secondary coordination sphere to facilitate an astounding variety of transformations. Similarly, synthetic chemists have found metal-ligand cooperativity to be a powerful strategy for designing complexes that can mediate challenging reactivity. In particular, this strategy has been used to facilitate two electron reactions with first row transition metals that more typically engage in one electron redox processes. While NNN pincer ligands feature prominently in this area, examples which can potentially engage in both proton and electron transfer are less common. Dihydrazonopyrrole (DHP) ligands have been isolated in a variety of redox and protonation states when complexed to Ni. However, the redox-state of this ligand scaffold is less obvious when complexed to metal centers with more accessible redox couples. Here, we synthesize a new series of Fe-DHP complexes in two distinct oxidation states. Detailed characterization supports that the redox-chemistry in this set is still primarily ligand based. Finally, these complexes exist as 5-coordinate species with an open coordination site offering the possibility of enhanced reactivity.

Engineering Vanadium Pentoxide Cathode for the Zero‐Strain Cation Storage via a Scalable Intercalation‐Polymerization Approach

AbstractThe layered V2O5 cathode exhibits appealing features of multiple electron redox processes and versatile cation‐storage capacities. However, the huge volume respiration induces structural collapse and limits its commercial‐scale deployment. Herein, a scalable water‐bath strategy is developed to tailor the (001) spacing of the bulk V2O5 from the original 4.37 Å to its triple value (14.2 Å). The intercalated polyaniline (PANI) molecules act as pillars in the V2O5 interlayer, thus affording the abundant storage sites and enhanced cation diffusivities of Li+, Na+, or hydrated Zn2+. Upon various cations (de‐)intercalation, transmission‐mode operando X‐ray diffraction is employed to document the zero‐strain behavior of the PANI‐intercalated V2O5. This scalable intercalation‐polymerization strategy, coupled with the compatibility study of the ionic radius and the c‐lattice for the layered structure, enables the rational engineering of the intercalation‐type cathodes toward facile reaction kinetics.

Applications of Modified Biochar-Based Materials for the Removal of Environment Pollutants: A Mini Review

The biochar treated through several processes can be modified and utilized as catalyst or catalyst support due to specific properties with various available functional groups on the surface. The functional groups attached to the biochar surface can initiate active radical species to play an important role, which lead to the destruction of contaminants as a catalyst and the removal of adsorbent by involving electron transfer or redox processes. Centering on the high potential to be developed in field applications, this paper reviews more feasible and sustainable biochar-based materials resulting in efficient removals of environmental pollutants as catalyst or support rather than describing them according to the technology category. This review addresses biochar-based materials for utilization as catalysts, metal catalyst supports of iron/iron oxides, and titanium dioxide because the advanced oxidation process using iron/iron oxides or titanium dioxides is more effective for the removal of contaminants. Biochar-based materials can be used for the removal of inorganic contaminants such as heavy meals and nitrate or phosphate to cause eutrophication of water. The biochar-based materials available for the remediation of eutrophic water by the release of N- or P-containing compounds is also reviewed.

Surface immobilisation of the Krebs type polyoxometalates with silver nanoparticles

Modified electrodes composed of the anionic Kreb type polyoxometalates, K10[Bi2W20Co2O70(H2O)6]nH2O, K10[Sb2W20Co2O70(H2O)6]nH2O and K8[Sb2W20Cu2O70(H2O)6]nH2O, and cationic Poly(ethyleneimine) (PEI) capped silver nanoparticles have been constructed through the layer-by-layer (LBL) technique onto carbon electrode surfaces. The cyclic voltammograms recorded during film construction exhibited redox activity associated with the Ag nanoparticles and each POM's tungsten-oxo four electron redox process. The modified electrodes were then investigated for their stability towards redox cycling at pH2.5, thin layer behaviour and pH dependent redox chemistry. Electrochemical impedance spectroscopy was employed for the modified electrode system showing the relatively low charge transfer resistance (RCT) of the POM based films.

Cd(II) complex constructed from dipyridyl imine ligand: Design, synthesis and exploration of its photocatalytic degradation properties

Abstract A new Cd(II) complex, obtained by the interaction of 2,2-dimethyl-N,N'-bis((pyridin-2-yl)methylene)propane-1,3-diamine with a Cd(II) ion, is reported. The prepared N4 mononuclear species is structurally characterized by microanalyses, FT-IR, ESI-MS, 1H, 13C- and Dept-135 NMR spectroscopy, and single crystal X-ray diffraction measurements. The electrochemical behavior of the complex is also reported, and exhibits irreversible one electron redox process. Furthermore, the synthesized Cd(II) complex showed significant fluorescence property, and worked as a strong photocatalyst to degrade the Alizarin Red S dye (ARS) under visible light irradiation. The results obtained are excellent showing 82% (approximately) degradation of ARS dye in 30 h.

Redox-Specific Allosteric Modulation of the Conformational Dynamics of κB DNA by Pirin in the NF-κB Supramolecular Complex.

The molecular basis of gene regulation by Nuclear Factor-κB (NF-κB) transcription factors and their coregulators is not well understood. This family of transcription factors controls a number of essential subcellular processes. Human Pirin, a nonheme iron (Fe) binding protein, has been shown to modulate the binding affinity between p65 homodimeric NF-κB and κB DNA. However, the allosteric effect of the active Fe(III) form of Pirin on the DNA has not been established. Here, we use multiple microsecond-long molecular dynamics simulations to explore the conformational dynamics of the free DNA, the p65-DNA complex, and the Pirin-p65-DNA supramolecular complex. We show that only the Fe(III) form of Pirin enhances the affinity between p65 and the DNA in the Pirin-p65-DNA supramolecular complex, in agreement with experiments. Additionally, the results provide atomistic details of the effect of the active Fe(III) form of Pirin on the DNA upon binding to the p65-DNA complex. In general, unlike the Fe(II) form of Pirin, binding of the Fe(III) form of Pirin to the p65-DNA complex significantly alters both the conformational dynamics of the DNA and the interactions between p65 and the DNA. The results provide atomic level understanding of the modulation of the DNA as a result of a redox-specific Fe(II)/Fe(III) coregulation of NF-κB by Pirin, knowledge that is necessary to fully understand normal and aberrant subcellular processes and the role of a subtle single electron redox process in gene regulation.

Electron transfer between the QmoABC membrane complex and adenosine 5′-phosphosulfate reductase

The dissimilatory adenosine 5′-phosphosulfate reductase (AprAB) is a key enzyme in the sulfate reduction pathway that catalyzes the reversible two electron reduction of adenosine 5′-phosphosulfate (APS) to sulfite and adenosine monophosphate (AMP). The physiological electron donor for AprAB is proposed to be the QmoABC membrane complex, coupling the quinone-pool to sulfate reduction. However, direct electron transfer between these two proteins has never been observed. In this work we demonstrate for the first time direct electron transfer between the Desulfovibrio desulfuricans ATCC 27774 QmoABC complex and AprAB. Cyclic voltammetry conducted with the modified Qmo electrode and AprAB in the electrolyte solution presented the Qmo electrochemical signature with two additional well-defined one electron redox processes, attributed to the AprAB FAD redox behavior. Moreover, experiments performed under catalytic conditions using the QmoABC modified electrode, with AprAB and APS in solution, show a catalytic current peak develop in the cathodic wave, attributed to substrate reduction, and which is not observed in the absence of QmoABC. Substrate dependence conducted with different electrode preparations (with and without immobilized Qmo) demonstrated that the QmoABC complex is essential for efficient electron delivery to AprAB, in order to sustain catalysis. These results confirm the role of Qmo in electron transfer to AprAB.

Synthesis, characterization, photoluminescence and electrochemical studies of NiII, CuII, ZnII, CdII and PdII complexes of the bidentate S-hexyl-β-N-(2-thienyl)methylenedithiocarbazate ligand

Divalent metal complexes of empirical formulation [ML2] (where M(II)=Ni, Cu, Zn, Cd and Pd; L=anionic form of the 2-thiophenecarboxaldehyde Schiff base of S-hexyldithiocarbazate) have been synthesized and characterized by physico-chemical techniques. Magnetic and spectroscopic data give support to a square-planar coordination geometry for these complexes with the exception of the ZnII and CdII species. The single crystal structures of the [NiL2] and [CuL2] complexes have been determined by X-ray diffraction analysis. In both the structurally characterized complexes the uninegatively charged bidentate ligands coordinate the metal (II) ion via the azomethine nitrogen and the thiolate sulfur atoms in a trans-planar configuration. The electrochemical properties of the Cu(II) complex have been studied by cyclic voltammetry. The voltammogram shows quasi-reversible, one electron redox process. Metal-mediated fluorescence quenching is observed on complexation of HL with all metal ions.

Synthetic advances inspired by the bioactive dinitrosyl iron unit.

Resulting from biochemical iron-NO interactions, dinitrosyl iron complexes (DNICs) are small organometallic-like molecules, considered to serve as vehicles for NO transport and storage in vivo. Formed by the interaction of NO with cellular iron sulfur clusters or with the cellular labile iron pool, DNICs have been documented to be the largest NO-derived adduct in cells, even surpassing the well-known nitrosothiols (RSNOs). Continuing efforts in biological chemistry are aimed at understanding the movement of DNICs in and out of cells, and their important role in NO-induced iron efflux leading to apoptosis in cells. Intrigued by the integrity of the unique dinitrosyl iron unit (DNIU) and the possibility of roles for it in human physiology or medicinal applications, the understanding of fundamental properties such as ligand effects on its ability to switch between two redox levels has been pursued through biomimetic complexes. Using metallodithiolates and N-heterocyclic carbenes (NHCs) as ligands to Fe(NO)2, the synthesis of a library of novel DNICs, in both the oxidized, {Fe(NO)2}(9), and reduced, {Fe(NO)2}(10), forms (Enemark-Feltham notation), offers opportunity to examine structural, reactivity, and spectroscopic features. The raison d'etre for the MN2S2·Fe(NO)2 synthesis development is for the potential to exploit the ease of accessing two redox levels on two different metal sites, a property presumably required for achieving two electron redox processes in base metals. Hence such molecules may be viewed as synthetic analogues of [NiFe]- or [FeFe]-hydrogenase active sites in nature, both of which use bridging thiolates for connection of the two centers. A particular success was the development of an Fe(NO)N2S2·Fe(NO)2(+/0) redox pair for proton reduction electrocatalysis. Monomeric, reduced NHC-DNICs of the L2Fe(NO)2 type are synthesized via the Fe(CO)2(NO)2 precursor, and oxidized thiolate-containing forms are derived from the dimeric (μ-RS)2[Fe(NO)2]2. Monomeric NHC-DNICs are four coordinate, pseudotetrahedral compounds with planar Fe(NO)2 units in which the slightly bent Fe-NO groups are directed symmetrically inward at both redox levels. They serve as stable analogues of biological histidine binding sites. In agreement with IR data, Mössbauer spectroscopic parameters, and DFT computations, the prototypic NHC-DNICs indicate extensive delocalization of the electron density of iron via π-backbonding. Such π-delocalization presents an unusual reaction path for the one electron process of RS(-)/RSSR interconversion. Comparisons with imidazole-DNICs find NHCs to be the "better" ligands to Fe(NO)2 and prompted investigations in (a) possible relationships between such imidazole- and NHC-containing DNICs, (b) systems that might mimic the reactivity of DNICs with the endogenous gaseotransmitter CO, and (c) mechanistic details of such processes. In a broader context, these studies aim to further describe the behavior of the {Fe(NO)2} unit as a single molecular entity when subjected to various ligand environments and reaction conditions.

Chronic Inflammation and Iron Metabolism

Iron is an essential component of almost all biological systems. It is required for energy production, oxygen transport and utilization, cellular proliferation, and destruction of pathogens. The biological properties of iron stem from the variability of its Fe2+/Fe3+ redox potential. Protein ligands adapt these redox potentials to meet various biological requirements. Iron containing proteins are essential to many biochemical functions including oxygen transport by the hemoproteins hemoglobin and myoglobin. Other hemoproteins include the activators of molecular oxygen; cytochrome oxidases, peroxidases, catalases, and cytochrome P450s as well as the cytochromes that transfer electrons from substrate oxidation to cytochrome c oxidase. Iron sulfur proteins are another class of iron containing proteins that mediate one electron redox processes as integral components of the respiratory chain in mitochondria. They are also involved in the control of gene expression, DNA damage recognition and repair, oxygen and nitrogen sensing, and the control of cellular iron acquisition and storage. The vital importance of maintaining iron supply is most obvious in children. Children, unlike adults, have high iron requirements because of significant cellular metabolic demands due to the high growth rates of their developing tissues and the rapid expansion of their red cell mass. The human brain at birth is the most highly metabolic organ, consuming ~50% of the body’s energy needs1. Highly metabolic organs need a plentiful supply of substrates, including iron, that support energy metabolism. This metabolic need is reflected in the different physiologic iron absorption requirements (per kilogram) at varying stages of development to maintain normal hemoglobin concentrations as the red cell volume expands with growth and for normal iron delivery to tissues. Per the Food and Nutrition Board of the Institutes of Medicine, the recommended dietary allowance for enteral iron starts at 0.27mg/day in the birth to 6 month age group, increases to 11mg/day in 7 to 12 month old infants, and then is 7mg/day in the 1 to 3 year age group. Women of child-bearing age require 18 mg/day and this value increases to 27mg/day during pregnancy2. Failure to maintain iron sufficiency during fetal life and in early childhood causes long-term alterations to developing organs, most importantly the brain3. Thus, ensuring adequate iron delivery to children during rapid growth phases is essential. Although maintaining iron delivery to children is vital to support their growth and neurodevelopment, there exists a conundrum in that there are potential negative consequences of iron supplementation in certain contexts such as infectious states. Iron supports the growth and differentiation of other rapidly growing cells including infectious agents. Bacteria are able to form biofilms and grow more rapidly when iron is abundant4–5. Bacteria have evolved mechanisms to acquire iron in low iron environments that include the secretion and reuptake of iron-binding organic molecules termed siderophores. Pathogens have developed the ability to acquire iron from host iron-binding proteins like hemoglobin, lactoferrin, and transferrin4. The body has evolved a finely tuned mechanism to limit iron availability during infection. In the short-term, this is advantageous and promotes basic survival by protecting from overwhelming infection. In the long-term, anemia of inflammation, also known as the anemia of chronic disease, can place the child’s growth and future development at risk by limiting iron availability. Given the potential for long lasting effects, we will discuss the important inter-relationships between chronic disease and iron metabolism.. Although there remain few pediatric specific examples in the literature, the mechanisms gleaned from the adult literature strongly suggest some of the same iron regulation events that take place with acute inflammation and iron metabolism apply to chronic disease in children. Therefore, we will: (1) provide background to explain the importance of the supply and demand and regulatory proteins involved in iron metabolism; (2) review how these regulation principles apply to anemia of inflammation; and (3) propose how these principles apply to anemia of chronic disease and provide clinically relevant examples.

V2O5 Aerogel as a Versatile Cathode Material for Lithium and Sodium Batteries

AbstractVanadium oxide gels are appealing cathode materials as they offer multiple electron redox processes leading to high cation‐storage capacities. Moreover, they are able to intercalate different ionic and molecular species. Apart from low electronic conductivity, one of the main factors hindering the use of highly porous V2O5 gels is the difficulty in preserving their unique morphology, made up of an entangled network of thin ribbons, during conventional laminated electrode preparation. In this study, we tune the V2O5 synthesis conditions and use an innovative and green binder system (polyacrylic acid and ethanol) to obtain electrodes with a morphology optimized for ion intercalation. The electrochemical performance of such electrodes, tested against lithium and sodium anodes, are shown to be excellent.

Operando X-ray absorption and EPR evidence for a single electron redox process in copper catalysis.

An unprecedented single electron redox process in copper catalysis is confirmed using operando X-ray absorption and EPR spectroscopies. The oxidation state of the copper species in the interaction between Cu(ii) and a sulfinic acid at room temperature, and the accurate characterization of the formed Cu(i) are clearly shown using operando X-ray absorption and EPR evidence. Further investigation of anion effects on Cu(ii) discloses that bromine ions can dramatically increase the rate of the redox process. Moreover, it is proven that the sulfinic acids are converted into sulfonyl radicals, which can be trapped by 2-arylacrylic acids and various valuable β-keto sulfones are synthesized with good to excellent yields under mild conditions.

Synthesis, Characterization and Properties of Terminal Alkynylate Modified Salen-Type Complexes

We synthesized two terminal alkynyl modified Salen ligands, H2L, and their metal complexes, ML (n=1, 2, M=Ni, Cu, Mn). The ligands and complexes were characterized by H nuclear magnetic resonance (H NMR) spectroscopy, electrospray ionization mass spectrometry (ESI-MS), elemental analysis, Fourier transform infrared (FT-IR) spectroscopy, and ultraviolet visible (UV-Vis) spectroscopy. The redox properties of the compounds were investigated with cyclic voltammetry (CV). Imine redox peaks appeared in the CV curves of all the ligands except H2L. The Ni and Cu complexes underwent two single electron redox processes in the scanning range. Mn complexes gave a pair of quasi-reversible voltammetric peaks, which corresponded to the redox process between Mn(III)/Mn(II). Molar conductivity measurements of the complexes showed that they were all weak electrolytes with certain conductivity.