Reversible Redox Properties Research Articles

Ferrocene-containing non-interlocked molecular machines.

Ferrocene is the prototypical organometallic sandwich complex and despite over 60 years passing since the discovery and elucidation of ferrocene's structure, research into ferrocene-containing compounds continues to grow as potential new applications in catalysis, biology and the material sciences are found. Ferrocene is chemically robust and readily functionalized which enables its facile incorporation into more complex molecular systems. This coupled with ferrocene's reversible redox properties and ability function as a "molecular ball bearing" has led to the use of ferrocene as a component in wide range of interlocked and non-interlocked synthetic molecular machine systems. This review will focus on the exploitation of ferrocene (and related sandwich complexes) for the development of non-interlocked synthetic molecular machines.

Thiophene quinoidal organic semiconductors for high performance n-channel organic field-effect transistors

Organic field-effect transistors have found wide applications in flexible displays, smart cards, sensors and so on because they can be fabricated on flexible substrates with large scale and low cost. Though great progress has been made on p-channel organic field effect transistors, the development of n-channel organic field-effect transistors is largely lagged behind their p-channel counterparts. The lack of high performance n-channel organic semiconductors has become one of the bottlenecks for organic field-effect transistors. Low LUMO energy level is one of the characteristics of n- type organic semiconductors. The low LUMO level of organic semiconductors can not only reduce the electron injection barrier, in favor of electrons transferring from the electrode into the semiconductor layer, but also prevent the electron charge carriers being trapped by air and water and obtain ambient stability. Thiophene quinoidal organic semiconductors have attracted great attentions recently because they have low-lying LUMO energy levels and strong intermolecular interactions, and usually display high electron mobility. This review summarizes the application of the thiophene quinoidal organic semiconductors in organic transistors in recent years. According to the characteristic of the molecular structures, in the review, the thiophene quinoidal organic semiconductors are divided into two classes: the oligo- thiophene quinoidal organic semiconductors and fused-ring thiophene quinoidal organic semiconductors. Compared to the extensive studied aromatic diimide n-type organic semiconductors, the research on thiophene quinoidal organic semiconductors is not sufficient and the molecular species of thiophene quinoidal compounds is not rich. However, the excellent electron transport properties of thiophene quinoidal organic semiconductors support their potential applications as high performance solution processable n-channel organic semiconductors. In addition to the application in organic transistors, thiophene quinoidal compounds usually have reversible redox property, high electron affinity and other characteristics, and will have potential applications in organic solar cells, charge transfer salts, organic memories and sensors. We believe that the research of thiophene quinoidal organic semiconductors will make more progress.

Synthesis of Soluble Ferrocene-Based Polythiophenes and Their Properties

Ferrocene-based polythiophenes are the promising class of the functional materials, but mostly the polythiophenes are insoluble in common solvents except some derivatives of polythiophenes like poly(3-hexylthiophene) (P3HT). Herein, two new ferrocene-based thiophene monomers, 2-(thiophen-3-yl) ethyl ferrocenoate and 2-(thiophen-3-yl) methyl ferrocenoate were synthesized and copolymerized with 3-hexylthiophene (3HT) respectively. The resulting polymers were soluble (in common organic solvents) and processable. The synthesis and the molecular weights were confirmed by the 1H-NMR and GPC studies respectively. Poly (TEF-co-3HT) was subjected to study the electrochemical properties in comparison of respective monomers and ferrocene. It was found that the resulting copolymer had the combined redox properties of its monomers. Also, very interestingly, the copolymer showed improved reversible redox properties which were not only better than its parent monomers but even better than the pure ferrocene. Photoemission spectra of P3HT and Poly (TEF-co-3HT) were also rerecorded and compared with each other.

Ultrasensitive ROS-Responsive Coassemblies of Tellurium-Containing Molecules and Phospholipids

Reactive oxygen species (ROS) play crucial roles in cell signaling and redox homeostasis and are strongly related to metabolic activities. The increase of the ROS concentration in organisms can result in several diseases, such as cardiovascular diseases and cancer. The concentration of ROS in biologically relevant conditions is typically as low as around tens of micromolars to 100 μM H2O2, which makes it necessary to develop ultrasensitive ROS-responsive systems. A general approach is reported here to fabricate an ultrasensitive ROS-responsive system via coassembly between tellurium-containing molecules and phospholipids, combining the ROS-responsiveness of tellurium and the biocompatibility of phospholipids. By using dynamic light scattering, transmission electron microscopy, scanning electron microscopy, and NMR spectra, coassembly behaviors and the responsiveness of the coassemblies have been investigated. These coassemblies can respond to 100 μM H2O2, which is a biologically relevant ROS concentration, and demonstrate reversible redox properties.

Radical Environments for Fast Charge Transport in the Stable Radical Polymer, Ptma

Non-conjugated, open-shell polymers with stable radical pendant groups have emerged as a unique class of electroactive materials for use in chemical or electronic devices traditionally dominated by conjugated conducting polymers or inorganic semiconductors. Their stability and reversible redox properties allow the neutral polymers to convert to cation or anion states analogous to doping a semiconductor p or n-type. The charge transport kinetics in these materials can be surprisingly on par with transition metal ion devices thus allowing the exciting opportunity to implement these materials in electronic devices, specifically for energy storage. The stable radical polymer poly(2,2,6,6-tetramethylpiperidine-4-yl-1-oxyl methacrylate) (PTMA) is one such redox active polymer that has recently been studied as potential candidate for cathodes in all organic battery devices and charge transport mitigating layers in super-capacitor / battery hybrid devices1. It is clear from the literature that the device properties are intimately connected to the polymer properties, most importantly, the pendant radical. The stable pendant radical is highly localized and therefore the electronic transport through the polymer is apparently governed by electron-hopping mechanisms. However, it is unclear whether the radical environment is optimal for the intended purpose, in this case, charge transport. For this work, we have used well-known electron paramagnetic resonance (EPR) methods to study the PTMA-TEMPO radical materials to determine structural information about the radical environment. Using synthetic techniques to control the radical mole fraction, X, on the methyl methacrylate backbone, we investigated the dependence of polymer conformation on radical concentration and attempt to link favorable radical environments to conditions of favorable charge transport. We call these oligomers PTMA-X and will present data for various values of X from 100% (PTMA), to 10%. The EPR data indicate that the majority of radicals in the PTMA assume a closest approach distance to each other when more than 60% of the backbone is populated with radical pendant groups. This distance is estimated to be about 5.6 Å and is consistent with recent theoretical work2. These small distances promote a strong coupling between radicals which therefore promote conditions of fast charge transport. We see evidence for subtle changes in the radical environment depending on characteristics of the solvent, but overall the radical-radical distances are unaltered. Perhaps most interestingly, the radical-radical distances do not change until there is less than about 60% radical mole fraction. For this regime, the polymer can accommodate larger radical-radical spacing by changing conformation. Small angle neutron scattering (SANS) experiments of these polymers in solution indeed confirm these conformation changes. Since the radical network appears unchanged from 60% to 100%, we expect only small differences in the transport properties such as conductivity to result as a function of X. Hence, these results indicate that PTMA-60 may be as good as PTMA with respect to charge transport, and may therefore serve as a better choice for charge transport layers in devices where gravimetric capacity is highly valued. In this talk, we will present these data, along with SANS and electrical transport measurements, and then discuss their implications on charge transport for these and other related stable radical polymers. 1. Oyaizu, K.; Nishide, H. Radical Polymers for Organic Electronic Devices: A Radical Departure from Conjugated Polymers? Advanced Materials 2009, 21 (22), 2339-2344. 2. Kemper, T. W.; Larsen, R. E.; Gennett, T. Relationship between Molecular Structure and Electron Transfer in a Polymeric Nitroxyl-Radical Energy Storage Material. The Journal of Physical Chemistry C 2014, 118 (31), 17213-17220.

Preparation and Photoelectronic Properties of Zinc Oxide/Perovskite Nanocomposites/Polypyrrole

La0.3Ca0.7Fe0.7Ni0.3O3 perovskite-type composite was prepared by glycine-nitrate combustion method , Zinc Oxide was prepared by liquid crystal precipitation, then we synthesized ZnO/La0.3Ca0.7Fe0.7Ni0.3O3/Ppy nanocomposites with different content of Ppy in situ method. XRD,SEM,UV-vis were used to characterized the crystal structure and morphology of the nanocomposites and their photocatalytic activity. Cyclic voltammetry of the composites were conducted in 1mol/L KCl solutions to discuss their electrochemical properties.According to the electrochemical properties, we found that with the increase of the zinc oxide content,the redox peak current of the composites becomes larger, also their reversible redox properties was improved.

Synthesis of electroconductive hydrogel films by an electro-controlled click reaction and their application to drug delivery systems

Electroconductive hydrogels are composed of 3-dimensionally structured hydrogels and conducting molecules with electrical, optical, and reversible redox properties.

Ferrocifen type anti cancer drugs.

Despite current developments in therapeutics focusing on biotechnologically-oriented species, the unflagging utility of small molecules or peptides in medicine is still producing strong results. In 2014 for example, of the 41 new medicines authorized for sale, 33 belonged to the category of small molecules, while in 2013 they represented 24 of 27, according to the FDA. This can be explained as the result of recent forays into new or long-neglected areas of chemistry. Medicinal organometallic chemistry can provide us with an antimalarial against resistant parasitic strains, as attested by the phase II clinical development of ferroquine, with a new framework for conceptual advances based on three-dimensional space-filling, and with redox or indeed catalytic intracellular properties. In this context, bioferrocene species with antiproliferative potential have for several years been the subject of sustained effort, based on some initial successes and on the nature of ferrocene as a stable aromatic, with low toxicity, low cost, and possessing reversible redox properties. We show here the different antitumoral approaches offered by ferrocifen derivatives, originally simple derivatives of tamoxifen, which over the course of their development have proved to possess remarkable structural and mechanistic diversity. These entities act via various targets, some of which have been identified, that are triggered according to the concentration of the products. They also act according to the nature of the cancer cells and their functionality, by mechanistic pathways that can operate either synergistically or not, in successive, concomitant or sequential ways, depending for example on newly identified signaling pathways inducing senescence or apoptosis. Here we present a first attempt to rationalize the behavior of these entities with various anticancer targets.

Synthesis of ferrocene-based polythiophenes and their applications

Individually, ferrocene and thiophenes have incredible properties and important applications. During the last two decades, scientists synthesized polythiophenes containing ferrocene in the main and side chains. Polythiophenes have redox, conducting, and optical properties. Because of these properties, polythiophenes have been used in sensing applications. In addition, ferrocene has reversible redox properties and accordingly has been used in a lot of sensing devices, such as glucose sensing. Ferrocene can have +2 or +3 oxidation state, which can correspond to “0” and “1”, and thus can be used as a memory storage material. When these two moieties are combined together, they show good compatibility. Therefore, the resulting materials/polymers have been used in memory storage and chemical sensing devices. Thus, we carefully selected studies that are only associated with ferrocene-based polythiophenes. In this review, we tried to focus on the synthesis and applications of ferrocene-based polythiophenes. There are many methods for the polymerization of thiophenes. Here, we discussed the electrochemical polymerization, oxidation polymerization, nickel mediated coupling reactions, and Suzuki polycondensation. In addition, polythiophenes can be decorated with ferrocene, pre- or post-polymerization. These materials were examined for important applications, including information storage, DNA sensing, protein sensing, and glucose sensing materials.

Synthesis of Metallo-supramolecular Polymers with a Bis-ONO-tridentate Ligand by Coordination Programming

Abstract A novel ONO-type bis-tridentate ligand L1 was synthesized by a diazocoupling reaction of 3,3′-dihydroxybenzidine with 6-octyl-2-naphthol in 58% yield. Azo-hydrazo tautomerization in L1 was indicated by the NMR and IR spectra. The 1:1 complexation of L1 and Mn(III) or Co(II) ions was confirmed by titration experiments at room temperature. Mn-, Co-, and Cr-based metallo-supramolecular polymers were prepared via the 1:1 complexation of the ditopic ligand with the metal ions at 100 °C. The Mn- and Cr-based polymers exhibited reversible redox properties.

Theoretical exploration on switchable NLO response induced by photochromic properties of covalently connected unsymmetrical spiropyran–polyoxometalate complex

In this paper, the relationship between reversible redox properties and second-order nonlinear optical (NLO) responses for photochromic unsymmetrical Mn-Anderson type polyoxometalate covalently linked to one spiropyran has been systematically investigated by using density functional theory (DFT) method. It is noticeable that the second-order NLO behaviors can be switched by reversible redox for this complex. The gaining and losing of electrons cause significant change on NLO response. Among these studied systems, the β0 value of two-electron-oxidized system, SP2−, is largest and ∼48 times as large as that of system SP. The charge-transfer transition corresponding to the dominant contributions to β0 values indicates that redox processes affect on intramolecular donor and acceptor character. Therefore, this kind of complex with the facile and reversible redox states might potentially be used for switching purposes in NLO molecular devices.

Electrochemical performance of cobalt hydroxide nanosheets formed by the delamination of layered cobalt hydroxide in water

We report the preparation of monometallic Co(2+)/Co(3+) layered double hydroxide, intercalated with lactate anions (LCoH-Lactate), and its spontaneous delamination in water to form cobalt hydroxide nanosheets. These hydroxide nanosheets formed stable aqueous dispersions. The thickness of a nanosheet was estimated to be approximately 1 nm by atomic force microscopy and small angle X-ray scattering experiments, and corresponds to a single hydroxide layer. Some of the Co(2+) cations were oxidised by oxygen, resulting in a mixed Co(2+)(0.76)Co(3+)(0.24) layer composition. Upon water evaporation, the nanosheets restacked to form transparent self-standing films with a layered structure like that of the original material. The coverage of the surface with side-by-side stacks of nanosheets indicated two-dimensional agglomeration and suggested that these dispersions could be applied to prepare large monolayers of nanosheets. The layers prepared by spin-coating were stable and featured reversible and reproducible redox properties in an alkaline electrolyte. In an evaluation of their electrochemical performance, the cobalt hydroxide nanosheets exhibited durability and fast charge transfer kinetics during repetitive potential cycling up to 200 mV s(-1). The nanosheets prepared by the present method show promise for use in nanocomposite materials for energy storage applications.

Asymmetric perylene bisimide dyes with strong solvatofluorism

Two asymmetric perylene bisimide dyes, 1-cyano-7-piperidinylperylene bisimide (1) and 1-bromo-7-piperidinylperylene bisimide (2), were synthesized and fully characterized. These molecules undergo an excited-state intramolecular electron transfer reaction, resulting in a unique charge transfer emission, of which the peak wavelength exhibits strong solvatochromism. They show both larger ground-state and excited-state dipole moments than those of the symmetric perylene bisimide 3; the dipole moments of these compounds have been estimated using density functional theory calculations and the Lippert–Mataga equation. Furthermore, these dyes (1–3) display good thermal stability as well as good optical stability and reversible redox properties. Their spectroscopic properties in various conditions and complementary time-dependent density functional theory calculations are reported.

Controlled Formation of Microspheres from Ferrocene-derivatized Amino Acids in Binary Aqueous/Organic Media

Abstract A novel amino acid derivative having two ferrocene units spontaneously forms regular microspheres in binary aqueous/tetrahydrofuran (THF) media. The size of the microspheres is controllable from nano to micro dimensions depending on the concentration and composition of the binary solvent. These microspheres display reversible redox properties, as characterized by cyclic voltammetry.

Fabrication and characterization of poly(vinylferrocenium) perchlorate/poly(3,4-ethylenedioxythiophene) composite-coated electrode in methylene chloride

Poly(vinylferrocenium) perchlorate/poly(3,4-ethylenedioxythiophene) (PVF+/PEDOT) composite film was synthesized electrochemically on Pt electrode in a methylene chloride solution containing a mixture of poly(vinylferrocene) (PVF) polymer and 3,4-ethylenedioxythiophene monomer. PVF polymer in composite film was used as an electron transfer mediator in the electrochemical oxidation of compounds due to its perfect reversible redox properties. The resulting composite film was characterized electrochemically, spectroscopically and conductivity measurements. Ascorbic acid (AA) was selected as a model compound to evaluate the electrocatalytical ability of the PVF+/PEDOT composite film-coated electrode. The resulting coating exhibits significant electrochemical activity toward AA in 0.1M phosphate buffer solution at pH 7, with high sensitivity and a wide linearity range. The steady state current vs. the concentration of AA are linear in the range of 2.22×10−4–6.4×10−2molL−1 and 6.4×10−2–2.16×10−1molL−1, respectively, for two linear regions. Limit of detection (LOD) was found to be 6.67×10−5molL−1 at 0.35V vs. SCE. The interaction of AA with PVF+ and PEDOT homopolymer films was investigated electrochemically and spectroscopically. The results showed that the catalytic activity of PEDOT-coated electrode was improved by the addition of PVF+. Applicability of the composite film was investigated by using pharmaceutical tablets, employing amperometric I–t method.

Electrochemically Triggered Selective Adsorption of Biotemplated Nanoparticles on Self‐Assembled Organometallic Diblock Copolymer Thin Films

AbstractThe controlled adsorption of the iron‐containing cage protein ferritin at the nanoscale using stimuli‐responsive self‐assembled diblock copolymer thin‐film templates is reported. The diblock copolymer used study consists of a cylinder‐forming polystyrene‐block‐polyferrocenylsilane (PS‐b‐PFS), with PFS as the minor block, and shows reversible redox properties. To prevent any spontaneous protein adsorption on either block, the electrolyte pH is selected to leave the ferritin negatively charged, and the protein concentration and solution ionic strength are carefully tuned. Selective adsorption of ferritin on the PFS domains of the self‐assembled thin films is then triggered in situ by applying a positive potential, simultaneously oxidizing the PFS and attracting the ferritin electrostatically.

Sandwich-Type Lanthanide(III) Dinaphthalocyanine Complexes Possessing an Intensive Absorption in the Near IR Region: Synthesis and Investigation of Properties

Phenoxysubstituted sandwich-type naphthalocyanine complexes of lanthanides were synthesized in a melt under the heating and using microwave irradiation assisted approach. The intensive absorption in the near IR region up to 2000 nm was found. All complexes obtained were characterized using MALDI-TOF mass spectrometry, UV/Vis/NIR and 1H NMR spectroscopy. The presence of reversible redox properties was demonstrated by cyclic voltammetry for a wide range of potentials (-1.6÷1.6 V).

Langmuir–Blodgett (LB) films of novel tetrathiafulvalene derivative containing diamino group

A new tetrathiafulvalene (TTF) derivative—5,6-diamino-2-(4,5-bis(decylthio)-1,3-dithio-2-ylidene)benzo[ d]-1,3-dithiole ( 1) with strong amphiphilic character and good reversible redox property has been synthesized. The Langmuir–Blodgett (LB) film of compound 1 was fabricated and its physical properties were characterized by UV–vis spectra, X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM) and surface profiler. The room temperature in-plane dc conductivity of the LB film increases from 10 −7 S cm −1 to 10 −5 S cm −1 after doped by iodine.

Synthesis, photophysical, and electrochromic properties of new triarylamino-containing polyphenylquinoxalines

New triarylamino-containing bis(α-diketones) are synthesized. On the basis of these compounds, a series of electrochromic organosoluble polyphenylquinoxalines with glass-transition temperatures of 224–315°C are prepared. All polymers intensively fluoresce in solutions and thin films with maxima at 535–600 and 530–560 nm, respectively. Cyclic voltammograms of polyphenylquinoxalines exhibit reversible redox properties in the range E 1/2 = 0.92–1.25 eV. It is shown that, after 15 cycles, all polymers preserve high stability and reversibility of electrochromic characteristics, but their color changes from yellow (neutral form) to wine red (oxidized form).

Carbon nanotubes/alizarin red S–poly(vinylferrocene) modified glassy carbon electrode for selective determination of dopamine in the presence of ascorbic acid

A modified electrode was fabricated by electrochemical formation of poly(vinylferrocene) on the multi-wall carbon nanotube-alizarin red S matrix covered glassy carbon electrode. A higher electrochemical activity was obtained to the electrocatalytic oxidation of dopamine. The electrode surface was characterized electrochemically and spectroscopically. Poly(vinylferrocene) (PVF) in electrode was used as an electron transfer mediator in the electrochemical oxidation of compounds due to its perfect reversible redox properties. Multi-wall carbon nanotubes (MWCNTs) / alizarin red S (ARS)–PVF electrode was used to the determination of dopamine in the presence of ascorbic acid in 0.1 M sulphate buffer solution at pH 7. The performance of the MWCNTs/ARS–PVF electrode was evaluated by DPV and amperometry.